Jackson Deserialiser : use @JsonCreator AND @JsonProperty on field?

Question

I'm trying to parse some Json into an Java object.
Some fields require custom behavior so i tried to use @JsonCreator on a constructor.

Well, it work, but for the other field annotate with @JsonProperty are not populated.
Didn't check yet, but i guess my object annotate with @JsonUnwrappedare not populated either.

In my search, i saw a comment that indicate that it is possible, but i can't figure how, if it is indeed possible.

There is around 400 field in the json, and only 5 or 6 that require custom behavior. So if i can avoid rewriting all constructor... that would be nice !

Exemple of what i tried :

public class MyObjectA {

  @JsonProperty("keyField1")
  private String myField1;

  @JsonUnwrapped
  private MyObjectB;

  private String[] myField2;

  @JsonCreator
  public MyObjectA(final Map<String, Object> properties){

    myField2  = ... //some Business logic 

  }

}

Junit :

ObjectMapper mapper = new ObjectMapper();
MyObjectA result = mapper.readValue(getJsonInputStream(JSON_FILE_PATH),MyObjectA.class);
Assert.notNull(result.getMyField1(),"should be populated")
Assert.notNull(result.getMyField2(),"should be populated")
Assert.notNull(result.getMyObjectB(),"should be populated")

Note : without the constructor, the other field are well populated

please share your code with problem... with sample json and your pojo — Optional, Oct 10 '17 at 08:51

Optional · Accepted Answer · 2017-10-10T09:36:48.680

Here it is. See the difference between commented and non commented @JsonConstructor usage. I am handling property something as custom handling and leaving name to be called using setName. Hope that helps

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Map;

public class Jackson2 {


    public static void main(String[] args) throws Exception {

        final ObjectMapper mapper = new ObjectMapper();
        final String jsonInString = "{\"name\":\"hello world\",\"something\":\"from string\"}";
        System.out.println(jsonInString);

        Foo newFoo = mapper.readValue(jsonInString, Foo.class);
        System.out.println(newFoo.getName());
        System.out.println(newFoo.getSomething());
    }
}

class Foo {

    @JsonProperty
    private String name;
    private String something;

    public String getSomething() {
        return something;
    }

    public void setSomething(String something) {
        this.something = something;
    }

    public String getName() {
        return name;
    }

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

    }

    Foo() {
    }

  // @JsonCreator
    public Foo(final Map<String, Object> properties) {
            System.out.println("printing.."+properties);
            something =  "Something from constructor";
     }
    @JsonCreator
    public Foo(@JsonProperty("something") String something ) {
            System.out.println("printing.."+name);
            this.something =  "Something from constructor appended"+something;
    }



}

So idea is that you use @JsonProperty in the constructor argument for properties you want to customize. :)

Jackson Deserialiser : use @JsonCreator AND @JsonProperty on field?

1 Answers1