Spring整合web开发

正常整合Servlet和Spring没有问题的

public class UserServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");UserService userService = (UserService) applicationContext.getBean("userService");userService.sayHello();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}
}

但是每次执行Servlet的时候都要加载Spring配置,加载Spring环境,极大地降低效率!!!

解决办法
　　1:在Servlet的init方法中加载Spring配置文件?(不好)
　　　　当前这个Servlet可以使用,但是其他的Servlet用不了了!!!如果要使用，必须每个Servlet的init方法中都要加载Spring配置文件，太麻烦(pass)
　　2:将加载的信息内容放到ServletContext中(正确)
　　　　ServletContext对象是全局的对象.服务器启动的时候创建的.在创建ServletContext的时候就加载Spring的环境,ServletContextListener用于监听ServletContext对象的创建和销毁
　　　　使用方法
　　　　　　1:导入Spring web开发jar包:spring-web-3.2.0.RELEASE.jar
　　　　　　2:将Spring容器初始化，交由web容器负责,配置核心监听器 ContextLoaderListener,配置全局参数contextConfigLocation(用于指定Spring的框架的配置文件位置)
　　　　　　　　在web.xml中配置

<listener><listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<context-param><param-name>contextConfigLocation</param-name><param-value>classpath:applicationContext.xml</param-value>
</context-param>

　　　　　　　　修改程序的代码

public class UserServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/*也可用这种方式获得applicationContext:WebApplicationContext applicationContext = (WebApplicationContext) getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);*/WebApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(getServletContext());UserService userService = (UserService) applicationContext.getBean("userService");userService.sayHello();}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}
}