java - ObjectMapper 读取值

Question

我加载一个资源文件json与文本格式

{
    "sources": [{
            "prop1": "1",
            "prop2": "2"

        },
        {
            "prop1": "1",
            "prop2": "2"

        },
    ],
    "redirection": [{
            "prop1": "1",
            "prop2": "2"

        }
    ]
}

我有一个具有此属性 prop1 和 prop2 的类

我想用 ObjectMapper 恢复一个列表类。什么方法？

此代码无效....

 Map<String, Object> mp =  mapper.readValue(jsonResource.getInputStream(),new TypeReference<Map<String, Object>>() {});
String sourceText= new ObjectMapper().readTree(jsonResource.getInputStream()).get("sources").asText();

 mapper.readValue(sourceText, new TypeReference<List<MyClass>>(){});

谢谢你的帮助

Answer 1

在您的情况下，我会编写自定义 JsonDeserializer。还没有真正测试代码，但我认为思路很清楚:

    final MyClassDeserializer myClassDeserializer = new MyClassDeserializer();
    final SimpleModule deserializerModule = new SimpleModule();
    deserializerModule.addDeserializer(MyClass.class, myClassDeserializer);

    final ObjectMapper mapper = new ObjectMapper();
    mapper.registerModule(deserializerModule);

JsonDeserializer 的代码:

    public class MyClassDeserializer extends JsonDeserializer<MyClass> {

    @Override
    public MyClass deserialize(final JsonParser jsonParser, final DeserializationContext context)
            throws IOException {
        final JsonNode node = jsonParser.getCodec().readTree(jsonParser);
        final JsonNode sourcesNode = node.get("sources");
        if(node.isArray()) {
            final ArrayNode arrayNode = (ArrayNode) node;
            final Iterable<JsonNode> nodes = arrayNode::elements;
            final Set<Source> set = StreamSupport.stream(nodes.spliterator(), false)
                    .map(mapper)
                    .collect(Collectors.toSet());
            ...
        }

        ...
    }