如何在 Jackson2JsonRedisSerializer 中反序列化 java.time.Instant

Question

我正在使用 Jackson2JsonRedisSerializer。

@Bean
    public RedisOperations<String , Aircraft> redisOperations(RedisConnectionFactory factory){
        Jackson2JsonRedisSerializer<Aircraft> serializer = new Jackson2JsonRedisSerializer<Aircraft>(Aircraft.class);
        RedisTemplate<String, Aircraft> template = new RedisTemplate<>();
        template.setConnectionFactory(factory);
        template.setDefaultSerializer(serializer);
        template.setKeySerializer(new StringRedisSerializer());
        return template;
    }

我的飛機具有 Instant 類型的字段。

    @JsonProperty("last_seen_time")
    private Instant lastSeenTime;

反序列化時出現錯誤：

Java 8 date/time type `java.time.Instant` not supported by default: add Module "com.fasterxml.jackson.datatype:jackson-datatype-jsr310" to enable handling (through reference chain: com.example.chapter6.sburredis.Aircraft["last_seen_time"])

我已經在我的 pom.xml 中添加了 maven 依賴項

<dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
            <version>2.14.1</version>
</dependency>

json文件如下：

{
  "aircraft": [
    {
      "id": 108,
      "callsign": "AMF4263",
      "squawk": "4136",
      "reg": "N49UC",
      "flightno": "",
      "route": "LAN-DFW",
      "type": "B190",
      "category": "A1",
      "altitude": 20000,
      "heading": 235,
      "speed": 248,
      "lat": 38.865905,
      "lon": -90.429382,
      "barometer": 0,
      "vert_rate": 0,
      "selected_altitude": 0,
      "polar_distance": 12.99378,
      "polar_bearing": 345.393951,
      "is_adsb": true,
      "is_on_ground": false,
      "last_seen_time": 1672576769,
      "pos_update_time": 1672576769,
      "bds40_seen_time": null
      }
  ]
}

Answer 1

當我們序列化一個 Java object 或反序列化 JSON 到 POJO 時，就會出現這個錯誤。 POJO 包含新的 Java 8+ 日期時間類，例如 LocalDate、LocalTime、LocalDateTime 等。
腳步：

1. 添加依賴

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jsr310</artifactId>
</dependency>

2. 使用 ObjectMapper 或 JsonMapper 注冊模塊JavaTimeModule

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule());

// If JsonMapper is used in application
JsonMapper jsonMapper = new JsonMapper();
jsonMapper.registerModule(new JavaTimeModule());

在這里，您在 bean 中使用Jackson2JsonRedisSerializer 。 因此，您可以創建 ObjectMapper object 並設置JavaTimeModule 。 之后將 ObjectMapper 注冊到 Jackson2JsonRedisSerializer object。

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule());
objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);

Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
jackson2JsonRedisSerializer.setObjectMapper(objectMapper);