Package org.apache.commons.jxpath

Class PackageFunctions

java.lang.Object

org.apache.commons.jxpath.PackageFunctions

All Implemented Interfaces:

Functions

public class PackageFunctions
extends Object
implements Functions

Extension functions provided by Java classes. The class prefix specified in the constructor is used when a constructor or a static method is called. Usually, a class prefix is a package name (hence the name of this class). Let's say, we declared a PackageFunction like this:

     new PackageFunctions("java.util.", "util")
 

We can now use XPaths like:

"util:Date.new()"

Equivalent to new java.util.Date()

"util:Collections.singleton('foo')"

Equivalent to java.util.Collections.singleton("foo")

"util:substring('foo', 1, 2)"

Equivalent to "foo".substring(1, 2). Note that in this case, the class prefix is not used. JXPath does not check that the first parameter of the function (the method target) is in fact a member of the package described by this PackageFunctions object.

If the first argument of a method or constructor is ExpressionContext, the expression context in which the function is evaluated is passed to the method.

There is one PackageFunctions object registered by default with each JXPathContext. It does not have a namespace and uses no class prefix. The existence of this object allows us to use XPaths like: "java.util.Date.new()" and "length('foo')" without the explicit registration of any extension functions.

Version:

$Revision: 670727 $ $Date: 2008-06-23 15:10:38 -0500 (Mon, 23 Jun 2008) $

Field Summary

Fields

Modifier and Type	Field	Description
private String	classPrefix
private static final Object[]	EMPTY_ARRAY
private String	namespace

Constructor Summary

Constructors

Constructor	Description
PackageFunctions(String classPrefix, String namespace)	Create a new PackageFunctions.

Method Summary

Modifier and Type	Method	Description
Function	getFunction(String namespace, String name, Object[] parameters)	Returns a Function, if found, for the specified namespace, name and parameter types.
Set	getUsedNamespaces()	Returns the namespace specified in the constructor

Methods inherited from class java.lang.Object

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

Field Details

classPrefix

private String classPrefix

namespace

private String namespace

EMPTY_ARRAY

private static final Object[] EMPTY_ARRAY

Constructor Details

PackageFunctions

public PackageFunctions(String classPrefix,
 String namespace)

Create a new PackageFunctions.

Parameters:

classPrefix - class prefix

namespace - namespace String

Method Details

getUsedNamespaces

public Set getUsedNamespaces()

Returns the namespace specified in the constructor

Specified by:

getUsedNamespaces in interface Functions

Returns:

(singleton) namespace Set

getFunction

public Function getFunction(String namespace,
 String name,
 Object[] parameters)

Returns a Function, if found, for the specified namespace, name and parameter types.

Specified by:

getFunction in interface Functions

Parameters:

namespace - - if it is not the same as specified in the construction, this method returns null

name - - name of the method, which can one these forms:

• methodname, if invoking a method on an object passed as the first parameter
• Classname.new, if looking for a constructor
• subpackage.subpackage.Classname.new, if looking for a constructor in a subpackage
• Classname.methodname, if looking for a static method
• subpackage.subpackage.Classname.methodname, if looking for a static method of a class in a subpackage

parameters - Object[] of parameters

Returns:

a MethodFunction, a ConstructorFunction or null if no function is found