/*
* $Header: /home/cvspublic/jakarta-commons/jxpath/src/java/org/apache/commons/jxpath/PackageFunctions.java,v 1.6 2002/06/16 03:22:22 dmitri Exp $
* $Revision: 1.6 $
* $Date: 2002/06/16 03:22:22 $
*
* ====================================================================
* The Apache Software License, Version 1.1
*
*
* Copyright (c) 1999-2001 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowlegement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowlegement may appear in the software itself,
* if and wherever such third-party acknowlegements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache"
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation and was
* originally based on software copyright (c) 2001, Plotnix, Inc,
* <http://www.plotnix.com/>.
* For more information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
package org.apache.commons.jxpath;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Set;
import org.apache.commons.jxpath.functions.ConstructorFunction;
import org.apache.commons.jxpath.functions.MethodFunction;
import org.apache.commons.jxpath.util.MethodLookupUtils;
/**
* 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:
* <blockquote><pre>
* new PackageFunctions("java.util.", "util")
* </pre></blockquote>
*
* We can now use XPaths like:
* <dl>
* <dt><code>"util:Date.new()"</code></dt>
* <dd>Equivalent to <code>new java.util.Date()</code></dd>
* <dt><code>"util:Collections.singleton('foo')"</code></dt>
* <dd>Equivalent to <code>java.util.Collections.singleton("foo")</code></dd>
* <dt><code>"util:substring('foo', 1, 2)"</code></dt>
* <dd>Equivalent to <code>"foo".substring(1, 2)</code>. 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.</dd>
* </dl>
*
* <p>
* 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.
* </p>
* <p>
* 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:
* <code>"java.util.Date.new()"</code> and <code>"length('foo')"</code>
* without the explicit registration of any extension functions.
* </p>
*
* @author Dmitri Plotnikov
* @version $Revision: 1.6 $ $Date: 2002/06/16 03:22:22 $
*/
public class PackageFunctions implements Functions {
private String classPrefix;
private String namespace;
private static final Object[] EMPTY_ARRAY = new Object[0];
public PackageFunctions(String classPrefix, String namespace) {
this.classPrefix = classPrefix;
this.namespace = namespace;
}
/**
* Returns the namespace specified in the constructor
*/
public Set getUsedNamespaces() {
return Collections.singleton(namespace);
}
/**
* Returns a Function, if any, for the specified namespace,
* name and parameter types.
* <p>
* @param namespace - if it is not the same as specified in the construction,
* this method returns null
* @param name - name of the method, which can one these forms:
* <ul>
* <li><b>methodname</b>, if invoking a method on an object passed as the first parameter</li>
* <li><b>Classname.new</b>, if looking for a constructor</li>
* <li><b>subpackage.subpackage.Classname.new</b>, if looking for a constructor in
* a subpackage</li>
* <li><b>Classname.methodname</b>, if looking for a static method</li>
* <li><b>subpackage.subpackage.Classname.methodname</b>, if looking for a
* static method of a class in a subpackage</li>
* </ul>
*
* @return a MethodFunction, a ConstructorFunction or null if no function is found
*/
public Function getFunction(String namespace, String name, Object[] parameters) {
if ((namespace == null && this.namespace != null)
|| (namespace != null && !namespace.equals(this.namespace))) {
return null;
}
if (parameters == null) {
parameters = EMPTY_ARRAY;
}
if (parameters.length >= 1) {
Object target = parameters[0];
if (target != null) {
if (target instanceof ExpressionContext) {
Pointer pointer = ((ExpressionContext) target).getContextNodePointer();
if (pointer != null) {
target = pointer.getValue();
}
else {
target = null;
}
}
}
if (target != null) {
Method method = MethodLookupUtils.
lookupMethod(target.getClass(), name, parameters);
if (method != null) {
return new MethodFunction(method);
}
}
}
String fullName = classPrefix + name;
int inx = fullName.lastIndexOf('.');
if (inx == -1) {
return null;
}
String className = fullName.substring(0, inx);
String methodName = fullName.substring(inx + 1);
Class functionClass;
try {
functionClass = Class.forName(className);
}
catch (ClassNotFoundException ex) {
throw new JXPathException("Cannot invoke extension function "
+ (namespace != null ? namespace + ":" + name : name),
ex);
}
if (methodName.endsWith("new")) {
Constructor constructor =
MethodLookupUtils.lookupConstructor(functionClass, parameters);
if (constructor != null) {
return new ConstructorFunction(constructor);
}
}
else {
Method method =
MethodLookupUtils.
lookupStaticMethod(functionClass, methodName, parameters);
if (method != null) {
return new MethodFunction(method);
}
}
return null;
}
}