Package 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

Abstracts path expressions.

Nested Class Summary

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

Expression.PointerIterator, Expression.ValueIterator

Field Summary

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

NOT_A_NUMBER, ONE, ZERO

Constructor Summary

Constructors

Constructor	Description
Path(Step[] steps)	Constructs a new Path.

Method Summary

Modifier and Type	Method	Description
protected boolean	areBasicPredicates(Expression[] predicates)	Tests whether the elements of the specified array are "basic" predicates.
protected EvalContext	buildContextChain(EvalContext context, int stepCount, boolean createInitialContext)	Build a context from a chain of contexts.
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()	Gets the steps.
boolean	isSimplePath()	Recognizes 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]".
protected 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

Constructor Details

Path

public Path(Step[] steps)

Constructs a new Path.

Parameters:

steps - that compose the Path

Method Details

areBasicPredicates

protected boolean areBasicPredicates(Expression[] predicates)

Tests whether the elements of the specified array are "basic" predicates.

Parameters:

predicates - the Expression[] to check

Returns:

boolean

buildContextChain

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

Build a context from a chain of contexts.

Parameters:

context - evaluation context

stepCount - number of steps to descend

createInitialContext - whether to create the initial context

Returns:

created context

computeContextDependent

public boolean computeContextDependent()

Description copied from class: Expression

Implemented by subclasses and result is cached by isContextDependent()

Specified by:

computeContextDependent in class Expression

Returns:

calculated context-dependentness as boolean

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.

Parameters:

context - evaluation context

axis - code

nodeTest - node test

Returns:

EvalContext

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.

Parameters:

context - evaluation context

Returns:

EvaluationContext

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.

Parameters:

context - evaluation context

Returns:

Pointer

getSteps

public Step[] getSteps()

Gets the steps.

Returns:

Step[]

isSimplePath

public boolean isSimplePath()

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

Returns:

true if this path is simple

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.

Parameters:

step - the step to check

Returns:

boolean

searchForPath

protected 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.

Parameters:

context - evaluation context

Returns:

Pointer