Question

我有一个Redisson客户端来存储一对String，LocalDateTime。它被配置为通过JCache API（JSR-107）使用。

存储已经完成，使用Jackson转换为2018-01-23T11:59:34.997834之类的值，但是检索不使用任何转换器并返回String，在cache#get调用中给出ClassCastException。

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

初始解决方法不是存储一对String, LocalDateTime，而是将LocalDateTime包装在包装类中：

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

这将使Jackson序列化一个json字符串，其中@class属性用信号表示LocalDateTimeWrapper类，从那里可以检索LocalDateTime作为类型，以便像2018-01-23T11:59:34.997834那样反序列化字符串。

更好的解决方案我在GitHub问题https://github.com/redisson/redisson/issues/1260#issuecomment-367272400中建议我尝试并为我工作，这样就可以扩展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);
    }

}

然后从配置中链接它（YAML格式）：

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

Redisson（通过JCache API）仅对String进行反序列化

1 个答案: