JAX-RS多态POST请求:我应该如何编写JSON?

我在尝试用JAX-RS解决此问题时遇到了麻烦，我认为这与编组/解组过程有关(我想我不太了解)，并且我想重新创建这个:

I'm having a bad time trying to solve this problem with JAX-RS and I believe that it has something to do with the marshalling/unmarshalling process (that I don't know very much about, I assume), and I want to recreate this:

1. 要发布信息的REST端点是/rest/register，因此我的服务定义如下:

1. The REST endpoint to make a post is /rest/register so my services are defined like this:

@ApplicationPath("/rest")
public interface RestRegistration {
    @POST
    @Path("/register")
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_JSON)
    String register(UsernameRegistration usernameAccess, String network) throws RegistrationException;

    @POST
    @Path("/register")
    @Produces(MediaType.APPLICATION_JSON)
    @Consumes(MediaType.APPLICATION_JSON)
    String register(EmailRegistration emailAccess, String network) throws RegistrationException;
}

public class RestRegistrationImpl implements RestRegistration {
    public String register(UsernameRegistration usernameAccess, String network) throws RegistrationException {
        return "* example: username=" + usernameAccess.getUser + ", network="+network;
    }

    public String register(EmailRegistration emailAccess, String network) throws RegistrationException{
        return "* example: email=" + emailAccess.getEmail + ", network="+network;
    }

}

{ "usernameAccess" : { "user" : "AUser", "password" : "APass"}, "network" : "Facebook"}

{ "emailAccess" : { "email" : "AnEmail@domain.com", "password" : "APass"}, "network" : "LinkedIn"}

public abstract class Registration {
    private Long _id; 
    private String _password; 
    private String _network;
    // usual getters and setters...
}

public class UsernameRegistration extends Registration {
    private String _user; 
    // usual getters and setters...
}

public class EmailRegistration extends Registration {
    private String _email; 
    // usual getters and setters...
}

所以，我现在的问题是:

So, my problem now is:

1. 通过此实现，我不断收到HTTP 500错误.
2. 我不确定如何分隔两个JSON节点:usernameAccess/emailAccess和network.
3. 也:使用"UsernameRegistration"和"EmailRegistration"两个类都继承自相同的"Registration"，使"upper"上的类看起来更加优雅，有什么办法可以改进我? /li>

1. With this implemenationt I keep receiving an HTTP 500 error.
2. And I'm not sure on how to separate the two JSON nodes: usernameAccess/emailAccess and network.
3. Also: is there any way on how can I improve using the fact that both classes "UsernameRegistration" and "EmailRegistration" inherit from the same "Registration", making the classes on the "upper" 1. look more elegant?

有人可以提供我的书目，文章或方法吗? 提前致谢！ :)

Is there any bibliography, article or howto someone can hand me over? Thanks in advance! :)