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.xsd
			http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
			http://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";
	@Autowired
	private DemoService service;

	/* (non-Javadoc)
	 * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
	 */
	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.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)
	 */
	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
}

DemoService:

package com.demo;

import org.apache.log4j.Logger;
import org.springframework.stereotype.Service;
@Service
public 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 >