Package org.codehaus.plexus.util

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 Summary

Modifier and Type	Method	Description
static void	bufferedCopy(InputStream input, OutputStream output)	Deprecated. Buffering streams is actively harmful!
static void	close(InputStream inputStream)	Deprecated. use try-with-resources instead
static void	close(OutputStream outputStream)	Deprecated. use try-with-resources instead
static void	close(Reader reader)	Deprecated. use try-with-resources instead
static void	close(Writer writer)	Deprecated. use try-with-resources instead
static void	close(Channel channel)	Deprecated. use try-with-resources instead
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, 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, 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)
static byte[]	toByteArray(InputStream input, int bufferSize)
static byte[]	toByteArray(Reader input)
static byte[]	toByteArray(Reader input, int bufferSize)
static byte[]	toByteArray(String input)
static byte[]	toByteArray(String input, int bufferSize)
static String	toString(byte[] input)
static String	toString(byte[] input, int bufferSize)
static String	toString(byte[] input, String encoding)
static String	toString(byte[] input, String encoding, int bufferSize)
static String	toString(InputStream input)
static String	toString(InputStream input, int bufferSize)
static String	toString(InputStream input, String encoding)
static String	toString(InputStream input, String encoding, int bufferSize)
static String	toString(Reader input)
static String	toString(Reader input, int bufferSize)

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(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.