Class Expression
- java.lang.Object
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- org.apache.xpath.Expression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,ExpressionNode
,XPathVisitable
- Direct Known Subclasses:
Function
,NodeTest
,Operation
,UnaryOperation
,UnionPattern
,Variable
,XObject
public abstract class Expression extends java.lang.Object implements java.io.Serializable, ExpressionNode, XPathVisitable
This abstract class serves as the base for all expression objects. An Expression can be executed to return aXObject
, 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.- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description Expression()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description DTMIterator
asIterator(XPathContext xctxt, int contextNode)
Given an select expression and a context, evaluate the XPath and return the resulting iterator.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.int
asNode(XPathContext xctxt)
Return the first node out of the nodeset, if this expression is a nodeset expression.void
assertion(boolean b, java.lang.String msg)
Tell the user of an assertion error, and probably throw an exception.boolean
bool(XPathContext xctxt)
Evaluate expression to a boolean.boolean
canTraverseOutsideSubtree()
Tell if this expression or it's subexpressions can traverse outside the current subtree.abstract boolean
deepEquals(Expression expr)
Compare this object with another object and see if they are equal, include the sub heararchy.void
error(XPathContext xctxt, java.lang.String msg, java.lang.Object[] args)
Tell the user of an error, and probably throw an exception.abstract XObject
execute(XPathContext xctxt)
Execute an expression in the XPath runtime context, and return the result of the expression.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.XObject
execute(XPathContext xctxt, int currentNode)
Execute an expression in the XPath runtime context, and return the result of the expression.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.void
executeCharsToContentHandler(XPathContext xctxt, org.xml.sax.ContentHandler handler)
Execute an expression in the XPath runtime context, and return the result of the expression.void
exprAddChild(ExpressionNode n, int i)
This method tells the node to add its argument to the node's list of children.ExpressionNode
exprGetChild(int i)
This method returns a child node.int
exprGetNumChildren()
Return the number of children the node has.ExpressionNode
exprGetParent()
void
exprSetParent(ExpressionNode n)
This pair of methods are used to inform the node of its parent.abstract void
fixupVariables(java.util.Vector vars, int globalsSize)
This function is used to fixup variables from QNames to stack frame indexes at stylesheet build time.int
getColumnNumber()
Return the character position where the current document event ends.ExpressionNode
getExpressionOwner()
Get the first non-Expression parent of this node.int
getLineNumber()
Return the line number where the current document event ends.java.lang.String
getPublicId()
Return the public identifier for the current document event.java.lang.String
getSystemId()
Return the system identifier for the current document event.boolean
isNodesetExpr()
Tell if the expression is a nodeset expression.boolean
isStableNumber()
Tell if this expression returns a stable number that will not change during iterations within the expression.double
num(XPathContext xctxt)
Evaluate expression to a number.void
warn(XPathContext xctxt, java.lang.String msg, java.lang.Object[] args)
Warn the user of an problem.XMLString
xstr(XPathContext xctxt)
Cast result object to a string.-
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface org.apache.xpath.XPathVisitable
callVisitors
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Method Detail
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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.
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execute
public XObject execute(XPathContext xctxt, int currentNode) throws javax.xml.transform.TransformerException
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.
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execute
public XObject execute(XPathContext xctxt, int currentNode, DTM dtm, int expType) throws javax.xml.transform.TransformerException
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.
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execute
public abstract XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
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.
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execute
public XObject execute(XPathContext xctxt, boolean destructiveOK) throws javax.xml.transform.TransformerException
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.
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num
public double num(XPathContext xctxt) throws javax.xml.transform.TransformerException
Evaluate expression to a number.- Parameters:
xctxt
- The XPath runtime context.- Returns:
- The expression evaluated as a double.
- Throws:
javax.xml.transform.TransformerException
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bool
public boolean bool(XPathContext xctxt) throws javax.xml.transform.TransformerException
Evaluate expression to a boolean.- Parameters:
xctxt
- The XPath runtime context.- Returns:
- false
- Throws:
javax.xml.transform.TransformerException
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xstr
public XMLString xstr(XPathContext xctxt) throws javax.xml.transform.TransformerException
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
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isNodesetExpr
public boolean isNodesetExpr()
Tell if the expression is a nodeset expression. In other words, tell if you can executeasNode
without an exception.- Returns:
- true if the expression can be represented as a nodeset.
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asNode
public int asNode(XPathContext xctxt) throws javax.xml.transform.TransformerException
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
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asIterator
public DTMIterator asIterator(XPathContext xctxt, int contextNode) throws javax.xml.transform.TransformerException
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:
javax.xml.transform.TransformerException
- thrown if the active ProblemListener decides the error condition is severe enough to halt processing.javax.xml.transform.TransformerException
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asIteratorRaw
public DTMIterator asIteratorRaw(XPathContext xctxt, int contextNode) throws javax.xml.transform.TransformerException
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:
javax.xml.transform.TransformerException
- thrown if the active ProblemListener decides the error condition is severe enough to halt processing.javax.xml.transform.TransformerException
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executeCharsToContentHandler
public void executeCharsToContentHandler(XPathContext xctxt, org.xml.sax.ContentHandler handler) throws javax.xml.transform.TransformerException, org.xml.sax.SAXException
Execute an expression in the XPath runtime context, and return the result of the expression.- Parameters:
xctxt
- The XPath runtime context. NEEDSDOC @param handler- Throws:
javax.xml.transform.TransformerException
- if a runtime exception occurs.org.xml.sax.SAXException
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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.
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fixupVariables
public abstract void fixupVariables(java.util.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
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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.
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warn
public void warn(XPathContext xctxt, java.lang.String msg, java.lang.Object[] args) throws javax.xml.transform.TransformerException
Warn the user of an problem.- Parameters:
xctxt
- The XPath runtime context.msg
- An error msgkey that corresponds to one of the conststants found inXPATHErrorResources
, which is a key for a format string.args
- An array of arguments represented in the format string, which may be null.- Throws:
javax.xml.transform.TransformerException
- if the current ErrorListoner determines to throw an exception.javax.xml.transform.TransformerException
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assertion
public void assertion(boolean b, java.lang.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:
java.lang.RuntimeException
- if the b argument is false.javax.xml.transform.TransformerException
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error
public void error(XPathContext xctxt, java.lang.String msg, java.lang.Object[] args) throws javax.xml.transform.TransformerException
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 inXPATHErrorResources
, which is a key for a format string.args
- An array of arguments represented in the format string, which may be null.- Throws:
javax.xml.transform.TransformerException
- if the current ErrorListoner determines to throw an exception.javax.xml.transform.TransformerException
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getExpressionOwner
public ExpressionNode getExpressionOwner()
Get the first non-Expression parent of this node.- Returns:
- null or first ancestor that is not an Expression.
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exprSetParent
public void exprSetParent(ExpressionNode n)
This pair of methods are used to inform the node of its parent.- Specified by:
exprSetParent
in interfaceExpressionNode
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exprGetParent
public ExpressionNode exprGetParent()
- Specified by:
exprGetParent
in interfaceExpressionNode
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exprAddChild
public void exprAddChild(ExpressionNode n, int i)
This method tells the node to add its argument to the node's list of children.- Specified by:
exprAddChild
in interfaceExpressionNode
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exprGetChild
public ExpressionNode exprGetChild(int i)
This method returns a child node. The children are numbered from zero, left to right.- Specified by:
exprGetChild
in interfaceExpressionNode
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exprGetNumChildren
public int exprGetNumChildren()
Return the number of children the node has.- Specified by:
exprGetNumChildren
in interfaceExpressionNode
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getPublicId
public java.lang.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.
- Specified by:
getPublicId
in interfacejavax.xml.transform.SourceLocator
- Returns:
- A string containing the public identifier, or null if none is available.
- See Also:
getSystemId()
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getSystemId
public java.lang.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.
- Specified by:
getSystemId
in interfacejavax.xml.transform.SourceLocator
- Returns:
- A string containing the system identifier, or null if none is available.
- See Also:
getPublicId()
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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.
- Specified by:
getLineNumber
in interfacejavax.xml.transform.SourceLocator
- Returns:
- The line number, or -1 if none is available.
- See Also:
getColumnNumber()
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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.
- Specified by:
getColumnNumber
in interfacejavax.xml.transform.SourceLocator
- Returns:
- The column number, or -1 if none is available.
- See Also:
getLineNumber()
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