Java之Jackson使用案例详解

public class Person {
 
    private String name;
    private int age;
     @JsonProperty("gender")
    private String gender;
 
   // @JsonIgnore//忽略该属性，不进行转换
    @JsonFormat(pattern = "yyyy-MM-dd")
    private Date birthday;
 
    public Date getBirthday() {
        return birthday;
    }
 
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public int getAge() {
        return age;
    }
 
    public void setAge(int age) {
        this.age = age;
    }
 
    public String getGender() {
        return gender;
    }
 
    public void setGender(String gender) {
        this.gender = gender;
    }
 
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' +
                '}';
    }
}

//将Json字符串转为Java对象
    @Test
    public  void  test5() throws Exception{
        //json字符串
        String str="{\"gender\":\"男\",\"name\":\"zhangsan\",\"age\":23}";
        //Jackson核心对象
        ObjectMapper mapper = new ObjectMapper();
        //使用readValue方法进行转换
        Person person = mapper.readValue(str, Person.class);
        System.out.println(person);
    }

 //Java对象转Json
    @Test
    public void test1() throws IOException {
 
        //1.创建Java对象
        Person p=new Person();
        p.setName("张三");
        p.setAge(23);
        p.setGender("男");
 
        //2.创建Jackson对象 ObjectMapper
        ObjectMapper mapper=new ObjectMapper();
        //3.转换为JSOn
        String json = mapper.writeValueAsString(p);
        System.out.println(json);
        mapper.writeValue(new File("d:\\jaon.txt"),json);
        mapper.writeValue(new FileWriter("d:\\json.txt"),json);
    }
 
 
    @Test
    public void test2() throws JsonProcessingException {
 
        //1.创建Java对象
        Person p = new Person();
        p.setName("张三");
        p.setAge(23);
        p.setGender("男");
        p.setBirthday(new Date());
        //2.创建Jackson对象 ObjectMapper
        ObjectMapper mapper = new ObjectMapper();
        //3.转换为JSOn
        String json = mapper.writeValueAsString(p);
        System.out.println(json);
    }
 
 
    @Test
    public void test3() throws Exception {
        //复杂格式的转换：list
        //1.创建Java对象
        Person p1 = new Person();
        p1.setName("张三");
        p1.setAge(23);
        p1.setGender("男");
        p1.setBirthday(new Date());
 
        Person p2 = new Person();
        p2.setName("张三");
        p2.setAge(23);
        p2.setGender("男");
        p2.setBirthday(new Date());
 
        List<Person> list=new ArrayList<>();
        list.add(p1);
        list.add(p1);
   
        //2.创建Jackson对象 ObjectMapper
        ObjectMapper mapper = new ObjectMapper();
        //3.转换为JSOn
        String json = mapper.writeValueAsString(list);
        System.out.println(json);//[{"name":"张三","age":23,"gender":"男","birthday":"2021-03-19"},{"name":"张三","age":23,"gender":"男","birthday":"2021-03-19"}]
 
    }
 
    @Test
    public  void   test4() throws Exception{
        //复杂格式的转换Map
        //1.创建map对象
        Map<String,Object> map=new HashMap<>();
        map.put("name","zhangsan");
        map.put("age",23);
        map.put("gender","男");
        //2.创建Jackson对象 ObjectMapper
        ObjectMapper mapper = new ObjectMapper();
        //3.转换为JSOn
        String json = mapper.writeValueAsString(map);
        System.out.println(json);//{"gender":"男","name":"zhangsan","age":23}
    }