注:Jackson 2.1.x。
问题很简单但到目前为止我找不到解决方案。我浏览了现有的文档等,但找不到答案。
基类是这样的:
@JsonTypeInfo(use = Id.NAME, include = As.PROPERTY, property = "op")
@JsonSubTypes({
@Type(name = "add", value = AddOperation.class),
@Type(name = "copy", value = CopyOperation.class),
@Type(name = "move", value = MoveOperation.class),
@Type(name = "remove", value = RemoveOperation.class),
@Type(name = "replace", value = ReplaceOperation.class),
@Type(name = "test", value = TestOperation.class)
})
public abstract class JsonPatchOperation
{
/*
* Note: no need for a custom deserializer, Jackson will try and find a
* constructor with a single string argument and use it
*/
protected final JsonPointer path;
protected JsonPatchOperation(final JsonPointer path)
{
this.path = path;
}
public abstract JsonNode apply(final JsonNode node)
throws JsonPatchException;
@Override
public String toString()
{
return "path = \"" + path + '"';
}
}
有问题的课是:
public abstract class PathValueOperation
extends JsonPatchOperation
{
protected final JsonNode value;
protected PathValueOperation(final JsonPointer path, final JsonNode value)
{
super(path);
this.value = value.deepCopy();
}
@Override
public String toString()
{
return super.toString() + ", value = " + value;
}
}
当我尝试反序列化时:
{ "op": "add", "path": "/x", "value": null }
我希望将null值反序列化为NullNode
,而不是Java null。到目前为止,我找不到办法。
你是如何实现这一目标的?
(注意:具体类的所有构造函数都是@JsonCreator
,带有适当的@JsonProperty
注释 - 它们没有问题,我唯一的问题是JSON null处理)
答案 0 :(得分:5)
好吧,我没有阅读足够的文档,事实上它非常简单。
JsonDeserializer
的{{3}}实现,您可以扩展。 JsonDeserializer
有一个JsonNodeDeserializer。
因此,自定义反序列化程序是有序的:
public final class JsonNullAwareDeserializer
extends JsonNodeDeserializer
{
@Override
public JsonNode getNullValue()
{
return NullNode.getInstance();
}
}
而且,在有问题的课程中:
@JsonDeserialize(using = JsonNullAwareDeserializer.class)
protected final JsonNode value;