Class IOUtil

java.lang.Object
org.codehaus.plexus.util.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).

Since:
4.0
Author:
Peter Donald, Jeff Turner
  • Method Details

    • copy

      public static void copy(InputStream input, OutputStream output) throws IOException
      Copy bytes from an InputStream to an OutputStream.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(InputStream input, OutputStream output, int bufferSize) throws IOException
      Copy bytes from an InputStream to an OutputStream.
      Parameters:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • copy

      public static void copy(Reader input, Writer output) throws IOException
      Copy chars from a Reader to a Writer.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(Reader input, Writer output, int bufferSize) throws IOException
      Copy chars from a Reader to a Writer.
      Parameters:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • copy

      public static void copy(InputStream input, 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.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(InputStream input, 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:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • copy

      public static void copy(InputStream input, Writer output, String encoding) throws IOException
      Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
      Parameters:
      input - to convert
      output - the result
      encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
      Throws:
      IOException - io issue
    • copy

      public static void copy(InputStream input, Writer output, String encoding, int bufferSize) throws IOException
      Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
      Parameters:
      input - to convert
      output - the result
      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 - io issue
    • toString

      public static String toString(InputStream input) throws IOException
      Parameters:
      input - to convert
      Returns:
      Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.
      Throws:
      IOException - io issue
    • toString

      public static String toString(InputStream input, int bufferSize) throws IOException
      Parameters:
      input - to convert
      bufferSize - Size of internal buffer to use.
      Returns:
      Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.
      Throws:
      IOException - io issue
    • toString

      public static String toString(InputStream input, String encoding) throws IOException
      Parameters:
      input - to convert
      encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
      Returns:
      Get the contents of an InputStream as a String.
      Throws:
      IOException - io issue
    • toString

      public static String toString(InputStream input, String encoding, int bufferSize) throws IOException
      Parameters:
      input - to convert
      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.
      Returns:
      Get the contents of an InputStream as a String.
      Throws:
      IOException - io issue
    • toByteArray

      public static byte[] toByteArray(InputStream input) throws IOException
      Parameters:
      input - to convert
      Returns:
      Get the contents of an InputStream as a byte[].
      Throws:
      IOException - io issue
    • toByteArray

      public static byte[] toByteArray(InputStream input, int bufferSize) throws IOException
      Parameters:
      input - to convert
      bufferSize - Size of internal buffer to use.
      Returns:
      Get the contents of an InputStream as a byte[].
      Throws:
      IOException - io issue
    • copy

      public static void copy(Reader input, OutputStream output) throws IOException
      Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(Reader input, OutputStream output, int bufferSize) throws IOException
      Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • toString

      public static String toString(Reader input) throws IOException
      Parameters:
      input - to convert
      Returns:
      Get the contents of a Reader as a String.
      Throws:
      IOException - io issue
    • toString

      public static String toString(Reader input, int bufferSize) throws IOException
      Parameters:
      input - to convert
      bufferSize - Size of internal buffer to use.
      Returns:
      Get the contents of a Reader as a String.
      Throws:
      IOException - io issue
    • toByteArray

      public static byte[] toByteArray(Reader input) throws IOException
      Parameters:
      input - to convert
      Returns:
      Get the contents of a Reader as a byte[].
      Throws:
      IOException - io issue
    • toByteArray

      public static byte[] toByteArray(Reader input, int bufferSize) throws IOException
      Parameters:
      input - to convert
      bufferSize - Size of internal buffer to use.
      Returns:
      Get the contents of a Reader as a byte[].
      Throws:
      IOException - io issue
    • copy

      public static void copy(String input, OutputStream output) throws IOException
      Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(String input, OutputStream output, int bufferSize) throws IOException
      Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • copy

      public static void copy(String input, Writer output) throws IOException
      Copy chars from a String to a Writer.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • bufferedCopy

      @Deprecated public static void bufferedCopy(InputStream input, OutputStream output) throws IOException
      Deprecated.
      Buffering streams is actively harmful! See the class description as to why. Use copy(InputStream, OutputStream) instead.
      Copy bytes from an InputStream to an OutputStream, with buffering. This is equivalent to passing a BufferedInputStream and BufferedOutputStream to copy(InputStream, OutputStream), and flushing the output stream afterwards. The streams are not closed after the copy.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • toByteArray

      public static byte[] toByteArray(String input) throws IOException
      Parameters:
      input - to convert
      Returns:
      Get the contents of a String as a byte[].
      Throws:
      IOException - io issue
    • toByteArray

      public static byte[] toByteArray(String input, int bufferSize) throws IOException
      Parameters:
      input - to convert
      bufferSize - Size of internal buffer to use.
      Returns:
      Get the contents of a String as a byte[].
      Throws:
      IOException - io issue
    • copy

      public static void copy(byte[] input, 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.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(byte[] input, 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:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • copy

      public static void copy(byte[] input, Writer output, String encoding) throws IOException
      Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.
      Parameters:
      input - to convert
      output - the result
      encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
      Throws:
      IOException - io issue
    • copy

      public static void copy(byte[] input, Writer output, String encoding, int bufferSize) throws IOException
      Copy and convert bytes from a byte[] to chars on a Writer, using the specified encoding.
      Parameters:
      input - to convert
      output - the result
      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 - io issue
    • toString

      public static String toString(byte[] input) throws IOException
      Parameters:
      input - to convert
      Returns:
      Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.
      Throws:
      IOException - io issue
    • toString

      public static String toString(byte[] input, int bufferSize) throws IOException
      Parameters:
      input - to convert
      bufferSize - Size of internal buffer to use.
      Returns:
      Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.
      Throws:
      IOException - io issue
    • toString

      public static String toString(byte[] input, String encoding) throws IOException
      Parameters:
      input - to convert
      encoding - The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
      Returns:
      Get the contents of a byte[] as a String.
      Throws:
      IOException - io issue
    • toString

      public static String toString(byte[] input, String encoding, int bufferSize) throws IOException
      Parameters:
      input - to convert
      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.
      Returns:
      the contents of a byte[] as a String.
      Throws:
      IOException - io issue
    • copy

      public static void copy(byte[] input, OutputStream output) throws IOException
      Copy bytes from a byte[] to an OutputStream.
      Parameters:
      input - to convert
      output - the result
      Throws:
      IOException - io issue
    • copy

      public static void copy(byte[] input, OutputStream output, int bufferSize) throws IOException
      Copy bytes from a byte[] to an OutputStream.
      Parameters:
      input - to convert
      output - the result
      bufferSize - Size of internal buffer to use.
      Throws:
      IOException - io issue
    • contentEquals

      public static boolean contentEquals(InputStream input1, 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 - io issue
    • close

      @Deprecated public static void close(InputStream inputStream)
      Deprecated.
      use try-with-resources instead
      Closes the input stream. The input stream can be null and any IOException's will be swallowed.
      Parameters:
      inputStream - The stream to close.
    • close

      @Deprecated public static void close(Channel channel)
      Deprecated.
      use try-with-resources instead
      Closes a channel. Channel can be null and any IOException's will be swallowed.
      Parameters:
      channel - The stream to close.
    • close

      @Deprecated public static void close(OutputStream outputStream)
      Deprecated.
      use try-with-resources instead
      Closes the output stream. The output stream can be null and any IOException's will be swallowed.
      Parameters:
      outputStream - The stream to close.
    • close

      @Deprecated public static void close(Reader reader)
      Deprecated.
      use try-with-resources instead
      Closes the reader. The reader can be null and any IOException's will be swallowed.
      Parameters:
      reader - The reader to close.
    • close

      @Deprecated public static void close(Writer writer)
      Deprecated.
      use try-with-resources instead
      Closes the writer. The writer can be null and any IOException's will be swallowed.
      Parameters:
      writer - The writer to close.