文章目录

  • 1.Json对象转换为java 对象
  • 2. Java对象转换JSON


1.Json对象转换为java 对象

  1. 导入jackson的相关jar包
  2. 创建Jackson核心对象 ObjectMapper
  3. 调用ObjectMapper的相关方法进行转换
@Test
 public void test5() throws IOException {
     //初始化Json对象
     String json = "{\"gender\":\"男\",\"name\":\"张三\",\"age\":23}";
     //创建ObjectMapper
     ObjectMapper mapper = new ObjectMapper();
     //转换为java对象
     Person person = mapper.readValue(json, Person.class);
     System.out.println(person);
 }

2. Java对象转换JSON

常见的解析器：Jsonlib，Gson，fastjson，jackson
1.导入jackson的相关jar包
2.创建Jackson核心对象 ObjectMapper
3.调用ObjectMapper的相关方法进行转换

public class JsonTest {
    //java对象转换为JSON字符串
    @Test
    public void test1() throws IOException {
        //1.创建Person对象
        Person p = new Person();
         p.setName("gh");
         p.setAge(20);
         p.setGender("女");

         //2.创建jackson的核心对象
        ObjectMapper mapper = new ObjectMapper();

        //调用writeValueAsString方法装换
        //String json = mapper.writeValueAsString(p);
        //System.out.println(json);

        //调用writeValue方法,将数据写到文件中
        //mapper.writeValue(new File("f://a.txt"),p);

        //调用writeValue方法，将数据写到字符输出流
        mapper.writeValue(new FileWriter("f://b.txt"),p);
    }
}

List集合转换为Json对象

@Test
    public void test3() throws JsonProcessingException {
        Person p = new Person();
        p.setName("gh");
        p.setAge(20);
        p.setGender("女");
        p.setBirthday(new Date());

        Person p1 = new Person();
        p1.setName("gh");
        p1.setAge(20);
        p1.setGender("女");
        p1.setBirthday(new Date());

        Person p2 = new Person();
        p2.setName("gh");
        p2.setAge(20);
        p2.setGender("女");
        p2.setBirthday(new Date());

        List<Person> ps = new ArrayList<Person>();
        ps.add(p);
        ps.add(p1);
        ps.add(p2);

        //2.转换
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(ps);
        System.out.println(json);
    }

Map集合转换为Json对象

@Test
    public void test4() throws JsonProcessingException {
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("name","zhnagsan");
        map.put("age",23);
        map.put("gender","nv");

        //2.转换
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(map);
        System.out.println(json);
    }

使用注解将java对象装换为字符串
@JsonIgnore：排除属性
@JsonFormat：属性值格式化

public class Person {
    private String name;
    private String gender;
    private int age;

    @JsonFormat(pattern = "yyyy-MM-dd")
    private Date birthday;
}
public class JsonTest {
@Test
  public void test2() throws JsonProcessingException {
      //1.创建Person对象
      Person p = new Person();
      p.setName("gh");
      p.setAge(20);
      p.setGender("女");
      p.setBirthday(new Date());

      //2.转换
      ObjectMapper mapper = new ObjectMapper();
      String json = mapper.writeValueAsString(p);
      System.out.println(json);
  }
}