详解Java-Jackson使用

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}
  }