使用Jackson ObjectMapper在java之间进行转换。时间Instant和java。util。日期

Question

我试图使用Jackson的ObjectMapper在两个类（例如SrcMessage和DestMessage）之间进行映射

我的SrcMessage类类似于：

class SrcMessage {
        public Instant workTime;
}

我的消息类如下所示：

class DestMessage {
   public Date workTime;
}

我正在使用ObjectMapper，如下所示：

SrcMessage src = new SrcMessage ();
src.workTime = Instant.now ();

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

DestMessage dest = mapper.convertValue (src, DestMessage.class);

当我进行convertValue调用时，我收到一条异常消息：

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.Date` out of VALUE_NUMBER_FLOAT token
 at [Source: UNKNOWN; line: -1, column: -1] (through reference chain: DestMessage["workTime"])
    at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
    at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1468)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1242)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1148)
    at com.fasterxml.jackson.databind.deser.std.StdDeserializer._parseDate(StdDeserializer.java:517)
    at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateBasedDeserializer._parseDate(DateDeserializers.java:200)
    at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:290)
    at com.fasterxml.jackson.databind.deser.std.DateDeserializers$DateDeserializer.deserialize(DateDeserializers.java:273)
    at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:138)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:156)
    at com.fasterxml.jackson.databind.ObjectMapper._convert(ObjectMapper.java:4231)

我卡住了。我认为JavaTimeModule足以处理这种转换，但显然不行。我还需要其他模块吗？关于如何实现这一目标的其他建议？到目前为止，我找到的唯一解决方案是在进行映射时忽略workTime字段，然后在映射程序完成后转换该值。不用说，这适用于一个简单的情况，但我不想枚举所有的Instant/Date字段并手动处理它们。我宁愿让杰克逊自己处理

有什么想法吗

Answer 1

对于转换日期，我建议使用类型的优点，而不是使用Jackson ObjectMapper。使用Date from(Instant instant)静态方法将java.time.Instant类型转换为java.util.Date类型

您可以按照示例中的说明进行操作：

import java.time.Instant;
import java.util.Date;

public class StackOverflowAnswer {
    public static void main(String[] args) {
        SrcMessage srcMessage = new SrcMessage(Instant.now());
        DestMessage destMessage = DestMessage.fromSrcMessage(srcMessage);
    }
}

class SrcMessage {
    public Instant workTime;

    public SrcMessage(Instant workTime) {
        this.workTime = workTime;
    }
}

class DestMessage {
    public Date workTime;

    DestMessage(Date workTime) {
        this.workTime = workTime;
    }

    static DestMessage fromSrcMessage(SrcMessage srcMessage) {
        return new DestMessage(Date.from(srcMessage.workTime));
    }
}