java - Redisson(通过 JCache API)仅反序列化为 String

Question

我有一个Redisson客户端来存储一对字符串，LocalDateTime。它配置为通过 JCache API (JSR-107) 使用。

存储完成，使用 Jackson 转换为诸如 2018-01-23T11:59:34.997834 之类的值，但检索时不使用任何转换器并返回字符串，在 cache#get 调用。

我在这里缺少什么？

@Test
public void getCacheInline() {
    Config redissonCfg = new Config();
    redissonCfg
        .setCodec(new JsonJacksonCodec(buildObjectMapper()))
        .useSingleServer()
        .setAddress("redis://redis:6379");

    MutableConfiguration<String, LocalDateTime> jcacheConfig = new MutableConfiguration<String, LocalDateTime>()
        .setTypes(String.class, LocalDateTime.class)
        .setExpiryPolicyFactory((Factory<ExpiryPolicy>) () -> new CreatedExpiryPolicy(new Duration(SECONDS, 100)));

    Configuration<String, LocalDateTime> configuration = RedissonConfiguration.fromConfig(redissonCfg, jcacheConfig);


    Cache<String, LocalDateTime> cache = cacheManager.createCache(CACHE_NAME, configuration);
    LocalDateTime expectedDateTime = LocalDateTime.now();
    cache.put("testKey", expectedDateTime);

    // In this line: java.lang.ClassCastException: java.base/java.lang.String cannot be cast to java.base/java.time.LocalDateTime
    LocalDateTime actualDateTime = cache.get("testKey");
    assertThat(actualDateTime, is(equalTo(expectedDateTime)));
}

private ObjectMapper buildObjectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.registerModule(new JavaTimeModule());
    objectMapper.configure(FAIL_ON_UNKNOWN_PROPERTIES, false);
    objectMapper.configure(WRITE_DATES_AS_TIMESTAMPS, false);
    objectMapper.configure(READ_DATE_TIMESTAMPS_AS_NANOSECONDS, false);
    objectMapper.setSerializationInclusion(NON_NULL);
    return objectMapper;
}

Answer 1

最初的解决方法是不存储一对 String, LocalDateTime ，将 LocalDateTime 包装在包装类中:

public class LocalDateTimeWrapper {
    private LocalDateTime value;
    ...
}

这将使 Jackson 使用 @class 序列化 json 字符串。属性指示 LocalDateTimeWrapper 类，并且可以从那里检索 LocalDateTime 作为反序列化字符串的类型，如 2018-01-23T11:59:34.997834到。

我尝试过并为我工作的更好的解决方案是 GitHub 问题 https://github.com/redisson/redisson/issues/1260#issuecomment-367272400 中建议的解决方案像这样扩展 JsonJacksonMapCodec:

public static class ExtendedJsonJacksonMapCodec extends JsonJacksonMapCodec {

    public ExtendedJsonJacksonMapCodec() {
        super(String.class, LocalDateTime.class);
    }

    @Override
    protected void init(ObjectMapper objectMapper) {
        objectMapper.registerModule(new JavaTimeModule());
        super.init(objectMapper);
    }

}

然后像这样从配置链接它(YAML 格式):

singleServerConfig:
    address: "redis://localhost:6379"
codec: !<com.example.ExtendedJsonJacksonMapCodec> {}