JSON字符串和java对象的相互转化

<!-- 引入jackson依赖-->
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.10.3</version>
</dependency>



@Test
public void testJsonSerializer() throws JsonProcessingException {
    User user = new User(1, "abc",18,10000.0,new Date());
    //使用JSON工具将对象转换为json字符串
    ObjectMapper mapper = new ObjectMapper();
    String userJson = mapper.writeValueAsString(user);

    Jedis jedis = JedisUtils.getJedis();
    jedis.set("u", userJson);

    String userJson2 = jedis.get("u");

    //使用JSON工具将json字符串转换为对象
    User user2 = mapper.readValue(userJson2, User.class);
    System.out.println("user2 = " + user2);

    JedisUtils.close(jedis);

}

`Json字符串与Object对象相互转换的几种方式`
Json-Lib、Org.Json、Jackson、Gson、FastJson五种方式转换json类型
只列举了最省事的方式。不涉及复制情况和速度。

测试用例，一个User类，属性name，age，location。重写toString()。

public class User {
    private String name;
    private Integer age;
    private String location;
 
    public User() {
    }
    public User(String name) {
        this.name = name;
    }
    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
    public User(String name, Integer age, String location) {
        this.name = name;
        this.age = age;
        this.location = location;
    }
 
    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 String getLocation() {
        return location;
    }
    public void setLocation(String location) {
        this.location = location;
    }
 
    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", location='" + location + '\'' +
                '}';
    }
}

# 1、Json-Lib
maven依赖如下，需注意<classifier>jdk15</classifier>，jar包区分jdk1.3和jdk1.5版本
 
    <dependency>
      <groupId>net.sf.json-lib</groupId>
      <artifactId>json-lib</artifactId>
      <version>2.4</version>
      <classifier>jdk15</classifier>
    </dependency>


# 测试demo
 
import net.sf.json.JSONObject;
 
public class JsonLibDemo {
 
    public static void main(String[] args) {
        //创建测试object
        User user = new User("李宁",24,"北京");
        System.out.println(user);
 
        //转成json字符串
        JSONObject jsonObject = JSONObject.fromObject(user);
        String json = jsonObject.toString();
        System.out.println(json);
 
        //json字符串转成对象
        JSONObject jsonObject1 = JSONObject.fromObject(json);
        User user1 = (User) JSONObject.toBean(jsonObject1,User.class);
        System.out.println(user1);
    }
}
 

# 2、org.json
maven依赖如下
 
    <dependency>
      <groupId>org.json</groupId>
      <artifactId>json</artifactId>
      <version>20170516</version>
    </dependency>
 
# 测试demo
 
import org.json.JSONObject;
 
public class OrgJsonDemo {
    public static void main(String[] args) {
        //创建测试object
        User user = new User("李宁",24,"北京");
        System.out.println(user);
 
        //转成json字符串
        String json = new JSONObject(user).toString();
        System.out.println(json);
 
        //json字符串转成对象
        JSONObject jsonObject = new JSONObject(json);
        String name = jsonObject.getString("name");
        Integer age = jsonObject.getInt("age");
        String location = jsonObject.getString("location");
        User user1 = new User(name,age,location);
        System.out.println(user1);
    }
}

# 4、Gson
maven依赖
 
    <dependency>
      <groupId>com.google.code.gson</groupId>
      <artifactId>gson</artifactId>
      <version>2.8.1</version>
    </dependency>
 
# 测试demo
 
import com.google.gson.Gson;
 
public class GsonDemo {
    public static void main(String[] args) {
        //创建测试object
        User user = new User("李宁",24,"北京");
        System.out.println(user);
 
        //转成json字符串
        Gson gson = new Gson();
        String json = gson.toJson(user);
        System.out.println(json);
 
        //json字符串转成对象
        User user1 = gson.fromJson(json,User.class);
        System.out.println(user1);
    }
}

# 5、FastJson
maven依赖

   <dependency>
     <groupId>com.alibaba</groupId>
     <artifactId>fastjson</artifactId>
     <version>1.2.37</version>
   </dependency>

# 测试demo

import com.alibaba.fastjson.JSON;

public class FastJsonDemo {
   public static void main(String[] args) {
       //创建测试object
       User user = new User("李宁",24,"北京");
       System.out.println(user);

       //转成json字符串
       String json = JSON.toJSON(user).toString();
       System.out.println(json);

       //json字符串转成对象
       User user1 = JSON.parseObject(json,User.class);
       System.out.println(user1);

   }
}

json-lib时间有些久远，jar包只更新到2010年
org.json用起来有些繁琐
Jackson、Gson、FastJson只需一两句话就可以搞定