如何反序列化包含 List<?, ?> 作为值的 Map<?>...例如地图<Long, List<Long>？

Question

我正在尝试使用杰克逊反序列化地图。当我尝试调用反序列化方法时，出现编译时错误。我使用的映射器是 com.fasterxml.jackson.databind.ObjectMapper。我在下面包含了以下代码：Mapper 初始化、反序列化方法、导致编译类型错误的 JUnit 测试和实际错误 itself。

//. ObjectMapper initialization
    public static final ObjectMapper objectMapper = JsonMapper.builder()
      .addModule(new JavaTimeModule())
      .addModule(new SimpleModule()
          .addAbstractTypeMapping(Claims.class, DefaultClaims.class)
          .addAbstractTypeMapping(GrantedAuthority.class, SimpleGrantedAuthority.class)
      )
      .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
      .addMixIn(PersonTraits.class, PersonTraitsMixIn.class)
      .addMixIn(SimpleGrantedAuthority.class, SimpleGrantedAuthorityMixin.class)
      .build();

反序列化方法：

    `public static <K, V, T extends Map<?, ?>> Map<K, List<V>> deserializeMap(String` genericObject, Class<T> mapClass,
              Class<K> keyClass, Class<List<V>> valueClass) throws Exception {
            if (genericObject == null) {
              return null;
            }
            try {
              return objectMapper.readValue(genericObject, objectMapper.getTypeFactory().constructMapType(mapClass, keyClass, valueClass));
            } catch (JsonProcessingException e) {
              //. Do something
              throw e;
            }
          }

JUnit 测试用例：

      @Test
      public void testDeserializeMapContainingListAsValue() throws Exception {
        // given
        Map<Long, List<Long>> mapToSerialize = new HashMap<>();
        List<Long> valueList = new ArrayList<>();
        valueList.add(2L);
        mapToSerialize.put(1L, valueList);
        String serializedMap = SerializationUtil.serializeObject(mapToSerialize);
    
        // when
        final Map<Long, List<Long>> result = SerializationUtil.deserializeMap(serializedMap, HashMap.class, Long.class,
            List.class);
    
        // then
        assertNotNull(result);
      }

The when statement is throwing the error:
 

     // when
            final Map<Long, List<Long>> result = SerializationUtil.deserializeMap(serializedMap1, HashMap.class, Long.class,
                List.class);

    The error says:  
    
                 Required type.      Provided
    mapClass:    Class<T>.           Class<HashMap>
    keyClass:    Class<K>            Class<Long>
    valueClass:  Class<List<V>>.     Class<List>
    reason: Incompatible equality constraint: List<V> and List

有谁知道发生了什么事以及如何解决它？如果上面的代码中存在我遗漏的明显问题，我深表歉意。我对编程相当陌生。任何帮助将不胜感激。 谢谢大家，保重！

Answer 1

你可能需要做类似的事情

JavaType keyType = typeFactory.constructType(Long.class);
JavaType valueType = typeFactory.constructType(new TypeReference<List<Long>>() {});
return objectMapper.readValue(genericObject, objectMapper.getTypeFactory().constructMapType(mapClass, keyType, valueType));