Struts example source code file (SpringObjectFactory.java)

This example Struts source code file (SpringObjectFactory.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Struts tags/keywords

applicationcontextaware, autowirecapablebeanfactory, autowirecapablebeanfactory, class, class, configurableapplicationcontext, exception, map, object, object, objectfactory, override, setting, setting, util

The Struts SpringObjectFactory.java source code

/*
 * Copyright 2002-2006,2009 The Apache Software Foundation.
 * 
 * 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 com.opensymphony.xwork2.spring;

import com.opensymphony.xwork2.ObjectFactory;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.UnsatisfiedDependencyException;
import org.springframework.beans.factory.config.AutowireCapableBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import java.util.HashMap;
import java.util.Map;

/**
 * Simple implementation of the ObjectFactory that makes use of Spring's application context if one has been configured,
 * before falling back on the default mechanism of instantiating a new class using the class name. <p/> In order to use
 * this class in your application, you will need to instantiate a copy of this class and set it as XWork's ObjectFactory
 * before the xwork.xml file is parsed. In a servlet environment, this could be done using a ServletContextListener.
 *
 * @author Simon Stewart (sms@lateral.net)
 */
public class SpringObjectFactory extends ObjectFactory implements ApplicationContextAware {
    private static final Logger LOG = LoggerFactory.getLogger(SpringObjectFactory.class);

    protected ApplicationContext appContext;
    protected AutowireCapableBeanFactory autoWiringFactory;
    protected int autowireStrategy = AutowireCapableBeanFactory.AUTOWIRE_BY_NAME;
    private final Map<String, Object> classes = new HashMap();
    private boolean useClassCache = true;
    private boolean alwaysRespectAutowireStrategy = false;

    @Inject(value="applicationContextPath",required=false)
    public void setApplicationContextPath(String ctx) {
        if (ctx != null) {
            setApplicationContext(new ClassPathXmlApplicationContext(ctx));
        }
    }

    /**
     * Set the Spring ApplicationContext that should be used to look beans up with.
     *
     * @param appContext The Spring ApplicationContext that should be used to look beans up with.
     */
    public void setApplicationContext(ApplicationContext appContext)
            throws BeansException {
        this.appContext = appContext;
        autoWiringFactory = findAutoWiringBeanFactory(this.appContext);
    }

    /**
     * Sets the autowiring strategy
     *
     * @param autowireStrategy
     */
    public void setAutowireStrategy(int autowireStrategy) {
        switch (autowireStrategy) {
            case AutowireCapableBeanFactory.AUTOWIRE_AUTODETECT:
                LOG.info("Setting autowire strategy to autodetect");
                this.autowireStrategy = autowireStrategy;
                break;
            case AutowireCapableBeanFactory.AUTOWIRE_BY_NAME:
                LOG.info("Setting autowire strategy to name");
                this.autowireStrategy = autowireStrategy;
                break;
            case AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE:
                LOG.info("Setting autowire strategy to type");
                this.autowireStrategy = autowireStrategy;
                break;
            case AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR:
                LOG.info("Setting autowire strategy to constructor");
                this.autowireStrategy = autowireStrategy;
                break;
            case AutowireCapableBeanFactory.AUTOWIRE_NO:
                LOG.info("Setting autowire strategy to none");
                this.autowireStrategy = autowireStrategy;
                break;
            default:
                throw new IllegalStateException("Invalid autowire type set");
        }
    }

    public int getAutowireStrategy() {
        return autowireStrategy;
    }


    /**
     * If the given context is assignable to AutowireCapbleBeanFactory or contains a parent or a factory that is, then
     * set the autoWiringFactory appropriately.
     *
     * @param context
     */
    protected AutowireCapableBeanFactory findAutoWiringBeanFactory(ApplicationContext context) {
        if (context instanceof AutowireCapableBeanFactory) {
            // Check the context
            return (AutowireCapableBeanFactory) context;
        } else if (context instanceof ConfigurableApplicationContext) {
            // Try and grab the beanFactory
            return ((ConfigurableApplicationContext) context).getBeanFactory();
        } else if (context.getParent() != null) {
            // And if all else fails, try again with the parent context
            return findAutoWiringBeanFactory(context.getParent());
        }
        return null;
    }

    /**
     * Looks up beans using Spring's application context before falling back to the method defined in the {@link
     * ObjectFactory}.
     *
     * @param beanName     The name of the bean to look up in the application context
     * @param extraContext
     * @return A bean from Spring or the result of calling the overridden
     *         method.
     * @throws Exception
     */
    @Override
    public Object buildBean(String beanName, Map<String, Object> extraContext, boolean injectInternal) throws Exception {
        Object o = null;
        
        if (appContext.containsBeanDefinition(beanName)) {
            o = appContext.getBean(beanName);
        } else {
            Class beanClazz = getClassInstance(beanName);
            o = buildBean(beanClazz, extraContext);
        }
        if (injectInternal) {
            injectInternalBeans(o);
        }
        return o;
    }

    /**
     * @param clazz
     * @param extraContext
     * @throws Exception
     */
    @Override
    public Object buildBean(Class clazz, Map<String, Object> extraContext) throws Exception {
        Object bean;

        try {
            // Decide to follow autowire strategy or use the legacy approach which mixes injection strategies
            if (alwaysRespectAutowireStrategy) {
                // Leave the creation up to Spring
                bean = autoWiringFactory.createBean(clazz, autowireStrategy, false);
                injectApplicationContext(bean);
                return injectInternalBeans(bean);
            } else {
                bean = autoWiringFactory.autowire(clazz, AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR, false);
                bean = autoWiringFactory.applyBeanPostProcessorsBeforeInitialization(bean, bean.getClass().getName());
                // We don't need to call the init-method since one won't be registered.
                bean = autoWiringFactory.applyBeanPostProcessorsAfterInitialization(bean, bean.getClass().getName());
                return autoWireBean(bean, autoWiringFactory);
            }
        } catch (UnsatisfiedDependencyException e) {
            if (LOG.isErrorEnabled())
                LOG.error("Error building bean", e);
            // Fall back
            return autoWireBean(super.buildBean(clazz, extraContext), autoWiringFactory);
        }
    }

    public Object autoWireBean(Object bean) {
        return autoWireBean(bean, autoWiringFactory);
    }

    /**
     * @param bean
     * @param autoWiringFactory
     */
    public Object autoWireBean(Object bean, AutowireCapableBeanFactory autoWiringFactory) {
        if (autoWiringFactory != null) {
            autoWiringFactory.autowireBeanProperties(bean,
                    autowireStrategy, false);
        }
        injectApplicationContext(bean);

        injectInternalBeans(bean);

        return bean;
    }

    private void injectApplicationContext(Object bean) {
        if (bean instanceof ApplicationContextAware) {
            ((ApplicationContextAware) bean).setApplicationContext(appContext);
        }
    }

    public Class getClassInstance(String className) throws ClassNotFoundException {
        Class clazz = null;
        if (useClassCache) {
            synchronized(classes) {
                // this cache of classes is needed because Spring sucks at dealing with situations where the
                // class instance changes
                clazz = (Class) classes.get(className);
            }
        }

        if (clazz == null) {
            if (appContext.containsBean(className)) {
                clazz = appContext.getBean(className).getClass();
            } else {
                clazz = super.getClassInstance(className);
            }

            if (useClassCache) {
                synchronized(classes) {
                    classes.put(className, clazz);
                }
            }
        }

        return clazz;
    }

    /**
     * This method sets the ObjectFactory used by XWork to this object. It's best used as the "init-method" of a Spring
     * bean definition in order to hook Spring and XWork together properly (as an alternative to the
     * org.apache.struts2.spring.lifecycle.SpringObjectFactoryListener)
     * @deprecated Since 2.1 as it isn't necessary
     */
    @Deprecated public void initObjectFactory() {
        // not necessary anymore
    }

    /**
     * Allows for ObjectFactory implementations that support
     * Actions without no-arg constructors.
     *
     * @return false
     */
    @Override
    public boolean isNoArgConstructorRequired() {
        return false;
    }

    /**
     *  Enable / disable caching of classes loaded by Spring.
     *
     * @param useClassCache
     */
    public void setUseClassCache(boolean useClassCache) {
        this.useClassCache = useClassCache;
    }

    /**
     * Determines if the autowire strategy is always followed when creating beans
     *
     * @param alwaysRespectAutowireStrategy True if the strategy is always used
     */
    public void setAlwaysRespectAutowireStrategy(boolean alwaysRespectAutowireStrategy) {
        this.alwaysRespectAutowireStrategy = alwaysRespectAutowireStrategy;
    }
}