Briefly describe session usage and detailed records in java

<!-- 使用@ResponseBody注解所需的2个包 -->
<dependency>
 <groupId>org.codehaus.jackson</groupId>
 <artifactId>jackson-core-asl</artifactId>
 <version>1.9.13</version>
</dependency>
<dependency>
 <groupId>org.codehaus.jackson</groupId>
 <artifactId>jackson-mapper-asl</artifactId>
 <version>1.9.13</version>
</dependency>

package test.dmh.session;

import java.util.Enumeration;

import javax.servlet.http.HttpSession;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.bind.support.SessionStatus;

/**
 * @SessionAttributes 只声明了参数test1
 */
@Controller
@SessionAttributes(value={"test1"})
public class HomeController {
 
 private static final Logger logger = LoggerFactory.getLogger(HomeController.class);
 
 @RequestMapping(value = "/show1")
 public String show(ModelMap modelMap, HttpSession session) {
  logger.info("show session");
  for (Object key : modelMap.keySet()) {
   Object value = modelMap.get(key);
   System.out.println(key + " = " + value);
  }
  System.out.println("***********************************");
  Enumeration<String> e = session.getAttributeNames();
  while (e.hasMoreElements()) {
   String s = e.nextElement();
   System.out.println(s + " == " + session.getAttribute(s));
  }
  System.out.println("***********************************");
  return "home";
 }
 
 @RequestMapping("/set1")
 public String setSession(ModelMap modelMap) {
  logger.info("set session 1");
  modelMap.addAttribute("test1", "value 1"); //设置一个在@SessionAttributes中声明过的参数
  modelMap.addAttribute("test2", "value 2"); //设置一个未在@SessionAttributes中声明过的参数
  return "home";
 }
 
 @RequestMapping("/setM")
 public String setSessionM(Model model) {
  logger.info("set session 1");
  model.addAttribute("test1", "value 1"); //设置一个在@SessionAttributes中声明过的参数
  model.addAttribute("test2", "value 2"); //设置一个未在@SessionAttributes中声明过的参数
  return "home";
 }
 
 @RequestMapping("/clear1")
 public String clear(SessionStatus status) {
  logger.info("clear session 1");
  status.setComplete();
  return "home";
 }
 
}

package test.dmh.session.controller;

import javax.servlet.http.HttpSession;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;

/**
 * 没有使用@SessionAttributes注解
 */
@Controller
public class IndexController {
 
 private static final Logger logger = LoggerFactory.getLogger(IndexController.class);
 
 @RequestMapping("/set2")
 public String setSession(ModelMap modelMap, HttpSession session) {
  logger.info("set session 2 : without @SessionAttributes");
  modelMap.addAttribute("test3", "value 3");
  session.setAttribute("test4", "value 4");
  return "home";
 }
 
}

package test.dmh.session.controller;

import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpSession;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.bind.support.SessionStatus;

@Controller
@SessionAttributes(value={"test5", "index"})
public class IndexController2 {
 
 private static final Logger logger = LoggerFactory.getLogger(IndexController2.class);
 
 @RequestMapping("/set3")
 public String setSession(ModelMap modelMap, HttpSession session) {
  logger.info("set session 3");
  modelMap.addAttribute("test5", "value 5");
  session.setAttribute("test6", "value 6");
  
  ModelMap map = new ModelMap();
  map.addAttribute("test7", "value 7");
  
  this.setValueToSession(modelMap, session, "Hello World");
  
  return "home";
 }
 
 @ResponseBody
 @RequestMapping(value="/login")
 public Map<String, Object> login(ModelMap modelMap, HttpSession session) {
  logger.info("login");
  
  Map<String, Object> map = new HashMap<String, Object>();
  
  map.put("success", true);
  map.put("info", "登录成功！");
  
  modelMap.addAttribute("testAjax", "test ajax value");
  session.setAttribute("httpTestAjax", "http test ajax Value");
  
  setValueToSession(modelMap, session, "This is Ajax");
  
  return map;
 }
 
 private void setValueToSession(ModelMap modelMap, HttpSession session, String value) {
  logger.info("set session private");
  modelMap.addAttribute("index", value);
  session.setAttribute("httpIndex", value);
 }
 
 @RequestMapping("/clear2")
 public String clear(SessionStatus status) {
  logger.info("clear session 2");
  status.setComplete();
  return "home";
 }
 
 @RequestMapping(value = "/show2")
 public String show(ModelMap modelMap, HttpSession session) {
  logger.info("show session");
  for (Object key : modelMap.keySet()) {
   Object value = modelMap.get(key);
   System.out.println(key + " = " + value);
  }
  System.out.println("***********************************");
  Enumeration<String> e = session.getAttributeNames();
  while (e.hasMoreElements()) {
   String s = e.nextElement();
   System.out.println(s + " == " + session.getAttribute(s));
  }
  System.out.println("***********************************");
  return "home";
 }
 
}

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
4 <html>
<head>
 <title>Home</title>
</head>
<body>
<h1>
 Hello world! 
</h1>

<p> The test1 is ${sessionScope.test1}. </p>
<p> The test2 is ${sessionScope.test2}. </p>
<p> The test3 is ${sessionScope.test3}. </p>
<p> The test4 is ${sessionScope.test4}. </p>
<p> The test5 is ${sessionScope.test5}. </p>
<p> The test6 is ${sessionScope.test6}. </p>
<p> The test7 is ${sessionScope.test7}. </p>
<p> The index is ${sessionScope.index}. </p>
<p> The httpIndex is ${sessionScope.httpIndex}. </p>

<br>
<input type="button" value="test" onclick="test();">

<script src="resources/js/jquery.min.js"></script>
<script type="text/javascript">
function test() {
 $.ajax({
  type : "POST",
  url : "login",
  dataType : "json",
  success : function(data) {
   console.log(data);
   window.open("/session/test", "_self");
  },
  error : function() {
   alert("出错了！");
  }
 });
}
</script>
</body>
</html>

package test.dmh.session.controller;

import java.util.Enumeration;

import javax.servlet.http.HttpSession;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;
import org.springframework.web.bind.support.SessionStatus;

@Controller
@SessionAttributes(value={"index1", "index2"}, types={String.class, Integer.class})
public class IndexController3 {
 
 private static final Logger logger = LoggerFactory.getLogger(IndexController3.class);
 
 @RequestMapping("/setIndex")
 public String setSession(ModelMap modelMap) {
  logger.info("set session index");
  modelMap.addAttribute("index1", "aaa");
  modelMap.addAttribute("index2", "bbb");
  modelMap.addAttribute("index2", "ccc");
  modelMap.addAttribute("DDD");
  modelMap.addAttribute("FFF");
  modelMap.addAttribute(22);
  
  return "home";
 }
 
 @RequestMapping(value = "/showIndex")
 public String show(ModelMap modelMap, HttpSession session) {
  logger.info("show session");
  for (Object key : modelMap.keySet()) {
   Object value = modelMap.get(key);
   System.out.println(key + " = " + value);
  }
  System.out.println("***********************************");
  Enumeration<String> e = session.getAttributeNames();
  while (e.hasMoreElements()) {
   String s = e.nextElement();
   System.out.println(s + " == " + session.getAttribute(s));
  }
  System.out.println("***********************************");
  return "home";
 }
 
 @RequestMapping("/clearIndex")
 public String clear(SessionStatus status) {
  logger.info("clear session index");
  status.setComplete();
  return "home";
 }
 
}