| package org.apache.commons.digester3.plugins.strategies; |
| |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| |
| import java.util.Properties; |
| |
| import org.apache.commons.digester3.Digester; |
| import org.apache.commons.digester3.plugins.PluginException; |
| import org.apache.commons.digester3.plugins.RuleFinder; |
| import org.apache.commons.digester3.plugins.RuleLoader; |
| |
| /** |
| * A rule-finding algorithm which expects the caller to specify a classname and methodname as plugin properties. |
| * |
| * @since 1.6 |
| */ |
| public class FinderFromClass |
| extends RuleFinder |
| { |
| private static final String DFLT_RULECLASS_ATTR = "ruleclass"; |
| |
| private static final String DFLT_METHOD_ATTR = "method"; |
| |
| private static final String DFLT_METHOD_NAME = "addRules"; |
| |
| private final String ruleClassAttr; |
| |
| private final String methodAttr; |
| |
| private final String dfltMethodName; |
| |
| /** |
| * See {@link #findLoader}. |
| */ |
| public FinderFromClass() |
| { |
| this( DFLT_RULECLASS_ATTR, DFLT_METHOD_ATTR, DFLT_METHOD_NAME ); |
| } |
| |
| /** |
| * Create a rule-finder which invokes a user-specified method on a user-specified class whenever dynamic rules for a |
| * plugin need to be loaded. See the findRules method for more info. |
| * |
| * @param ruleClassAttr must be non-null. |
| * @param methodAttr may be null. |
| * @param dfltMethodName may be null. |
| */ |
| public FinderFromClass( final String ruleClassAttr, final String methodAttr, final String dfltMethodName ) |
| { |
| this.ruleClassAttr = ruleClassAttr; |
| this.methodAttr = methodAttr; |
| this.dfltMethodName = dfltMethodName; |
| } |
| |
| /** |
| * If there exists a property with the name matching constructor param ruleClassAttr, then load the specified class, |
| * locate the appropriate rules-adding method on that class, and return an object encapsulating that info. |
| * <p> |
| * If there is no matching property provided, then just return null. |
| * <p> |
| * The returned object (when non-null) will invoke the target method on the selected class whenever its addRules |
| * method is invoked. The target method is expected to have the following prototype: |
| * <code> public static void xxxxx(Digester d, String patternPrefix); </code> |
| * <p> |
| * The target method can be specified in several ways. If this object's constructor was passed a non-null methodAttr |
| * parameter, and the properties defines a value with that key, then that is taken as the target method name. If |
| * there is no matching property, or the constructor was passed null for methodAttr, then the dfltMethodName passed |
| * to the constructor is used as the name of the method on the target class. And if that was null, then |
| * DFLT_METHOD_NAME will be used. |
| * <p> |
| * When the user explicitly declares a plugin in the input xml, the xml attributes on the declaration tag are passed |
| * here as properties, so the user can select any class in the classpath (and any method on that class provided it |
| * has the correct prototype) as the source of dynamic rules for the plugged-in class. |
| * |
| * @param digester The digester instance where locating plugin classes |
| * @param pluginClass The plugin Java class |
| * @param p The properties object that holds any xml attributes the user may have specified on the plugin |
| * declaration in order to indicate how to locate the plugin rules. |
| * @return a source of digester rules for the specified plugin class. |
| * @throws PluginException if the algorithm finds a source of rules, but there is something invalid |
| * about that source. |
| */ |
| @Override |
| public RuleLoader findLoader( final Digester digester, final Class<?> pluginClass, final Properties p ) |
| throws PluginException |
| { |
| final String ruleClassName = p.getProperty( ruleClassAttr ); |
| if ( ruleClassName == null ) |
| { |
| // nope, user hasn't requested dynamic rules to be loaded |
| // from a specific class. |
| return null; |
| } |
| |
| // ok, we are in business |
| String methodName = null; |
| if ( methodAttr != null ) |
| { |
| methodName = p.getProperty( methodAttr ); |
| } |
| if ( methodName == null ) |
| { |
| methodName = dfltMethodName; |
| } |
| if ( methodName == null ) |
| { |
| methodName = DFLT_METHOD_NAME; |
| } |
| |
| Class<?> ruleClass; |
| try |
| { |
| // load the plugin class object |
| ruleClass = digester.getClassLoader().loadClass( ruleClassName ); |
| } |
| catch ( final ClassNotFoundException cnfe ) |
| { |
| throw new PluginException( "Unable to load class " + ruleClassName, cnfe ); |
| } |
| |
| return new LoaderFromClass( ruleClass, methodName ); |
| } |
| |
| } |