Jackson Manual

引用jar：jackson-core，jackson-databind，jackson-annotations

1, jackson basic use

1.1, create a Person object

public class Person {
    private String name;
    private Integer age;

    public Person(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }
}

1.2, Main method calls

NOTE: The object has properties need to turn json get methods (except annotation method)

import com.fasterxml.jackson.databind.ObjectMapper;

public class Main {
    public static void main(String[] arges) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        Person person = new Person("jackson",20);
        System.out.println(mapper.writeValueAsString(person));
    }
}

The output is:

{"name":"jackson"}

2, the use of annotations

2.1, @ JsonProperty use annotation

@JsonProperty annotations similar in sql alias fields, a sequence of using annotations field properties, replace the original field properties

@JsonProperty("userName")
    private String name;

Sequence of results: In the serialized json string, userName replace the name

{"userName":"jackson"}

2.2, @ JsonIgnore use annotation

@JsonIgnore comment is to ignore the field when serializing

  @JsonIgnore
    @JsonProperty("userName")
    private String name;
    @JsonProperty("userAge")
    private Integer age;

Serialization result is: { "userAge": 20}

{"userAge":20}

2.3, @ JsonIgnoreProperties use annotation

2.3.1, with a sequence of similar @JsonIgnoreProperties @JsonIgnore, for the class, using the annotation field aliases

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;

@JsonIgnoreProperties(value={"name","userAge"})
public class Person {
    @JsonIgnore
    @JsonProperty("userName")
    private String name;
    @JsonProperty("userAge")
    private Integer age;
    @JsonProperty("userHeight")
    private Integer height;

    public Person(String name, Integer age, Integer height) {
        this.name = name;
        this.age = age;
        this.height = height;
    }
}

ObjectMapper mapper = new ObjectMapper();
Person person = new Person("jackson",20,175);
System.out.println(mapper.writeValueAsString(person));

Run results: { "userHeight": 175}

{"userHeight":175}

2.3.2, @ JsonIgnoreProperties (ignoreUnknown = true ) for ignoring fields do not match, the equivalent mapper.disable (DeserializationFeature. FAIL_ON_UNKNOWN_PROPERTIES);

Note: deserialization need no-argument constructor

ObjectMapper mapper = new ObjectMapper();
Person person = new Person("jackson",20,175);
System.out.println(mapper.writeValueAsString(person));
//mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
System.out.println(mapper.readValue("{\"sheight\":172}", Person.class).getHeight());

2.4 @ JsonTypeName @JsonTypeInfo

@JsonTypeName(value = "user")
@JsonTypeInfo(include = JsonTypeInfo.As.WRAPPER_OBJECT, use = JsonTypeInfo.Id.NAME)

Layer is increased in the sequence of

Serialization result is: { "user": { "height": 175}}

{"user":{"height":175}}

2.5, @ JsonRootName comment

　　Composition equal to 2.4 based on annotations @JsonRootName ( "user") and mapper.enable (SerializationFeature.WRAP_ROOT_VALUE);

2.6, @ JsonFormat annotation format date format

@JsonFormat(pattern="yyyy-MM-dd HH:mm:ss:SSS",timezone="GMT+8")
private Date date;

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