如何用Spring将Service注入到Servlet中

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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; @Overridepublic 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

<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>launchActivityQueryServlet</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; @Componentpublic class LaunchActivityQueryServlet extends HttpServlet { private static final long serialVersionUID = 1L; //注入IPbaActivityInfoCurrentDAO@Resourceprivate 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！