我怎样才能让杰克逊反序列化一个长期的日期对象？

发布于 2024-10-27 19:09:54 字数 833 浏览 3 评论 0原文

我正在映射中序列化一些 java.util.Dates 。日期被序列化为 Long（Jackson 将 Date 实例的 Long 值写入 JSON 字符串），但是，它们不会被反序列化回 Date 实例，但作为 Long 实例。

我希望 Jackson 将日期反序列化回 Date 对象（而不是格式化字符串或长整型），我怎样才能实现这一点？

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

生产

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

什么都可以。但是，当我希望日期字符串成为 java.util.Date 的实例时，它会被反序列化（膨胀）回 java.lang.Long 的实例 -这就是它开始的样子。即地图更改现在包含三个条目；描述为 String，速率为 Float，日期为 Long。

原文

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.

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我的黑色迷你裙 2024-11-03 19:09:54

您想要使用 org.codehaus.jackson.map.JsonDeserializer 并编写自定义反序列化代码。类似于：

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

我想您必须弄清楚何时必须将 Long 属性反序列化为 Date。也许在你的 pojo 上使用注释？

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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奢欲 2024-11-03 19:09:54

我不知道日期的字符串表示是否有帮助？

如果是，那么您可以尝试在 ObjectMapper 上设置 DateFormat。然后反序列化将采用可读的字符串格式。

例如，对于下面的代码，输出将类似于 [{"birthDate":"March 30, 2011"}]

    @Test
public void testJsonConvertDate(){

    ObjectMapper mapper = new ObjectMapper();
    mapper.getSerializationConfig().setDateFormat(DateFormat.getDateInstance(DateFormat.LONG));
    StringWriter stringWriter = new StringWriter();
    try {
        mapper.writeValue(stringWriter, Arrays.asList(new TestUser(new Date())));
    }
    catch (IOException e) {
        e.printStackTrace();
    }

    System.out.println(stringWriter.toString());
}

private class TestUser {
    Date birthDate;

    private TestUser(Date birthDate) {
        this.birthDate = birthDate;
    }

    public Date getBirthDate() {
        return birthDate;
    }

    public void setBirthDate(Date birthDate) {
        this.birthDate = birthDate;
    }
}

I don't know if a String representation of the Date would be of any help?

If yes, then you could try setting the DateFormat on the ObjectMapper. The deserialization would then be in the readable String format.

E.g for the below code, the output would be like [{"birthDate":"March 30, 2011"}]

    @Test
public void testJsonConvertDate(){

    ObjectMapper mapper = new ObjectMapper();
    mapper.getSerializationConfig().setDateFormat(DateFormat.getDateInstance(DateFormat.LONG));
    StringWriter stringWriter = new StringWriter();
    try {
        mapper.writeValue(stringWriter, Arrays.asList(new TestUser(new Date())));
    }
    catch (IOException e) {
        e.printStackTrace();
    }

    System.out.println(stringWriter.toString());
}

private class TestUser {
    Date birthDate;

    private TestUser(Date birthDate) {
        this.birthDate = birthDate;
    }

    public Date getBirthDate() {
        return birthDate;
    }

    public void setBirthDate(Date birthDate) {
        this.birthDate = birthDate;
    }
}

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