Hibernate中的ManyToOne关系出错[重复]

Question

我有两门课：

@Entity
@Table(name = "user_role",uniqueConstraints = @UniqueConstraint(columnNames = {"role","username"}))
public class UserRole {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "user_role_id", unique = true, nullable = false)
    private Integer userRoleId;
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "username", nullable = false)
    private User user;
    @Column(name = "role",nullable = false, length = 45)
    private String role;

@Entity
@Table(name = "users")
public class User {
    @Column(name = "firstname", nullable = false)
    private String firstName;
    @Column(name = "lastname", nullable = false)
    private String lastName;
    @Column(name = "surname", nullable = true)
    private String surName;
    @Id
    @Column(name = "username", unique = true, nullable = false, length = 45)
    private String username;
    @Column(name = "password", nullable = false, length = 60)
    private String password;
    @Column(name = "email", nullable = false, length = 255)
    private String email;
    @Column(name = "enabled", nullable = false)
    private boolean enabled;
    @OneToMany(fetch = FetchType.LAZY)
    private Set<UserRole> userRole = new HashSet<>(0);
    @OneToMany(fetch = FetchType.LAZY)
    private List<AddressBook> addressBooks = new ArrayList<>(0);
    @OneToMany(fetch = FetchType.LAZY)
    private List<Message> messages = new ArrayList<>(0);

当我用UserRole保存User时,出现了一个奇怪的错误：

2016-03-16 16:52:36.480 DEBUG 8280 --- [nio-8090-exec-9] org.hibernate.SQL                        : insert into users_user_role (users_username, user_role_user_role_id) values (?, ?)
2016-03-16 16:52:36.489 DEBUG 8280 --- [nio-8090-exec-9] o.h.engine.jdbc.spi.SqlExceptionHelper   : could not execute statement [n/a]

org.postgresql.util.PSQLException: ERROR: column "user_role_user_role_id" of relation "users_user_role" does not exist

如果它创建了userrole_user_role_id，为什么要使用User_Role_ID？我该怎么修好它？

Answer 1

将user中的userRole映射更改为

@OneToMany(fetch = FetchType.LAZY, mappedBy = "user")
private Set<UserRole> userRole = new HashSet<>(0);

mappedby是Hibernate必须要知道这是双向关系的另一面。