java与json相互转化

2023-06-06 00:07| 来源: 网络整理| 查看: 265

日志概述

在日常实践中通常会对JSON数据和Java对象进行相互转换，转换需要用到JSON解析器，常见的解析器如下：

Jsonlib（JSON官方）Gson（Google）Jackson（Spring官方）Fastjson（Alibaba）

作为 Spring MVC / SpringBoot 技术栈开发的话，用默认的Jackson是最好的！

数据量少时：Gson快

数据量多时：FastJson快

数据量无论多少：Jackson最稳定

Jackson

SpringBoot2 中的 web starter 中就内置了 jackson 三个jar依赖

Maven构建地址 | Github地址

目前最新版为 2.12.3 其中三个jar 各自大小为

jackson-core 314Kbjackson-databind 1.3Mbjackson-annotations 65Kb 快速入门引入依赖

pom.xml

springboot\springmvc内置，不需要在引入

com.fasterxml.jackson.core jackson-core 2.12.3 com.fasterxml.jackson.core jackson-databind 2.12.3 com.fasterxml.jackson.core jackson-annotations 2.12.3 代码测试

Java代码：

package com.demo; import com.demo.entity.User; import com.demo.mapper.UserMapper; import com.fasterxml.jackson.core.type.TypeReference; import com.fasterxml.jackson.databind.ObjectMapper; import org.junit.jupiter.api.Test; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.context.SpringBootTest; import java.io.IOException; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; @SpringBootTest class SpringbootalinbabaSsmStart01ApplicationTests { private static final Logger LOGGER = LoggerFactory.getLogger(SpringbootalinbabaSsmStart01ApplicationTests.class); @Autowired private UserMapper userMapper; @Test public void test1() { List userList = userMapper.queryAllUser(); for (User user : userList) { LOGGER.info("数据为：{}", user); } } @Test public void test2() throws IOException { //创建对象 User user = new User(); user.setId(0L); user.setUsername("张三"); user.setEmail("[email protected]"); user.setPassword("123"); user.setPhoneNum("456"); User[] users = {user,new User(2L,"李四","邮箱","密码","电话")}; ArrayList list = new ArrayList(); list.add("苹果"); list.add("橘子"); HashMap map = new HashMap(); map.put("name", "张三"); map.put("age", 20); //创建jackson的核心对象 ObjectMapper objectMapper = new ObjectMapper(); //java对象(包括list、map)转json字符串 String pStr1 = objectMapper.writeValueAsString(user); String pStr2 = objectMapper.writeValueAsString(list); String pStr3 = objectMapper.writeValueAsString(map); String pStr4 = objectMapper.writeValueAsString(users); LOGGER.info("bean=》json：{}",pStr1); LOGGER.info("list=》json：{}",pStr2); LOGGER.info("map=》json：{}",pStr3); LOGGER.info("beans=》jsons：{}",pStr4); //json字符串转java对象： String json = "{\"id\":0,\"username\":\"张三\",\"email\":\"[email protected]\",\"password\":\"123\",\"phoneNum\":\"456\"}"; User bean = new ObjectMapper().readValue(json, User.class); LOGGER.info("json =》bean：{},username ={}",bean,bean.getUsername()); //json字符串转list对象：TypeReference匿名内部类，指明对象类型 String json2 = "[\"苹果\",\"橘子\"]"; List beanList = new ObjectMapper().readValue(json2, new TypeReference() {}); LOGGER.info("list =》bean：{}",beanList); //json字符串转map对象： String json3 ="{\"name\":\"张三\",\"age\":20}"; Map beanMap = new ObjectMapper().readValue(json3, new TypeReference(){}); LOGGER.info("map =》bean：{}",beanMap); //JSON数组字符串->对象数组 String json4 = "[{\"id\":0,\"username\":\"张三\",\"email\":\"[email protected]\",\"password\":\"123\",\"phoneNum\":\"456\"},{\"id\":2,\"username\":\"李四\",\"email\":\"邮箱\",\"password\":\"密码\",\"phoneNum\":\"电话\"}]"; User[] cars2 = objectMapper.readValue(json4, User[].class); LOGGER.info("jsons =》beans：{}",beanMap); } }

打印如下

2023-05-30 01:03:54.842 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : bean=》json：{"id":0,"username":"张三","email":"[email protected]","password":"123","phoneNum":"456"} 2023-05-30 01:03:54.842 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : list=》json：["苹果","橘子"] 2023-05-30 01:03:54.842 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : map=》json：{"name":"张三","age":20} 2023-05-30 01:03:54.842 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : beans=》jsons：[{"id":0,"username":"张三","email":"[email protected]","password":"123","phoneNum":"456"},{"id":2,"username":"李四","email":"邮箱","password":"密码","phoneNum":"电话"}] 2023-05-30 01:03:54.866 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : json =》bean：User(id=0, username=张三, [email protected], password=123, phoneNum=456),username =张三 2023-05-30 01:03:54.866 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : list =》bean：[苹果, 橘子] 2023-05-30 01:03:54.872 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : map =》bean：{name=张三, age=20} 2023-05-30 01:03:54.872 INFO 14444 --- [ main] ngbootalinbabaSsmStart01ApplicationTests : jsons =》beans：{name=张三, age=20} Java对象转JSON相关注解

@JsonIgnore：排除属性。 @JsonFormat：属性值得格式化

@JsonFormat(pattern = “yyyy-MM-dd”)

Person类

package com.demo.entity; import com.fasterxml.jackson.annotation.JsonFormat; import com.fasterxml.jackson.annotation.JsonIgnore; import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; import java.util.Date; @Data @AllArgsConstructor @NoArgsConstructor public class Person { private Integer id; private String name; @JsonIgnore private Integer age; @JsonIgnore private String addr; @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss") private Date birthday; }

测试方法

@Test public void test3() throws Exception { Person person = new Person(); person.setId(20); person.setName("Tom"); person.setAge(23); person.setAddr("QD"); person.setBirthday(new Date()); ObjectMapper objectMapper = new ObjectMapper(); String s = objectMapper.writeValueAsString(person); System.out.println(s); // {"id":20,"name":"Tom","birthday":"2023-05-29 17:07:35"} } Fastjson使用（Alibaba）

Maven构件地址 | Github地址

目前最新版本为 1.2.76 jar包大小为 533kb

阿里出品的json库,解析速度非常快。但是被曝出过漏洞问题，使用最新版的就好。

快速入门引入依赖

pom.xml

com.alibaba fastjson 1.2.62 代码测试 package com.demo; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.JSONObject; import com.demo.entity.User; import org.junit.jupiter.api.Test; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.boot.test.context.SpringBootTest; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; @SpringBootTest class Test02 { private static final Logger LOGGER = LoggerFactory.getLogger(Test02.class); @Test public void test6() { //创建对象 User user = new User(); user.setId(0L); user.setUsername("张三"); user.setEmail("[email protected]"); user.setPassword("123"); user.setPhoneNum("456"); User[] users = {user,new User(2L,"李四","邮箱","密码","电话")}; ArrayList list = new ArrayList(); list.add("苹果"); list.add("橘子"); HashMap map = new HashMap(); map.put("name", "张三"); map.put("age", 20); //java对象(包括list、map)转json字符串 String pStr1 = JSON.toJSONString(user); String pStr2 = JSON.toJSONString(list); String pStr3 = JSON.toJSONString(map); String pStr4 = JSON.toJSONString(users); System.out.println("bean=》json："+pStr1); System.out.println("list=》json："+pStr2); System.out.println("map=》json："+pStr3); System.out.println("beans=》jsons："+pStr4); //json字符串转java对象： User bean= JSONObject.parseObject("{\"username\":\"张三\"}", User.class); System.out.println(bean); //json字符串转list对象： List beanList =JSONObject.parseArray("[\"苹果\",\"橘子\"]", String.class); System.out.println(beanList); //json字符串转map对象： Map beanMap = ( Map )JSONObject.parse("{\"name\":\"张三\",\"age\":20}"); System.out.println(beanMap); } } bean=》json：{"email":"[email protected]","id":0,"password":"123","phoneNum":"456","username":"张三"} list=》json：["苹果","橘子"] map=》json：{"name":"张三","age":20} beans=》jsons：[{"email":"[email protected]","id":0,"password":"123","phoneNum":"456","username":"张三"},{"email":"邮箱","id":2,"password":"密码","phoneNum":"电话","username":"李四"}] User(id=null, username=张三, email=null, password=null, phoneNum=null) [苹果, 橘子] {"name":"张三","age":20} 2023-05-30 01:24:15.688 INFO 13616 --- [ionShutdownHook] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closing ... 2023-05-30 01:24:15.688 INFO 13616 --- [ionShutdownHook] com.alibaba.druid.pool.DruidDataSource : {dataSource-1} closed Disconnected from the target VM, address: '127.0.0.1:14228', transport: 'socket' Gson

功能最全的json解析器，google谷歌出品

Maven构件地址 | Github地址

目前最新版为 2.8.6 其jar大小为 235kb

快速入门引入依赖 com.google.code.gson gson 2.8.6 代码测试 package com.demo; import com.demo.entity.User; import com.google.gson.Gson; import com.google.gson.reflect.TypeToken; import org.junit.jupiter.api.Test; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.boot.test.context.SpringBootTest; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; @SpringBootTest class Test03 { private static final Logger LOGGER = LoggerFactory.getLogger(Test03.class); @Test public void test6() { //创建对象 User user = new User(); user.setId(0L); user.setUsername("张三"); user.setEmail("[email protected]"); user.setPassword("123"); user.setPhoneNum("456"); User[] users = {user,new User(2L,"李四","邮箱","密码","电话")}; ArrayList list = new ArrayList(); list.add("苹果"); list.add("橘子"); HashMap map = new HashMap(); map.put("name", "张三"); map.put("age", 20); //java对象(包括list、map)转json字符串 String pStr1 = new Gson().toJson(user); String pStr2 = new Gson().toJson(list); String pStr3 = new Gson().toJson(map); String pStr4 = new Gson().toJson(users); System.out.println("bean=》json："+pStr1); System.out.println("list=》json："+pStr2); System.out.println("map=》json："+pStr3); System.out.println("beans=》jsons："+pStr4); //json字符串转java对象： User bean= new Gson().fromJson("{\"username\":\"张三\"}", User.class); System.out.println(bean); //json字符串转list对象： List beanList =new Gson().fromJson("[\"苹果\",\"橘子\"]", new TypeToken(){}.getType()); System.out.println(beanList); //json字符串转map对象： Map beanMap = new Gson().fromJson("{\"name\":\"张三\",\"age\":20}", new TypeToken(){}.getType()); System.out.println(beanMap); } } list=》json：["苹果","橘子"] map=》json：{"name":"张三","age":20} beans=》jsons：[{"id":0,"username":"张三","email":"[email protected]","password":"123","phoneNum":"456"},{"id":2,"username":"李四","email":"邮箱","password":"密码","phoneNum":"电话"}] User(id=null, username=张三, email=null, password=null, phoneNum=null) [苹果, 橘子] {name=张三, age=20.0}

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