org.mule.runtime.module.xml.xpath

Class JaxpXPathEvaluator

java.lang.Object

org.mule.runtime.module.xml.xpath.JaxpXPathEvaluator

All Implemented Interfaces:

XPathVariableResolver, XPathEvaluator

Direct Known Subclasses:

SaxonXpathEvaluator

public abstract class JaxpXPathEvaluator
extends Object
implements XPathEvaluator, XPathVariableResolver

This is the preferred base implementation of XPathEvaluator. Because it's based on the JAXP API (JSR-206), it's ideal for keeping a common code base which can work with different engines, as long as they implement that API. This base class contains all of the logic necessary to comply with the XPathEvaluator contract. Implementations only need to implement createXPathFactory() in order to provide the XPathFactory implementation it wishes to use. Another important feature of this implementation is that it caches compiled versions of executed expressions to provide better performance. Expressions that haven't been used for more than a minute are automatically evicted. In addition to the registerNamespaces(Map) and registerNamespaces(NamespaceManager) methods, this implementation also provides out of the box support for the standard namespaces defined in XPathNamespaceContext In order to allow binding expression parameters to flow variables, this class also implements the XPathVariableResolver interface. Because this class caches compiled expressions which might be executed concurrently in different threads, we need a way to correlate different Event instances to each invocation of the resolveVariable(QName) method. To do that, it uses a ThreadLocal in the evaluationEvent attribute, so that we can determine the corresponding event for each thread evaluating an XPath expression. Notice that because xpath evaluation is an operation that happens in RAM memory (basically because the DOM Node needs to be completely loaded), we can use a ThreadLocal without risking failure if this is executed in a non-blocking environment.

Since:

3.6.0

Constructor Summary

Constructors

Constructor and Description
JaxpXPathEvaluator()

Method Summary

Modifier and Type	Method and Description
protected XPathExpression	compile(String expression)
protected abstract XPathFactory	createXPathFactory() Returns the XPathFactory to be used when compiling expressions
String	evaluate(String xpathExpression, Node input, Event event) Evaluates the xpathExpression over the input and returns the evaluation as a String.
Object	evaluate(String xpathExpression, Node input, XPathReturnType returnType, Event event) Evaluates the xpathExpression over the input and returns the evaluation as a type in concordance with returnType.
Map<String,String>	getRegisteredNamespaces() Returns a Map with the registered namespaces.
protected NamespaceContext	newNamespaceContext()
protected XPath	newXPath()
void	registerNamespaces(Map<String,String> namespaces) Registers the given namespaces so that they can be recognized during evaluation
void	registerNamespaces(NamespaceManager namespaceManager) Registers the namespaces in namespaceManager
Object	resolveVariable(QName variableName) Resolves the given variable against the flow variables in the Event held by evaluationEvent

Methods inherited from class java.lang.Object

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

Constructor Detail

JaxpXPathEvaluator

public JaxpXPathEvaluator()

Method Detail

createXPathFactory

protected abstract XPathFactory createXPathFactory()

Returns the XPathFactory to be used when compiling expressions

Returns:

a XPathFactory

evaluate

public String evaluate(String xpathExpression,
                       Node input,
                       Event event)

Evaluates the xpathExpression over the input and returns the evaluation as a String.

If xpathExpression contains parameters, they will be resolved against the flow variables in event

Specified by:

evaluate in interface XPathEvaluator

Parameters:

xpathExpression - the xpathExpression to be evaluated

input - a Node

event - the current Event.

Returns:

the result of the evaluation as a String

evaluate

public Object evaluate(String xpathExpression,
                       Node input,
                       XPathReturnType returnType,
                       Event event)

Evaluates the xpathExpression over the input and returns the evaluation as a type in concordance with returnType.

If xpathExpression contains parameters, they will be resolved against the flow variables in event

Specified by:

evaluate in interface XPathEvaluator

Parameters:

xpathExpression - the xpathExpression to be evaluated

input - a Node

returnType - a XPathReturnType that will be used to decide the return type of the evaluation

event - the current Event.

Returns:

the result of the evaluation in concordance with returnType

resolveVariable

public Object resolveVariable(QName variableName)

Resolves the given variable against the flow variables in the Event held by evaluationEvent

Specified by:

resolveVariable in interface XPathVariableResolver

Parameters:

variableName - the variable name

Returns:

the variable value. Might be null

registerNamespaces

public void registerNamespaces(Map<String,String> namespaces)

Registers the given namespaces so that they can be recognized during evaluation

Specified by:

registerNamespaces in interface XPathEvaluator

Parameters:

namespaces - a Map in which the key is a namespace prefix and the value is its URI as a String

registerNamespaces

public void registerNamespaces(NamespaceManager namespaceManager)

Registers the namespaces in namespaceManager

Specified by:

registerNamespaces in interface XPathEvaluator

Parameters:

namespaceManager - a NamespaceManager

getRegisteredNamespaces

public Map<String,String> getRegisteredNamespaces()

Returns a Map with the registered namespaces. The key of the map is the namespace prefix and the value is its URI as a String Returns an immutable map with the current registered namespaces. The returned map will not reflect any changes performed afterwards.

Specified by:

getRegisteredNamespaces in interface XPathEvaluator

Returns:

a Map

newXPath

protected XPath newXPath()

compile

protected XPathExpression compile(String expression)
                           throws XPathExpressionException

Throws:

XPathExpressionException

newNamespaceContext

protected NamespaceContext newNamespaceContext()