Package com.atlassian.jira.util

Class IOUtil

java.lang.Object

com.atlassian.jira.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).

Version:

CVS $Revision: 1.1 $ $Date: 2004/05/28 12:45:22 $

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! See the class description as to why.
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(File src, File dst)	Copy the contents from one file to another.
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[]	getLeadingBytes(InputStream is, int numBytes)	Reads at most the given number of bytes from the input stream and returns them in an array.
static void	shutdownReader(Reader input)	Unconditionally close an Reader.
static void	shutdownStream(InputStream input)	Unconditionally close an InputStream.
static void	shutdownStream(OutputStream output)	Unconditionally close an OutputStream.
static void	shutdownWriter(Writer output)	Unconditionally close an 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 Details

shutdownReader

public static void shutdownReader(Reader input)

Unconditionally close an Reader. Equivalent to Reader.close(), except any exceptions will be ignored.

Parameters:

input - A (possibly null) Reader

shutdownWriter

public static void shutdownWriter(Writer output)

Unconditionally close an Writer. Equivalent to Writer.close(), except any exceptions will be ignored.

Parameters:

output - A (possibly null) Writer

shutdownStream

public static void shutdownStream(OutputStream output)

Unconditionally close an OutputStream. Equivalent to OutputStream.close(), except any exceptions will be ignored.

Parameters:

output - A (possibly null) OutputStream

shutdownStream

public static void shutdownStream(InputStream input)

Unconditionally close an InputStream. Equivalent to InputStream.close(), except any exceptions will be ignored.

Parameters:

input - A (possibly null) InputStream

copy

public static void copy(InputStream input,
 OutputStream output)
                 throws IOException

Copy bytes from an InputStream to an OutputStream.

Throws:

IOException

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.

Throws:

IOException

copy

public static void copy(Reader input,
 Writer output)
                 throws IOException

Copy chars from a Reader to a Writer.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

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:

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(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.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

toString

public static String toString(InputStream input,
 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

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.

Throws:

IOException

toByteArray

public static byte[] toByteArray(InputStream input)
                          throws IOException

Get the contents of an InputStream as a byte[].

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

toString

public static String toString(Reader input)
                       throws IOException

Get the contents of a Reader as a String.

Throws:

IOException

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.

Throws:

IOException

toByteArray

public static byte[] toByteArray(Reader input)
                          throws IOException

Get the contents of a Reader as a byte[].

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

copy

public static void copy(String input,
 Writer output)
                 throws IOException

Copy chars from a String to a Writer.

Throws:

IOException

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

Throws:

IOException

toByteArray

public static byte[] toByteArray(String input)
                          throws IOException

Get the contents of a String as a byte[].

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

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:

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(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.

Throws:

IOException

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.

Throws:

IOException

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.

Throws:

IOException

toString

public static String toString(byte[] input,
 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

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.

Throws:

IOException

copy

public static void copy(byte[] input,
 OutputStream output)
                 throws IOException

Copy bytes from a byte[] to an OutputStream.

Throws:

IOException

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.

Throws:

IOException

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

getLeadingBytes

public static byte[] getLeadingBytes(InputStream is,
 int numBytes)
                              throws IOException

Reads at most the given number of bytes from the input stream and returns them in an array. Does not close the InputStream.

Parameters:

is - the InputStream to read bytes from.

numBytes - the maximum number of bytes to return.

Returns:

the first numBytes bytes (or all if there are less in the stream).

Throws:

IOException - if the stream cannot be read.

copy

public static void copy(File src,
 File dst)
                 throws IOException

Copy the contents from one file to another.

Parameters:

src - the file to be copied

dst - the file to be copied to

Throws:

IOException - if there are any problems in the copy operation