GSON：无知地将JSON转换为对象

Question

I had JSON model for success some this

{
    data: {
        .....
    }
}

so I've create model:

Class Model{
    public Data data;
}

and I've used new Gson().fromJson(Model.class) to convert in Object. It works fine. Now my problem starts with when I get error in same API and its json Get changed

{
    message: {
        .....
    }
}

I want to use same model to be serialized in Json.

Class Model{
    public Data data;
    public Massage message;
}

But it gives me following Exception: Expected a string but was BEGIN_OBJECT at line 1 column 13

Answer 1

Just configure and use ObjectMapper from Jackson lib:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.8.3</version>
</dependency>

The mapper should be defined as

ObjectMapper mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

Please see full Demo example

public class Demo {

    public static void main(String[] args) throws IOException {

        String jsonData = "{" +
                "    \"data\": {" +
                "    }" +
                "}";
        String jsonMessage = "{" +
                "    \"message\": {" +
                "    }" +
                "}";

        ObjectMapper mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

        Model modelData = mapper.readValue(jsonData, Model.class);
        Model modelMessage = mapper.readValue(jsonMessage, Model.class);


        System.out.println(modelData);
        System.out.println(modelMessage);


    }
}


class Model {

    private Data data;
    private Message message;

    @Override
    public String toString() {
        return "Model{" +
                "data=" + data +
                ", message=" + message +
                '}';
    }

    public Data getData() {
        return data;
    }

    public void setData(Data data) {
        this.data = data;
    }

    public Message getMessage() {
        return message;
    }

    public void setMessage(Message message) {
        this.message = message;
    }

    private static class Data {}
    private static class Message {}
}

BTW, ObjectMapper is Thread Safe, so you can define one constant to not create it each time when you read Json.

More info you can find here: http://fasterxml.github.io/jackson-databind/javadoc/2.8/com/fasterxml/jackson/databind/ObjectMapper.html