Java中Jackson的用法

0.添加依赖

 <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.11.2</version>
 </dependency>

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1.实体类

package com.cat.domain;

public class Person {
    public  String name;
    public  String sex;
    public  int age;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", age=" + age +
                '}';
    }
}

2. list转json

我们写一个test类或者在Controller中直接构造，本文是使用的是直接在Controller中调用。

package com.cat.controller;

import com.cat.domain.Person;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

@Controller
@RequestMapping(produces="text/html;charset=UTF-8")
public class IndexController {
    List<Person> PersonList  =new ArrayList<>();
    //返回json格式
    @RequestMapping(value = "/hello2" )
    @ResponseBody
    public Object hello2() throws IOException {
        Person Person4 = new Person();
        Person Person5 = new Person();
        Person Person6 = new Person();
        Person4.name ="王晓红";
        Person5.name ="王晓绿";
        Person6.name ="王晓蓝";
        Person4.age =13;
        Person5.age =14;
        Person6.age =16;
        Person4.sex ="男";
        Person5.sex ="女";
        Person6.sex ="男";
        PersonList.add(Person4);
        PersonList.add(Person5);
        PersonList.add(Person6);
        System.out.println(PersonList);
        ObjectMapper mapper = new ObjectMapper();
        String str = mapper.writeValueAsString(PersonList);
        System.out.println(str);
        return str;
    }
}

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可以看出，控制台中输出了两端，第一段是list对象，第二段是json格式。

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3.json转对象（反序列化）

我们这次自己编写一个类用来测试。

import com.cat.domain.Person;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Arrays;
import java.util.List;
public class main {

    public static void main(String[] args) throws Exception {
        String json = "[{\"name\":\"王晓红\",\"sex\":\"男\",\"age\":13},{\"name\":\"王晓绿\",\"sex\":\"女\",\"age\":14},{\"name\":\"王晓蓝\",\"sex\":\"男\",\"age\":16}]";
        ObjectMapper mapper = new ObjectMapper();

        // json 转数组对象
        Person[] person = mapper.readValue(json,Person[].class);
        for(Person person1:person)
            System.out.println(person1);
    }
}

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4.json转List（反序列化）

import com.cat.domain.Person;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Arrays;
import java.util.List;
public class main {
    public static void main(String[] args) throws Exception {
        String json = "[{\"name\":\"王晓红\",\"sex\":\"男\",\"age\":13},{\"name\":\"王晓绿\",\"sex\":\"女\",\"age\":14},{\"name\":\"王晓蓝\",\"sex\":\"男\",\"age\":16}]";
        ObjectMapper mapper = new ObjectMapper();
        // json 转List对象
        List<Person> person2 =  Arrays.asList(mapper.readValue(json,Person[].class));
        System.out.println(person2);
    }
}

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