Is @JsonProperty annotation required on accessor methods?

Question

I've inherited the following:

import com.fasterxml.jackson.annotation.JsonProperty;
public class MyClass {
  @JsonProperty("id")
  private String id;

  @JsonProperty("id")
  public String getId(){
    ...code...
  }

  @JsonProperty("id")
  public String setId(String id) {
    ...code...
  }
}

Are the repeated JsonProperty annotations required on the getter and setter, or would jackson handle the serialization/deserialization automatically if I only annotated the private member?

Answer 1

In your example, and with default ObjectMapper settings, no annotations should be needed, when using Jackson 1.8 or newer.

Jackson can auto-detect properties from public getters (like "public int getValue()"), setters ("public void setValue(int v);" and fields ("public int value;"). In addition, as long as one public setter, getter or field is found, then matching but (otherwise) non-visible setter/field is also included.

Note, however, that with old Jackson versions (1.7 and earlier) did NOT do second part, and both setter and getter needed to be public.

Answer 2

You definitely don't need all those @jsonProperty. Jackson mapper can be initialized to sereliazie/deserialize according to getters or private members, you of course need only the one you are using. By default it is by getters.

To define the mapper by members:

    ObjectMapper mapper = new ObjectMapper();
    mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
    mapper.disable(MapperFeature.AUTO_DETECT_GETTERS);

I would recommend anyway also to add this definition:

   mapper.configure(JsonParser.Feature.ALLOW_SINGLE_QUOTES, true);