public final class

IOUtil

extends Object
java.lang.Object
   ↳ com.atlassian.jira.util.IOUtil

Class Overview

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 read(byte[], int, int) 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 read(byte[], int, int) 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).

Summary

Public Methods
static void bufferedCopy(InputStream input, OutputStream output)
This method is deprecated. Buffering streams is actively harmful! See the class description as to why. Use copy(InputStream, OutputStream) 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(InputStream input, OutputStream output, int bufferSize)
Copy bytes from an InputStream 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(Reader input, OutputStream output)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
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)
Copy and convert bytes from an InputStream to chars on a Writer.
static void copy(String input, Writer output)
Copy chars from a String to a Writer.
static void copy(File src, File dst)
Copy the contents from one file to another.
static void copy(Reader input, Writer output)
Copy chars from a Reader to a Writer.
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, OutputStream output, int bufferSize)
Copy bytes from a byte[] to an OutputStream.
static void copy(String input, OutputStream output)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
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(String input, OutputStream output, int bufferSize)
Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
static void copy(Reader input, Writer output, int bufferSize)
Copy chars from a Reader to 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(Reader input, OutputStream output, int bufferSize)
Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
static void copy(InputStream input, OutputStream output)
Copy bytes from an InputStream to an OutputStream.
static void copy(byte[] input, OutputStream output)
Copy bytes from a byte[] to an OutputStream.
static void copy(byte[] input, Writer output, int bufferSize)
Copy and convert bytes from a byte[] to chars on 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(OutputStream output)
Unconditionally close an OutputStream.
static void shutdownStream(InputStream input)
Unconditionally close an InputStream.
static void shutdownWriter(Writer output)
Unconditionally close an Writer.
static byte[] toByteArray(Reader input, int bufferSize)
Get the contents of a Reader as a byte[].
static byte[] toByteArray(Reader input)
Get the contents of a Reader as a byte[].
static byte[] toByteArray(InputStream input)
Get the contents of an InputStream as a byte[].
static byte[] toByteArray(String input, int bufferSize)
Get the contents of a String as a byte[].
static byte[] toByteArray(InputStream input, int bufferSize)
Get the contents of an InputStream as a byte[].
static byte[] toByteArray(String input)
Get the contents of a String as a byte[].
static String toString(byte[] input, String encoding, int bufferSize)
Get the contents of a byte[] 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(InputStream input, int bufferSize)
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)
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(byte[] input, String encoding)
Get the contents of a byte[] as a String.
static String toString(InputStream input, String encoding)
Get the contents of an InputStream as a String.
static String toString(byte[] input, int bufferSize)
Get the contents of a byte[] as a String.
[Expand]
Inherited Methods
From class java.lang.Object

Public Methods

public static void bufferedCopy (InputStream input, OutputStream output)

This method is 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.

Throws
IOException

public static boolean contentEquals (InputStream input1, InputStream input2)

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

public static void copy (InputStream input, OutputStream output, int bufferSize)

Copy bytes from an InputStream to an OutputStream.

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static void copy (byte[] input, Writer output)

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

public static void copy (Reader input, OutputStream output)

Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

Throws
IOException

public 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.

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

public 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.

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

public static void copy (InputStream input, Writer output)

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

public static void copy (String input, Writer output)

Copy chars from a String to a Writer.

Throws
IOException

public static void copy (File src, File dst)

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

public static void copy (Reader input, Writer output)

Copy chars from a Reader to a Writer.

Throws
IOException

public 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.

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

public static void copy (byte[] input, OutputStream output, int bufferSize)

Copy bytes from a byte[] to an OutputStream.

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static void copy (String input, OutputStream output)

Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

Throws
IOException

public 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.

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

public static void copy (String input, OutputStream output, int bufferSize)

Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static void copy (Reader input, Writer output, int bufferSize)

Copy chars from a Reader to a Writer.

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static void copy (InputStream input, Writer output, int bufferSize)

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

public static void copy (Reader input, OutputStream output, int bufferSize)

Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static void copy (InputStream input, OutputStream output)

Copy bytes from an InputStream to an OutputStream.

Throws
IOException

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

Copy bytes from a byte[] to an OutputStream.

Throws
IOException

public static void copy (byte[] input, Writer output, int bufferSize)

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

public 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. 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.

public static void shutdownReader (Reader input)

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

Parameters
input A (possibly null) Reader

public static void shutdownStream (OutputStream output)

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

Parameters
output A (possibly null) OutputStream

public static void shutdownStream (InputStream input)

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

Parameters
input A (possibly null) InputStream

public static void shutdownWriter (Writer output)

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

Parameters
output A (possibly null) Writer

public static byte[] toByteArray (Reader input, int bufferSize)

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

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static byte[] toByteArray (Reader input)

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

Throws
IOException

public static byte[] toByteArray (InputStream input)

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

Throws
IOException

public static byte[] toByteArray (String input, int bufferSize)

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

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static byte[] toByteArray (InputStream input, int bufferSize)

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

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static byte[] toByteArray (String input)

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

Throws
IOException

public static String toString (byte[] input, String encoding, int bufferSize)

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

public static String toString (Reader input, int bufferSize)

Get the contents of a Reader as a String.

Parameters
bufferSize Size of internal buffer to use.
Throws
IOException

public static String toString (byte[] input)

Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.

Throws
IOException

public static String toString (InputStream input, int bufferSize)

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

public static String toString (InputStream input, String encoding, int bufferSize)

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

public static String toString (InputStream input)

Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.

Throws
IOException

public static String toString (Reader input)

Get the contents of a Reader as a String.

Throws
IOException

public static String toString (byte[] input, String encoding)

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

public static String toString (InputStream input, String encoding)

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

public static String toString (byte[] input, int bufferSize)

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