解决Redis序列化LocalDateTime的问题

在项目中从redis获取带有LocalDateTime类型属性的对象时出现了以下异常：

org.springframework.data.redis.serializer.SerializationException: Could not read JSON: Can not construct instance of java.time.LocalDateTime: no suitable constructor found, can not deserialize from Object value (missing default constructor or creator, or perhaps need to add/enable type information?)
......
......

这是因为我们将数据存入redis时，Jackson默认将LocalDateTime类型序列化为以下形式：

"createTime": {
    "dayOfYear":141,
    "dayOfWeek":"WEDNESDAY",
    "month":"MAY",
    "dayOfMonth":20,
    "year":2020,
    "monthValue":5,
    "hour":19,
    "minute":50,
    "second":47,
    "nano":364000000,
    "chronology":{
        "calendarType":"iso8601",
        "id":"ISO"
    }
}

我们从redis获取数据，Jackson反序列化LocalDateTime类型时出错，无法进行反序列化，就报了上面的异常。

方式一：局部配置

1、引入依赖：

		<dependency>
            <groupId>com.fasterxml.jackson.coregroupId>
            <artifactId>jackson-annotationsartifactId>
        dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.coregroupId>
            <artifactId>jackson-databindartifactId>
        dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatypegroupId>
            <artifactId>jackson-datatype-jsr310artifactId>
        dependency>

2、在需要序列化的LocalDateTime属性上添加序列化注解

	import com.fasterxml.jackson.databind.annotation.JsonSerialize;
	import com.fasterxml.jackson.datatype.jsr310.ser.LocalDateTimeSerializer;

	@JsonSerialize(using = LocalDateTimeSerializer.class)

添加注解之后的序列化结果：[2020,5,14,10,25,19,494000000]

3、在需要反序列化的LocalDateTime属性上添加反序列化注解

	import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
	import com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer;

	@JsonDeserialize(using = LocalDateTimeDeserializer.class)

添加注解之后的反序列化结果：2020-05-14T10:25:19.494

4、格式化序列化和反序列化注解：

	import com.fasterxml.jackson.annotation.JsonFormat;

	@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")

格式化之后：
序列化结果：2020-05-14 10:30:17
反序列化结果：2020-05-14T10:30:17

5、示例

    @JsonDeserialize(using = LocalDateTimeDeserializer.class)
    @JsonSerialize(using = LocalDateTimeSerializer.class)
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    @ApiModelProperty(value = "激活时间")
    private LocalDateTime activeTime;

方式二：全局配置

1、引入依赖：

		<dependency>
            <groupId>com.fasterxml.jackson.coregroupId>
            <artifactId>jackson-annotationsartifactId>
        dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.coregroupId>
            <artifactId>jackson-databindartifactId>
        dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.datatypegroupId>
            <artifactId>jackson-datatype-jsr310artifactId>
        dependency>

2、编写全局公共常量接口

CommonConstant.interface

public interface CommonConstant {
	ObjectMapper JacksonMapper = new ObjectMapper()
            .registerModule(new JavaTimeModule());
}

3、存入redis

通过CommonConstant.JacksonMapper.writeValueAsString(object)将对象序列化之后存入redis

redisService.putHash(key, hashKey,
CommonConstant.JacksonMapper.writeValueAsString(device));

4、读取数据

String result = (String) redisService.getHash(
                key, hashKey);
Device device = CommonConstant.JacksonMapper
                    .readValue(result, Device.class);