json包下载
- 下载jar包当然是下大厂滴
- 推荐Alibaba的fastjson
- 推荐Google的gjson
- 本文讲fastjson
https://github.com/alibaba/fastjson.git
json的常见格式
- key - value 键值对
{"key":"value"}
- 多个key - value对
{"key1":"value", "key2":"value"}
- Java中的List集合
[
{"k1":"v1", "k2":"v2"},
{"k1":"v1", "k2":"v2"}
]
- Java中的map集合（字典）
{
"key1": {"k1":"v1", "k2":"v2"},
"key2": {"k1":"v1", "k2":"v2"}
}
fast-json包使用–Java中对象转换为json字符串
- 先以学生实体类为demo
package com.lovely.entity;
import java.sql.Date;
import java.sql.Timestamp;
import com.alibaba.fastjson.annotation.JSONField;
public class Student {
private Integer id;
private String name;
private Integer age;
@JSONField(format="yyyy-MM-dd")
private Date date;
@JSONField(format="yyyy-MM-dd HH:mm:ss")
private Timestamp time;
public Student() {}
public Student(Integer id, String name, Integer age, Date date,
Timestamp time) {
super();
this.id = id;
this.name = name;
this.age = age;
this.date = date;
this.time = time;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public Timestamp getTime() {
return time;
}
public void setTime(Timestamp time) {
this.time = time;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age
+ ", date=" + date + ", time=" + time + "]\n";
}
}
- 把学生对象，list集合，map集合转换为json字符串
// 对于有日期的在属性上加上注解！上面加了。
static Student stu1 = new Student(1, "rye", 20, new Date(System.currentTimeMillis()), new Timestamp(System.currentTimeMillis()));
static Student stu2 = new Student(2, "bitQian", 19, new Date(System.currentTimeMillis()), new Timestamp(System.currentTimeMillis()));
/**
* 对象转换为json字符串 (有时间 日期的 加上@JSONField(format="yyyy-MM-dd") 注解)
* {"key1":"value", "key2":"value"}
*/
static void objToJson1() {
// 对于日期的转型 字段要添加注解
Object json = JSON.toJSONString(stu1, true);
System.out.println(json);
}
/**
* 集合转成json字符串
* [
* {"k1":"v1", "k2":"v2"},
* {"k1":"v1", "k2":"v2"}
* ]
*/
static String arrToJson2() {
List<Student> list = new ArrayList<Student>();
list.add(stu1);
list.add(stu2);
String json = JSON.toJSONString(list, true);
System.out.println(json);
return json;
}
/**
* map集合转换为json字符串
* {
* "key1": {"k1":"v1", "k2":"v2"},
* "key2": {"k1":"v1", "k2":"v2"}
* }
*/
static String mapToJson3() {
Map<String, Student> map = new LinkedHashMap<>();
map.put("stu1", stu1);
map.put("stu2", stu2);
String json = JSON.toJSONString(map, true);
System.out.println(json);
return json;
}
- json字符串转换为对象
// 返序列化 把json字符串->student对象/集合对象/map字典对象
static void jsonToObj1() {
String json = JSON.toJSONString(stu1);
Student obj = JSON.parseObject(json, Student.class);
// 重写了student toString()
System.out.println(obj);
}
static void jsonToArr2() {
String json = arrToJson2();
List<Student> list = JSON.parseArray(json, Student.class);
System.out.println(list);
}
static void jsonToMap3() {
String json = mapToJson3();
Map<?, ?> map = JSON.parseObject(json, Map.class);
System.out.println(map);
}
- 测试map的json格式转换为map集合
public class Test1 {
public static void main(String[] args) {
// objToJson1();
// arrToJson2();
// mapToJson3();
// jsonToObj1();
// jsonToArr2();
jsonToMap3();
}
}
{
"stu1":{
"age":20,
"date":"2020-07-10",
"id":1,
"name":"rye",
"time":"2020-07-10 21:13:31"
},
"stu2":{
"age":19,
"date":"2020-07-10",
"id":2,
"name":"bitQian",
"time":"2020-07-10 21:13:31"
}
}
{stu1={"id":1,"time":"2020-07-10 21:13:31","name":"rye","age":20,"date":"2020-07-10"}, stu2={"id":2,"time":"2020-07-10 21:13:31","name":"bitQian","age":19,"date":"2020-07-10"}}
Ajax请求servlet，以json作为数据格式交互
- 后台servlet
package com.lovely.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.alibaba.fastjson.JSON;
import com.lovely.entity.Student;
public class LoadDataServlet extends HttpServlet {
/**
* @author echo lovely
*
*/
private static final long serialVersionUID = 1L;
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String stuJson = "";
/**
*三种json(object list map)对象的取值
*/
String msg = req.getParameter("msg");
Student stu1 = new Student();
stu1.setId(1);
stu1.setName("rye");
stu1.setAge(20);
Student stu2 = new Student();
stu2.setId(2);
stu2.setName("bitQian");
stu2.setAge(19);
if ("object".equals(msg)) {
stuJson = JSON.toJSONString(stu1);
} else if ("list".equals(msg)) {
ArrayList<Student> list = new ArrayList<Student>();
list.add(stu1);
list.add(stu2);
stuJson = JSON.toJSONString(list);
} else if ("map".equals(msg)) {
HashMap<String,Student> map = new HashMap<String, Student>();
map.put("stu1", stu1);
map.put("stu2", stu2);
stuJson = JSON.toJSONString(map);
}
// 响应json格式字符串
resp.setContentType("text/json;charset=utf-8");
PrintWriter out = resp.getWriter();
out.print(stuJson);
out.close();
}
}
- 页面Ajax请求
<html>
<head>
<title>My JSP 'list.jsp' starting page</title>
<script type="text/javascript" src="js/jquery-3.2.1.js"></script>
<script type="text/javascript">
$(function() { // ready 函数...
/*
测试三种json(object list map)对象的取值
*/
$("#btn1").click(function() {
$.get(
"LoadDataServlet",
{
"msg": "object"
},
function(data) {
console.log(data);
console.log(data.id + "\t" + data.name + "\t" + data.age);
}
);
});
$("#btn2").click(function() {
$.get(
"LoadDataServlet",
{
"msg": "list"
},
function(list) {
console.log(list);
// 遍历list json数组
for (var i = 0; i < list.length; i ++) {
console.log(list[i]);
}
}
);
});
$("#btn3").click(function() {
$.post(
"LoadDataServlet",
{
"msg": "map"
},
function (data) {
console.log(data);
for (var stu in data) {
console.log(data[stu].id + "\t" + data[stu].name + "\t" + data[stu].age);
}
}
);
});
});
</script>
</head>
<body>
<!-- 测试三种json格式字符串 -->
<input type="button" value="object" id="btn1"/>
<input type="button" value="list" id="btn2"/>
<input type="button" value="map" id="btn3"/>
</body>
</html>
-
单个student对象
-
list集合对象
-
map集合对象
- 更新…