org.apache.commons.jxpath
Class PackageFunctions

java.lang.Object
  org.apache.commons.jxpath.PackageFunctions

All Implemented Interfaces:

Functions

public class PackageFunctions

extends java.lang.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: 1.14 $ $Date: 2004/04/04 23:16:23 $

Author:

Dmitri Plotnikov

Field Summary

private java.lang.String	classPrefix
private static java.lang.Object[]	EMPTY_ARRAY
private java.lang.String	namespace

Constructor Summary

PackageFunctions(java.lang.String classPrefix, java.lang.String namespace)

Method Summary

Function	getFunction(java.lang.String namespace, java.lang.String name, java.lang.Object[] parameters) Returns a Function, if any, for the specified namespace, name and parameter types.
java.util.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 Detail

classPrefix

private java.lang.String classPrefix

namespace

private java.lang.String namespace

EMPTY_ARRAY

private static final java.lang.Object[] EMPTY_ARRAY

Constructor Detail

PackageFunctions

public PackageFunctions(java.lang.String classPrefix,
                        java.lang.String namespace)

Method Detail

getUsedNamespaces

public java.util.Set getUsedNamespaces()

Returns the namespace specified in the constructor

Specified by:

getUsedNamespaces in interface Functions

getFunction

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

Returns a Function, if any, 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

Returns:

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