spring集成servlet的疑惑
<servlet> <description></description> <display-name>UserActionImpl2</display-name> <servlet-name>UserActionImpl2</servlet-name> <servlet-class>com.action.MyAction</servlet-class> </servlet> <servlet-mapping> <servlet-name>UserActionImpl2</servlet-name> <url-pattern>/user</url-pattern> </servlet-mapping>
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package com.action;import java.io.IOException;import javax.servlet.Servlet;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;/** * Servlet implementation class UserAction */public class MyAction extends HttpServlet {private static final long serialVersionUID = 1L;protected Servlet servlet;/** * @see HttpServlet#HttpServlet() */ public MyAction() { super(); }/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {servlet.service(request, response);}@Overridepublic void init() throws ServletException {System.out.println("init");String servletName = getServletConfig().getServletName(); WebApplicationContext webapplicationcontext = WebApplicationContextUtils .getRequiredWebApplicationContext(getServletContext()); this.servlet = (Servlet) webapplicationcontext.getBean(servletName); }/** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {servlet.service(request, response);}}package com.action.impl;import java.io.IOException;import javax.servlet.Servlet;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;import com.action.MyAction;import com.pojo.User;import com.services.UserServices;public class UserActionImpl2 extends MyAction {private static final long serialVersionUID = 1L;private static final int size = 5;private UserServices userServices;public void setUserServices(UserServices userServices) {this.userServices = userServices;}@Overrideprotected void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {}@Overrideprotected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}protected Servlet servlet;@Overridepublic void init() throws ServletException {System.out.println("init children");String servletName = getServletConfig().getServletName(); WebApplicationContext webapplicationcontext = WebApplicationContextUtils .getRequiredWebApplicationContext(getServletContext()); this.servlet = (Servlet) webapplicationcontext.getBean(servletName); }}为什么web.xml里面一定得配置com.action.Myaction才能获得spring提供的servlet对象，配置子类UserActonImpl2，也是通过init从spring获取servlet对象，为什么userServices为NULL？
我对配置子类UserActonImpl2的理解：因为UserActonImpl2已经从web服务器获取到，然后通过init方法来对servlet注入对象！这样就不会为userServices注入对象了！
对配置父类com.action.Myaction不能很理解，求javaeye的哥哥姐姐们指点下，解释下这2者是怎么获取servlet对象的，还有就是怎么样可以在web.xml里面直接配置子类UserActonImpl2能够获取userServices？
语言表达能力有限，描述了N久，才这样，我是hold不住了，哥哥姐姐们一定的hold住