Class PackageFunctions

All Implemented Interfaces:

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:
Equivalent to new java.util.Date()
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: "" and "length('foo')" without the explicit registration of any extension functions.

$Revision: 1.10 $ $Date: 2003/03/11 00:59:12 $
Dmitri Plotnikov

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

Constructor Detail


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


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


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
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
  •, if looking for a constructor
  •, 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
a MethodFunction, a ConstructorFunction or null if no function is found

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