用Spring将Service注入到Servlet中（注解模式）

〈转〉原文地址：http://www.coridc.com/archives/2758.html

将Servlet与Spring进行整合，使Service层能注入到Servlet中，当然，这里的Servlet是纯正的Servlet 3，而不是Struts的ActionServlet或者是SpringMVC啥啥的。

解决方法有两种（推荐使用第二种）

方法一：

直接重写Servlet的Init()方法，代码如下：

public void init(ServletConfig servletConfig) throws ServletException {
ServletContext servletContext = servletConfig.getServletContext();
WebApplicationContext webApplicationContext = WebApplicationContextUtils
.getWebApplicationContext(servletContext);
AutowireCapableBeanFactory autowireCapableBeanFactory = webApplicationContext
.getAutowireCapableBeanFactory();
autowireCapableBeanFactory.configureBean(this, BEAN_NAME);
}
这里的BEAN_NAME即为我们需要注入到Spring容器中的服务，但这并不是一个好的方法，因为我们需要在每一个Servlet中都进行这样的操作。

方法二：

我们可以写一个类似于“org.springframework.web.struts.DelegatingRequestProcessor”的委托的Bean，然后通过配置的方法把我们的服务注入到servlet中，具体方法如下，

Step 1：编写委托类DelegatingServletProxy

package com.telek.pba.base.util;

import java.io.IOException;

import javax.servlet.GenericServlet;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;


/**
* 以下是类似org.springframework.web.struts.DelegatingRequestProcessor的一个委托
* 用于通过配置的方法，在Servlet中注入Service
* @author liyinwei
*
*/
public class DelegatingServletProxy extends GenericServlet{

/**
*
*/
private static final long serialVersionUID = 1L;
private String targetBean;
private Servlet proxy;

@Override
public void service(ServletRequest req, ServletResponse res)
throws ServletException, IOException {
proxy.service(req, res);
}

/**
* 初始化
*/
public void init() throws ServletException {
this.targetBean = getServletName();
getServletBean();
proxy.init(getServletConfig());
}

/**
* 获取Bean
*/
private void getServletBean() {
WebApplicationContext wac = WebApplicationContextUtils
.getRequiredWebApplicationContext(getServletContext());
this.proxy = (Servlet) wac.getBean(targetBean);
}

}
Step 2：修改Web.xml配置

在纯Servlet模式下，我们的配置方式如下（以下由于代码高亮插件的问题，请将代码中的#替换成尖括号）

<servlet>
  <description>活动发起模块活动查询分页Servlet</description>
  #display-name#launchActivityQueryServlet#/display#
  #servlet-name#LaunchActivityQueryServlet#/servlet-name#
  #servlet-class#com.telek.pba.launch.servlet.LaunchActivityQueryServlet#/servlet-class#
#servlet#

#servlet-mapping#
  #servlet-name#LaunchActivityQueryServlet#/servlet-name#
  #url-pattern#/servlet/launch/LaunchActivityQueryServlet#/url-pattern#
#/servlet-mapping#
</servlet>
如果采用我们这种代理的方法，则配置应该修改为：

<servlet>
  <description>活动发起模块活动查询分页Servlet</description>
  #display-name#launchActivityQueryServlet#/display#
  #servlet-name#launchActivityQueryServlet#/servlet-name#
  #servlet-class#com.telek.pba.base.util.DelegatingServletProxy#/servlet-class#
#servlet#

#servlet-mapping#
  #servlet-name#launchActivityQuery#/servlet-name#
  #url-pattern#/servlet/launch/LaunchActivityQueryServlet#/url-pattern#
#/servlet-mapping#
</servlet>
注意：默认情况下，Servlet的配置中，LaunchActivityQuery的首字母一般为大写，而我们的标题中已注明，我们采用Spring的注解模式，如果是自动扫描注解的话，默认情况下，注解的value值为首字母小写，即：launchActivityQuery，因此，在我们新的配置中，要注意将首字母改为小写，否则会报无法找到Bean的错误。

Step 3：至此，我们就可以像SSH的注入方式一样，注入Servlet了，以下是个小示例：

package com.telek.pba.launch.servlet;

import java.io.IOException;

import javax.annotation.Resource;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Component;

import com.telek.pba.base.model.PbaUserInfo;
import com.telek.pba.launch.dao.IPbaActivityInfoCurrentDAO;

@Component
public class LaunchActivityQueryServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

//注入IPbaActivityInfoCurrentDAO
@Resource
private IPbaActivityInfoCurrentDAO pbaActivityInfoCurrentDAO;


/**
* Constructor of the object.
*/
public LaunchActivityQueryServlet() {
super();
}

/**
* Destruction of the servlet. <br />
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}

/**
* The doGet method of the servlet. <br />
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//sth to do
}

/**
* The doPost method of the servlet. <br />
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//sth to do
}

/**
* Initialization of the servlet. <br />
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}

}
最后，请留心在Spring配置文件中，配置上自动扫描包的路径：

<context:component -scan base-package="com.telek.pba.*.dao.impl,
com.telek.pba.*.service.impl,
com.telek.pba.*.servlet"></context:component>
大功告成！