Simple serialization/deserialization via ObjectMapper

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(cat);
Cat cat = mapper.readValue(json, Cat.class);

What fields will be serialized/deserialized?

  • public fields
  • if getter is available (serializable and deserializable)
  • if setter is available (only deserializable)
  • apply @JsonAutoDetect (for example, @JsonAutoDetect(fieldVisibility = Visibility.ANY) )

Note: marshalling is getters-based, if there is getCalculatedValue() method (and there is no such field), Jackson will serialize calculatedValue. Use @JsonAutoDetect(fieldVisibility=Visibility.ANY, getterVisibility=Visibility.NONE, isGetterVisibility=Visibility.NONE, setterVisibility=Visibility.NONE) to chose what you’d like to marshall.

@JsonIgnore can be added to a field itself or to getter/setter.

Jackson requires either no-arg constructor or @JsonCreator. The latter works for custom deserialization.

@JsonCreator
public ImportResultItemImpl(@JsonProperty("name") String name, 
        @JsonProperty("resultType") ImportResultItemType resultType, 
        @JsonProperty("message") String message) {
    super();
    this.resultType = resultType;
    this.message = message;
    this.name = name;
}

Note: won’t work for non-static inner class http://www.cowtowncoder.com/blog/archives/2010/08/entry_411.html

Rename fields, set required flag

  • @JsonProperty is for a field
  • @JsonGetter / @JsonSetter are for getter/setter.
  • @JsonAlias - several possible names for one field
@JsonProperty(
    value="Value",
    required=true,
    defaultValue="Empty",
    access= Access.READ_WRITE)
public String _value; 
  
@JsonGetter("name")
public String getTheName() {
  return name;
}

Enum (and not only enum) to single value

public enum TypeEnumWithValue {
    TYPE1(1, "Type A"), TYPE2(2, "Type 2");

    private Integer id;
    private String name;

    @JsonValue
    public String getName() {
        return name;
    }
}

Jackson Polymorphic Type Handling Annotations

  • @JsonTypeInfo – indicates details of what type information to include in serialization
  • @JsonSubTypes – indicates sub-types of the annotated type
  • @JsonTypeName – defines a logical type name to use for annotated class

Good example is available on Baeldung

Changes in original objects

Skip unknown properties: objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);