datetime反序列化错误

Question

我尝试用DateTime作为属性来反序列化一个类:

import org.joda.time.DateTime;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.datatype.joda.deser.DateTimeDeserializer;
import com.fasterxml.jackson.datatype.joda.ser.DateTimeSerializer;
class MyClass {
    private DateTime alertTimestamp;
    private String name;
    @JsonSerialize(using = DateTimeSerializer.class)
    public DateTime getAlertTimestamp() {
        return alertTimestamp;
    }
    @JsonDeserialize(using = DateTimeDeserializer.class)
    public void setAlertTimestamp(DateTime now) {
        this.alertTimestamp = now;
    }
    //...
}

但是当我尝试反序列化时，我有这个异常:

com.fasterxml.jackson.datatype.joda.deser.DateTimeDeserializer has no default (no arg) constructor

我用它来反序列化:

ObjectMapper mapper = new ObjectMapper();
mapper.readValue(jsonData, MyClass.class);

和jsonData的一个例子:

{    
    "name":"test",
    "alertTimestamp":       {"year":2014,"era":1,"dayOfMonth":24,"dayOfWeek":1,"dayOfYear":83,"weekOfWeekyear":13,"weekyear":2014,"monthOfYear":3,"yearOfEra":2014,"yearOfCentury":14,"centuryOfEra":20,"millisOfSecond":232,"millisOfDay":45143232,"secondOfMinute":23,"secondOfDay":45143,"minuteOfHour":32,"minuteOfDay":752,"hourOfDay":12,"zone":{"uncachedZone":{"cachable":true,"fixed":false,"id":"America/Los_Angeles"},"fixed":false,"id":"America/Los_Angeles"},"millis":1395689543232,"chronology":{"zone":{"uncachedZone":{"cachable":true,"fixed":false,"id":"America/Los_Angeles"},"fixed":false,"id":"America/Los_Angeles"}},"afterNow":false,"beforeNow":false,"equalNow":true}
}

Answer 1

@JsonDeserialize期望JsonDeserializer具有无参数构造函数。最新版本的DateTimeDeserializer没有这样的构造函数。

如果你修改了格式，alertTimestamp应该只是一个时间戳，然后您可以简单地将JodaModule注册为ObjectMapper。对于DateTime字段，它将在内部使用DateTimeDeserializer。您可以去掉@JsonDeserialize注释。

mapper.registerModule(new JodaModule());

您需要添加jackson-datatype-joda库