无法使用 Jackson 反序列化 ZonedDateTime

Question

我正在使用带有 Jackson 的 Jersey 作为 JSON 提供程序。我可以将ZonedDateTime 序列化为 JSON，但是当我想反序列化时，它会给我如下错误。

能否请您帮我说出完成此反序列化工作所需的确切配置。

原因：com.fasterxml.jackson.databind.JsonMappingException：无法从字符串值（'2016-01-21T21:00:00Z'）实例化类型[简单类型，类 java.time.ZonedDateTime] 的值；没有单字符串构造函数/工厂方法

我的mapper配置如下：

@Provider
public class ObjectMapperContextResolver implements ContextResolver<ObjectMapper> {  
    private final ObjectMapper MAPPER;

    public ObjectMapperContextResolver() {
        MAPPER = new ObjectMapper();
        //This would add JSR310 (Datetime) support while converting date to JSON using JAXRS service
        MAPPER.registerModule(new JavaTimeModule());
        //Below line would disable use of timestamps (numbers), 
        //and instead use a [ISO-8601 ]-compliant notation, which gets output as something like: "1970-01-01T00:00:00.000+0000".
        MAPPER.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return MAPPER;
    }  
}

Answer 1

我发现了问题，实际上问题不在于使用标准杰克逊提供程序进行反序列化。就我而言，我使用 Jersey 客户端获取 JSON，然后使用 readEntity 方法进行反序列化。

问题是 jersey 客户端不知道 jsr310 模块，因此通过注册添加了 jsr310 的 contextresolver 解决了该问题。所以简而言之，如果使用普通的杰克逊提供者，你不需要对ZonedDateTime的序列化和反序列化做任何事情。

下面是我在这里引用的参考代码，以便更清楚。

public class RESTClientImpl{

    /*
     * ***This is very important, JacksonJsonProvider is the implementation of
     * MessageBodyWriter/Reader which is required for "readEntity" method, 
     * else it would throw MessageBodyWriter/Reader not found exception
     * 
     * https://jersey.java.net/documentation/latest/message-body-workers.html#mbw.ex.client.mbr.reg
     *
     * Registering of ObjectMapperContextResolver is important as we have registered JSR310 module there and without registering this, 
     * Jersey client is not aware of JSR310 module, so it will not be able to de-serialize ZonedDateTime
     */
    private final Client client = ClientBuilder.newClient(new ClientConfig().register(LoggingFilter.class)).register(JacksonJsonProvider.class)
            .register(ObjectMapperContextResolver.class);

    public User get(URI uri) {
        WebTarget webTarget = client.target(uri);

        Invocation.Builder invocationBuilder = webTarget.request(MediaType.APPLICATION_JSON);
        Response response = invocationBuilder.get();    
        User user = response.readEntity(User.class);
        return user;
    }
}


@Provider
public class ObjectMapperContextResolver implements ContextResolver<ObjectMapper> {  
    private final ObjectMapper MAPPER;

    public ObjectMapperContextResolver() {
        MAPPER = new ObjectMapper();
        //This would add JSR310 (Datetime) support while converting date to JSON using JAXRS service
        MAPPER.registerModule(new JavaTimeModule());
        //Below line would disable use of timestamps (numbers), 
        //and instead use a [ISO-8601 ]-compliant notation, which gets output as something like: "1970-01-01T00:00:00.000+0000".
        MAPPER.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

        SimpleModule simpleModule = new SimpleModule();
        simpleModule.addDeserializer(Object.class, new ZonedDateTimeDeserializer());
        MAPPER.registerModule(simpleModule);
    }

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return MAPPER;
    }  
}