假设我有以下JSON:
{
"id":"decaa828741611e58bcffeff819cdc9f",
"statement":"question statement",
"exercise_type":"QUESTION"
}
然后,根据exercise_type
字段,我想要实例化不同的对象实例(ExerciseResponseDTO
的子类)。为了实现这一点,我尝试创建了这个混合体:
@JsonTypeInfo(
use = JsonTypeInfo.Id.NAME,
include = JsonTypeInfo.As.PROPERTY,
property = "exercise_type")
@JsonSubTypes({
@Type(value = ExerciseChoiceResponseDTO.class, name = "CHOICE"),
@Type(value = ExerciseQuestionResponseDTO.class, name = "QUESTION")})
public abstract class ExerciseMixIn
{}
public abstract class ExerciseResponseDTO {
private String id;
private String statement;
@JsonProperty(value = "exercise_type") private String exerciseType;
// Getters and setters
}
public class ExerciseQuestionResponseDTO
extends ExerciseResponseDTO {}
public class ExerciseChoiceResponseDTO
extends ExerciseResponseDTO {}
然后将映射器ObjectMapper
设置如下
ObjectMapper mapper = new ObjectMapper();
mapper.addMixIn(ExerciseResponseDTO.class, ExerciseMixIn.class);
但出于某些原因,这个测试失败了:
ExerciseResponseDTO exercise = mapper.readValue(serviceResponse, ExerciseResponseDTO.class)
Assert.assertTrue(exercise.getClass() == ExerciseQuestionResponseDTO.class); // OK
Assert.assertEquals("decaa828741611e58bcffeff819cdc9f" exercise.getId()); // OK
Assert.assertEquals("question statement", exercise.getStatement()); // OK
Assert.assertEquals("QUESTION", exercise.getExerciseType()); // FAIL. Expected: "QUESTION", actual: null
看起来存在一个问题,特别是与exercise_type
属性的映射似乎出了一些问题,因为所有其他字段都映射得很好。您有什么想法是什么原因导致这种情况吗?