package org.apache.maven.plugins.javadoc;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import java.io.BufferedReader;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.io.PrintStream;
  import java.io.UnsupportedEncodingException;
  import java.lang.reflect.Modifier;
  import java.net.SocketTimeoutException;
  import java.net.URI;
  import java.net.URISyntaxException;
  import java.net.URL;
  import java.net.URLClassLoader;
  import java.nio.charset.Charset;
  import java.nio.charset.IllegalCharsetNameException;
  import java.nio.file.FileVisitResult;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.nio.file.SimpleFileVisitor;
  import java.nio.file.attribute.BasicFileAttributes;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Locale;
  import java.util.NoSuchElementException;
  import java.util.Properties;
  import java.util.Set;
  import java.util.StringTokenizer;
  import java.util.jar.JarEntry;
  import java.util.jar.JarInputStream;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  import java.util.regex.PatternSyntaxException;
  
  import org.apache.http.HttpHeaders;
  import org.apache.http.HttpHost;
  import org.apache.http.HttpResponse;
  import org.apache.http.HttpStatus;
  import org.apache.http.auth.AuthScope;
  import org.apache.http.auth.Credentials;
  import org.apache.http.auth.UsernamePasswordCredentials;
  import org.apache.http.client.CredentialsProvider;
  import org.apache.http.client.config.CookieSpecs;
  import org.apache.http.client.config.RequestConfig;
  import org.apache.http.client.methods.HttpGet;
  import org.apache.http.client.protocol.HttpClientContext;
  import org.apache.http.config.Registry;
  import org.apache.http.config.RegistryBuilder;
  import org.apache.http.conn.socket.ConnectionSocketFactory;
  import org.apache.http.conn.socket.PlainConnectionSocketFactory;
  import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
  import org.apache.http.impl.client.BasicCredentialsProvider;
  import org.apache.http.impl.client.CloseableHttpClient;
  import org.apache.http.impl.client.HttpClientBuilder;
  import org.apache.http.impl.client.HttpClients;
  import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
  import org.apache.http.message.BasicHeader;
  import org.apache.maven.plugin.logging.Log;
  import org.apache.maven.project.MavenProject;
  import org.apache.maven.settings.Proxy;
  import org.apache.maven.settings.Settings;
  import org.apache.maven.shared.invoker.DefaultInvocationRequest;
  import org.apache.maven.shared.invoker.DefaultInvoker;
  import org.apache.maven.shared.invoker.InvocationOutputHandler;
  import org.apache.maven.shared.invoker.InvocationRequest;
  import org.apache.maven.shared.invoker.InvocationResult;
  import org.apache.maven.shared.invoker.Invoker;
  import org.apache.maven.shared.invoker.MavenInvocationException;
  import org.apache.maven.shared.invoker.PrintStreamHandler;
  import org.apache.maven.wagon.proxy.ProxyInfo;
  import org.apache.maven.wagon.proxy.ProxyUtils;
 import org.codehaus.plexus.languages.java.version.JavaVersion;
 import org.codehaus.plexus.util.DirectoryScanner;
 import org.codehaus.plexus.util.FileUtils;
 import org.codehaus.plexus.util.IOUtil;
 import org.codehaus.plexus.util.Os;
 import org.codehaus.plexus.util.StringUtils;
 import org.codehaus.plexus.util.cli.CommandLineException;
 import org.codehaus.plexus.util.cli.CommandLineUtils;
 import org.codehaus.plexus.util.cli.Commandline;
 
 /**
  * Set of utilities methods for Javadoc.
  *
  * @author <a href="mailto:vincent.siveton@gmail.com">Vincent Siveton</a>
  * @since 2.4
  */
 public class JavadocUtil
 {
     /** The default timeout used when fetching url, i.e. 2000. */
     public static final int DEFAULT_TIMEOUT = 2000;
 
     /** Error message when VM could not be started using invoker. */
     protected static final String ERROR_INIT_VM =
         "Error occurred during initialization of VM, try to reduce the Java heap size for the MAVEN_OPTS "
             + "environment variable using -Xms:<size> and -Xmx:<size>.";
 
     /**
      * Method that removes the invalid directories in the specified directories. <b>Note</b>: All elements in
      * <code>dirs</code> could be an absolute or relative against the project's base directory <code>String</code> path.
      *
      * @param project the current Maven project not null
      * @param dirs the collection of <code>String</code> directories path that will be validated.
      * @return a List of valid <code>String</code> directories absolute paths.
      */
     public static Collection<Path> pruneDirs( MavenProject project, Collection<String> dirs )
     {
         final Path projectBasedir = project.getBasedir().toPath();
 
         Set<Path> pruned = new LinkedHashSet<>( dirs.size() );
         for ( String dir : dirs )
         {
             if ( dir == null )
             {
                 continue;
             }
 
             Path directory = projectBasedir.resolve( dir );
 
             if ( Files.isDirectory( directory ) )
             {
                 pruned.add( directory.toAbsolutePath() );
             }
         }
 
         return pruned;
     }
 
     /**
      * Method that removes the invalid files in the specified files. <b>Note</b>: All elements in <code>files</code>
      * should be an absolute <code>String</code> path.
      *
      * @param files the list of <code>String</code> files paths that will be validated.
      * @return a List of valid <code>File</code> objects.
      */
     protected static List<String> pruneFiles( Collection<String> files )
     {
         List<String> pruned = new ArrayList<>( files.size() );
         for ( String f : files )
         {
             if ( !shouldPruneFile( f, pruned ) )
             {
                 pruned.add( f );
             }
         }
 
         return pruned;
     }
 
     /**
      * Determine whether a file should be excluded from the provided list of paths, based on whether it exists and is
      * already present in the list.
      *
      * @param f The files.
      * @param pruned The list of pruned files..
      * @return true if the file could be pruned false otherwise.
      */
     public static boolean shouldPruneFile( String f, List<String> pruned )
     {
         if ( f != null )
         {
             if ( Files.isRegularFile( Paths.get( f ) ) && !pruned.contains( f ) )
             {
                 return false;
             }
         }
 
         return true;
     }
 
     /**
      * Method that gets all the source files to be excluded from the javadoc on the given source paths.
      *
      * @param sourcePaths the path to the source files
      * @param excludedPackages the package names to be excluded in the javadoc
      * @return a List of the packages to be excluded in the generated javadoc
      */
     protected static List<String> getExcludedPackages( Collection<Path> sourcePaths,
                                                        Collection<String> excludedPackages )
     {
         List<String> excludedNames = new ArrayList<>();
         for ( Path sourcePath : sourcePaths )
         {
             excludedNames.addAll( getExcludedPackages( sourcePath, excludedPackages ) );
         }
 
         return excludedNames;
     }
 
     /**
      * Convenience method to wrap an argument value in single quotes (i.e. <code>'</code>). Intended for values which
      * may contain whitespaces. <br>
      * To prevent javadoc error, the line separator (i.e. <code>\n</code>) are skipped.
      *
      * @param value the argument value.
      * @return argument with quote
      */
     protected static String quotedArgument( String value )
     {
         String arg = value;
 
         if ( StringUtils.isNotEmpty( arg ) )
         {
             if ( arg.contains( "'" ) )
             {
                 arg = StringUtils.replace( arg, "'", "\\'" );
             }
             arg = "'" + arg + "'";
 
             // To prevent javadoc error
             arg = StringUtils.replace( arg, "\n", " " );
         }
 
         return arg;
     }
 
     /**
      * Convenience method to format a path argument so that it is properly interpreted by the javadoc tool. Intended for
      * path values which may contain whitespaces.
      *
      * @param value the argument value.
      * @return path argument with quote
      */
     protected static String quotedPathArgument( String value )
     {
         String path = value;
 
         if ( StringUtils.isNotEmpty( path ) )
         {
             path = path.replace( '\\', '/' );
             if ( path.contains( "\'" ) )
             {
                 String split[] = path.split( "\'" );
                 path = "";
 
                 for ( int i = 0; i < split.length; i++ )
                 {
                     if ( i != split.length - 1 )
                     {
                         path = path + split[i] + "\\'";
                     }
                     else
                     {
                         path = path + split[i];
                     }
                 }
             }
             path = "'" + path + "'";
         }
 
         return path;
     }
 
     /**
      * Convenience method that copy all <code>doc-files</code> directories from <code>javadocDir</code> to the
      * <code>outputDirectory</code>.
      *
      * @param outputDirectory the output directory
      * @param javadocDir the javadoc directory
      * @param excludedocfilessubdir the excludedocfilessubdir parameter
      * @throws IOException if any
      * @since 2.5
      */
     protected static void copyJavadocResources( File outputDirectory, File javadocDir, String excludedocfilessubdir )
         throws IOException
     {
         if ( !javadocDir.isDirectory() )
         {
             return;
         }
 
         List<String> excludes = new ArrayList<>( Arrays.asList( FileUtils.getDefaultExcludes() ) );
 
         if ( StringUtils.isNotEmpty( excludedocfilessubdir ) )
         {
             StringTokenizer st = new StringTokenizer( excludedocfilessubdir, ":" );
             String current;
             while ( st.hasMoreTokens() )
             {
                 current = st.nextToken();
                 excludes.add( "**/" + current + "/**" );
             }
         }
 
         List<String> docFiles =
             FileUtils.getDirectoryNames( javadocDir, "resources,**/doc-files",
                                          StringUtils.join( excludes.iterator(), "," ), false, true );
         for ( String docFile : docFiles )
         {
             File docFileOutput = new File( outputDirectory, docFile );
             FileUtils.mkdir( docFileOutput.getAbsolutePath() );
             FileUtils.copyDirectoryStructure( new File( javadocDir, docFile ), docFileOutput );
             List<String> files =
                 FileUtils.getFileAndDirectoryNames( docFileOutput, StringUtils.join( excludes.iterator(), "," ), null,
                                                     true, true, true, true );
             for ( String filename : files )
             {
                 File file = new File( filename );
 
                 if ( file.isDirectory() )
                 {
                     FileUtils.deleteDirectory( file );
                 }
                 else
                 {
                     file.delete();
                 }
             }
         }
     }
 
     /**
      * Method that gets the files or classes that would be included in the javadocs using the subpackages parameter.
      *
      * @param sourceDirectory the directory where the source files are located
      * @param fileList the list of all relative files found in the sourceDirectory
      * @param excludePackages package names to be excluded in the javadoc
      * @return a StringBuilder that contains the appended file names of the files to be included in the javadoc
      */
     protected static List<String> getIncludedFiles( File sourceDirectory, String[] fileList,
                                                     Collection<String> excludePackages )
     {
         List<String> files = new ArrayList<>();
 
         List<Pattern> excludePackagePatterns = new ArrayList<>( excludePackages.size() );
         for ( String excludePackage :  excludePackages )
         {
             excludePackagePatterns.add( Pattern.compile( excludePackage.replace( '.', File.separatorChar )
                                                                        .replace( "\\", "\\\\" )
                                                                        .replace( "*", ".+" )
                                                                        .concat( "[\\\\/][^\\\\/]+\\.java" )
                                                                                 ) );
         }
 
         for ( String file : fileList )
         {
             boolean excluded = false;
             for ( Pattern excludePackagePattern :  excludePackagePatterns )
             {
                 if ( excludePackagePattern.matcher( file ).matches() )
                 {
                     excluded = true;
                     break;
                 }
             }
 
             if ( !excluded )
             {
                 files.add( file );
             }
         }
 
         return files;
     }
 
     /**
      * Method that gets the complete package names (including subpackages) of the packages that were defined in the
      * excludePackageNames parameter.
      *
      * @param sourceDirectory the directory where the source files are located
      * @param excludePackagenames package names to be excluded in the javadoc
      * @return a List of the packagenames to be excluded
      */
     protected static Collection<String> getExcludedPackages( final Path sourceDirectory,
                                                              Collection<String> excludePackagenames )
     {
         final String regexFileSeparator = File.separator.replace( "\\", "\\\\" );
 
         final Collection<String> fileList = new ArrayList<>();
 
         try
         {
             Files.walkFileTree( sourceDirectory, new SimpleFileVisitor<Path>()
             {
                 @Override
                 public FileVisitResult visitFile( Path file, BasicFileAttributes attrs )
                     throws IOException
                 {
                     if ( file.getFileName().toString().endsWith( ".java" ) )
                     {
                         fileList.add( sourceDirectory.relativize( file.getParent() ).toString() );
                     }
                     return FileVisitResult.CONTINUE;
                 }
             } );
         }
         catch ( IOException e )
         {
             // noop
         }
 
         List<String> files = new ArrayList<>();
         for ( String excludePackagename : excludePackagenames )
         {
             // Usage of wildcard was bad specified and bad implemented, i.e. using String.contains()
             //   without respecting surrounding context
             // Following implementation should match requirements as defined in the examples:
             // - A wildcard at the beginning should match 1 or more folders
             // - Any other wildcard must match exactly one folder
             Pattern p = Pattern.compile( excludePackagename.replace( ".", regexFileSeparator )
                                                            .replaceFirst( "^\\*", ".+" )
                                                            .replace( "*", "[^" + regexFileSeparator + "]+" ) );
 
             for ( String aFileList : fileList )
             {
                 if ( p.matcher( aFileList ).matches() )
                 {
                     files.add( aFileList.replace( File.separatorChar, '.' ) );
                 }
             }
         }
 
         return files;
     }
 
     /**
      * Convenience method that gets the files to be included in the javadoc.
      *
      * @param sourceDirectory the directory where the source files are located
      * @param excludePackages the packages to be excluded in the javadocs
      * @param sourceFileIncludes files to include.
      * @param sourceFileExcludes files to exclude.
      */
     protected static List<String> getFilesFromSource( File sourceDirectory, List<String> sourceFileIncludes,
                                                       List<String> sourceFileExcludes,
                                                       Collection<String> excludePackages )
     {
         DirectoryScanner ds = new DirectoryScanner();
         if ( sourceFileIncludes == null )
         {
             sourceFileIncludes = Collections.singletonList( "**/*.java" );
         }
         ds.setIncludes( sourceFileIncludes.toArray( new String[sourceFileIncludes.size()] ) );
         if ( sourceFileExcludes != null && sourceFileExcludes.size() > 0 )
         {
             ds.setExcludes( sourceFileExcludes.toArray( new String[sourceFileExcludes.size()] ) );
         }
         ds.setBasedir( sourceDirectory );
         ds.scan();
 
         String[] fileList = ds.getIncludedFiles();
 
         List<String> files = new ArrayList<>();
         if ( fileList.length != 0 )
         {
             for ( String includedFile : getIncludedFiles( sourceDirectory, fileList, excludePackages ) )
             {
                 files.add( includedFile );
             }
         }
 
         return files;
     }
 
     /**
      * Call the Javadoc tool and parse its output to find its version, i.e.:
      *
      * <pre>
      * javadoc.exe( or.sh ) - J - version
      * </pre>
      *
      * @param javadocExe not null file
      * @return the javadoc version as float
      * @throws IOException if javadocExe is null, doesn't exist or is not a file
      * @throws CommandLineException if any
      * @throws IllegalArgumentException if no output was found in the command line
      * @throws PatternSyntaxException if the output contains a syntax error in the regular-expression pattern.
      * @see #extractJavadocVersion(String)
      */
     protected static JavaVersion getJavadocVersion( File javadocExe )
         throws IOException, CommandLineException, IllegalArgumentException
     {
         if ( ( javadocExe == null ) || ( !javadocExe.exists() ) || ( !javadocExe.isFile() ) )
         {
             throw new IOException( "The javadoc executable '" + javadocExe + "' doesn't exist or is not a file. " );
         }
 
         Commandline cmd = new Commandline();
         cmd.setExecutable( javadocExe.getAbsolutePath() );
         cmd.setWorkingDirectory( javadocExe.getParentFile() );
         cmd.createArg().setValue( "-J-version" );
 
         CommandLineUtils.StringStreamConsumer out = new JavadocOutputStreamConsumer();
         CommandLineUtils.StringStreamConsumer err = new JavadocOutputStreamConsumer();
 
         int exitCode = CommandLineUtils.executeCommandLine( cmd, out, err );
 
         if ( exitCode != 0 )
         {
             StringBuilder msg = new StringBuilder( "Exit code: " + exitCode + " - " + err.getOutput() );
             msg.append( '\n' );
             msg.append( "Command line was:" + CommandLineUtils.toString( cmd.getCommandline() ) );
             throw new CommandLineException( msg.toString() );
         }
 
         if ( StringUtils.isNotEmpty( err.getOutput() ) )
         {
             return JavaVersion.parse( extractJavadocVersion( err.getOutput() ) );
         }
         else if ( StringUtils.isNotEmpty( out.getOutput() ) )
         {
             return JavaVersion.parse( extractJavadocVersion( out.getOutput() ) );
         }
 
         throw new IllegalArgumentException( "No output found from the command line 'javadoc -J-version'" );
     }
 
     /**
      * Parse the output for 'javadoc -J-version' and return the javadoc version recognized. <br>
      * Here are some output for 'javadoc -J-version' depending the JDK used:
      * <table summary="Output for 'javadoc -J-version' per JDK">
      * <tr>
      * <th>JDK</th>
      * <th>Output for 'javadoc -J-version'</th>
      * </tr>
      * <tr>
      * <td>Sun 1.4</td>
      * <td>java full version "1.4.2_12-b03"</td>
      * </tr>
      * <tr>
      * <td>Sun 1.5</td>
      * <td>java full version "1.5.0_07-164"</td>
      * </tr>
      * <tr>
      * <td>IBM 1.4</td>
      * <td>javadoc full version "J2RE 1.4.2 IBM Windows 32 build cn1420-20040626"</td>
      * </tr>
      * <tr>
      * <td>IBM 1.5 (French JVM)</td>
      * <td>javadoc version complète de "J2RE 1.5.0 IBM Windows 32 build pwi32pdev-20070426a"</td>
      * </tr>
      * <tr>
      * <td>FreeBSD 1.5</td>
      * <td>java full version "diablo-1.5.0-b01"</td>
      * </tr>
      * <tr>
      * <td>BEA jrockit 1.5</td>
      * <td>java full version "1.5.0_11-b03"</td>
      * </tr>
      * </table>
      *
      * @param output for 'javadoc -J-version'
      * @return the version of the javadoc for the output, only digits and dots
      * @throws PatternSyntaxException if the output doesn't match with the output pattern
      *             <tt>(?s).*?[^a-zA-Z]([0-9]+\\.?[0-9]*)(\\.([0-9]+))?.*</tt>.
      * @throws IllegalArgumentException if the output is null
      */
     protected static String extractJavadocVersion( String output )
         throws IllegalArgumentException
     {
         if ( StringUtils.isEmpty( output ) )
         {
             throw new IllegalArgumentException( "The output could not be null." );
         }
 
         Pattern pattern = Pattern.compile( "(?s).*?[^a-zA-Z](([0-9]+\\.?[0-9]*)(\\.[0-9]+)?).*" );
 
         Matcher matcher = pattern.matcher( output );
         if ( !matcher.matches() )
         {
             throw new PatternSyntaxException( "Unrecognized version of Javadoc: '" + output + "'", pattern.pattern(),
                                               pattern.toString().length() - 1 );
         }
 
         return matcher.group( 1 );
     }
 
     /**
      * Parse a memory string which be used in the JVM arguments <code>-Xms</code> or <code>-Xmx</code>. <br>
      * Here are some supported memory string depending the JDK used:
      * <table summary="Memory argument support per JDK">
      * <tr>
      * <th>JDK</th>
      * <th>Memory argument support for <code>-Xms</code> or <code>-Xmx</code></th>
      * </tr>
      * <tr>
      * <td>SUN</td>
      * <td>1024k | 128m | 1g | 1t</td>
      * </tr>
      * <tr>
      * <td>IBM</td>
      * <td>1024k | 1024b | 128m | 128mb | 1g | 1gb</td>
      * </tr>
      * <tr>
      * <td>BEA</td>
      * <td>1024k | 1024kb | 128m | 128mb | 1g | 1gb</td>
      * </tr>
      * </table>
      *
      * @param memory the memory to be parsed, not null.
      * @return the memory parsed with a supported unit. If no unit specified in the <code>memory</code> parameter, the
      *         default unit is <code>m</code>. The units <code>g | gb</code> or <code>t | tb</code> will be converted in
      *         <code>m</code>.
      * @throws IllegalArgumentException if the <code>memory</code> parameter is null or doesn't match any pattern.
      */
     protected static String parseJavadocMemory( String memory )
         throws IllegalArgumentException
     {
         if ( StringUtils.isEmpty( memory ) )
         {
             throw new IllegalArgumentException( "The memory could not be null." );
         }
 
         Pattern p = Pattern.compile( "^\\s*(\\d+)\\s*?\\s*$" );
         Matcher m = p.matcher( memory );
         if ( m.matches() )
         {
             return m.group( 1 ) + "m";
         }
 
         p = Pattern.compile( "^\\s*(\\d+)\\s*k(b)?\\s*$", Pattern.CASE_INSENSITIVE );
         m = p.matcher( memory );
         if ( m.matches() )
         {
             return m.group( 1 ) + "k";
         }
 
         p = Pattern.compile( "^\\s*(\\d+)\\s*m(b)?\\s*$", Pattern.CASE_INSENSITIVE );
         m = p.matcher( memory );
         if ( m.matches() )
         {
             return m.group( 1 ) + "m";
         }
 
         p = Pattern.compile( "^\\s*(\\d+)\\s*g(b)?\\s*$", Pattern.CASE_INSENSITIVE );
         m = p.matcher( memory );
         if ( m.matches() )
         {
             return ( Integer.parseInt( m.group( 1 ) ) * 1024 ) + "m";
         }
 
         p = Pattern.compile( "^\\s*(\\d+)\\s*t(b)?\\s*$", Pattern.CASE_INSENSITIVE );
         m = p.matcher( memory );
         if ( m.matches() )
         {
             return ( Integer.parseInt( m.group( 1 ) ) * 1024 * 1024 ) + "m";
         }
 
         throw new IllegalArgumentException( "Could convert not to a memory size: " + memory );
     }
 
     /**
      * Validate if a charset is supported on this platform.
      *
      * @param charsetName the charsetName to be check.
      * @return <code>true</code> if the given charset is supported by the JVM, <code>false</code> otherwise.
      */
     protected static boolean validateEncoding( String charsetName )
     {
         if ( StringUtils.isEmpty( charsetName ) )
         {
             return false;
         }
 
         try
         {
             return Charset.isSupported( charsetName );
         }
         catch ( IllegalCharsetNameException e )
         {
             return false;
         }
     }
 
     /**
      * Auto-detect the class names of the implementation of <code>com.sun.tools.doclets.Taglet</code> class from a given
      * jar file. <br>
      * <b>Note</b>: <code>JAVA_HOME/lib/tools.jar</code> is a requirement to find
      * <code>com.sun.tools.doclets.Taglet</code> class.
      *
      * @param jarFile not null
      * @return the list of <code>com.sun.tools.doclets.Taglet</code> class names from a given jarFile.
      * @throws IOException if jarFile is invalid or not found, or if the <code>JAVA_HOME/lib/tools.jar</code> is not
      *             found.
      * @throws ClassNotFoundException if any
      * @throws NoClassDefFoundError if any
      */
     protected static List<String> getTagletClassNames( File jarFile )
         throws IOException, ClassNotFoundException, NoClassDefFoundError
     {
         List<String> classes = getClassNamesFromJar( jarFile );
         ClassLoader cl;
 
         // Needed to find com.sun.tools.doclets.Taglet class
         File tools = new File( System.getProperty( "java.home" ), "../lib/tools.jar" );
         if ( tools.exists() && tools.isFile() )
         {
             cl = new URLClassLoader( new URL[] { jarFile.toURI().toURL(), tools.toURI().toURL() }, null );
         }
         else
         {
             cl = new URLClassLoader( new URL[] { jarFile.toURI().toURL() }, ClassLoader.getSystemClassLoader() );
         }
 
         List<String> tagletClasses = new ArrayList<>();
 
         Class<?> tagletClass;
 
         try
         {
             tagletClass = cl.loadClass( "com.sun.tools.doclets.Taglet" );
         }
         catch ( ClassNotFoundException e )
         {
             tagletClass = cl.loadClass( "jdk.javadoc.doclet.Taglet" );
         }
 
         for ( String s : classes )
         {
             Class<?> c = cl.loadClass( s );
 
             if ( tagletClass.isAssignableFrom( c ) && !Modifier.isAbstract( c.getModifiers() ) )
             {
                 tagletClasses.add( c.getName() );
             }
         }
 
         return tagletClasses;
     }
 
     /**
      * Copy the given url to the given file.
      *
      * @param url not null url
      * @param file not null file where the url will be created
      * @throws IOException if any
      * @since 2.6
      */
     protected static void copyResource( URL url, File file )
         throws IOException
     {
         if ( file == null )
         {
             throw new IOException( "The file can't be null." );
         }
         if ( url == null )
         {
             throw new IOException( "The url could not be null." );
         }
 
         FileUtils.copyURLToFile( url, file );
     }
 
     /**
      * Invoke Maven for the given project file with a list of goals and properties, the output will be in the invokerlog
      * file. <br>
      * <b>Note</b>: the Maven Home should be defined in the <code>maven.home</code> Java system property or defined in
      * <code>M2_HOME</code> system env variables.
      *
      * @param log a logger could be null.
      * @param localRepositoryDir the localRepository not null.
      * @param projectFile a not null project file.
      * @param goals a not null goals list.
      * @param properties the properties for the goals, could be null.
      * @param invokerLog the log file where the invoker will be written, if null using <code>System.out</code>.
      * @param globalSettingsFile reference to settings file, could be null.
      * @throws MavenInvocationException if any
      * @since 2.6
      */
     protected static void invokeMaven( Log log, File localRepositoryDir, File projectFile, List<String> goals,
                                        Properties properties, File invokerLog, File globalSettingsFile )
         throws MavenInvocationException
     {
         if ( projectFile == null )
         {
             throw new IllegalArgumentException( "projectFile should be not null." );
         }
         if ( !projectFile.isFile() )
         {
             throw new IllegalArgumentException( projectFile.getAbsolutePath() + " is not a file." );
         }
         if ( goals == null || goals.size() == 0 )
         {
             throw new IllegalArgumentException( "goals should be not empty." );
         }
         if ( localRepositoryDir == null || !localRepositoryDir.isDirectory() )
         {
             throw new IllegalArgumentException( "localRepositoryDir '" + localRepositoryDir
                 + "' should be a directory." );
         }
 
         String mavenHome = getMavenHome( log );
         if ( StringUtils.isEmpty( mavenHome ) )
         {
             String msg = "Could NOT invoke Maven because no Maven Home is defined. You need to have set the M2_HOME "
                 + "system env variable or a maven.home Java system properties.";
             if ( log != null )
             {
                 log.error( msg );
             }
             else
             {
                 System.err.println( msg );
             }
             return;
         }
 
         Invoker invoker = new DefaultInvoker();
         invoker.setMavenHome( new File( mavenHome ) );
         invoker.setLocalRepositoryDirectory( localRepositoryDir );
 
         InvocationRequest request = new DefaultInvocationRequest();
         request.setBaseDirectory( projectFile.getParentFile() );
         request.setPomFile( projectFile );
         request.setGlobalSettingsFile( globalSettingsFile );
         request.setBatchMode( true );
         if ( log != null )
         {
             request.setDebug( log.isDebugEnabled() );
         }
         else
         {
             request.setDebug( true );
         }
         request.setGoals( goals );
         if ( properties != null )
         {
             request.setProperties( properties );
         }
         File javaHome = getJavaHome( log );
         if ( javaHome != null )
         {
             request.setJavaHome( javaHome );
         }
 
         if ( log != null && log.isDebugEnabled() )
         {
             log.debug( "Invoking Maven for the goals: " + goals + " with "
                 + ( properties == null ? "no properties" : "properties=" + properties ) );
         }
         InvocationResult result = invoke( log, invoker, request, invokerLog, goals, properties, null );
 
         if ( result.getExitCode() != 0 )
         {
             String invokerLogContent = readFile( invokerLog, "UTF-8" );
 
             // see DefaultMaven
             if ( invokerLogContent != null && ( !invokerLogContent.contains( "Scanning for projects..." )
                 || invokerLogContent.contains( OutOfMemoryError.class.getName() ) ) )
             {
                 if ( log != null )
                 {
                     log.error( "Error occurred during initialization of VM, trying to use an empty MAVEN_OPTS..." );
 
                     if ( log.isDebugEnabled() )
                     {
                         log.debug( "Reinvoking Maven for the goals: " + goals + " with an empty MAVEN_OPTS..." );
                     }
                 }
                 result = invoke( log, invoker, request, invokerLog, goals, properties, "" );
             }
         }
 
         if ( result.getExitCode() != 0 )
         {
             String invokerLogContent = readFile( invokerLog, "UTF-8" );
 
             // see DefaultMaven
             if ( invokerLogContent != null && ( !invokerLogContent.contains( "Scanning for projects..." )
                 || invokerLogContent.contains( OutOfMemoryError.class.getName() ) ) )
             {
                 throw new MavenInvocationException( ERROR_INIT_VM );
             }
 
             throw new MavenInvocationException( "Error when invoking Maven, consult the invoker log file: "
                 + invokerLog.getAbsolutePath() );
         }
     }
 
     /**
      * Read the given file and return the content or null if an IOException occurs.
      *
      * @param javaFile not null
      * @param encoding could be null
      * @return the content with unified line separator of the given javaFile using the given encoding.
      * @see FileUtils#fileRead(File, String)
      * @since 2.6.1
      */
     protected static String readFile( final File javaFile, final String encoding )
     {
         try
         {
             return FileUtils.fileRead( javaFile, encoding );
         }
         catch ( IOException e )
         {
             return null;
         }
     }
 
     /**
      * Split the given path with colon and semi-colon, to support Solaris and Windows path. Examples:
      *
      * <pre>
      * splitPath( "/home:/tmp" )     = ["/home", "/tmp"]
      * splitPath( "/home;/tmp" )     = ["/home", "/tmp"]
      * splitPath( "C:/home:C:/tmp" ) = ["C:/home", "C:/tmp"]
      * splitPath( "C:/home;C:/tmp" ) = ["C:/home", "C:/tmp"]
      * </pre>
      *
      * @param path which can contain multiple paths separated with a colon (<code>:</code>) or a semi-colon
      *            (<code>;</code>), platform independent. Could be null.
      * @return the path splitted by colon or semi-colon or <code>null</code> if path was <code>null</code>.
      * @since 2.6.1
      */
     protected static String[] splitPath( final String path )
     {
         if ( path == null )
         {
             return null;
         }
 
         List<String> subpaths = new ArrayList<>();
         PathTokenizer pathTokenizer = new PathTokenizer( path );
         while ( pathTokenizer.hasMoreTokens() )
         {
             subpaths.add( pathTokenizer.nextToken() );
         }
 
         return subpaths.toArray( new String[subpaths.size()] );
     }
 
     /**
      * Unify the given path with the current System path separator, to be platform independent. Examples:
      *
      * <pre>
      * unifyPathSeparator( "/home:/tmp" ) = "/home:/tmp" (Solaris box)
      * unifyPathSeparator( "/home:/tmp" ) = "/home;/tmp" (Windows box)
      * </pre>
      *
      * @param path which can contain multiple paths by separating them with a colon (<code>:</code>) or a semi-colon
      *            (<code>;</code>), platform independent. Could be null.
      * @return the same path but separated with the current System path separator or <code>null</code> if path was
      *         <code>null</code>.
      * @since 2.6.1
      * @see #splitPath(String)
      * @see File#pathSeparator
      */
     protected static String unifyPathSeparator( final String path )
     {
         if ( path == null )
         {
             return null;
         }
 
         return StringUtils.join( splitPath( path ), File.pathSeparator );
     }
 
     // ----------------------------------------------------------------------
     // private methods
     // ----------------------------------------------------------------------
 
     /**
      * @param jarFile not null
      * @return all class names from the given jar file.
      * @throws IOException if any or if the jarFile is null or doesn't exist.
      */
     private static List<String> getClassNamesFromJar( File jarFile )
         throws IOException
     {
         if ( jarFile == null || !jarFile.exists() || !jarFile.isFile() )
         {
             throw new IOException( "The jar '" + jarFile + "' doesn't exist or is not a file." );
         }
 
         List<String> classes = new ArrayList<>();
         try ( JarInputStream jarStream = new JarInputStream( new FileInputStream( jarFile ) ) )
         {
             for ( JarEntry jarEntry = jarStream.getNextJarEntry(); jarEntry != null; jarEntry =
                 jarStream.getNextJarEntry() )
             {
                 if ( jarEntry.getName().toLowerCase( Locale.ENGLISH ).endsWith( ".class" ) )
                 {
                     String name = jarEntry.getName().substring( 0, jarEntry.getName().indexOf( "." ) );
 
                     classes.add( name.replaceAll( "/", "\\." ) );
                 }
 
                 jarStream.closeEntry();
             }
         }
 
         return classes;
     }
 
     /**
      * @param log could be null
      * @param invoker not null
      * @param request not null
      * @param invokerLog not null
      * @param goals not null
      * @param properties could be null
      * @param mavenOpts could be null
      * @return the invocation result
      * @throws MavenInvocationException if any
      * @since 2.6
      */
     private static InvocationResult invoke( Log log, Invoker invoker, InvocationRequest request, File invokerLog,
                                             List<String> goals, Properties properties, String mavenOpts )
         throws MavenInvocationException
     {
         PrintStream ps;
         OutputStream os = null;
         if ( invokerLog != null )
         {
             if ( log != null && log.isDebugEnabled() )
             {
                 log.debug( "Using " + invokerLog.getAbsolutePath() + " to log the invoker" );
             }
 
             try
             {
                 if ( !invokerLog.exists() )
                 {
                     // noinspection ResultOfMethodCallIgnored
                     invokerLog.getParentFile().mkdirs();
                 }
                 os = new FileOutputStream( invokerLog );
                 ps = new PrintStream( os, true, "UTF-8" );
             }
             catch ( FileNotFoundException e )
             {
                 if ( log != null && log.isErrorEnabled() )
                 {
                     log.error( "FileNotFoundException: " + e.getMessage() + ". Using System.out to log the invoker." );
                 }
                 ps = System.out;
             }
             catch ( UnsupportedEncodingException e )
             {
                 if ( log != null && log.isErrorEnabled() )
                 {
                     log.error( "UnsupportedEncodingException: " + e.getMessage()
                         + ". Using System.out to log the invoker." );
                 }
                 ps = System.out;
             }
         }
         else
         {
             if ( log != null && log.isDebugEnabled() )
             {
                 log.debug( "Using System.out to log the invoker." );
             }
 
             ps = System.out;
         }
 
         if ( mavenOpts != null )
         {
             request.setMavenOpts( mavenOpts );
         }
 
         InvocationOutputHandler outputHandler = new PrintStreamHandler( ps, false );
         request.setOutputHandler( outputHandler );
 
         try
         {
             outputHandler.consumeLine( "Invoking Maven for the goals: " + goals + " with "
                 + ( properties == null ? "no properties" : "properties=" + properties ) );
             outputHandler.consumeLine( "" );
             outputHandler.consumeLine( "M2_HOME=" + getMavenHome( log ) );
             outputHandler.consumeLine( "MAVEN_OPTS=" + getMavenOpts( log ) );
             outputHandler.consumeLine( "JAVA_HOME=" + getJavaHome( log ) );
             outputHandler.consumeLine( "JAVA_OPTS=" + getJavaOpts( log ) );
             outputHandler.consumeLine( "" );
         }
         catch ( IOException ioe )
         {
             throw new MavenInvocationException( "IOException while consuming invocation output", ioe );
         }
 
         try
         {
             return invoker.execute( request );
         }
         finally
         {
             IOUtil.close( os );
         }
     }
 
     /**
      * @param log a logger could be null
      * @return the Maven home defined in the <code>maven.home</code> system property or defined in <code>M2_HOME</code>
      *         system env variables or null if never set.
      * @since 2.6
      */
     private static String getMavenHome( Log log )
     {
         String mavenHome = System.getProperty( "maven.home" );
         if ( mavenHome == null )
         {
             try
             {
                 mavenHome = CommandLineUtils.getSystemEnvVars().getProperty( "M2_HOME" );
             }
             catch ( IOException e )
             {
                 if ( log != null && log.isDebugEnabled() )
                 {
                     log.debug( "IOException: " + e.getMessage() );
                 }
             }
         }
 
         File m2Home = new File( mavenHome );
         if ( !m2Home.exists() )
         {
             if ( log != null && log.isErrorEnabled() )
             {
                 log.error( "Cannot find Maven application directory. Either specify \'maven.home\' system property, or "
                     + "M2_HOME environment variable." );
             }
         }
 
         return mavenHome;
     }
 
     /**
      * @param log a logger could be null
      * @return the <code>MAVEN_OPTS</code> env variable value
      * @since 2.6
      */
     private static String getMavenOpts( Log log )
     {
         String mavenOpts = null;
         try
         {
             mavenOpts = CommandLineUtils.getSystemEnvVars().getProperty( "MAVEN_OPTS" );
         }
         catch ( IOException e )
         {
             if ( log != null && log.isDebugEnabled() )
             {
                 log.debug( "IOException: " + e.getMessage() );
             }
         }
 
         return mavenOpts;
     }
 
     /**
      * @param log a logger could be null
      * @return the <code>JAVA_HOME</code> from System.getProperty( "java.home" ) By default,
      *         <code>System.getProperty( "java.home" ) = JRE_HOME</code> and <code>JRE_HOME</code> should be in the
      *         <code>JDK_HOME</code>
      * @since 2.6
      */
     private static File getJavaHome( Log log )
     {
         File javaHome = null;
 
         String javaHomeValue = null;
         try
         {
             javaHomeValue = CommandLineUtils.getSystemEnvVars().getProperty( "JAVA_HOME" );
         }
         catch ( IOException e )
         {
             if ( log != null && log.isDebugEnabled() )
             {
                 log.debug( "IOException: " + e.getMessage() );
             }
         }
 
         // if maven.home is set, we can assume JAVA_HOME must be used for testing
         if ( System.getProperty( "maven.home" ) == null || javaHomeValue == null )
         {
             // JEP220 (Java9) restructured the JRE/JDK runtime image
             if ( SystemUtils.IS_OS_MAC_OSX || JavaVersion.JAVA_VERSION.isAtLeast( "9" ) )
             {
                 javaHome = SystemUtils.getJavaHome();
             }
             else
             {
                 javaHome = new File( SystemUtils.getJavaHome(), ".." );
             }
         }
 
         if ( javaHome == null || !javaHome.exists() )
         {
             javaHome = new File( javaHomeValue );
         }
 
         if ( javaHome == null || !javaHome.exists() )
         {
             if ( log != null && log.isErrorEnabled() )
             {
                 log.error( "Cannot find Java application directory. Either specify \'java.home\' system property, or "
                     + "JAVA_HOME environment variable." );
             }
         }
 
         return javaHome;
     }
 
     /**
      * @param log a logger could be null
      * @return the <code>JAVA_OPTS</code> env variable value
      * @since 2.6
      */
     private static String getJavaOpts( Log log )
     {
         String javaOpts = null;
         try
         {
             javaOpts = CommandLineUtils.getSystemEnvVars().getProperty( "JAVA_OPTS" );
         }
         catch ( IOException e )
         {
             if ( log != null && log.isDebugEnabled() )
             {
                 log.debug( "IOException: " + e.getMessage() );
             }
         }
 
         return javaOpts;
     }
 
     /**
      * A Path tokenizer takes a path and returns the components that make up that path. The path can use path separators
      * of either ':' or ';' and file separators of either '/' or '\'.
      *
      * @version revision 439418 taken on 2009-09-12 from Ant Project (see
      *          http://svn.apache.org/repos/asf/ant/core/trunk/src/main/org/apache/tools/ant/PathTokenizer.java)
      */
     private static class PathTokenizer
     {
         /**
          * A tokenizer to break the string up based on the ':' or ';' separators.
          */
         private StringTokenizer tokenizer;
 
         /**
          * A String which stores any path components which have been read ahead due to DOS filesystem compensation.
          */
         private String lookahead = null;
 
         /**
          * A boolean that determines if we are running on Novell NetWare, which exhibits slightly different path name
          * characteristics (multi-character volume / drive names)
          */
         private boolean onNetWare = Os.isFamily( "netware" );
 
         /**
          * Flag to indicate whether or not we are running on a platform with a DOS style filesystem
          */
         private boolean dosStyleFilesystem;
 
         /**
          * Constructs a path tokenizer for the specified path.
          *
          * @param path The path to tokenize. Must not be <code>null</code>.
          */
         PathTokenizer( String path )
         {
             if ( onNetWare )
             {
                 // For NetWare, use the boolean=true mode, so we can use delimiter
                 // information to make a better decision later.
                 tokenizer = new StringTokenizer( path, ":;", true );
             }
             else
             {
                 // on Windows and Unix, we can ignore delimiters and still have
                 // enough information to tokenize correctly.
                 tokenizer = new StringTokenizer( path, ":;", false );
             }
             dosStyleFilesystem = File.pathSeparatorChar == ';';
         }
 
         /**
          * Tests if there are more path elements available from this tokenizer's path. If this method returns
          * <code>true</code>, then a subsequent call to nextToken will successfully return a token.
          *
          * @return <code>true</code> if and only if there is at least one token in the string after the current
          *         position; <code>false</code> otherwise.
          */
         public boolean hasMoreTokens()
         {
             return lookahead != null || tokenizer.hasMoreTokens();
 
         }
 
         /**
          * Returns the next path element from this tokenizer.
          *
          * @return the next path element from this tokenizer.
          * @exception NoSuchElementException if there are no more elements in this tokenizer's path.
          */
         public String nextToken()
             throws NoSuchElementException
         {
             String token;
             if ( lookahead != null )
             {
                 token = lookahead;
                 lookahead = null;
             }
             else
             {
                 token = tokenizer.nextToken().trim();
             }
 
             if ( !onNetWare )
             {
                 if ( token.length() == 1 && Character.isLetter( token.charAt( 0 ) ) && dosStyleFilesystem
                     && tokenizer.hasMoreTokens() )
                 {
                     // we are on a dos style system so this path could be a drive
                     // spec. We look at the next token
                     String nextToken = tokenizer.nextToken().trim();
                     if ( nextToken.startsWith( "\\" ) || nextToken.startsWith( "/" ) )
                     {
                         // we know we are on a DOS style platform and the next path
                         // starts with a slash or backslash, so we know this is a
                         // drive spec
                         token += ":" + nextToken;
                     }
                     else
                     {
                         // store the token just read for next time
                         lookahead = nextToken;
                     }
                 }
             }
             else
             {
                 // we are on NetWare, tokenizing is handled a little differently,
                 // due to the fact that NetWare has multiple-character volume names.
                 if ( token.equals( File.pathSeparator ) || token.equals( ":" ) )
                 {
                     // ignore ";" and get the next token
                     token = tokenizer.nextToken().trim();
                 }
 
                 if ( tokenizer.hasMoreTokens() )
                 {
                     // this path could be a drive spec, so look at the next token
                     String nextToken = tokenizer.nextToken().trim();
 
                     // make sure we aren't going to get the path separator next
                     if ( !nextToken.equals( File.pathSeparator ) )
                     {
                         if ( nextToken.equals( ":" ) )
                         {
                             if ( !token.startsWith( "/" ) && !token.startsWith( "\\" ) && !token.startsWith( "." )
                                 && !token.startsWith( ".." ) )
                             {
                                 // it indeed is a drive spec, get the next bit
                                 String oneMore = tokenizer.nextToken().trim();
                                 if ( !oneMore.equals( File.pathSeparator ) )
                                 {
                                     token += ":" + oneMore;
                                 }
                                 else
                                 {
                                     token += ":";
                                     lookahead = oneMore;
                                 }
                             }
                             // implicit else: ignore the ':' since we have either a
                             // UNIX or a relative path
                         }
                         else
                         {
                             // store the token just read for next time
                             lookahead = nextToken;
                         }
                     }
                 }
             }
             return token;
         }
     }
 
     /**
      * Ignores line like 'Picked up JAVA_TOOL_OPTIONS: ...' as can happen on CI servers.
      *
      * @author Robert Scholte
      * @since 3.0.1
      */
     protected static class JavadocOutputStreamConsumer
         extends CommandLineUtils.StringStreamConsumer
     {
         @Override
         public void consumeLine( String line )
         {
             if ( !line.startsWith( "Picked up " ) )
             {
                 super.consumeLine( line );
             }
         }
     }
 
     static List<String> toList( String src )
     {
         return toList( src, null, null );
     }
 
     static List<String> toList( String src, String elementPrefix, String elementSuffix )
     {
         if ( StringUtils.isEmpty( src ) )
         {
             return null;
         }
 
         List<String> result = new ArrayList<>();
 
         StringTokenizer st = new StringTokenizer( src, "[,:;]" );
         StringBuilder sb = new StringBuilder( 256 );
         while ( st.hasMoreTokens() )
         {
             sb.setLength( 0 );
             if ( StringUtils.isNotEmpty( elementPrefix ) )
             {
                 sb.append( elementPrefix );
             }
 
             sb.append( st.nextToken() );
 
             if ( StringUtils.isNotEmpty( elementSuffix ) )
             {
                 sb.append( elementSuffix );
             }
 
             result.add( sb.toString() );
         }
 
         return result;
     }
 
     static <T> List<T> toList( T[] multiple )
     {
         return toList( null, multiple );
     }
 
     static <T> List<T> toList( T single, T[] multiple )
     {
         if ( single == null && ( multiple == null || multiple.length < 1 ) )
         {
             return null;
         }
 
         List<T> result = new ArrayList<>();
         if ( single != null )
         {
             result.add( single );
         }
 
         if ( multiple != null && multiple.length > 0 )
         {
             result.addAll( Arrays.asList( multiple ) );
         }
 
         return result;
     }
 
     // TODO: move to plexus-utils or use something appropriate from there
     public static String toRelative( File basedir, String absolutePath )
     {
         String relative;
 
         absolutePath = absolutePath.replace( '\\', '/' );
         String basedirPath = basedir.getAbsolutePath().replace( '\\', '/' );
 
         if ( absolutePath.startsWith( basedirPath ) )
         {
             relative = absolutePath.substring( basedirPath.length() );
             if ( relative.startsWith( "/" ) )
             {
                 relative = relative.substring( 1 );
             }
             if ( relative.length() <= 0 )
             {
                 relative = ".";
             }
         }
         else
         {
             relative = absolutePath;
         }
 
         return relative;
     }
 
     /**
      * Convenience method to determine that a collection is not empty or null.
      * @param collection the collection to verify
      * @return {@code true} if not {@code null} and not empty, otherwise {@code false}
      */
     public static boolean isNotEmpty( final Collection<?> collection )
     {
         return collection != null && !collection.isEmpty();
     }
 
     /**
      * Convenience method to determine that a collection is empty or null.
      * @param collection the collection to verify
      * @return {@code true} if {@code null} or empty, otherwise {@code false}
      */
     public static boolean isEmpty( final Collection<?> collection )
     {
         return collection == null || collection.isEmpty();
     }
 
     /**
      * Execute an Http request at the given URL, follows redirects, and returns the last redirect locations. For URLs
      * that aren't http/https, this does nothing and simply returns the given URL unchanged.
      *
      * @param url URL.
      * @param settings Maven settings.
      * @return Last redirect location.
      * @throws IOException if there was an error during the Http request.
      */
     protected static URL getRedirectUrl( URL url, Settings settings )
         throws IOException
     {
         String protocol = url.getProtocol();
         if ( !"http".equals( protocol ) && !"https".equals( protocol ) )
         {
             return url;
         }
 
         try ( CloseableHttpClient httpClient = createHttpClient( settings, url ) )
         {
             HttpClientContext httpContext = HttpClientContext.create();
             HttpGet httpMethod = new HttpGet( url.toString() );
             HttpResponse response = httpClient.execute( httpMethod, httpContext );
             int status = response.getStatusLine().getStatusCode();
             if ( status != HttpStatus.SC_OK )
             {
                 throw new FileNotFoundException( "Unexpected HTTP status code " + status + " getting resource "
                     + url.toExternalForm() + "." );
             }
 
             List<URI> redirects = httpContext.getRedirectLocations();
 
             if ( isEmpty( redirects ) )
             {
                 return url;
             }
             else
             {
                 URI last = redirects.get( redirects.size() - 1 );
 
                 // URI must refer to directory, so prevent redirects to index.html
                 // see https://issues.apache.org/jira/browse/MJAVADOC-539
                 String truncate = "index.html";
                 if ( last.getPath().endsWith( "/" + truncate ) )
                 {
                     try
                     {
                         String fixedPath = last.getPath().substring( 0, last.getPath().length() - truncate.length() );
                         last = new URI( last.getScheme(), last.getAuthority(), fixedPath, last.getQuery(),
                                 last.getFragment() );
                     }
                     catch ( URISyntaxException ex )
                     {
                         // not supposed to happen, but when it does just keep the last URI
                     }
                 }
                 return last.toURL();
             }
         }
     }
 
     /**
      * Validates an <code>URL</code> to point to a valid <code>package-list</code> resource.
      *
      * @param url The URL to validate.
      * @param settings The user settings used to configure the connection to the URL or {@code null}.
      * @param validateContent <code>true</code> to validate the content of the <code>package-list</code> resource;
      *            <code>false</code> to only check the existence of the <code>package-list</code> resource.
      * @return <code>true</code> if <code>url</code> points to a valid <code>package-list</code> resource;
      *         <code>false</code> else.
      * @throws IOException if reading the resource fails.
      * @see #createHttpClient(org.apache.maven.settings.Settings, java.net.URL)
      * @since 2.8
      */
     protected static boolean isValidPackageList( URL url, Settings settings, boolean validateContent )
         throws IOException
     {
         if ( url == null )
         {
             throw new IllegalArgumentException( "The url is null" );
         }
 
         try ( BufferedReader reader = getReader( url, settings ) )
         {
             if ( validateContent )
             {
                 for ( String line = reader.readLine(); line != null; line = reader.readLine() )
                 {
                     if ( !isValidPackageName( line ) )
                     {
                         return false;
                     }
                 }
             }
             return true;
         }
     }
 
     protected static boolean isValidElementList( URL url, Settings settings, boolean validateContent )
                     throws IOException
     {
         if ( url == null )
         {
             throw new IllegalArgumentException( "The url is null" );
         }
 
         try ( BufferedReader reader = getReader( url, settings ) )
         {
             if ( validateContent )
             {
                 for ( String line = reader.readLine(); line != null; line = reader.readLine() )
                 {
                     if ( line.startsWith( "module:" ) )
                     {
                         continue;
                     }
 
                     if ( !isValidPackageName( line ) )
                     {
                         return false;
                     }
                 }
             }
             return true;
         }
     }
 
     private static BufferedReader getReader( URL url, Settings settings ) throws IOException
     {
         BufferedReader reader = null;
 
         if ( "file".equals( url.getProtocol() ) )
         {
             // Intentionally using the platform default encoding here since this is what Javadoc uses internally.
             reader = new BufferedReader( new InputStreamReader( url.openStream() ) );
         }
         else
         {
             // http, https...
             final CloseableHttpClient httpClient = createHttpClient( settings, url );
 
             final HttpGet httpMethod = new HttpGet( url.toString() );
 
             HttpResponse response;
             HttpClientContext httpContext = HttpClientContext.create();
             try
             {
                 response = httpClient.execute( httpMethod, httpContext );
             }
             catch ( SocketTimeoutException e )
             {
                 // could be a sporadic failure, one more retry before we give up
                 response = httpClient.execute( httpMethod, httpContext );
             }
 
             int status = response.getStatusLine().getStatusCode();
             if ( status != HttpStatus.SC_OK )
             {
                 throw new FileNotFoundException( "Unexpected HTTP status code " + status + " getting resource "
                     + url.toExternalForm() + "." );
             }
             else
             {
                 int pos = url.getPath().lastIndexOf( '/' );
                 List<URI> redirects = httpContext.getRedirectLocations();
                 if ( pos >= 0 && isNotEmpty( redirects ) )
                 {
                     URI location = redirects.get( redirects.size() - 1 );
                     String suffix = url.getPath().substring( pos );
                     // Redirections shall point to the same file, e.g. /package-list
                     if ( !location.getPath().endsWith( suffix ) )
                     {
                         throw new FileNotFoundException( url.toExternalForm() + " redirects to "
                                 + location.toURL().toExternalForm() + "." );
                     }
                 }
             }
 
             // Intentionally using the platform default encoding here since this is what Javadoc uses internally.
             reader = new BufferedReader( new InputStreamReader( response.getEntity().getContent() ) )
             {
                 @Override
                 public void close()
                     throws IOException
                 {
                     super.close();
 
                     if ( httpMethod != null )
                     {
                         httpMethod.releaseConnection();
                     }
                     if ( httpClient != null )
                     {
                         httpClient.close();
                     }
                 }
             };
         }
 
         return reader;
     }
 
     private static boolean isValidPackageName( String str )
     {
         if ( StringUtils.isEmpty( str ) )
         {
             // unnamed package is valid (even if bad practice :) )
             return true;
         }
 
         int idx;
         while ( ( idx = str.indexOf( '.' ) ) != -1 )
         {
             if ( !isValidClassName( str.substring( 0, idx ) ) )
             {
                 return false;
             }
 
             str = str.substring( idx + 1 );
         }
 
         return isValidClassName( str );
     }
 
     private static boolean isValidClassName( String str )
     {
         if ( StringUtils.isEmpty( str ) || !Character.isJavaIdentifierStart( str.charAt( 0 ) ) )
         {
             return false;
         }
 
         for ( int i = str.length() - 1; i > 0; i-- )
         {
             if ( !Character.isJavaIdentifierPart( str.charAt( i ) ) )
             {
                 return false;
             }
         }
 
         return true;
     }
 
     /**
      * Creates a new {@code HttpClient} instance.
      *
      * @param settings The settings to use for setting up the client or {@code null}.
      * @param url The {@code URL} to use for setting up the client or {@code null}.
      * @return A new {@code HttpClient} instance.
      * @see #DEFAULT_TIMEOUT
      * @since 2.8
      */
     private static CloseableHttpClient createHttpClient( Settings settings, URL url )
     {
         HttpClientBuilder builder = HttpClients.custom();
         
         Registry<ConnectionSocketFactory> csfRegistry =
             RegistryBuilder.<ConnectionSocketFactory>create()
                 .register( "http", PlainConnectionSocketFactory.getSocketFactory() )
                 .register( "https", SSLConnectionSocketFactory.getSystemSocketFactory() )
                 .build();
         
         builder.setConnectionManager( new PoolingHttpClientConnectionManager( csfRegistry ) );
         builder.setDefaultRequestConfig( RequestConfig.custom()
                                          .setSocketTimeout( DEFAULT_TIMEOUT )
                                          .setConnectTimeout( DEFAULT_TIMEOUT )
                                          .setCircularRedirectsAllowed( true )
                                          .setCookieSpec( CookieSpecs.IGNORE_COOKIES )
                                          .build() );
         
         // Some web servers don't allow the default user-agent sent by httpClient
         builder.setUserAgent( "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)" );
 
         // Some server reject requests that do not have an Accept header
         builder.setDefaultHeaders( Arrays.asList( new BasicHeader( HttpHeaders.ACCEPT, "*/*" ) ) );
 
         if ( settings != null && settings.getActiveProxy() != null )
         {
             Proxy activeProxy = settings.getActiveProxy();
 
             ProxyInfo proxyInfo = new ProxyInfo();
             proxyInfo.setNonProxyHosts( activeProxy.getNonProxyHosts() );
 
             if ( StringUtils.isNotEmpty( activeProxy.getHost() )
                 && ( url == null || !ProxyUtils.validateNonProxyHosts( proxyInfo, url.getHost() ) ) )
             {
                 HttpHost proxy = new HttpHost( activeProxy.getHost(), activeProxy.getPort() );
                 builder.setProxy( proxy );
 
                 if ( StringUtils.isNotEmpty( activeProxy.getUsername() ) && activeProxy.getPassword() != null )
                 {
                     Credentials credentials =
                         new UsernamePasswordCredentials( activeProxy.getUsername(), activeProxy.getPassword() );
 
                     CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
                     credentialsProvider.setCredentials( AuthScope.ANY, credentials );
                     builder.setDefaultCredentialsProvider( credentialsProvider );
                 }
             }
         }
         return builder.build();
     }
 
     static boolean equalsIgnoreCase( String value, String... strings )
     {
         for ( String s : strings )
         {
             if ( s.equalsIgnoreCase( value ) )
             {
                 return true;
             }
         }
         return false;
     }
 
     static boolean equals( String value, String... strings )
     {
         for ( String s : strings )
         {
             if ( s.equals( value ) )
             {
                 return true;
             }
         }
         return false;
     }
 }