Spring Boot enum JSON serializer

Question

Below is the object that I want to convert to JSON;

public class TestDto{
    private ResponseType responseType;
    private Long id;
    private String name;
}

The ResponseType below is an enum;

public enum ResponseType{ 
    TEST1("test message 1"), TEST2("test message 2"), TEST3("test message 3");
    private String message;
}

Below is the JSON which I want to create:

{"code":"TEST1", "message":"test message 1", "id":1, "name":"name"}

and code in the JSON response points the name of the enum and the message in the JSON response points the message field of the enum.

Is there any way to do it?

Yes. Take a look at the JSON support in the Jackson library. Good luck! — Jamie Bisotti
– Jamie Bisotti, Commented Nov 10, 2020 at 15:10

Slimu · Accepted Answer · 2020-11-11 08:28:46Z

2

I have updated my previous answer as it wasn't correct. You can use @JsonFormat(shape = JsonFormat.Shape.OBJECT) to indicate that the enum should be serialized like an object (based on the getters).

    @JsonFormat(shape = JsonFormat.Shape.OBJECT)
    public enum ResponseType{
       TEST1("test message 1"), TEST2("test message 2"), TEST3("test message 3");
       private String message;

       ResponseType(String message) {
          this.message = message;
       }

       public String getMessage() {
          return message;
       }

       public String getCode() {
          return this.toString();
      }
   }

After that, you must also use @JsonUnwrapped on the Enum field to avoid having it's fields serialized as an object.

    public static class TestDto {
       @JsonUnwrapped private ResponseType responseType;
       private Long id;
       private String name;
    }

Running the following code

    TestDto testDto = new TestDto(ResponseType.TEST1, 1234356L, "First Response");
    result = mapper.writeValueAsString(testDto);
    System.out.println(result);

I get the result {"message":"test message 1","code":"TEST1","id":1234356,"name":"First Response"}

edited Nov 11, 2020 at 8:28

answered Nov 10, 2020 at 15:18

Slimu

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4 Comments

Andreas Over a year ago

That does not output 2 properties for the 1 enum: response field -> "code" and "message".

Slimu Over a year ago

I misunderstood the request, will update the answer to match the problem.

Mateusz Sobczak Over a year ago

@Slimu with this annotations I got json {"message":"test message 1", "id":1234356,"name":"First Response"} without name of enum value

Slimu Over a year ago

Did you add the explicit getter in the enum?

Andreas · Accepted Answer · 2020-11-10 15:39:24Z

Easiest way to do this is to add derived getters/setters to TestDto, and suppress JSON serialization of the responseType field.

class TestDto {
    private ResponseType responseType;
    private Long id;
    private String name;

    @JsonIgnore // Suppress JSON serialization
    public ResponseType getResponseType() {
        return this.responseType;
    }
    public void setResponseType(ResponseType responseType) {
        this.responseType = responseType;
    }

    public String getCode() { // Derived getter for "code" property
        return this.responseType.name();
    }
    public void setCode(String code) { // Derived setter for "code" property
        this.responseType = (code == null ? null : ResponseType.valueOf(code));
    }

    public String getMessage() { // Derived getter for "message" property
        return this.responseType.getMessage();
    }
    @Deprecated // Shouldn't be called by Java code, since it's a dummy stub method
    @SuppressWarnings("unused")
    public void setMessage(String message) { // Derived setter for "message" property
        // Ignore value
    }

    public Long getId() {
        return this.id;
    }
    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return this.name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

Two-way test

TestDto testDto = new TestDto();
testDto.setResponseType(ResponseType.TEST1);
testDto.setId(1L);
testDto.setName("name");

ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(testDto);
System.out.println(json);

TestDto testDto2 = mapper.readValue(json, TestDto.class);
System.out.println(testDto2.getResponseType());
System.out.println(testDto2.getId());
System.out.println(testDto2.getName());

Output

{"id":1,"name":"name","message":"test message 1","code":"TEST1"}
TEST1
1
name

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