Class com.ibm.xml.parser.MakeDigestVisitor

java.lang.Object
    |
    +----com.ibm.xml.parser.NOOPVisitor
            |
            +----com.ibm.xml.parser.MakeDigestVisitor

public class MakeDigestVisitor

extends NOOPVisitor

implements Visitor

Digests can be made for the following Node types:

• TXElement
• TXAttribute
• TXPI
• TXComment
• TXText

The following sample code uses the MakeDigestVisitor on a hierarchy of nodes:

 MakeDigestVisitor makeDigestVisitor = new MakeDigestVisitor(this.getFactory().createMessageDigest());
 new NonRecursivePreorderTreeTraversal(makeDigestVisitor).traverse(this);

 

Version:

Revision: 45 1.3 src/com/ibm/xml/parser/MakeDigestVisitor.java, xml4jsrc, xml4j-jtcsv, xml4j_1_0_4

See Also:

Visitor, NOOPVisitor, TreeTraversal, NonRecursivePreorderTreeTraversal

Field Summary
java.security.MessageDigest	messageDigest

 

Constructor Summary

MakeDigestVisitor(java.security.MessageDigest messageDigest) Constructor.

 

Method Summary
void	visitAttributePre(TXAttribute attribute) Calculates and sets a digest for the specified attribute.
void	visitCommentPre(TXComment comment) Calculates and sets a digest for the specified comment.
void	visitElementPost(TXElement element) Calculates and sets a digest for the specified element.
void	visitElementPre(TXElement element) If the specified element already has a calculated digest, throw an exception to avoid unnecessary traversal of children.
void	visitPIPre(TXPI pi) Calculates and sets a digest for the specified pi.
void	visitTextPre(TXText text) Calculates and sets a digest for the specified text.

 

Methods inherited from class com.ibm.xml.parser.NOOPVisitor

visitAttDefPost, visitAttDefPre, visitAttlistPost, visitAttlistPre, visitAttributePost, visitAttributePre, visitCommentPost, visitCommentPre, visitDocumentPost, visitDocumentPre, visitDTDPost, visitDTDPre, visitElementDeclPost, visitElementDeclPre, visitElementPost, visitElementPre, visitEntityPost, visitEntityPre, visitGeneralReferencePost, visitGeneralReferencePre, visitNotationPost, visitNotationPre, visitPIPost, visitPIPre, visitPseudoNodePost, visitPseudoNodePre, visitTextPost, visitTextPre

 

Methods inherited from class java.lang.Object

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

 

Field Detail

messageDigest

protected java.security.MessageDigest messageDigest

MakeDigestVisitor

public MakeDigestVisitor(java.security.MessageDigest messageDigest)

Constructor.

Parameters:

messageDigest - Message digest instance to use when visitting.

See Also:

createMessageDigest

visitElementPre

public void visitElementPre(TXElement element) throws ToNextSiblingTraversalException

If the specified element already has a calculated digest, throw an exception to avoid unnecessary traversal of children.

Implements:

visitElementPre in interface Visitor

Parameters:

element - Node to calculate and set a digest.

Throws:

ToNextSiblingTraversalException - Thrown if this Node already has a digest.

Overrides:

visitElementPre in class NOOPVisitor

See Also:

TXElement, visitElementPost

visitElementPost

public void visitElementPost(TXElement element) throws LibraryException

Calculates and sets a digest for the specified element.

A digest of a TXElement Node consists of its:

• Node type
• Name
• Number of attributes
• Attribute digests (orderred according to the attribute's name (using String#compareTo()).
• Number of immediate children (consecutive Child Text Nodes are counted as 1).
• Immediate children digests (digests for consecutive Child Text Nodes are combined into a single digest).

Implements:

visitElementPost in interface Visitor

Parameters:

element - Node to calculate and set a digest.

Throws:

LibraryException - Thrown if this Node can not be visitted because of a problem in calculating the digest. Often, this is because the message digest specified on the constructor is invalid, the JVM does not support UnicodeBigUnmarked encoding, or the JVM does not have the required security providers for the message digest.

Overrides:

visitElementPost in class NOOPVisitor

See Also:

TXElement, visitElementPre

visitAttributePre

public void visitAttributePre(TXAttribute attribute) throws LibraryException

Calculates and sets a digest for the specified attribute.

A digest of a TXAttribute Node consists of its Node type, its name, and its value.

Note that TXAttribute Nodes are not parsed into the document object hierarchy by the XML4J parser; attributes exist as part of a TXElement Node.

Implements:

visitAttributePre in interface Visitor

Parameters:

attribute - Node to calculate and set a digest.

Throws:

LibraryException - Thrown if this Node can not be visitted because of a problem in calculating the digest. Often, this is because the message digest specified on the constructor is invalid, the JVM does not support UnicodeBigUnmarked encoding, or the JVM does not have the required security providers for the message digest.

Overrides:

visitAttributePre in class NOOPVisitor

See Also:

TXAttribute

visitPIPre

public void visitPIPre(TXPI pi) throws LibraryException

Calculates and sets a digest for the specified pi.

A digest of a TXPI Node consists of its Node type, its name, and its data.

Implements:

visitPIPre in interface Visitor

Parameters:

pi - Node to calculate and set a digest.

Throws:

LibraryException - Thrown if this Node can not be visitted because of a problem in calculating the digest. Often, this is because the message digest specified on the constructor is invalid, the JVM does not support UnicodeBigUnmarked encoding, or the JVM does not have the required security providers for the message digest.

Overrides:

visitPIPre in class NOOPVisitor

See Also:

TXPI

visitCommentPre

public void visitCommentPre(TXComment comment) throws LibraryException

Calculates and sets a digest for the specified comment.

A digest of a TXComment Node consists of its Node type and its data.

Implements:

visitCommentPre in interface Visitor

Parameters:

comment - Node to calculate and set a digest.

Throws:

LibraryException - Thrown if this Node can not be visitted because of a problem in calculating the digest. Often, this is because the message digest specified on the constructor is invalid, the JVM does not support UnicodeBigUnmarked encoding, or the JVM does not have the required security providers for the message digest.

Overrides:

visitCommentPre in class NOOPVisitor

See Also:

TXComment

visitTextPre

public void visitTextPre(TXText text) throws LibraryException

Calculates and sets a digest for the specified text.

A digest of a TXText Node consists of its Node type and its data.

Implements:

visitTextPre in interface Visitor

Parameters:

text - Node to calculate and set a digest.

Throws:

LibraryException - Thrown if this Node can not be visitted because of a problem in calculating the digest. Often, this is because the message digest specified on the constructor is invalid, the JVM does not support UnicodeBigUnmarked encoding, or the JVM does not have the required security providers for the message digest.

Overrides:

visitTextPre in class NOOPVisitor

See Also:

TXText