org.codehaus.plexus.util

Class IOUtil


public final class IOUtil
extends java.lang.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 java.io.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:
$Id: IOUtil.java 5958 2007-02-28 10:29:55Z olamy $
Authors:
Peter Donald
Jeff Turner
Since:
4.0

Method Summary

static void
bufferedCopy(InputStream input, OutputStream output)
Deprecated. Buffering streams is actively harmful! See the class description as to why.
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(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, 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(InputStream input, Writer output, int bufferSize)
Copy and convert bytes from an InputStream to chars on a Writer.
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 void
copy(byte[] input, OutputStream output)
Copy bytes from a byte[] to an OutputStream.
static void
copy(byte[] input, OutputStream output, int bufferSize)
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, 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(byte[] input, Writer output, int bufferSize)
Copy and convert bytes from a byte[] to chars on 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(InputStream input)
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(InputStream input, 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.
static String
toString(byte[] input)
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(byte[] input, int bufferSize)
Get the contents of a byte[] as a String.

Method Details

bufferedCopy

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 java.io.BufferedInputStream and java.io.BufferedOutputStream to copy(InputStream,OutputStream), and flushing the output stream afterwards. The streams are not closed after the copy.

close

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

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

copy

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

copy

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

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.

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.

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:
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.

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:
bufferSize - Size of internal buffer to use.

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.

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:
bufferSize - Size of internal buffer to use.

copy

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

copy

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

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.

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:
bufferSize - Size of internal buffer to use.

copy

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

copy

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

copy

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

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.

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.

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:
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.

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:
bufferSize - Size of internal buffer to use.

toByteArray

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

toByteArray

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

toByteArray

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

toByteArray

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

toByteArray

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

toByteArray

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

toString

public static String toString(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.

toString

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

toString

public static String toString(InputStream input,
                              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.

toString

public static String toString(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.

toString

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

toString

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

toString

public static String toString(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.

toString

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

toString

public static String toString(byte[] input,
                              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.

toString

public static String toString(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.