Class DigestOutputStream

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

java.security.DigestOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

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.

Since:

1.2

See Also:

• MessageDigest
• DigestInputStream

Field Summary

Fields

Modifier and Type	Field	Description
protected MessageDigest	digest	The message digest associated with this stream.

Fields declared in class FilterOutputStream

out

Modifier and Type	Field	Description
protected OutputStream	out	The underlying output stream to be filtered.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method	Description
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.

Methods declared in class FilterOutputStream

close, flush, write

Modifier and Type	Method	Description
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.

Methods declared in class OutputStream

nullOutputStream

Modifier and Type	Method	Description
static OutputStream	nullOutputStream()	Returns a new OutputStream which discards all bytes.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Field Details

digest

protected MessageDigest digest

The message digest associated with this stream.

Constructor Details

DigestOutputStream

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.

Method Details

getMessageDigest

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)

setMessageDigest

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()

write

public void write(int b)
           throws IOException

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.

Overrides:

write in class FilterOutputStream

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)

write

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

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.

Overrides:

write in class FilterOutputStream

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)

on

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.

toString

public String toString()

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

Overrides:

toString in class Object

Returns:

a string representation of the object