org.apache.xpath

Class Expression

public abstract class Expression extends Object implements Serializable, ExpressionNode, XPathVisitable

This abstract class serves as the base for all expression objects. An Expression can be executed to return a XObject, normally has a location within a document or DOM, can send error and warning events, and normally do not hold state and are meant to be immutable once construction has completed. An exception to the immutibility rule is iterators and walkers, which must be cloned in order to be used -- the original must still be immutable.
Method Summary
DTMIteratorasIterator(XPathContext xctxt, int contextNode)
Given an select expression and a context, evaluate the XPath and return the resulting iterator.
DTMIteratorasIteratorRaw(XPathContext xctxt, int contextNode)
Given an select expression and a context, evaluate the XPath and return the resulting iterator, but do not clone.
intasNode(XPathContext xctxt)
Return the first node out of the nodeset, if this expression is a nodeset expression.
voidassertion(boolean b, String msg)
Tell the user of an assertion error, and probably throw an exception.
booleanbool(XPathContext xctxt)
Evaluate expression to a boolean.
booleancanTraverseOutsideSubtree()
Tell if this expression or it's subexpressions can traverse outside the current subtree.
abstract booleandeepEquals(Expression expr)
Compare this object with another object and see if they are equal, include the sub heararchy.
voiderror(XPathContext xctxt, String msg, Object[] args)
Tell the user of an error, and probably throw an exception.
XObjectexecute(XPathContext xctxt, int currentNode)
Execute an expression in the XPath runtime context, and return the result of the expression.
XObjectexecute(XPathContext xctxt, int currentNode, DTM dtm, int expType)
Execute an expression in the XPath runtime context, and return the result of the expression.
abstract XObjectexecute(XPathContext xctxt)
Execute an expression in the XPath runtime context, and return the result of the expression.
XObjectexecute(XPathContext xctxt, boolean destructiveOK)
Execute an expression in the XPath runtime context, and return the result of the expression, but tell that a "safe" object doesn't have to be returned.
voidexecuteCharsToContentHandler(XPathContext xctxt, ContentHandler handler)
Execute an expression in the XPath runtime context, and return the result of the expression.
voidexprAddChild(ExpressionNode n, int i)
This method tells the node to add its argument to the node's list of children.
ExpressionNodeexprGetChild(int i)
This method returns a child node.
intexprGetNumChildren()
Return the number of children the node has.
ExpressionNodeexprGetParent()
voidexprSetParent(ExpressionNode n)
This pair of methods are used to inform the node of its parent.
abstract voidfixupVariables(Vector vars, int globalsSize)
This function is used to fixup variables from QNames to stack frame indexes at stylesheet build time.
intgetColumnNumber()
Return the character position where the current document event ends.
ExpressionNodegetExpressionOwner()
Get the first non-Expression parent of this node.
intgetLineNumber()
Return the line number where the current document event ends.
StringgetPublicId()
Return the public identifier for the current document event.
StringgetSystemId()
Return the system identifier for the current document event.
booleanisNodesetExpr()
Tell if the expression is a nodeset expression.
booleanisStableNumber()
Tell if this expression returns a stable number that will not change during iterations within the expression.
doublenum(XPathContext xctxt)
Evaluate expression to a number.
voidwarn(XPathContext xctxt, String msg, Object[] args)
Warn the user of an problem.
XMLStringxstr(XPathContext xctxt)
Cast result object to a string.

Method Detail

asIterator

public DTMIterator asIterator(XPathContext xctxt, int contextNode)
Given an select expression and a context, evaluate the XPath and return the resulting iterator.

Parameters: xctxt The execution context. contextNode The node that "." expresses.

Returns: A valid DTMIterator.

Throws: TransformerException thrown if the active ProblemListener decides the error condition is severe enough to halt processing. javax.xml.transform.TransformerException

UNKNOWN: experimental

asIteratorRaw

public DTMIterator asIteratorRaw(XPathContext xctxt, int contextNode)
Given an select expression and a context, evaluate the XPath and return the resulting iterator, but do not clone.

Parameters: xctxt The execution context. contextNode The node that "." expresses.

Returns: A valid DTMIterator.

Throws: TransformerException thrown if the active ProblemListener decides the error condition is severe enough to halt processing. javax.xml.transform.TransformerException

UNKNOWN: experimental

asNode

public int asNode(XPathContext xctxt)
Return the first node out of the nodeset, if this expression is a nodeset expression.

Parameters: xctxt The XPath runtime context.

Returns: the first node out of the nodeset, or DTM.NULL.

Throws: javax.xml.transform.TransformerException

assertion

public void assertion(boolean b, String msg)
Tell the user of an assertion error, and probably throw an exception.

Parameters: b If false, a runtime exception will be thrown. msg The assertion message, which should be informative.

Throws: RuntimeException if the b argument is false. javax.xml.transform.TransformerException

bool

public boolean bool(XPathContext xctxt)
Evaluate expression to a boolean.

Parameters: xctxt The XPath runtime context.

Returns: false

Throws: javax.xml.transform.TransformerException

canTraverseOutsideSubtree

public boolean canTraverseOutsideSubtree()
Tell if this expression or it's subexpressions can traverse outside the current subtree.

Returns: true if traversal outside the context node's subtree can occur.

deepEquals

public abstract boolean deepEquals(Expression expr)
Compare this object with another object and see if they are equal, include the sub heararchy.

Parameters: expr Another expression object.

Returns: true if this objects class and the expr object's class are the same, and the data contained within both objects are considered equal.

error

public void error(XPathContext xctxt, String msg, Object[] args)
Tell the user of an error, and probably throw an exception.

Parameters: xctxt The XPath runtime context. msg An error msgkey that corresponds to one of the constants found in XPATHErrorResources, which is a key for a format string. args An array of arguments represented in the format string, which may be null.

Throws: TransformerException if the current ErrorListoner determines to throw an exception. javax.xml.transform.TransformerException

execute

public XObject execute(XPathContext xctxt, int currentNode)
Execute an expression in the XPath runtime context, and return the result of the expression.

Parameters: xctxt The XPath runtime context. currentNode The currentNode.

Returns: The result of the expression in the form of a XObject.

Throws: javax.xml.transform.TransformerException if a runtime exception occurs.

execute

public XObject execute(XPathContext xctxt, int currentNode, DTM dtm, int expType)
Execute an expression in the XPath runtime context, and return the result of the expression.

Parameters: xctxt The XPath runtime context. currentNode The currentNode. dtm The DTM of the current node. expType The expanded type ID of the current node.

Returns: The result of the expression in the form of a XObject.

Throws: javax.xml.transform.TransformerException if a runtime exception occurs.

execute

public abstract XObject execute(XPathContext xctxt)
Execute an expression in the XPath runtime context, and return the result of the expression.

Parameters: xctxt The XPath runtime context.

Returns: The result of the expression in the form of a XObject.

Throws: javax.xml.transform.TransformerException if a runtime exception occurs.

execute

public XObject execute(XPathContext xctxt, boolean destructiveOK)
Execute an expression in the XPath runtime context, and return the result of the expression, but tell that a "safe" object doesn't have to be returned. The default implementation just calls execute(xctxt).

Parameters: xctxt The XPath runtime context. destructiveOK true if a "safe" object doesn't need to be returned.

Returns: The result of the expression in the form of a XObject.

Throws: javax.xml.transform.TransformerException if a runtime exception occurs.

executeCharsToContentHandler

public void executeCharsToContentHandler(XPathContext xctxt, ContentHandler handler)
Execute an expression in the XPath runtime context, and return the result of the expression.

Parameters: xctxt The XPath runtime context. NEEDSDOC @param handler

Returns: The result of the expression in the form of a XObject.

Throws: javax.xml.transform.TransformerException if a runtime exception occurs. org.xml.sax.SAXException

exprAddChild

public void exprAddChild(ExpressionNode n, int i)
This method tells the node to add its argument to the node's list of children.

exprGetChild

public ExpressionNode exprGetChild(int i)
This method returns a child node. The children are numbered from zero, left to right.

exprGetNumChildren

public int exprGetNumChildren()
Return the number of children the node has.

exprGetParent

public ExpressionNode exprGetParent()

exprSetParent

public void exprSetParent(ExpressionNode n)
This pair of methods are used to inform the node of its parent.

fixupVariables

public abstract void fixupVariables(Vector vars, int globalsSize)
This function is used to fixup variables from QNames to stack frame indexes at stylesheet build time.

Parameters: vars List of QNames that correspond to variables. This list should be searched backwards for the first qualified name that corresponds to the variable reference qname. The position of the QName in the vector from the start of the vector will be its position in the stack frame (but variables above the globalsTop value will need to be offset to the current stack frame). NEEDSDOC @param globalsSize

getColumnNumber

public int getColumnNumber()
Return the character position where the current document event ends.

Warning: The return value from the method is intended only as an approximation for the sake of error reporting; it is not intended to provide sufficient information to edit the character content of the original XML document.

The return value is an approximation of the column number in the document entity or external parsed entity where the markup that triggered the event appears.

Returns: The column number, or -1 if none is available.

See Also: Expression

getExpressionOwner

public ExpressionNode getExpressionOwner()
Get the first non-Expression parent of this node.

Returns: null or first ancestor that is not an Expression.

getLineNumber

public int getLineNumber()
Return the line number where the current document event ends.

Warning: The return value from the method is intended only as an approximation for the sake of error reporting; it is not intended to provide sufficient information to edit the character content of the original XML document.

The return value is an approximation of the line number in the document entity or external parsed entity where the markup that triggered the event appears.

Returns: The line number, or -1 if none is available.

See Also: Expression

getPublicId

public String getPublicId()
Return the public identifier for the current document event.

The return value is the public identifier of the document entity or of the external parsed entity in which the markup that triggered the event appears.

Returns: A string containing the public identifier, or null if none is available.

See Also: Expression

getSystemId

public String getSystemId()
Return the system identifier for the current document event.

The return value is the system identifier of the document entity or of the external parsed entity in which the markup that triggered the event appears.

If the system identifier is a URL, the parser must resolve it fully before passing it to the application.

Returns: A string containing the system identifier, or null if none is available.

See Also: Expression

isNodesetExpr

public boolean isNodesetExpr()
Tell if the expression is a nodeset expression. In other words, tell if you can execute asNode without an exception.

Returns: true if the expression can be represented as a nodeset.

isStableNumber

public boolean isStableNumber()
Tell if this expression returns a stable number that will not change during iterations within the expression. This is used to determine if a proximity position predicate can indicate that no more searching has to occur.

Returns: true if the expression represents a stable number.

num

public double num(XPathContext xctxt)
Evaluate expression to a number.

Parameters: xctxt The XPath runtime context.

Returns: The expression evaluated as a double.

Throws: javax.xml.transform.TransformerException

warn

public void warn(XPathContext xctxt, String msg, Object[] args)
Warn the user of an problem.

Parameters: xctxt The XPath runtime context. msg An error msgkey that corresponds to one of the conststants found in XPATHErrorResources, which is a key for a format string. args An array of arguments represented in the format string, which may be null.

Throws: TransformerException if the current ErrorListoner determines to throw an exception. javax.xml.transform.TransformerException

xstr

public XMLString xstr(XPathContext xctxt)
Cast result object to a string.

Parameters: xctxt The XPath runtime context.

Returns: The string this wraps or the empty string if null

Throws: javax.xml.transform.TransformerException

Copyright B) 2006 Apache XML Project. All Rights Reserved.