如何使用Jackson序列化注释

Question

I have a simple annotation class:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface WebService { // with methods}

And a pojo

class Pojo {
    Webservice webservice;
}

Whenever I try to serialize Pojo , all the fields get serialized except the Webservice field.

I'm not interested in deserializing, only serialization.

Is that a restriction in Jackson ?

Answer 1

A good question. Serialization works fine if you put a @JsonProperty annotation on your annotation type methods. Here is an example:

@JacksonAnnotationSerialization.MyAnnotation(a = "abc", b = 123)
public class JacksonAnnotationSerialization {

    @Retention(RetentionPolicy.RUNTIME)
    @interface MyAnnotation {
        @JsonProperty
        String a();
        @JsonProperty
        int b();
    }

    static class Thing {
        public final String field;
        public final MyAnnotation myAnnotation;

        Thing(final String field, final MyAnnotation myAnnotation) {
            this.field = field;
            this.myAnnotation = myAnnotation;
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        final ObjectMapper objectMapper = new ObjectMapper();
        final MyAnnotation annotation
                = JacksonAnnotationSerialization.class.getAnnotation(MyAnnotation.class);
        final Thing thing = new Thing("value", annotation);
        System.out.println(objectMapper.writeValueAsString(thing));
    }
}

Output:

{"field":"value","myAnnotation":{"a":"abc","b":123}}