我有双向用户和组之间的多对多关系 .
@Entity
@Table(name = "UserTBL")
public class User {
@Id
@SequenceGenerator(name = "user_generator", sequenceName = "user_seq", allocationSize = 1, initialValue = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "user_generator")
private Long id;
private String username;
private String password;
@ManyToMany
private List<Group> groups;
}
@Entity
@Table(name = "GroupTBL")
public class Group {
@Id
@SequenceGenerator(name = "Group_generator", sequenceName = "group_seq", allocationSize = 1, initialValue = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "Group_generator")
private Long id;
private String name;
private String description;
@ManyToMany(mappedBy = "groups")
private List<User> users;
}
我正在使用java jax-rs web服务开发角度js应用程序，我正在使用jackson处理json绑定但是我得到了这个异常：
Can not instantiate value of type [simple type, class com.blog.models.Group] from JSON String; no single-String constructor/factory method (through reference chain: com.blog.models.User["groups"])
这是我发送到服务器的json对象：
{
"groups":[
"{\"id\":1,\"name\":\"admin\",\"description\":null,\"users\":[]}",
"{\"id\":2,\"name\":\"user\",\"description\":null,\"users\":[]}"
],
"username":"hussien",
"password":"ammar"
}
资源：
@Stateless
@Path("/users")
public class UserResource {
@EJB
private UserFacade userFacade;
@POST
@Consumes(MediaType.APPLICATION_JSON)
public void createUser(User user) {
userFacade.create(user);
}
}
1 回答
看起来在客户端，您可能会对JSON对象进行两次字符串化（组） . 你应该只调用一次 . 这就是JSON应该如何应对：