使用GSON将JSON数据转换为Java对象（包括Object类）

Question

Let's suppose to receive the following JSON data:

{
    "request" : "connection_status",
    "data" : { "id" : "foo", "username" : "bar" }
}

and you want to deserialize that to a Java object whose class is defined like this:

public class SingleJsonObjectRequest {
    private String request;
    private Object data;

    public String getRequest() {
        return request;
    }

    public void setRequest(String request) {
        this.request = request;
    }

    public Object getData() {
        return data;
    }

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

Clearly, you even have the following class:

public class UserInfo {
    private String id;
    private String username;

    public String getId() {
        return id;
    }

    public UserInfo setId(String id) {
        this.id = id;
        return this;
    }

    public String getUsername() {
        return username;
    }

    public UserInfo setUsername(String username) {
        this.username = username;
        return this;
    }
}

which can be included into SingleJsonObjectRequest by calling:

singleObjReq.setData(new UserInfo());

Is there any way to convert that JSON data to a SingleJsonObjectRequest object? I mean, you cannot use the following code:

SingleJsonObjectRequest singleObjReq = gson.fromJson(jsonReq, SingleJsonObjectRequest.class);

because SingleJsonObjectRequest has a general data Object, not a UserInfo object.

Answer 1

You can write a custom deserializer ( https://sites.google.com/site/gson/gson-user-guide#TOC-Writing-a-Deserializer ).

IMHO, you have to use separate class for each data type you want to send/receive. You can create a generic base class like this

class JsonRequest<T>{
  private String request;
    private T data;

    public String getRequest() {
        return request;
    }

    public void setRequest(String request) {
        this.request = request;
    }

    public T getData() {
        return data;
    }

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

and use subclasses for each type, because java doesnot store generic types information For example

class UserInfoRequest extends JsonRequest<UserInfo>{
//nothing in here
}