package com.swift;

public class User {
 private String userName;
 
 public void setUserName(String userName) {
  this.userName = userName;
 }
 public String fun() {
  return "User's fun is ready."+this.userName;
 }
}

<?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:p="http://www.springframework.org/schema/p"
 xsi:schemaLocation="
  http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- IoC 控制反转 SpringSpring根据XML配置文件生成对象 -->
<bean id="user" class="com.swift.User" p:userName="peach"></bean>
</beans>

package com.swift;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

@WebServlet("/test")
public class TestIOC extends HttpServlet {
 private static final long serialVersionUID = 1L;
 public TestIOC() {
  super();
 }
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.getWriter().append("Served at: ").append(request.getContextPath());
  @SuppressWarnings("resource")
  //就是下边这几句了
  ApplicationContext context=new ClassPathXmlApplicationContext("applicationContext.xml");
  User user=(User) context.getBean("user");
  String userInfo=user.fun();
  response.getWriter().println();
  response.getWriter().append(userInfo);
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  doGet(request, response);
 }

}