Question

我正在尝试在pojo类中的表之间进行映射。但是我正在为一个属性获取异常。 Pojo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;
    }

    }

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类的正确成员变量。但我这样得到例外

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role，usertype这样的属性，它们被映射而没有任何异常。对于组我正在获得此异常。有人可以帮我解决这个例外。

谢谢：）

Answer 1

在Groups类中，您首先将名为users的变量声明为Users的一组，这很好。因此，如果要在setter上注释@OneToMany，则名称必须与变量名称匹配。

此外，在您的Users表格中，您创建了一个Groups变量，并将其命名为groupId，但在Users表格中，您有一个int表格groupId }类型命名为private Groups group;，这将混淆休眠和导致问题。您应该将其重命名为：

@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;
}

所以应该是这样的：

RoleID

您没有问，但您还需要修复extension String { public func substringWithRange(range: Range<Index.Distance>) -> String { return substringWithRange(startIndex.advancedBy(range.startIndex)..<startIndex.advancedBy(range.endIndex)) } } str.substringWithRange(index..<index + length)表。我认为你真的不明白hibernate ORM是如何工作的，请看：

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

Answer 2

类用户和组的成员变量存在问题将变量名称 groupId 更改为 Users.pojo 的组，并将 mappedby 属性更改为组 in groups class set method。

这将解决您的问题。

Answer 3

一定是因为用户与用户之间存在差异。

Answer 4

您在Users bean中将Group对象的getter定义为：

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

这不是bean的最佳访问者名称。

尝试将用户中的群组对象从groupID重命名为group，并将映射注释更改为：

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

使用mappedby属性

4 个答案: