Java implements JSON string and object conversion

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The IDEA version used in this article is ultimate 2019.1, and the JDK version is 1.8.0_141.

1. Jackon ObjectMapper

Reference related jar packages

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

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

Entity Person.java

package testJsonToEntity;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;

@JsonPropertyOrder(value = {
    
    "ID","name","age"})
@JsonIgnoreProperties(ignoreUnknown = true)
public class Person {
    
    

    @JsonProperty("ID")
    private String id;

    @JsonInclude(JsonInclude.Include.NON_NULL)
    private String name;

    private int age;

    public String getId() {
    
    
        return id;
    }

    public void setId(String id) {
    
    
        this.id = id;
    }

    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;
    }

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

Note :

1. @JsonPropertyOrder This annotation is used to sort properties.

2. @JsonIgnoreProperties(ignoreUnknown = true), after writing this annotation on the class, fields that do not exist in the class will be ignored.

3. @JsonProperty This annotation is used on properties, and its role is to serialize the name of the property to another name, such as serializing the trueName property to name.

4. The role of @JsonInclude(Include.NON_NULL): the field that jackson entity turns json to NULL will not participate in serialization (that is, it will not be displayed)

Test class Test.java

package testJsonToEntity;

import com.fasterxml.jackson.databind.ObjectMapper;

public class Test {
    
    

    private static ObjectMapper mapper = new ObjectMapper();

    public static void main(String[] args) throws Exception {
    
    

        Person p = new Person();
        p.setId("1111");
        p.setAge(18);
        String jsonStr = mapper.writeValueAsString(p);
        System.out.println(jsonStr);

        String json = "{\"Id\":\"1111\",\"age\":18,\"sex\":\"male\"}";
        Person p1 = mapper.readValue(json, Person.class);
        System.out.println(p1.toString());
    }
}

The result is