Implement a solution for Infamous Type Erasure

[nmorel]

Implement a solution for Infamous Type Erasure

[nmorel]

The properties are mapped correctly. The only thing Jakcson does not see is your JsonTypeInfo annotation. You can create a wrapper like this :

public class ListWrapper extends List<MyEntityWithJsonTypeInfo> {
  public ListWrapper(List<? extends MyEntityWithJsonTypeInfo> list) {
     super(list); // may need a cast
  }
}

Or a little more generic :

public class Wrapper<T> {
  private final List<T> values;

  public Wrapper(List<T> values) {
    this.values=values;
  }

  @JsonTypeInfo(....)
  public List<T> getValues() {
    return values;
  }
}

Jackson will still see Wrapper and List but you annotated the property values with the JsonTypeInfo so it should see it.

And other way is to add JsonTypeInfo to Object via mix in annotation. This way, Jackson will add the type info to any class.

[nmorel]

I can't implement the solution. It's a problem on server-side.
gwt-jackson does not have this problem because the type is available in generators.
You have to find a workaround on server-side with your REST implementation and jackson.

As the author says in the comment, the problem seems to appear only if you use generics on root type. Use a wrapper and you should be ok.

[BenDol]

Yeah I am doing that, but I now have about 35 wrapper classes :S Well I'll look into how I can do this. Thanks!

[nmorel]

Maybe you can reduce to one wrapper by using your super class with the JsonTypeInfo.

[BenDol]

How could I do this? (If you don't mind explaining to me haha)

[BenDol]

Thanks for the reply, I tried the generic wrapper and it doesn't seem to work still

public class JacksonList<T> {
    private final List<T> elements;

    public JacksonList(List<T> elements) {
        this.elements=elements;
    }

    @JsonTypeInfo( use = JsonTypeInfo.Id.CLASS )
    public List<T> get() {
        return elements;
    }
}

Causes: com.github.nmorel.gwtjackson.client.exception.JsonDeserializationException: Cannot find the property @class containing the type information

[nmorel]

That's strange. Do you have the generated json ?
I'll try to do a few test when I find some time.

[BenDol]

[
   {
      "@id":1,
      "id":1,
      "owner":null,
      "description":"fghgfhfhf fhfghfghfghfghfgh fhfhf",
      "causesSummary":null,
      "consequencesSummary":null,
      "actionsSummary":null,
      "lessonsSummary":null,
      "conclusion":"ytryuytuuuuuuuuuuu",
      "creationDate":"2014-09-18T06:00:17.167+0000",
      "date":"2014-09-18T06:00:00.000+0000",
      "quantity":null,
      "secondaryQuantity":null,
      "product":null,
      "nptg":false,
      "transportRelated":false,
      "commitOpening":false,
      "commitInvestigation":true,
      "commitReview":false,
      "processState":{
         "@class":"nz.co.doltech.ims.shared.domains.Process",
         "@id":2,
         "id":3,
         "name":"Review",
         "description":"Review and Feedback Process",
         "nametoken":"review",
         "order":3,
         "removed":false
      }
   }

[nmorel]

how can it return an array when you are giving an object ?
You should have a json object with one property that is an array.

[BenDol]

Not sure I completely understand what you are meaning

return new JacksonList<Incident>(incidentService.getIncidents(filter, fetchCollections)).get();

That is the call I am making, getIncidents returns a List object.

[nmorel]

Oh, don't call get(). Return the JacksonList directly and rename the get() method to getValues() or anything else.

[BenDol]

Oh, so I don't need to call get? Instead I need to add JacksonList as the return type? I understand now :)

[nmorel]

Yes, if you don't, it's like before, you return a simple list.

[BenDol]

Right of course, awesome man! That makes sense haha.

[BenDol]

So I did this:

public class JacksonList<T> {
    private final ArrayList<T> elements;

    public JacksonList(ArrayList<T> elements) {
        this.elements = elements;
    }

    @JsonTypeInfo( use = JsonTypeInfo.Id.CLASS )
    public ArrayList<T> getElements() {
        return elements;
    }
}

getting this result and its still not working:

{
   "elements":[
      {
         "@id":1,
         "id":1,
         "owner":null,
         "description":"fghgfhfhf fhfghfghfghfghfgh fhfhf",
         "causesSummary":null,
         "consequencesSummary":null,
         "actionsSummary":null,
         "lessonsSummary":null,
         "conclusion":"ytryuytuuuuuuuuuuu",
         "creationDate":"2014-09-18T06:00:17.167+0000",
         "date":"2014-09-18T06:00:00.000+0000",
         "quantity":null,
         "secondaryQuantity":null,
         "product":null,
         "nptg":false,
         "transportRelated":false,
         "commitOpening":false,
         "commitInvestigation":true,
         "commitReview":false,
         "processState":{
            "@class":"nz.co.doltech.ims.shared.domains.Process",
            "@id":2,
            "id":3,
            "name":"Review",
            "description":"Review and Feedback Process",
            "nametoken":"review",
            "order":3,
            "removed":false,
            "incidentJoinProcesses":[

            ],
            "sections":[

            ]
      }
}

So sorry I'm spamming this bro, you've been such a great help. Thanks for that.

[nmorel]

Well, I don't know. I just did the test and it worked for me :

public static class Wrapper<T> {

    private final List<T> values;

    public Wrapper( List<T> values ) {this.values = values;}

    @JsonTypeInfo( use = Id.CLASS )
    public List<T> getValues() {
        return values;
    }
}

public static class Toto {

    public String name = "Toto";
}

@Test
public void testTypeInfo() throws IOException {
    Wrapper<?> wrapper = new Wrapper<Toto>( Arrays.asList( new Toto() ) );
    objectMapper.writeValue( System.out, wrapper );
}

The test prints :

{"values":[{"@class":"com.github.nmorel.gwtjackson.jackson.options.WriteNullMapValuesOptionJacksonTest$Toto","name":"Toto"}]}

[BenDol]

Ah well its not exactly the same as mine, I am using objects which super class is this:

@JsonTypeInfo( use = JsonTypeInfo.Id.CLASS )
@JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class)
public abstract class DomainObject implements Serializable, IsSerializable {

    public abstract int getId();

    public abstract void setId(int id);
}

That is the only difference I can think of here. Try add a super class with those values.

[BenDol]

Are you able to test this with the super class?

[nmorel]

Still works for me with the super class

public static class Wrapper<T> {

    private final List<T> values;

    public Wrapper( List<T> values ) {this.values = values;}

    @JsonTypeInfo( use = Id.CLASS )
    public List<T> getValues() {
        return values;
    }
}

@JsonTypeInfo( use = JsonTypeInfo.Id.CLASS )
@JsonIdentityInfo(generator=ObjectIdGenerators.IntSequenceGenerator.class)
public static abstract class DomainObject implements Serializable, IsSerializable {

    public abstract int getId();

    public abstract void setId(int id);
}

public static class Toto extends DomainObject {

    public String name = "Toto";

    @Override
    public int getId() {
        return 10;
    }

    @Override
    public void setId( int id ) {

    }
}

@Test
public void testTypeInfo() throws IOException {
    Wrapper<?> wrapper = new Wrapper<Toto>( Arrays.asList( new Toto() ) );
    objectMapper.writeValue( System.out, wrapper );
}

The output :

{
  "values" : [ {
    "@class" : "com.github.nmorel.gwtjackson.jackson.options.WriteNullMapValuesOptionJacksonTest$Toto",
    "@id" : 1,
    "name" : "Toto",
    "id" : 10
  } ]
}