org.apache.commons.jxpath

Class PackageFunctions

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()"
new java.util.Date()
"util:Collections.singleton('foo')"
java.util.Collections.singleton("foo")
"util:substring('foo', 1, 2)"
"foo".substring(1, 2)

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

Constructor Summary

PackageFunctions(String classPrefix, String namespace)

Method Summary

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

Constructor Details

PackageFunctions

public PackageFunctions(String classPrefix,
                        String namespace)

Method Details

getFunction

public Function getFunction(String namespace,
                            String name,
                            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

getUsedNamespaces

public Set getUsedNamespaces()
Returns the namespace specified in the constructor
Specified by:
getUsedNamespaces in interface Functions