spring服务定位器类

此文章是基于　　搭建Jquery+SpringMVC+Spring+Hibernate+MySQL平台

功能：通过持有的Spring应用场景ApplicationContext，可在任何地方获取bean。

1. 服务定位器类：ServiceLocator.java

 package com.ims.common;

 import org.apache.log4j.Logger;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;

 /**
  * 服务定位器
  * 持有Spring的应用场景, 可在任何地方获取bean.
  */
 public final class ServiceLocator implements ApplicationContextAware, DisposableBean {

     private static Logger logger = Logger.getLogger(ServiceLocator.class);
     private static ApplicationContext context = null;

     /**
      * 实现ApplicationContextAware接口, 注入Context到静态变量中.
      * @param context
      */
     @Override
     public void setApplicationContext(ApplicationContext context) {
         logger.debug("Injected the ApplicationContext into ServiceLocator:" + context);
         if (ServiceLocator.context != null) {
             logger.debug("[------------ ApplicationContext in the ServiceLocator " +
                                 "is covered, as the original ApplicationContext is:"
                                             + ServiceLocator.context + " ------------]");
         }
         ServiceLocator.context = context;
     }

     /**
      * 实现DisposableBean接口,在Context关闭时清理静态变量.
      */
     @Override
     public void destroy() throws Exception {
         ServiceLocator.clear();
     }

     /**
      * 取得存储在静态变量中的ApplicationContext.
      * @return
      */
     public static ApplicationContext getApplicationContext() {
         assertContextInjected();
         return context;
     }

     /**
      * 从Spring的应用场景中取得Bean, 自动转型为所赋值对象的类型.
      * @param name bean名称
      * @return bean对象
      */
     @SuppressWarnings("unchecked")
     public static <T> T getService(String name) {
         assertContextInjected();
         return (T) context.getBean(name);
     }

     /**
      * 从Spring的应用场景中取得Bean, 自动转型为所赋值对象的类型.
      * @param requiredType bean类
      * @return bean对象
      */
     public static <T> T getService(Class<T> requiredType) {
         assertContextInjected();
         return context.getBean(requiredType);
     }

     /**
      * 清除ServiceLocator中的ApplicationContext
      */
     public static void clear() {
         logger.debug("Clear ApplicationContext in ServiceLocator :" + context);
         context = null;
     }

     /**
      * 检查ApplicationContext不为空.
      */
     private static void assertContextInjected() {
         if (context == null) {
             throw new IllegalStateException("ApplicaitonContext not injected, " +
                             "as defined in the context.xml ServiceLocator");
         }
     }
 }

2. Spring上下文场景加载监听器：SpringContextLoaderListener.java

 package com.ims.web;

 import javax.servlet.ServletContextEvent;

 import org.springframework.web.context.ContextLoaderListener;

 import com.ims.common.ServiceLocator;

 /**
  * Spring场景加载监听器，用于加载/销毁Spring场景
  */
 public class SpringContextLoaderListener extends ContextLoaderListener {

     private final ServiceLocator locator = new ServiceLocator();

     public SpringContextLoaderListener() {
         super();
     }

     @Override
     public void contextInitialized(ServletContextEvent event) {
         super.contextInitialized(event);

         // 将Spring场景置入服务定位器中
         locator.setApplicationContext(getCurrentWebApplicationContext());
     }

     @Override
     public void contextDestroyed(ServletContextEvent event) {
         try {
             locator.destroy();
         }
         catch (Exception e) {
             e.printStackTrace();
         }        

         super.contextDestroyed(event);
     }
 }

3. 修改 web.xml

如果存在如下代码，则去掉

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>

然后添加上如下代码：

<listener>
     <listener-class>com.ims.web.SpringContextLoaderListener</listener-class>
  </listener>

4. 在 src/applicationContext.xml 中添加如下代码：

<bean class="com.ims.common.ServiceLocator"/>

5. 调用 ServiceLocator.java 中的 getService 函数，可分为按名称或类型获取bean。