java 使用 Jackson 反序列化数组
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Deserialization of arrays with Hymanson
提问by mirekys
i have something like JSON-RPC client, and i′m having trouble deserializing incoming json string into my java object. The incoming json format is:
我有类似 JSON-RPC 客户端的东西，我在将传入的 json 字符串反序列化为我的 java 对象时遇到了麻烦。传入的json格式为：
{"value":"xxxx","type":"xxxx"}
The object i want to deserialize to:
我想反序列化的对象：
@JsonAutoDetect
@JsonDeserialize()
public class ReturnValue {
private Object value;
private String type;
@JsonCreator
public ReturnValue(@JsonProperty("value") String val, @JsonProperty("type") String type) {
value = val;
this.type = type;
}
...getters, setters...
This seems to work ok, if the value is String, but if it′s of array type, it throws JsonMapping Exception - Can not deserialize instance of java.lang.String out of START_ARRAY token for the json like this:
这似乎工作正常，如果值是字符串，但如果它是数组类型，它会抛出 JsonMapping 异常 - 不能像这样从 START_ARRAY 令牌中反序列化 java.lang.String 的实例：
{\"value\":[8, 10], \"type\":\"[int]\"}
The code is:
代码是：
int[] arr = (int[])getReturnValue(jsonString).getValue();
Where getReturnValue is nothing special:
getReturnValue 没有什么特别之处：
ObjectMapper om = new ObjectMapper();
ReturnValue rv = null;
rv = om.readValue(json, ReturnValue.class);
return rv;
The another problem is that i would want the type property to be of Class type, but this would throw another mapping exception. Is there any way in Hymanson to do it, or do i have to convert from string to appropriate class myself. Thank you for any advice.
另一个问题是我希望 type 属性为 Class 类型，但这会引发另一个映射异常。Hyman逊有什么方法可以做到这一点，还是我必须自己从字符串转换为适当的类。谢谢你的任何建议。
回答by StaxMan
Change your constructor to be:
将您的构造函数更改为：
@JsonCreator
public ReturnValue(@JsonProperty("value") Object val, @JsonProperty("type") String type) {
since, like error points out, it does not know how to make a String out of array. But both String and JSON Array can be converted to Object; if so, it'll be Java String, or Java List (for JSON arrays), or Java Map (for JSON objects).
因为，就像错误指出的那样，它不知道如何从数组中生成一个字符串。但是String和JSON Array都可以转为Object；如果是这样，它将是 Java String，或 Java List（对于 JSON 数组）或 Java Map（对于 JSON 对象）。
