package com.swift;

public class Book {
 private String bookName;

 public void setBook(String bookName) {
  this.bookName = bookName;
 }

 @Override
 public String toString() {
  return "Book [book=" + bookName + "]";
 }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 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配置文件注入属性 -->
<bean id="book" class="com.swift.Book">
<property name="bookName" value="三体——黑暗森林"></property>
</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("/book")
public class BookServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
 public BookServlet() {
  super();
 }
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.setCharacterEncoding("utf-8");
  response.setContentType("text/html;charset=utf-8");
  response.getWriter().append("Served at: ").append(request.getContextPath());
  @SuppressWarnings("resource")
  //就是下边这几句了
  ApplicationContext context=new ClassPathXmlApplicationContext("a.xml");
  Book book=(Book) context.getBean("book");
  String bookInfo=book.fun();
  response.getWriter().println();
  response.getWriter().append(bookInfo);
 }

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

}