org.restlet.representation

Class DigesterRepresentation

java.lang.Object

org.restlet.representation.Variant

org.restlet.representation.RepresentationInfo

org.restlet.representation.Representation

org.restlet.util.WrapperRepresentation

org.restlet.representation.DigesterRepresentation

public class DigesterRepresentation
extends WrapperRepresentation

Representation capable of computing a digest. It wraps another representation and allows to get the computed digest of the wrapped entity after reading or writing operations. The final digest value is guaranteed to be correct only after the wrapped representation has been entirely exhausted (that is to say read or written).

This wrapper allows to get the computed digest at the same time the representation is read or written. It does not need two separate operations which may require specific attention for transient representations.

Author:

Jerome Louvel

See Also:

Representation.isTransient().

Field Summary

Fields inherited from class org.restlet.representation.Representation

UNKNOWN_SIZE

Constructor Summary

Constructors

Constructor and Description
DigesterRepresentation(Representation wrappedRepresentation) Constructor.
DigesterRepresentation(Representation wrappedRepresentation, java.lang.String algorithm) Constructor.

Method Summary

Modifier and Type	Method and Description
boolean	checkDigest() Check that the digest computed from the representation content and the digest declared by the representation are the same.
boolean	checkDigest(java.lang.String algorithm) Check that the digest computed from the representation content and the digest declared by the representation are the same.
Digest	computeDigest() Compute the representation digest according to MD5 algorithm.
Digest	computeDigest(java.lang.String algorithm) Compute the representation digest according to the given algorithm.
long	exhaust() Exhausts the content of the representation by reading it and silently discarding anything read.
java.nio.channels.ReadableByteChannel	getChannel() Returns a channel with the representation's content.
Digest	getComputedDigest() Returns the current computed digest value of the representation.
java.io.Reader	getReader() Returns a characters reader with the representation's content.
java.io.InputStream	getStream() Returns a stream with the representation's content.
java.lang.String	getText() Converts the representation to a string value.
void	write(java.io.OutputStream outputStream) Writes the representation to a byte stream.
void	write(java.nio.channels.WritableByteChannel writableChannel) Writes the representation to a byte channel.
void	write(java.io.Writer writer) Writes the representation to a characters writer.

Methods inherited from class org.restlet.util.WrapperRepresentation

getAvailableSize, getCharacterSet, getDigest, getDisposition, getEncodings, getExpirationDate, getLanguages, getLocationRef, getMediaType, getModificationDate, getRange, getRegistration, getSize, getTag, getWrappedRepresentation, isAvailable, isSelectable, isTransient, release, setAvailable, setCharacterSet, setDigest, setDisposition, setEncodings, setExpirationDate, setLanguages, setLocationRef, setLocationRef, setMediaType, setModificationDate, setRange, setSize, setTag, setTransient

Methods inherited from class org.restlet.representation.Representation

append, hasKnownSize, isEmpty, setListener

Methods inherited from class org.restlet.representation.Variant

createClientInfo, equals, hashCode, includes, isCompatible, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

DigesterRepresentation

public DigesterRepresentation(Representation wrappedRepresentation)
                       throws java.security.NoSuchAlgorithmException

Constructor.
By default, the instance relies on the Digest.ALGORITHM_MD5 digest algorithm.

Parameters:

wrappedRepresentation - The wrapped representation.

Throws:

java.security.NoSuchAlgorithmException

DigesterRepresentation

public DigesterRepresentation(Representation wrappedRepresentation,
                              java.lang.String algorithm)
                       throws java.security.NoSuchAlgorithmException

Constructor.

Parameters:

wrappedRepresentation - The wrapped representation.

algorithm - The digest algorithm.

Throws:

java.security.NoSuchAlgorithmException

Method Detail

checkDigest

public boolean checkDigest()

Check that the digest computed from the representation content and the digest declared by the representation are the same.
Since this method relies on the computeDigest(String) method, and since this method reads entirely the representation's stream, user must take care of the content of the representation in case the latter is transient. WrapperRepresentation.isTransient()

Returns:

True if both digests are not null and equals.

checkDigest

public boolean checkDigest(java.lang.String algorithm)

Check that the digest computed from the representation content and the digest declared by the representation are the same. It also first checks that the algorithms are the same.
Since this method relies on the computeDigest(String) method, and since this method reads entirely the representation's stream, user must take care of the content of the representation in case the latter is transient. WrapperRepresentation.isTransient()

Parameters:

algorithm - The algorithm used to compute the digest to compare with. See constant values in Digest.

Returns:

True if both digests are not null and equals.

computeDigest

public Digest computeDigest()

Compute the representation digest according to MD5 algorithm.
If case this algorithm is the same than the one provided at instantiation, the computation operation is made with the current stored computed value and does not require to exhaust entirely the representation's stream.

computeDigest

public Digest computeDigest(java.lang.String algorithm)

Compute the representation digest according to the given algorithm.
Since this method reads entirely the representation's stream, user must take care of the content of the representation in case the latter is transient. WrapperRepresentation.isTransient()

Parameters:

algorithm - The algorithm used to compute the digest. See constant values in Digest.

Returns:

The computed digest or null if the digest cannot be computed.

exhaust

public long exhaust()
             throws java.io.IOException

Exhausts the content of the representation by reading it and silently discarding anything read.

Overrides:

exhaust in class WrapperRepresentation

Returns:

The number of bytes consumed or -1 if unknown.

Throws:

java.io.IOException

getChannel

public java.nio.channels.ReadableByteChannel getChannel()
                                                 throws java.io.IOException

Description copied from class: Representation

Returns a channel with the representation's content.
If it is supported by a file, a read-only instance of FileChannel is returned.
This method is ensured to return a fresh channel for each invocation unless it is a transient representation, in which case null is returned.

Overrides:

getChannel in class WrapperRepresentation

Returns:

A channel with the representation's content.

Throws:

java.io.IOException

getComputedDigest

public Digest getComputedDigest()

Returns the current computed digest value of the representation. User must be aware that, if the representation has not been entirely read or written, the computed digest value may not be accurate.

Returns:

The current computed digest value.

getReader

public java.io.Reader getReader()
                         throws java.io.IOException

Description copied from class: Representation

Returns a characters reader with the representation's content. This method is ensured to return a fresh reader for each invocation unless it is a transient representation, in which case null is returned. If the representation has no character set defined, the system's default one will be used.

Overrides:

getReader in class WrapperRepresentation

Returns:

A reader with the representation's content.

Throws:

java.io.IOException

getStream

public java.io.InputStream getStream()
                              throws java.io.IOException

Returns a stream with the representation's content. This method is ensured to return a fresh stream for each invocation unless it is a transient representation, in which case null is returned.
The stream of the underlying representation is wrapped with a new instance of the DigestInputStream class, which allows to compute progressively the digest value.

Overrides:

getStream in class WrapperRepresentation

Returns:

A stream with the representation's content.

Throws:

java.io.IOException

getText

public java.lang.String getText()
                         throws java.io.IOException

Description copied from class: Representation

Converts the representation to a string value. Be careful when using this method as the conversion of large content to a string fully stored in memory can result in OutOfMemoryErrors being thrown.

Overrides:

getText in class WrapperRepresentation

Returns:

The representation as a string value.

Throws:

java.io.IOException

write

public void write(java.io.OutputStream outputStream)
           throws java.io.IOException

Writes the representation to a byte stream. This method is ensured to write the full content for each invocation unless it is a transient representation, in which case an exception is thrown.

Note that the class implementing this method shouldn't flush or close the given OutputStream after writing to it as this will be handled by the Restlet connectors automatically.
The output stream is wrapped with a new instance of the DigestOutputStream class, which allows to compute progressively the digest value.

Overrides:

write in class WrapperRepresentation

Parameters:

outputStream - The output stream.

Throws:

java.io.IOException

write

public void write(java.nio.channels.WritableByteChannel writableChannel)
           throws java.io.IOException

Description copied from class: Representation

Writes the representation to a byte channel. This method is ensured to write the full content for each invocation unless it is a transient representation, in which case an exception is thrown.

Overrides:

write in class WrapperRepresentation

Parameters:

writableChannel - A writable byte channel.

Throws:

java.io.IOException

write

public void write(java.io.Writer writer)
           throws java.io.IOException

Description copied from class: Representation

Writes the representation to a characters writer. This method is ensured to write the full content for each invocation unless it is a transient representation, in which case an exception is thrown.

Note that the class implementing this method shouldn't flush or close the given Writer after writing to it as this will be handled by the Restlet connectors automatically.

Overrides:

write in class WrapperRepresentation

Parameters:

writer - The characters writer.

Throws:

java.io.IOException