Java tutorial
/******************************************************************************* * Copyright (c)2013 Prometheus Consulting * * Licensed 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. *******************************************************************************/ package nz.co.senanque.madura.configuration; import java.lang.reflect.Constructor; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import org.apache.commons.configuration.beanutils.BeanDeclaration; import org.apache.commons.configuration.beanutils.DefaultBeanFactory; import org.apache.commons.configuration.beanutils.XMLBeanDeclaration; import org.apache.commons.configuration.tree.ConfigurationNode; /** * * This is a factory for apache.commons.config. * You can configure it to return any class that takes zero or more constructors like this:<br/> * <code> * <myurl2 config-class="java.net.URL" config-factory="nz.co.senanque.madura.configuration.ConstuctorBeanFactory" * constructor-arg="http://localhost:8080/hello"/> * </code> * <br/> * Multiple constructor arguments just have numbers eg constructor-arg0, constructor-arg1, constructor-arg2 ... * Only String constructor arguments will work and no other setters are called. * * @author Roger Parkinson * @version $Revision: 1.3 $ */ public class ConstructorBeanFactory extends DefaultBeanFactory { /** A map for the so far created instances.*/ private Map<String, Object> beans; public ConstructorBeanFactory() { super(); beans = new HashMap<String, Object>(); } // Creates the bean. Checks if already an instance exists. public synchronized Object createBean(Class beanClass, BeanDeclaration decl, Object param) throws Exception { Map m = decl.getBeanProperties(); XMLBeanDeclaration xmlDecl = (XMLBeanDeclaration) decl; ConfigurationNode n = xmlDecl.getNode(); String nodeName = n.getName(); n = n.getParentNode(); while (n != null) { if (n.getName() != null) nodeName = n.getName() + "/" + nodeName; n = n.getParentNode(); } Object bean = beans.get(nodeName); if (bean != null) { // Yes, there is already an instance return bean; } else { // No, create it now (done by the super class) List<Class> constructorClasses = new ArrayList<Class>(); List<Object> constructorArguments = new ArrayList<Object>(); Object o = m.get("constructor-arg"); if (o != null) { constructorClasses.add(o.getClass()); constructorArguments.add(o); } o = m.get("constructor-arg0"); if (o != null) { constructorClasses.add(o.getClass()); constructorArguments.add(o); } for (int i = 1; i < 10; i++) { o = m.get("constructor-arg" + i); if (o == null) break; constructorClasses.add(o.getClass()); constructorArguments.add(o); } Constructor constructor = beanClass .getDeclaredConstructor(constructorClasses.toArray(new Class[constructorClasses.size()])); bean = constructor.newInstance(constructorArguments.toArray(new Object[constructorArguments.size()])); // Store it in map beans.put(nodeName, bean); return bean; } } }