Myujth

The second junit test serializes an instance of a class which has a type parameter. The instance is of type ParametricType<SubType>. The serializer was initialized by using constructParametricType(ParametricType.class, SuperType.class) as type information. We can see that we initialized the serializer with the super type SuperType for the type parameter. We would now expect to get serialized json, containing only fields of the super type. But the field B of the sub type is also included.

It works in the first example where we do not wrap our SuperType in ParametricType.

So what are we missing in order to get only the super type fields as serialized output when we use a parametric type?

public static class SuperType 
 public int A;


public static class SubType extends SuperType 
 public int B;


public static class ParametricType<T> 
 public T Value;


@Test
public void doNotSerializeSubClassFieldsTest() throws Exception 
 var mapper = new ObjectMapper();
 var writer = mapper.writerFor(SuperType.class);

 var subType = new SubType();
 subType.A = 1;
 subType.B = 2;

 var expectedValue = ""A":1";
 var data = writer.writeValueAsString(subType);

 assertEquals(expectedValue, data);


@Test
public void serializeNotSubclassAuthenticatedMessageTest() throws Exception 
 var mapper = new ObjectMapper();
 var javaType = mapper.getTypeFactory().constructParametricType(ParametricType.class, SuperType.class);
 var writer = mapper.writerFor(javaType);

 var subType = new SubType();
 subType.A = 1;
 subType.B = 2;
 var parametricType = new ParametricType<>();
 parametricType.Value = subType;

 var expectedValue = ""Value":"A":1";
 var data = writer.writeValueAsString(parametricType);

 // it is actually ""Value":"A":1,"B":2"
 assertEquals(expectedValue, data);