php editor Youzi brings you the Java Q&A topic of this article: "Checking the type of Json attribute value when converting to a Java class". During the development process, we often need to convert JSON data into Java objects, but how to effectively check and handle the type of attribute values is an important skill in this process. This article will answer this question for you and help you better understand and use JSON data conversion technology.
Suppose I have the following json data. Here I have an id of integer type. The type of id in the java class is string.
{ "id": 1, "name": "user1" }
@lombok.data @allargsconstructor @noargsconstructor class data { string id; string name; }
I want to convert json to the class while strictly checking whether the value of the json attribute is the same type as the class field.
String json = "{\"id\":1,\"name\":\"user1\"}"; ObjectMapper objectMapper = new ObjectMapper(new JsonFactory()); Data data = objectMapper.readValue(json, Data.class); System.out.println(data);
data(id=1, name=user1)
I hope no conversion should happen here, but it will be converted.
One way I guess is to use a custom deserializer and do a simple type check:
public class customdeserializer extends stddeserializer<string> { protected customdeserializer() { this(null); } protected customdeserializer(class<?> vc) { super(vc); } @override public string deserialize(jsonparser p, deserializationcontext ctxt) throws ioexception, jacksonexception { if (p.currenttoken() != jsontoken.value_string) { throw new invalidformatexception(p, "expected string type", p.getvalueasstring(), string.class); } return p.getvalueasstring(); } }
Then use this deserializer in the field you want to check:
public class Data { @JsonDeserialize(using = CustomDeserializer.class) String id; }
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