Spring容器启动后自动执行Servlet进行预处理
本文是转载自：http://www.cnblogs.com/chenguanwei/archive/2010/04/03/1703837.html。
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通常做法是定义一个Servlet，并在web.xml中配置Servlet的启动顺序<load-on-startup>的值在DispatcherServlet之后。但这样做的缺点是在Servlet中无法使用Spring的依赖注入功能，只能使用WebApplicationContext的getBean()方法获取bean。
找到的解决办法如下：
1、自定义一个用于代理启动Servlet的类DelegatingServletProxy：
package com.test.common.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;public class DelegatingServletProxy extends GenericServlet {private String targetBean;private Servlet proxy;@Overridepublic void service(ServletRequest arg0, ServletResponse arg1)throws ServletException, IOException {proxy.service(arg0, arg1);}@Overridepublic void init() throws ServletException {this.targetBean = getServletName();getServletBean();proxy.init(getServletConfig());}private void getServletBean() {WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());this.proxy = (Servlet)wac.getBean(targetBean);}}?2、编写启动Servlet：
package com.test.common.util;import java.io.IOException;import java.util.List;import javax.annotation.Resource;import javax.servlet.ServletConfig;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 cn.edu.swu.oa.agency.model.Department;import cn.edu.swu.oa.agency.model.Group;import cn.edu.swu.oa.agency.service.DepService;import cn.edu.swu.oa.agency.service.GroService;import cn.edu.swu.oa.common.model.SysCode;import cn.edu.swu.oa.safe.model.User;import cn.edu.swu.oa.safe.service.UserService;/** * * * 类型解释：Spring启动完成后执行初始化操作 * 类型表述：预读某些实体的Key-Value，放入map，方便以后使用 * @author * @version * */@Component("initialServlet")public class InitialServlet extends HttpServlet {private static final long serialVersionUID = 1L;@Resourceprivate UserService userService;@Resourceprivate DepService depService; @Resourceprivate GroService groService; /** * @see HttpServlet#HttpServlet() */ public InitialServlet() { super(); }/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub}@Overridepublic void init(ServletConfig config) throws ServletException {//初始化eserMapList<User> users = userService.getUsers();for(int i = 0; i < users.size(); i++) {User user = users.get(i);Integer userId = user.getUserId();String userName = user.getUserName();SysCode.userMap.put(userId, userName);}//初始化depMapList<Department> deps = depService.getAllDeps();for(int i = 0; i < deps.size(); i++) {Department dep = deps.get(i);Integer depId = dep.getDepId();String depName = dep.getDepName();SysCode.depMap.put(depId, depName);}//初始化groMapList<Group> gros = groService.getAllGroups();for(int i = 0; i < gros.size(); i++) {Group gro = gros.get(i);Integer groId = gro.getGroId();String groName = gro.getGroName();SysCode.groMap.put(groId, groName);}}}?3、在web.xml文件中配置InitialServlet ：
<servlet> <description></description> <display-name>InitialServlet</display-name> <servlet-name>initialServlet</servlet-name> <servlet-class> com.test.common.util.DelegatingServletProxy </servlet-class> <load-on-startup>2</load-on-startup></servlet><servlet-mapping> <servlet-name>initialServlet</servlet-name> <url-pattern>/InitialServlet</url-pattern></servlet-mapping>?完成这些操作后，就可以在Spring容器启动后执行自定义的Servlet，并且在自定义Servlet中可以使用Spring Annotation的自动注入功能。<script></script>