一、maven安装jackson依赖
- <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
- <dependency>
- <groupId>com.fasterxml.jackson.core</groupId>
- <artifactId>jackson-databind</artifactId>
- <version>2.12.3</version>
- </dependency>
二、Jackson的使用
实体类转化JSON
把实体类转化为JSON格式数据,返回给前端
创建 ObjectMapper obj = new ObjectMapper(); 对象,对象的 writeValueAsString 方法 会把一个实体类(必须有get、set方法)转化为JSON对象。
- package com.lxc.springboot.controller;
- import com.fasterxml.jackson.databind.ObjectMapper;
- import org.springframework.web.bind.annotation.RequestMapping;
- import org.springframework.web.bind.annotation.RestController;
- @RestController // 这个类下边的所有方法,都会返回json,不会返回一个视图!
- public class Json {
- @RequestMapping(value = "/json")
- public String json() throws Exception{
- User user = new User("吕星辰", "888", 20);
- ObjectMapper obj = new ObjectMapper();
- String jsonObject = obj.writeValueAsString(user);
- return jsonObject;
- }
- // 为测试方便,在这里写一个实体类
- public static class User {
- private String userName;
- public String getUserName() {
- return userName;
- }
- public void setUserName(String userName) {
- this.userName = userName;
- }
- public String getPassword() {
- return password;
- }
- public void setPassword(String password) {
- this.password = password;
- }
- public int getAge() {
- return age;
- }
- public void setAge(int age) {
- this.age = age;
- }
- private String password;
- private int age;
- public User(String userName, String password, int age) {
- this.userName = userName;
- this.password = password;
- this.age = age;
- }
- }
- }
测试:
集合转化JSON
前端结果是:一个数组,里边是一个个对象
- package com.lxc.springboot.controller;
- import com.fasterxml.jackson.databind.ObjectMapper;
- import org.springframework.web.bind.annotation.RequestMapping;
- import org.springframework.web.bind.annotation.RestController;
- import java.util.ArrayList;
- import java.util.List;
- @RestController
- public class Json {
- @RequestMapping(value = "/json")
- public String json() throws Exception{
- // 创建一个集合
- List<User> userList = new ArrayList<>();
- for(int i = 0; i < 3; i ++) {
- userList.add(new User("用户名"+i, "密码"+i, 20+i));
- }
- ObjectMapper obj = new ObjectMapper();
- String jsonObject = obj.writeValueAsString(userList);
- return jsonObject;
- }
- // 上边有实体类,这里省略
- }
测试:
Map转化JSON
- @RestController
- public class Json {
- @RequestMapping(value = "/json")
- public String json() throws Exception{
- // 创建一个Map
- Map<String, Object> map = new HashMap<>();
- map.put("name", "测试名");
- map.put("age", 20);
- ObjectMapper obj = new ObjectMapper();
- String jsonObject = obj.writeValueAsString(map);
- return jsonObject;
- }
- }
前端结果是:对象
new Date() 转化JSON
- @RestController
- public class Json {
- @RequestMapping(value = "/json")
- public String json() throws Exception{
- Date date = new Date();
- ObjectMapper obj = new ObjectMapper();
- String jsonObject = obj.writeValueAsString(date);
- return jsonObject;
- }
- }
前端结果是:时间戳
当然,也可以自定义时间格式
- @RestController
- public class Json {
- @RequestMapping(value = "/json")
- public String json() throws Exception{
- Date date = new Date();
- SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
- String time = sdf.format(date); // "2021-06-27 05:19:33"
- ObjectMapper obj = new ObjectMapper();
- String jsonObject = obj.writeValueAsString(time);
- return jsonObject;
- }
- }
封装
- package com.lxc.springboot.utils;
- import com.fasterxml.jackson.core.JsonProcessingException;
- import com.fasterxml.jackson.databind.ObjectMapper;
- import com.fasterxml.jackson.databind.SerializationFeature;
- import java.text.SimpleDateFormat;
- public class JavaUtils {
- /**
- * 使用下边方法需要导入依赖包:
- * <dependency>
- * <groupId>com.fasterxml.jackson.core</groupId>
- * <artifactId>jackson-databind</artifactId>
- * <version>2.12.3</version>
- * </dependency>
- *
- * @param object 集合(List)、Map(HashMap)、对象(new Date)
- * @param format 时间格式化 yyyy-MM-dd hh:mm:ss
- * @return JSON格式化的字符串
- */
- public static String getJson(Object object, String format) {
- ObjectMapper objectMapper = new ObjectMapper();
- // 不使用时间戳的方式
- objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
- // 自定义时间格式
- SimpleDateFormat sdf = new SimpleDateFormat(format);
- // 设置时间格式化
- objectMapper.setDateFormat(sdf);
- try {
- String jsonValue = objectMapper.writeValueAsString(object);
- return jsonValue;
- } catch (JsonProcessingException e) {
- e.printStackTrace();
- }
- return null;
- }
- public static String getJson(Object object) {
- return getJson(object, "yyyy-MM-dd hh:mm:ss");
- }
- }
二、FastJson的使用
使用maven导入依赖包
- <!--下边依赖跟aop没关系,只是项目中用到了 JSONObject,所以引入fastjson-->
- <dependency>
- <groupId>com.alibaba</groupId>
- <artifactId>fastjson</artifactId>
- <version>1.2.70</version>
- </dependency>
常用方法:
(1)JSON.toJSONString(obejct) - java对象转JSON字符串
(2)JSON.parseObject(string, User.class) - JSON字符串转java对象
使用
- @RestController
- public class Json {
- @RequestMapping(value = "/json")
- public String json() throws Exception{
- List<User> userList = new ArrayList<>();
- userList.add(new User("1", "1", 20));
- String res = JSON.toJSONString(userList);
- return res;
- }
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原文链接:https://blog.csdn.net/qq_42778001/article/details/118270837