spring管理servlet的利器--SimpleServletHandlerAdapter

servlet现在有许多项目仍在使用，一般作为接口调用，很早以前我曾发表过一篇关于《Spring管理Filter和Servlet 》的文章，后来发现spring提供了更为简单的管理servlet的方式，那就是使用SimpleServletHandlerAdapter，基于这个适配器，可以将servlet像普通bean一样声明到spring配置文件中，而无需在web.xml中声明。

先来说一下SimpleServletHandlerAdapter，它是spring提供的处理适配器，专门适配类型为javax.servlet.Servlet的处理器，spring提供了多种适配器，分别负责不同的处理器适配，比如我们现在很常用的基于注解的MVC,就是使用的AnnotationMethodHandlerAdapter这个适配器。

不过这里要说明的是，spring的默认策略中并不包含SimpleServletHandlerAdapter，所以在使用时需要明确声明，另外，如果还用了其它的处理器，也要明确声明那个适配器，因为默认配置已经被替换了，比如用了springMVC注解，就需要明确声明AnnotationMethodHandlerAdapter这个适配器。

一个简单的基于注解注入的配置文件如下：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  xmlns:context="http://www.springframework.org/schema/context"xmlns:ehcache="http://www.springmodules.org/schema/ehcache"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsdhttp://www.springmodules.org/schema/ehcache http://www.springmodules.org/schema/cache/springmodules-ehcache.xsd"default-lazy-init="true"><!--启用注解   定义组件查找规则 --><context:component-scan base-package="com.demo"><context:include-filter type="annotation"expression="org.springframework.stereotype.Service" /></context:component-scan><!-- servlet适配器，这里必须明确声明，因为spring默认没有初始化该适配器 --><bean id="servletHandlerAdapter" class="org.springframework.web.servlet.handler.SimpleServletHandlerAdapter"/> <!-- demo servlet --> <bean name="/demo.do" class="com.demo.DemoServlet"/></beans>

此时web.xml中无需声明servlet配置。

DemoServlet:

package com.demo;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.beans.factory.annotation.Autowired;@SuppressWarnings("serial")public class DemoServlet extends HttpServlet{private static final String CONTENT_TYPE = "application/xml; charset=UTF-8";@Autowiredprivate DemoService service;/* (non-Javadoc) * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) */@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubresponse.setContentType(CONTENT_TYPE);        response.setHeader("Pragma", "No-cache");        response.setHeader("Cache-Control", "no-cache");        response.setDateHeader("Expires", 0);String result = service.testDemo();PrintWriter out = response.getWriter();out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");out.println("<root>\n");out.println("<result>"+result+"</result>\n");out.println("</root>\n");out.flush();out.close();}/* (non-Javadoc) * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) */@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

DemoService:

package com.demo;import org.apache.log4j.Logger;import org.springframework.stereotype.Service;@Servicepublic class DemoService {private static Logger logger = Logger.getLogger(DemoService.class);/**                                                          * 描述 : <描述函数实现的功能>. <br>*<p>                                                                                                                                                                                                                * @return                                                                                       */public String testDemo(){logger.info("demo");return "test";}}

启动服务器，请求http://localhost:8080/servlet/demo.do

输出结果：

<?xml version="1.0" encoding="UTF-8" ?>

<root>

  <result>test</result>

</root>