org.apache.commons.jxpath.ri.compiler
Class Path

java.lang.Object
  org.apache.commons.jxpath.ri.compiler.Expression
      org.apache.commons.jxpath.ri.compiler.Path

Direct Known Subclasses:

ExpressionPath, LocationPath

public abstract class Path

extends Expression

Version:

$Revision: 1.14 $ $Date: 2004/04/01 02:55:32 $

Author:

Dmitri Plotnikov

Nested Class Summary

Nested classes inherited from class org.apache.commons.jxpath.ri.compiler.Expression

Expression.PointerIterator, Expression.ValueIterator

Field Summary

private boolean	basic
private boolean	basicKnown
private Step[]	steps

Fields inherited from class org.apache.commons.jxpath.ri.compiler.Expression

NOT_A_NUMBER, ONE, ZERO

Constructor Summary

Path(Step[] steps)

Method Summary

protected boolean	areBasicPredicates(Expression[] predicates)
private EvalContext	buildContextChain(EvalContext context, int stepCount, boolean createInitialContext)
boolean	computeContextDependent() Implemented by subclasses and result is cached by isContextDependent()
protected EvalContext	createContextForStep(EvalContext context, int axis, NodeTest nodeTest) Different axes are serviced by different contexts.
protected EvalContext	evalSteps(EvalContext context) Given a root context, walks a path therefrom and builds a context that contains all nodes matching the path.
protected Pointer	getSingleNodePointerForSteps(EvalContext context) Given a root context, walks a path therefrom and finds the pointer to the first element matching the path.
Step[]	getSteps()
boolean	isSimplePath() Recognized paths formatted as foo/bar[3]/baz[@name = 'biz'] .
protected boolean	isSimpleStep(Step step) A Step is "simple" if it takes one of these forms: ".", "/foo", "@bar", "/foo[3]".
private Pointer	searchForPath(EvalContext context) The idea here is to return a NullPointer rather than null if that's at all possible.

Methods inherited from class org.apache.commons.jxpath.ri.compiler.Expression

compute, computeValue, isContextDependent, iterate, iteratePointers

Methods inherited from class java.lang.Object

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

Field Detail

steps

private Step[] steps

basicKnown

private boolean basicKnown

basic

private boolean basic

Constructor Detail

Path

public Path(Step[] steps)

Method Detail

getSteps

public Step[] getSteps()

computeContextDependent

public boolean computeContextDependent()

Description copied from class: Expression

Implemented by subclasses and result is cached by isContextDependent()

Specified by:

computeContextDependent in class Expression

isSimplePath

public boolean isSimplePath()

Recognized paths formatted as foo/bar[3]/baz[@name = 'biz'] . The evaluation of such "simple" paths is optimized and streamlined.

isSimpleStep

protected boolean isSimpleStep(Step step)

A Step is "simple" if it takes one of these forms: ".", "/foo", "@bar", "/foo[3]". If there are predicates, they should be context independent for the step to still be considered simple.

areBasicPredicates

protected boolean areBasicPredicates(Expression[] predicates)

getSingleNodePointerForSteps

protected Pointer getSingleNodePointerForSteps(EvalContext context)

Given a root context, walks a path therefrom and finds the pointer to the first element matching the path.

searchForPath

private Pointer searchForPath(EvalContext context)

The idea here is to return a NullPointer rather than null if that's at all possible. Take for example this path: "//map/key". Let's say, "map" is an existing node, but "key" is not there. We will create a NullPointer that can be used to set/create the "key" property.

However, a path like "//key" would still produce null, because we have no way of knowing where "key" would be if it existed.

To accomplish this, we first try the path itself. If it does not find anything, we chop off last step of the path, as long as it is a simple one like child:: or attribute:: and try to evaluate the truncated path. If it finds exactly one node - create a NullPointer and return. If it fails, chop off another step and repeat. If it finds more than one location - return null.

evalSteps

protected EvalContext evalSteps(EvalContext context)

Given a root context, walks a path therefrom and builds a context that contains all nodes matching the path.

buildContextChain

private EvalContext buildContextChain(EvalContext context,
                                      int stepCount,
                                      boolean createInitialContext)

createContextForStep

protected EvalContext createContextForStep(EvalContext context,
                                           int axis,
                                           NodeTest nodeTest)

Different axes are serviced by different contexts. This method allocates the right context for the supplied step.