Package org.apache.tomcat.util.http.fileupload

Class IOUtils

java.lang.Object

org.apache.tomcat.util.http.fileupload.IOUtils

public class IOUtils
extends Object

General IO stream manipulation utilities.

This class provides static utility methods for input/output operations.

• closeQuietly - these methods close a stream ignoring nulls and exceptions
• toXxx/read - these methods read data from a stream
• write - these methods write data to a stream
• copy - these methods copy all the data from one stream to another
• contentEquals - these methods compare the content of two streams

The byte-to-char methods and char-to-byte methods involve a conversion step. Two methods are provided in each case, one that uses the platform default encoding and the other which allows you to specify an encoding. You are encouraged to always specify an encoding because relying on the platform default can lead to unexpected results, for example when moving from development to production.

All the methods in this class that read a stream are buffered internally. This means that there is no cause to use a BufferedInputStream or BufferedReader. The default buffer size of 4K has been shown to be efficient in tests.

Wherever possible, the methods in this class do not flush or close the stream. This is to avoid making non-portable assumptions about the streams' origin and further use. Thus the caller is still responsible for closing streams after use.

Origin of code: Excalibur.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	EOF	Represents the end-of-file (or stream).

Constructor Summary

Constructors

Constructor	Description
IOUtils()

Method Summary

Modifier and Type	Method	Description
static void	closeQuietly(Closeable closeable)	Closes a Closeable unconditionally.
static int	copy(InputStream input, OutputStream output)	Copies bytes from an InputStream to an OutputStream.
static long	copyLarge(InputStream input, OutputStream output)	Copies bytes from a large (over 2GB) InputStream to an OutputStream.
static int	read(InputStream input, byte[] buffer, int offset, int length)	Reads bytes from an input stream.
static void	readFully(InputStream input, byte[] buffer)	Reads the requested number of bytes or fail if there are not enough left.
static void	readFully(InputStream input, byte[] buffer, int offset, int length)	Reads the requested number of bytes or fail if there are not enough left.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

EOF

public static final int EOF

Represents the end-of-file (or stream).

Since:

IO 2.5 (made public)

See Also:

• Constant Field Values

Constructor Details

IOUtils

public IOUtils()

Method Details

closeQuietly

public static void closeQuietly(Closeable closeable)

Closes a Closeable unconditionally.

Equivalent to Closeable.close(), except any exceptions will be ignored. This is typically used in finally blocks.

Example code:

 Closeable closeable = null;
 try {
     closeable = new FileReader("foo.txt");
     // process closeable
     closeable.close();
 } catch (Exception e) {
     // error handling
 } finally {
     IOUtils.closeQuietly(closeable);
 }
 

Closing all streams:

 try {
     return IOUtils.copy(inputStream, outputStream);
 } finally {
     IOUtils.closeQuietly(inputStream);
     IOUtils.closeQuietly(outputStream);
 }
 

Parameters:

closeable - the objects to close, may be null or already closed

Since:

IO 2.0

copy

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

Copies bytes from an InputStream to an OutputStream.

This method buffers the input internally, so there is no need to use a BufferedInputStream.

Large streams (over 2GB) will return a bytes copied value of -1 after the copy has completed since the correct number of bytes cannot be returned as an int. For large streams use the copyLarge(InputStream, OutputStream) method.

Parameters:

input - the InputStream to read from

output - the OutputStream to write to

Returns:

the number of bytes copied, or -1 if > Integer.MAX_VALUE

Throws:

NullPointerException - if the input or output is null

IOException - if an I/O error occurs

Since:

IO 1.1

copyLarge

public static long copyLarge(InputStream input,
 OutputStream output)
                      throws IOException

Copies bytes from a large (over 2GB) InputStream to an OutputStream.

This method buffers the input internally, so there is no need to use a BufferedInputStream.

The buffer size is given by DEFAULT_BUFFER_SIZE.

Parameters:

input - the InputStream to read from

output - the OutputStream to write to

Returns:

the number of bytes copied

Throws:

NullPointerException - if the input or output is null

IOException - if an I/O error occurs

Since:

IO 1.3

read

public static int read(InputStream input,
 byte[] buffer,
 int offset,
 int length)
                throws IOException

Reads bytes from an input stream. This implementation guarantees that it will read as many bytes as possible before giving up; this may not always be the case for subclasses of InputStream.

Parameters:

input - where to read input from

buffer - destination

offset - initial offset into buffer

length - length to read, must be >= 0

Returns:

actual length read; may be less than requested if EOF was reached

Throws:

IOException - if a read error occurs

Since:

IO 2.2

readFully

public static void readFully(InputStream input,
 byte[] buffer,
 int offset,
 int length)
                      throws IOException

Reads the requested number of bytes or fail if there are not enough left.

This allows for the possibility that InputStream.read(byte[], int, int) may not read as many bytes as requested (most likely because of reaching EOF).

Parameters:

input - where to read input from

buffer - destination

offset - initial offset into buffer

length - length to read, must be >= 0

Throws:

IOException - if there is a problem reading the file

IllegalArgumentException - if length is negative

EOFException - if the number of bytes read was incorrect

Since:

IO 2.2

readFully

public static void readFully(InputStream input,
 byte[] buffer)
                      throws IOException

Reads the requested number of bytes or fail if there are not enough left.

This allows for the possibility that InputStream.read(byte[], int, int) may not read as many bytes as requested (most likely because of reaching EOF).

Parameters:

input - where to read input from

buffer - destination

Throws:

IOException - if there is a problem reading the file

IllegalArgumentException - if length is negative

EOFException - if the number of bytes read was incorrect

Since:

IO 2.2