How to globally add a custom Serializer to Jackson and be used by default-CodePudding

Let's say I want to serialize Boolean into Number by default.

I know I can do it field-by-field

@JsonFormat(shape = Shape.NUMBER)
private Boolean success;

But can I "register" my custom Serializer so that when I return an Object from my API, the Booleans in the class will be serialized into Number in the json response.

I have the following Serializer

public class MyBooleanSerializer extends JsonSerializer<Boolean> {
    @Override
    public void serialize(
                    Boolean value, 
                    JsonGenerator gen, 
                    SerializerProvider serializers) throws IOException {

        gen.writeString(value ? "1" : "0");

    }
}

And I have the following class

@Data
public class MyResponse {
    private Boolean success;
    private String message;
}

It will be used like this

@GetMapping("/hello")
public MyResponse hello() {
    Boolean success = true;
    String message = "Hi there";
    return new MyResponse(success, message);
}

And when I GET this API, I am expecting this response

{
  success: 1,
  message: "Hi there"
}

I am expecting some Beans to be injected. I have tried

@Bean
@Primary
ObjectMapper objectMapper() {
    SimpleModule module = new SimpleModule();
    module.addSerializer(new MyBooleanSerializer());
    return new ObjectMapper()
            .setSerializationInclusion(JsonInclude.Include.NON_NULL)
            .registerModule(module);
}

but it does not work.

I have read this tutorial and seems like it needs to create the jsonMapper every time I want to serialize an object. All I want is whenever I return MyResponse from an API, the Booleans are serialized into Numbers.

Thanks.

CodePudding user response：

Because of the serializer, the boolean value is converted into the form of true or false public class NumericBooleanSerializer extends JsonSerializer {

public void serialize(Boolean b, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException {
    jsonGenerator.writeNumber(b ? 1 : 0);
}

} hat will serialize booleans as 1 or 0.

CodePudding user response：

Can be done with a custom StdSerializer like

class CustomBooleanSerializer extends StdSerializer<Boolean> {

    public CustomBooleanSerializer(){
        super(Boolean.class);
    }

    @Override
    public void serialize(Boolean value, JsonGenerator generator, SerializerProvider provider) throws IOException {
        generator.writeNumber(value ? 1 : 0);
    }
}

And configure this via a Jackson2ObjectMapperBuilderCustomizer

@Bean
public Jackson2ObjectMapperBuilderCustomizer jsonCustomizer() {
  return builder ->
    builder.serializationInclusion(JsonInclude.Include.USE_DEFAULTS) // <-- optional
           .serializers(new CustomBooleanSerializer());
}