我正在处理一些服务器代码，其中客户端以JSON形式发送请求。我的问题是，有许多可能的请求，每个请求的实现细节都不尽相同。因此，我想使用一个Request接口，它定义为：

public interface Request {
    Response process ( );
}

从那里，我在名为LoginRequest如下的类中实现了接口：

public class LoginRequest implements Request {
    private String type = "LOGIN";
    private String username;
    private String password;

    public LoginRequest(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }

    /**
     * This method is what actually runs the login process, returning an
     * appropriate response depending on the outcome of the process.
     */
    @Override
    public Response process() {
        // TODO: Authenticate the user - Does username/password combo exist
        // TODO: If the user details are ok, create the Player and add to list of available players
        // TODO: Return a response indicating success or failure of the authentication
        return null;
    }

    @Override
    public String toString() {
        return "LoginRequest [type=" + type + ", username=" + username
            + ", password=" + password + "]";
    }
}

为了使用JSON，我创建了一个GsonBuilder实例并注册了一个InstanceCreator，如下所示：

public class LoginRequestCreator implements InstanceCreator<LoginRequest> {
    @Override
    public LoginRequest createInstance(Type arg0) {
        return new LoginRequest("username", "password");
    }
}

然后，如下面的代码片段所示，我使用了它：

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(LoginRequest.class, new LoginRequestCreator());
Gson parser = builder.create();
Request request = parser.fromJson(completeInput, LoginRequest.class);
System.out.println(request);

我得到了预期的输出。

我希望做的是用Request request = parser.fromJson(completeInput, LoginRequest.class);类似于以下内容的内容替换该行，Request request = parser.fromJson(completeInput, Request.class);但是这样做是行不通的，因为这Request是一个接口。

我希望我Gson根据收到的JSON返回适当的请求类型。

我传递给服务器的JSON示例如下所示：

{
    "type":"LOGIN",
    "username":"someuser",
    "password":"somepass"
}

重申一下，我正在寻找一种方法来解析来自客户端的请求（在JSON中）并返回实现该Request接口的类的对象