javax.persistence.NonUniqueResultException：查询未返回唯一结果：3

Question

**hi big community! someone can help me**
 **here: Role entity**

        @Entity
        @Table(name="roles")
        public class Role implements Serializable {
        @Id @GeneratedValue(strategy = GenerationType.AUTO)
        private Integer id;  
        private String obser;
        public Role() {
            super();
        }

    public Role(Integer id, String obser) {
        super();
        this.id = id;
        this.obser = obser;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getObser() {
        return obser;
    }

    public void setObser(String obser) {
        this.obser = obser;
    }}



    @Entity
    @Table(name="users")
    public class User implements Serializable{

    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;
    private String username;
    private String password;
    private Boolean active;
    private String email;


      @ManyToMany
      @JoinTable(name="USERS_ROLES", 
              joinColumns={@JoinColumn(name="username", referencedColumnName="username")},
               inverseJoinColumns={@JoinColumn(name="obser", referencedColumnName="obser")}

              )
    private Collection<Role>roles;
    public Collection<Role> getRoles() {
        return roles;
    }
    public void setRoles(Collection<Role> roles) {
        this.roles = roles;
    }
    public User() {
        super();
    }
    public User(Integer id,String username, String password, Boolean active, String email) {
        super();
        this.id = id;
        this.username = username;
        this.password = password;
        this.active = active;
        this.email = email;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    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;
    }
    public Boolean getActive() {
        return active;
    }
    public void setActive(Boolean active) {
        this.active = active;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }}

**here is y Role RoleRepository:**


    public interface RoleRepository extends JpaRepository<Role, Integer> {
        List<Role> findAll();
        Role findByObser(String obser);
    }

**here is my User RoleRepository:**

    public interface UserRepository extends JpaRepository<User, Integer> {
        User findByUsername(String username);
    }


**here is my function AddRoleToUser in  my UserService:**
**When I want to add a role to a user, I use this method**

    @RequestMapping(value="/addRoleToUser")
    public User addRoleToUser(String username, String role) {
        User u = userRepository.findByUsername(username);
        Role r = roleRepository.findByObser(role);



      u.getRoles().add(r); 
              userRepository.save(u);
            return u;
    }

不幸的是，它没有将角色分配给用户，并且会创建以下类型的异常： 查询未返回唯一结果：3；嵌套异常是 javax.persistence.NonUniqueResultException：查询没有返回唯一结果：3 然后我问是否有人可以帮助我 其他方法如添加角色，添加用户其权杖问题

Answer 1

这可能是因为您可能有不止一个用户具有相同的username，因此您可以将username 设置为唯一，或者将user_id 用于所有事务或持久性。