001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.jxpath; 018 019 import java.lang.reflect.Constructor; 020 import java.lang.reflect.Method; 021 import java.util.Collection; 022 import java.util.Collections; 023 import java.util.Iterator; 024 import java.util.Set; 025 026 import org.apache.commons.jxpath.functions.ConstructorFunction; 027 import org.apache.commons.jxpath.functions.MethodFunction; 028 import org.apache.commons.jxpath.util.MethodLookupUtils; 029 import org.apache.commons.jxpath.util.TypeUtils; 030 031 /** 032 * Extension functions provided by Java classes. The class prefix specified 033 * in the constructor is used when a constructor or a static method is called. 034 * Usually, a class prefix is a package name (hence the name of this class). 035 * 036 * Let's say, we declared a PackageFunction like this: 037 * <blockquote><pre> 038 * new PackageFunctions("java.util.", "util") 039 * </pre></blockquote> 040 * 041 * We can now use XPaths like: 042 * <dl> 043 * <dt><code>"util:Date.new()"</code></dt> 044 * <dd>Equivalent to <code>new java.util.Date()</code></dd> 045 * <dt><code>"util:Collections.singleton('foo')"</code></dt> 046 * <dd>Equivalent to <code>java.util.Collections.singleton("foo")</code></dd> 047 * <dt><code>"util:substring('foo', 1, 2)"</code></dt> 048 * <dd>Equivalent to <code>"foo".substring(1, 2)</code>. Note that in 049 * this case, the class prefix is not used. JXPath does not check that 050 * the first parameter of the function (the method target) is in fact 051 * a member of the package described by this PackageFunctions object.</dd> 052 * </dl> 053 * 054 * <p> 055 * If the first argument of a method or constructor is {@link ExpressionContext}, 056 * the expression context in which the function is evaluated is passed to 057 * the method. 058 * </p> 059 * <p> 060 * There is one PackageFunctions object registered by default with each 061 * JXPathContext. It does not have a namespace and uses no class prefix. 062 * The existence of this object allows us to use XPaths like: 063 * <code>"java.util.Date.new()"</code> and <code>"length('foo')"</code> 064 * without the explicit registration of any extension functions. 065 * </p> 066 * 067 * @author Dmitri Plotnikov 068 * @version $Revision: 670727 $ $Date: 2008-06-23 15:10:38 -0500 (Mon, 23 Jun 2008) $ 069 */ 070 public class PackageFunctions implements Functions { 071 private String classPrefix; 072 private String namespace; 073 private static final Object[] EMPTY_ARRAY = new Object[0]; 074 075 /** 076 * Create a new PackageFunctions. 077 * @param classPrefix class prefix 078 * @param namespace namespace String 079 */ 080 public PackageFunctions(String classPrefix, String namespace) { 081 this.classPrefix = classPrefix; 082 this.namespace = namespace; 083 } 084 085 /** 086 * Returns the namespace specified in the constructor 087 * @return (singleton) namespace Set 088 */ 089 public Set getUsedNamespaces() { 090 return Collections.singleton(namespace); 091 } 092 093 /** 094 * Returns a {@link Function}, if found, for the specified namespace, 095 * name and parameter types. 096 * <p> 097 * @param namespace - if it is not the same as specified in the 098 * construction, this method returns null 099 * @param name - name of the method, which can one these forms: 100 * <ul> 101 * <li><b>methodname</b>, if invoking a method on an object passed as the 102 * first parameter</li> 103 * <li><b>Classname.new</b>, if looking for a constructor</li> 104 * <li><b>subpackage.subpackage.Classname.new</b>, if looking for a 105 * constructor in a subpackage</li> 106 * <li><b>Classname.methodname</b>, if looking for a static method</li> 107 * <li><b>subpackage.subpackage.Classname.methodname</b>, if looking for a 108 * static method of a class in a subpackage</li> 109 * </ul> 110 * @param parameters Object[] of parameters 111 * @return a MethodFunction, a ConstructorFunction or null if no function 112 * is found 113 */ 114 public Function getFunction( 115 String namespace, 116 String name, 117 Object[] parameters) { 118 if ((namespace == null && this.namespace != null) //NOPMD 119 || (namespace != null && !namespace.equals(this.namespace))) { 120 return null; 121 } 122 123 if (parameters == null) { 124 parameters = EMPTY_ARRAY; 125 } 126 127 if (parameters.length >= 1) { 128 Object target = TypeUtils.convert(parameters[0], Object.class); 129 if (target != null) { 130 Method method = 131 MethodLookupUtils.lookupMethod( 132 target.getClass(), 133 name, 134 parameters); 135 if (method != null) { 136 return new MethodFunction(method); 137 } 138 139 if (target instanceof NodeSet) { 140 target = ((NodeSet) target).getPointers(); 141 } 142 143 method = 144 MethodLookupUtils.lookupMethod( 145 target.getClass(), 146 name, 147 parameters); 148 if (method != null) { 149 return new MethodFunction(method); 150 } 151 152 if (target instanceof Collection) { 153 Iterator iter = ((Collection) target).iterator(); 154 if (iter.hasNext()) { 155 target = iter.next(); 156 if (target instanceof Pointer) { 157 target = ((Pointer) target).getValue(); 158 } 159 } 160 else { 161 target = null; 162 } 163 } 164 } 165 if (target != null) { 166 Method method = 167 MethodLookupUtils.lookupMethod( 168 target.getClass(), 169 name, 170 parameters); 171 if (method != null) { 172 return new MethodFunction(method); 173 } 174 } 175 } 176 177 String fullName = classPrefix + name; 178 int inx = fullName.lastIndexOf('.'); 179 if (inx == -1) { 180 return null; 181 } 182 183 String className = fullName.substring(0, inx); 184 String methodName = fullName.substring(inx + 1); 185 186 Class functionClass; 187 try { 188 functionClass = Class.forName(className); 189 } 190 catch (ClassNotFoundException ex) { 191 throw new JXPathException( 192 "Cannot invoke extension function " 193 + (namespace != null ? namespace + ":" + name : name), 194 ex); 195 } 196 197 if (methodName.equals("new")) { 198 Constructor constructor = 199 MethodLookupUtils.lookupConstructor(functionClass, parameters); 200 if (constructor != null) { 201 return new ConstructorFunction(constructor); 202 } 203 } 204 else { 205 Method method = 206 MethodLookupUtils.lookupStaticMethod( 207 functionClass, 208 methodName, 209 parameters); 210 if (method != null) { 211 return new MethodFunction(method); 212 } 213 } 214 return null; 215 } 216 }