java Jackson：无法反序列化 START_OBJECT 令牌中的 Number 实例
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Hymanson: Can not deserialize instance of Number out of START_OBJECT token
提问by LancerX
My GWT service returns LinkedList<VisualData>. This is how VisualDatalooks:
我的 GWT 服务返回LinkedList<VisualData>. 这是VisualData看起来的样子：
import javax.xml.bind.annotation.XmlRootElement;
import com.google.gwt.user.client.rpc.IsSerializable;
@XmlRootElement
public class VisualData implements IsSerializable {
private Number value;
private long timestamp;
public VisualData() {
}
public VisualData(Number value, long timestamp) {
this.value = value;
this.timestamp = timestamp;
}
public long getTimestamp() {
return timestamp;
}
public Number getValue() {
return value;
}
public void setTimestamp(long timestamp) {
this.timestamp = timestamp;
}
public void setValue(Number value) {
this.value = value;
}
}
I get the following excepion connected with field private Number value.
我得到以下与 field 相关的异常private Number value。
SEVERE: The exception contained within MappableContainerException could not be mapped to a response, re-throwing to the HTTP container
org.codehaus.Hymanson.map.JsonMappingException: Can not deserialize instance of java.lang.Number out of START_OBJECT token
at [Source: org.apache.catalina.connector.CoyoteInputStream@a0eb51; line: 1, column: 29] (through reference chain: org.jage.charts.client.VisualData["value"])
When I change private Number valueto private Object value, all getters and setters I get:
当我更改private Number value为 时private Object value，我得到的所有 getter 和 setter：
SEVERE: WebModule[/AgECharts]Exception while dispatching incoming RPC call
com.google.gwt.user.client.rpc.SerializationException: Type 'org.jage.charts.client.VisualData' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, this type will not be serialized.: instance = Value:{@type=xs:int, $=6}, timestamp:1360240281439
at com.google.gwt.user.server.rpc.impl.ServerSerializationStreamWriter.serialize(ServerSerializationStreamWriter.java:619)
This second case is quite clear, the Objectclass is not serializable. But why do I get Can not deserialize instance of java.lang.Number out of START_OBJECT token?
第二种情况很清楚，Object该类不可序列化。但为什么我得到Can not deserialize instance of java.lang.Number out of START_OBJECT token？
回答by Perception
You won't be able to deserialize data into this object without supplying additional type information for your valuefield. This is because the Numberclass is abstract and cannot be instantiated. Changing the field to Objectwill not help, since there are no writable fields on that class that Hymanson can deserialize data into.
如果不为您的value字段提供其他类型信息，您将无法将数据反序列化到此对象中。这是因为Number该类是抽象的，无法实例化。将字段更改为Object将无济于事，因为该类上没有可写字段，Hyman逊可以将数据反序列化为。
You should change the field to be one of the concrete implementations of the Numberclass (Integer, Long, Doubleetc).
你应该改变的领域是的具体实现的一个Number类（Integer，Long，Double等）。
