DigestOutputStream

public class DigestOutputStream extends FilterOutputStream

A transparent stream that updates the associated message digest using the bits going through the stream.

To complete the message digest computation, call one of the digest methods on the associated message digest after your calls to one of this digest output stream's write methods.

It is possible to turn this stream on or off (see on). When it is on, a call to one of the write methods results in an update on the message digest. But when it is off, the message digest is not updated. The default is for the stream to be on.

See Also

• MessageDigest
• DigestInputStream

Field Summary

protected MessageDigest

digest

The message digest associated with this stream.

Inherited Field Summary

From class java.io.FilterOutputStream

protected OutputStream

out

The underlying output stream to be filtered.

Public Constructor Summary

DigestOutputStream(OutputStream stream, MessageDigest digest) Creates a digest output stream, using the specified output stream and message digest.

Public Method Summary

MessageDigest	getMessageDigest() Returns the message digest associated with this stream.
void	on(boolean on) Turns the digest function on or off.
void	setMessageDigest(MessageDigest digest) Associates the specified message digest with this stream.
String	toString() Prints a string representation of this digest output stream and its associated message digest object.
void	write(byte[] b, int off, int len) Updates the message digest (if the digest function is on) using the specified subarray, and in any case writes the subarray to the output stream.
void	write(int b) Updates the message digest (if the digest function is on) using the specified byte, and in any case writes the byte to the output stream.

Inherited Method Summary

From class java.io.FilterOutputStream

void	close() Closes this output stream and releases any system resources associated with the stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out to the stream.
void	write(byte[] b) Writes b.length bytes to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
void	write(int b) Writes the specified byte to this output stream.

From class java.io.OutputStream

void	close() Closes this output stream and releases any system resources associated with this stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out.
void	write(byte[] b) Writes b.length bytes from the specified byte array to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
abstract void	write(int b) Writes the specified byte to this output stream.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.io.Closeable

abstract void

close() Closes this stream and releases any system resources associated with it.

From interface java.io.Flushable

abstract void

flush() Flushes this stream by writing any buffered output to the underlying stream.

From interface java.lang.AutoCloseable

abstract void

close() Closes this resource, relinquishing any underlying resources.

Fields

protected MessageDigest digest

The message digest associated with this stream.

Public Constructors

public DigestOutputStream (OutputStream stream, MessageDigest digest)

Creates a digest output stream, using the specified output stream and message digest.

Parameters

stream	the output stream.
digest	the message digest to associate with this stream.

Public Methods

public MessageDigest getMessageDigest ()

Returns the message digest associated with this stream.

Returns

• the message digest associated with this stream.

See Also

• setMessageDigest(java.security.MessageDigest)

public void on (boolean on)

Turns the digest function on or off. The default is on. When it is on, a call to one of the write methods results in an update on the message digest. But when it is off, the message digest is not updated.

Parameters

on	true to turn the digest function on, false to turn it off.

public void setMessageDigest (MessageDigest digest)

Associates the specified message digest with this stream.

Parameters

digest	the message digest to be associated with this stream.

See Also

• getMessageDigest()

public String toString ()

Prints a string representation of this digest output stream and its associated message digest object.

Returns

• a printable representation of this object.

public void write (byte[] b, int off, int len)

Updates the message digest (if the digest function is on) using the specified subarray, and in any case writes the subarray to the output stream. That is, if the digest function is on (see on), this method calls update on the message digest associated with this stream, passing it the subarray specifications. This method then writes the subarray bytes to the output stream, blocking until the bytes are actually written.

Parameters

b	the array containing the subarray to be used for updating and writing to the output stream.
off	the offset into b of the first byte to be updated and written.
len	the number of bytes of data to be updated and written from b, starting at offset off.

Throws

IOException	if an I/O error occurs.

See Also

• MessageDigest.update(byte[], int, int)

public void write (int b)

Updates the message digest (if the digest function is on) using the specified byte, and in any case writes the byte to the output stream. That is, if the digest function is on (see on), this method calls update on the message digest associated with this stream, passing it the byte b. This method then writes the byte to the output stream, blocking until the byte is actually written.

Parameters

b	the byte to be used for updating and writing to the output stream.

Throws

IOException	if an I/O error occurs.

See Also

• MessageDigest.update(byte)