使用 mappedby 属性时的 Hibernate 异常

Question

我正在尝试在 pojo 中的表之间进行映射 class.But 我收到一个属性的异常。波乔类

用户：

@Entity
@Table(name = "Users")
public class Users implements java.io.Serializable {

    private int userId;
    private Role role;
    private Groups groupId;
    private UserType userType;
    private String userName;
    private Boolean isActive;



    public Users() {
    }

    public Users(int userId, Role role, Groups groupId ,UserType userType, String userName, boolean isActive) {
        this.userId = userId;
        this.role = role;
        this.groupId = groupId;
        this.userType = userType;
        this.userName = userName;
        this.isActive = isActive;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "UserID", unique = true, nullable = false)
    public int getUserId() {
        return this.userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "RoleID", nullable = false)
    public Role getRole() {
        return this.role;
    }

    public void setRole(Role role) {
        this.role = role;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "GroupId", nullable = false)
    public Groups getGroup() {
        return this.groupId;
    }

    public void setGroup(Groups group) {
        this.groupId = group;
    }

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "UserTypeID", nullable = false)
    public UserType getUserType() {
        return this.userType;
    }

    public void setUserType(UserType userType) {
        this.userType = userType;
    }

    @Column(name = "UserName", nullable = false)
    public String getUserName() {
        return this.userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    @Column(name = "IsActive", nullable = false, columnDefinition = "BIT")
    public Boolean isIsActive() {
        return this.isActive;
    }

    public void setIsActive(Boolean isActive) {
        this.isActive = isActive;
    }

    }

群组：

@Entity
@Table(name = "Groups")
public class Groups implements java.io.Serializable{

    private int groupId;
    private String groupName;
    private String groupDesc;

    private Set<Users> users = new HashSet<Users>(0);

    public Groups (){

    }

    public Groups(int groupId, String groupName, String groupDesc){
        super();
        this.groupId = groupId;
        this.groupName = groupName;
        this.groupDesc = groupDesc;
    }

    public Groups(int groupId, String groupName, String groupDesc, Set<Users> users) {
        super();
        this.groupId = groupId;
        this.groupName = groupName;
        this.groupDesc = groupDesc;
        this.users = users;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name ="GroupID", nullable = false)
    public int getGroupId() {
        return groupId;
    }

    public void setGroupId(int groupId) {
        this.groupId = groupId;
    }

    @Column(name = "GroupName", nullable = false)
    public String getGroupName() {
        return groupName;
    }

    public void setGroupName(String groupName) {
        this.groupName = groupName;
    }

    @Column(name = "GroupDesc", nullable = false)
    public String getGroupDesc() {
        return groupDesc;
    }

    public void setGroupDesc(String groupDesc) {
        this.groupDesc = groupDesc;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "groupId") //Error
    public Set<Users> getUserse() {
        return this.userse;
    }

    public void setUserse(Set<Users> users) {
        this.users = users;
    }


}

我正在映射 Users class 的正确成员变量。但是我遇到了这样的异常

org.hibernate.AnnotationException: mappedBy reference an unknown target     entity property: com.project.pojo.Users.groupId in com.project.pojo.Groups.users

在用户 pojo 中，我有像角色、用户类型这样的属性，这些属性没有任何 exception.Whereas 组映射，我得到了这个异常。有人可以帮我解决这个异常吗？

谢谢:)

Answer 1

一定是因为 users 和 userse 不同。

Answer 2

在您的 Groups class 中，您首先将一个名为 users 的变量声明为一组 Users，这很好。因此，如果您要在设置器上注释 @OneToMany，则名称必须与变量名称相匹配。

此外，在您的 Users table 中，您创建了一个 Groups 变量并将其命名为 groupId，但在您的 Users table 你有一个名为 groupId 的 int 类型，这会混淆休眠并导致问题。您应该将其重命名为：

private Groups group;

所以它应该是这样的：

@OneToMany(fetch = FetchType.LAZY, mappedBy = "group")
public Set<Users> getUsers() {
    return this.users;
}

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "group", nullable = false)
public Groups getGroup() {
    return this.group;
}

你没有问，但你也需要修复你的 RoleID table。我认为你还没有真正理解 hibernate ORM 是如何工作的，看这个：

http://www.mkyong.com/hibernate/hibernate-one-to-many-relationship-example-annotation/

Answer 3

您为用户 bean 中的组对象定义 getter 为：

@ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "GroupId", nullable = false)
    public Groups getGroup() {
        return this.groupId;
    }

这不是 Bean 的最佳访问器名称。

尝试将用户中的组对象从 groupID 重命名为 group 并将映射注释更改为类似以下内容：

@OneToMany(fetch = FetchType.LAZY, mappedBy = "group")
    public Set<Users> getUserse() {
        return this.userse;
    }

Answer 4

你的classes用户和组的成员变量有问题将groupId的变量名groupId改成Users.pojo的group，改成 mappedby attribute to group in groups class set method.

这将解决您的问题。

使用 mappedby 属性时的 Hibernate 异常

Hibernate Exception when using mappedby attribute

java

hibernate

pojo

one-to-many