org.apache.beehive.controls.api.bean.Controls.java Source code

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Here is the source code for org.apache.beehive.controls.api.bean.Controls.java

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/*
 * 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.
 *
 * $Header:$
 */
package org.apache.beehive.controls.api.bean;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

import org.apache.beehive.controls.api.properties.PropertyMap;
import org.apache.beehive.controls.api.context.ControlBeanContext;
import org.apache.beehive.controls.api.ControlException;
import org.apache.beehive.controls.spi.bean.ControlFactory;
import org.apache.beehive.controls.spi.bean.JavaControlFactory;
import org.apache.commons.discovery.tools.DiscoverClass;

/**
 * Helper class for using controls.  Includes static methods to help instantiate controls, and initialize
 * declarative control clients.
 */
public class Controls {
    final private static String DEFAULT_FACTORY_CLASS = JavaControlFactory.class.getName();

    /**
     * Factory method for instantiating controls.  Controls instantiated using this method will be associated with the
     * current thread-local ControlBeanContext (possibly none), and have an auto-generated ID.
     *
     * @param cl the classloader used to load the ControlBean.  If null, the system classloader will be used.
     * @param beanName the fully qualified name of the ControlBean class.
     * @param props an optional PropertyMap containing initial property values for the control.  May be null.
     * @return an instance of the specified ControlBean.
     * @throws ClassNotFoundException
     */
    public static ControlBean instantiate(ClassLoader cl, String beanName, PropertyMap props)
            throws ClassNotFoundException {
        return instantiate(cl, beanName, props, null, null);
    }

    /**
     * Factory method for instantiating controls.
     *
     * @param cl the classloader used to load the ControlBean.  If null, the system classloader will be used.
     * @param beanName the fully qualified name of the ControlBean class.
     * @param props an optional PropertyMap containing initial property values for the control.  May be null.
     * @param cbc the ControlBeanContext that will nest the created control.  If null, the thread-local context
     *            (possibly none) will be used.
     * @param id a unique ID for the created control.  If null, an ID will be auto-generated.
     * @return an instance of the specified ControlBean.
     * @throws ClassNotFoundException
     */
    public static ControlBean instantiate(ClassLoader cl, String beanName, PropertyMap props,
            ControlBeanContext cbc, String id) throws ClassNotFoundException {
        Class beanClass = (cl == null) ? Class.forName(beanName) : cl.loadClass(beanName);
        return instantiate(beanClass, props, cbc, id);
    }

    /**
     * Factory method for instantiating controls.
     *
     * @param beanClass the ControlBean class to instantiate
     * @param props an optional PropertyMap containing initial property values for the control.  
     * may be null.
     * @param context the ControlBeanContext that will nest the created control.  If null, the 
     * thread-local context (possibly none) will be used.
     * @param id a unique ID for the created control.  If null, an ID will be auto-generated.
     * @return an instance of the specified ControlBean.
     */
    public static <T extends ControlBean> T instantiate(Class<T> beanClass, PropertyMap props,
            ControlBeanContext context, String id) {
        try {
            DiscoverClass discoverer = new DiscoverClass();
            Class factoryClass = discoverer.find(ControlFactory.class, DEFAULT_FACTORY_CLASS);
            ControlFactory factory = (ControlFactory) factoryClass.newInstance();
            return factory.instantiate(beanClass, props, context, id);
        } catch (Exception e) {
            throw new ControlException("Exception creating ControlBean", e);
        }
    }

    /**
     * Helper method for initializing instances of declarative control clients (objects that use controls via @Control
     * and @EventHandler annotations).  This method runs the client-specific generated ClientInitializer class to do
     * its initialization work.
     *
     * @param cl the classloader used to load the ClientInitializer.  If null, defaults to the classloader used to
     *           load the client object being initialized.
     * @param client the client object being initialized.
     * @param cbc the ControlBeanContext to be associated with the client object (that will nest the controls the client
     *            defines).  If null, the thread-local context (possibly none) will be used.
     * @throws ControlException
     * @throws ClassNotFoundException
     */
    public static void initializeClient(ClassLoader cl, Object client, ControlBeanContext cbc)
            throws ClassNotFoundException {
        Class clientClass = client.getClass();
        String clientName = clientClass.getName();

        if (cl == null)
            cl = clientClass.getClassLoader();

        String initName = clientName + "ClientInitializer";
        Class initClass = cl.loadClass(initName);

        try {
            Method m = initClass.getMethod("initialize", ControlBeanContext.class, clientClass);
            m.invoke(null, cbc, client);
        } catch (Throwable e) {
            if (e instanceof InvocationTargetException) {
                if (e.getCause() != null) {
                    e = e.getCause();
                }
            }

            throw new ControlException(
                    "Exception trying to run client initializer: " + e.getClass().getName() + ", " + e.getMessage(),
                    e);
        }
    }
}