我如何使杰克逊反序列化一个长日期对象？ [英] How can I make Jackson deserialize a Long to a Date Object?

问题描述

我正在序列化Map中的一些java.util.Dates。日期序列化为Longs（Jackson将 Date 实例的 Long 值写入JSON字符串），但是，它们没有被反序列化为 Date 实例，而是作为 Long 实例。

我希望杰克逊将日期重新排序为Date对象（而不是格式化的String或Longs），我该如何实现？ b
$ b

  Map< String，Comparable<？>> change = new HashMap< String，Comparable<？>>（）; 
 change.put（DESCRIPTION，LIBOR）; 
 change.put（RATE，1.8）; 
 change.put（DATE，Util.newDate（2009,7,1））; //返回一个java.util.Date 
  

生成

  {DESCRIPTION：LIBOR}，{RATE：1.8}，{DATE：1246402800000}，...} 
  

哪个是好的但是，日期字符串被反序列化（膨胀）回到 java.lang.Long 的实例，当我想要它是一个 java的实例.util.Date - 这是它开始的。
即地图更改现在包含三个条目;描述为 String ，作为浮动和日期作为长。

解决方案

您要使用org.codehaus.jackson.map.JsonDeserializer并编写自定义反序列化代码。如下所示：

  public class DateDeserializer extends JsonDeserializer< Long> {
 @Override 
 public Long deserialize（JsonParser jp，DeserializationContext ctxt）throws IOException，JsonProcessingException {
 ...自定义逻辑
} 
} 
  

我想你必须弄清楚Long属性何时被反序列化为Date。也许在你的pojos上使用注释？

I'm serializing some java.util.Dates within a Map. The dates are serialized into Longs (Jackson writes the Long value of the Date instance to the JSON string), however, they're not being de-serialized back to Date instances, but as Long instances.

I'd like Jackson to de-serialize the dates back to Date objects (rather than formatted Strings or Longs), how can I achieve this?

Map<String, Comparable<?>> change = new HashMap<String, Comparable<?>>();
    change.put("DESCRIPTION", "LIBOR");
    change.put("RATE", "1.8");
    change.put("DATE", Util.newDate(2009, 7, 1)); // Returns a java.util.Date

Produces

{"DESCRIPTION":"LIBOR"},{"RATE":"1.8"},{"DATE":1246402800000}, ... }

Which is okay. However, the date String is deserialized (inflated) back into an instance of java.lang.Long, when I want it to be an instance of java.util.Date - which is what it started as. i.e. Map change now contains three entries; Description as a String, Rate as a Float and Date as a Long.

解决方案

You want to use org.codehaus.jackson.map.JsonDeserializer and write the custom deserialization code. Something like:

public class DateDeserializer extends JsonDeserializer<Long> {
    @Override
    public Long deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
       ... custom logic
    }
}

I guess you have to figure out when a Long property has to be deserialized to Date. Maybe using annotations on your pojos?

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