org.apache.maven.shared.utils.io
Class IOUtil

java.lang.Object
  extended by org.apache.maven.shared.utils.io.IOUtil

public final class IOUtil
extends Object

General IO Stream manipulation.

This class provides static utility methods for input/output operations, particularly buffered copying between sources (InputStream, Reader, String and byte[]) and destinations (OutputStream, Writer, String and byte[]).

Unless otherwise noted, these copy methods do not flush or close the streams. Often, doing so would require making non-portable assumptions about the streams' origin and further use. This means that both streams' close() methods must be called after copying. if one omits this step, then the stream resources (sockets, file descriptors) are released when the associated Stream is garbage-collected. It is not a good idea to rely on this mechanism. For a good overview of the distinction between "memory management" and "resource management", see this UnixReview article

For each copy method, a variant is provided that allows the caller to specify the buffer size (the default is 4k). As the buffer size can have a fairly large impact on speed, this may be worth tweaking. Often "large buffer -> faster" does not hold, even for large data transfers.

For byte-to-char methods, a copy variant allows the encoding to be selected (otherwise the platform default is used).

The copy methods use an internal buffer when copying. It is therefore advisable not to deliberately wrap the stream arguments to the copy methods in Buffered* streams. For example, don't do the following:

copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );

The rationale is as follows:

Imagine that an InputStream's read() is a very expensive operation, which would usually suggest wrapping in a BufferedInputStream. The BufferedInputStream works by issuing infrequent InputStream.read(byte[] b, int off, int len) requests on the underlying InputStream, to fill an internal buffer, from which further read requests can inexpensively get their data (until the buffer runs out).

However, the copy methods do the same thing, keeping an internal buffer, populated by InputStream.read(byte[] b, int off, int len) requests. Having two buffers (or three if the destination stream is also buffered) is pointless, and the unnecessary buffer management hurts performance slightly (about 3%, according to some simple experiments).

Version:
CVS $Revision: 925654 $ $Date: 2014-10-13 22:12:40 +0200 (Mon, 13 Oct 2014) $
Author:
Peter Donald, Jeff Turner

Method Summary
static void close(Channel channel)
          Closes a channel.
static void close(InputStream inputStream)
          Closes the input stream.
static void close(OutputStream outputStream)
          Closes the output stream.
static void close(Reader reader)
          Closes the reader.
static void close(Writer writer)
          Closes the writer.
static boolean contentEquals(InputStream input1, InputStream input2)
          Compare the contents of two Streams to determine if they are equal or not.
static void copy(byte[] input, OutputStream output)
          Copy bytes from a byte[] to an OutputStream.
static void copy(byte[] input, Writer output)
          Copy and convert bytes from a byte[] to chars on a Writer.
static void copy(byte[] input, Writer output, int bufferSize)
          Copy and convert bytes from a byte[] to chars on a Writer.
static void copy(byte[] input, Writer output, String encoding)
          Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.
static void copy(byte[] input, Writer output, String encoding, int bufferSize)
          Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.
static void copy(InputStream input, OutputStream output)
          Copy bytes from an InputStream to an OutputStream.
static void copy(InputStream input, OutputStream output, int bufferSize)
          Copy bytes from an InputStream to an OutputStream.
static void copy(InputStream input, Writer output)
          Copy and convert bytes from an InputStream to chars on a Writer.
static void copy(InputStream input, Writer output, int bufferSize)
          Copy and convert bytes from an InputStream to chars on a Writer.
static void copy(InputStream input, Writer output, String encoding)
          Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
static void copy(InputStream input, Writer output, String encoding, int bufferSize)
          Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
static void copy(Reader input, OutputStream output)
          Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
static void copy(Reader input, OutputStream output, int bufferSize)
          Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
static void copy(Reader input, Writer output)
          Copy chars from a Reader to a Writer.
static void copy(Reader input, Writer output, int bufferSize)
          Copy chars from a Reader to a Writer.
static void copy(String input, OutputStream output)
          Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
static void copy(String input, OutputStream output, int bufferSize)
          Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
static void copy(String input, Writer output)
          Copy chars from a String to a Writer.
static byte[] toByteArray(InputStream input)
          Get the contents of an InputStream as a byte[].
static byte[] toByteArray(InputStream input, int bufferSize)
          Get the contents of an InputStream as a byte[].
static byte[] toByteArray(Reader input)
          Get the contents of a Reader as a byte[].
static byte[] toByteArray(Reader input, int bufferSize)
          Get the contents of a Reader as a byte[].
static byte[] toByteArray(String input)
          Get the contents of a String as a byte[].
static byte[] toByteArray(String input, int bufferSize)
          Get the contents of a String as a byte[].
static String toString(byte[] input)
          Get the contents of a byte[] as a String.
static String toString(byte[] input, int bufferSize)
          Get the contents of a byte[] as a String.
static String toString(byte[] input, String encoding)
          Get the contents of a byte[] as a String.
static String toString(byte[] input, String encoding, int bufferSize)
          Get the contents of a byte[] as a String.
static String toString(InputStream input)
          Get the contents of an InputStream as a String.
static String toString(InputStream input, int bufferSize)
          Get the contents of an InputStream as a String.
static String toString(InputStream input, String encoding)
          Get the contents of an InputStream as a String.
static String toString(InputStream input, String encoding, int bufferSize)
          Get the contents of an InputStream as a String.
static String toString(Reader input)
          Get the contents of a Reader as a String.
static String toString(Reader input, int bufferSize)
          Get the contents of a Reader as a String.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Method Detail

copy

public static void copy(@Nonnull
                        InputStream input,
                        @Nonnull
                        OutputStream output)
                 throws IOException
Copy bytes from an InputStream to an OutputStream.

Throws:
IOException

copy

public static void copy(@Nonnull
                        InputStream input,
                        @Nonnull
                        OutputStream output,
                        int bufferSize)
                 throws IOException
Copy bytes from an InputStream to an OutputStream.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        Reader input,
                        @Nonnull
                        Writer output)
                 throws IOException
Copy chars from a Reader to a Writer.

Throws:
IOException

copy

public static void copy(@Nonnull
                        Reader input,
                        @Nonnull
                        Writer output,
                        int bufferSize)
                 throws IOException
Copy chars from a Reader to a Writer.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        InputStream input,
                        @Nonnull
                        Writer output)
                 throws IOException
Copy and convert bytes from an InputStream to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.

Throws:
IOException

copy

public static void copy(@Nonnull
                        InputStream input,
                        @Nonnull
                        Writer output,
                        int bufferSize)
                 throws IOException
Copy and convert bytes from an InputStream to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        InputStream input,
                        @Nonnull
                        Writer output,
                        @Nonnull
                        String encoding)
                 throws IOException
Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
Throws:
IOException

copy

public static void copy(@Nonnull
                        InputStream input,
                        @Nonnull
                        Writer output,
                        @Nonnull
                        String encoding,
                        int bufferSize)
                 throws IOException
Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
bufferSize - Size of internal buffer to use.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      InputStream input)
                       throws IOException
Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.

Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      InputStream input,
                                      int bufferSize)
                       throws IOException
Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      InputStream input,
                                      @Nonnull
                                      String encoding)
                       throws IOException
Get the contents of an InputStream as a String.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      InputStream input,
                                      @Nonnull
                                      String encoding,
                                      int bufferSize)
                       throws IOException
Get the contents of an InputStream as a String.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
bufferSize - Size of internal buffer to use.
Throws:
IOException

toByteArray

@Nonnull
public static byte[] toByteArray(@Nonnull
                                         InputStream input)
                          throws IOException
Get the contents of an InputStream as a byte[].

Throws:
IOException

toByteArray

@Nonnull
public static byte[] toByteArray(@Nonnull
                                         InputStream input,
                                         int bufferSize)
                          throws IOException
Get the contents of an InputStream as a byte[].

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        Reader input,
                        @Nonnull
                        OutputStream output)
                 throws IOException
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

Throws:
IOException

copy

public static void copy(@Nonnull
                        Reader input,
                        @Nonnull
                        OutputStream output,
                        int bufferSize)
                 throws IOException
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      Reader input)
                       throws IOException
Get the contents of a Reader as a String.

Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      Reader input,
                                      int bufferSize)
                       throws IOException
Get the contents of a Reader as a String.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

toByteArray

@Nonnull
public static byte[] toByteArray(@Nonnull
                                         Reader input)
                          throws IOException
Get the contents of a Reader as a byte[].

Throws:
IOException

toByteArray

@Nonnull
public static byte[] toByteArray(@Nonnull
                                         Reader input,
                                         int bufferSize)
                          throws IOException
Get the contents of a Reader as a byte[].

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        String input,
                        @Nonnull
                        OutputStream output)
                 throws IOException
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

Throws:
IOException

copy

public static void copy(@Nonnull
                        String input,
                        @Nonnull
                        OutputStream output,
                        int bufferSize)
                 throws IOException
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        String input,
                        @Nonnull
                        Writer output)
                 throws IOException
Copy chars from a String to a Writer.

Throws:
IOException

toByteArray

@Nonnull
public static byte[] toByteArray(@Nonnull
                                         String input)
                          throws IOException
Get the contents of a String as a byte[].

Throws:
IOException

toByteArray

@Nonnull
public static byte[] toByteArray(@Nonnull
                                         String input,
                                         int bufferSize)
                          throws IOException
Get the contents of a String as a byte[].

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        byte[] input,
                        @Nonnull
                        Writer output)
                 throws IOException
Copy and convert bytes from a byte[] to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.

Throws:
IOException

copy

public static void copy(@Nonnull
                        byte[] input,
                        @Nonnull
                        Writer output,
                        int bufferSize)
                 throws IOException
Copy and convert bytes from a byte[] to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        byte[] input,
                        @Nonnull
                        Writer output,
                        String encoding)
                 throws IOException
Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
Throws:
IOException

copy

public static void copy(@Nonnull
                        byte[] input,
                        @Nonnull
                        Writer output,
                        @Nonnull
                        String encoding,
                        int bufferSize)
                 throws IOException
Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
bufferSize - Size of internal buffer to use.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      byte[] input)
                       throws IOException
Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.

Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      byte[] input,
                                      int bufferSize)
                       throws IOException
Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.

Parameters:
bufferSize - Size of internal buffer to use.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      byte[] input,
                                      @Nonnull
                                      String encoding)
                       throws IOException
Get the contents of a byte[] as a String.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
Throws:
IOException

toString

@Nonnull
public static String toString(@Nonnull
                                      byte[] input,
                                      @Nonnull
                                      String encoding,
                                      int bufferSize)
                       throws IOException
Get the contents of a byte[] as a String.

Parameters:
encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
bufferSize - Size of internal buffer to use.
Throws:
IOException

copy

public static void copy(@Nonnull
                        byte[] input,
                        @Nonnull
                        OutputStream output)
                 throws IOException
Copy bytes from a byte[] to an OutputStream.

Throws:
IOException

contentEquals

public static boolean contentEquals(@Nonnull
                                    InputStream input1,
                                    @Nonnull
                                    InputStream input2)
                             throws IOException
Compare the contents of two Streams to determine if they are equal or not.

Parameters:
input1 - the first stream
input2 - the second stream
Returns:
true if the content of the streams are equal or they both don't exist, false otherwise
Throws:
IOException

close

public static void close(@Nullable
                         Channel channel)
Closes a channel. Channel can be null and any IOException's will be swallowed.

Parameters:
channel - The stream to close.

close

public static void close(@Nullable
                         InputStream inputStream)
Closes the input stream. The input stream can be null and any IOException's will be swallowed.

Parameters:
inputStream - The stream to close.

close

public static void close(@Nullable
                         OutputStream outputStream)
Closes the output stream. The output stream can be null and any IOException's will be swallowed.

Parameters:
outputStream - The stream to close.

close

public static void close(@Nullable
                         Reader reader)
Closes the reader. The reader can be null and any IOException's will be swallowed.

Parameters:
reader - The reader to close.

close

public static void close(@Nullable
                         Writer writer)
Closes the writer. The writer can be null and any IOException's will be swallowed.

Parameters:
writer - The writer to close.


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