HQL o->m & m<-->n

最新推荐文章于 2025-07-06 23:51:47 发布

最新推荐文章于 2025-07-06 23:51:47 发布 · 159 阅读

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本文介绍了一种在实体关系映射中处理多对多关系的方法，通过使用join(left join fetch)来实现MenuGroup、MenuNode及EnterpriseDepartment之间的关联查询。具体展示了如何在Java实体类中定义这些关系，并给出了相应的HQL查询语句。

from MenuGroup mg

left join fetch mg.menuNodes mns

[color=red][b]join[/b][/color] mns.enterpriseDepartments eds

where mg.id=mns.menuGroup and eds.id = ?

from MenuGroup mg left join fetch mg.menuNodes mns 这句参见我的另外一个日志

多对多采用 [color=red][b]join(left join fetch)[/b][/color] ,并且不用id直连

实体关系如下(只写出关键的代码了,呵呵):

MenuGroup 与 MenuNode 一对多

MenuNode 与 EnterpriseDepartment 多对多(单向关系)

@Entity
@Table(name = "PERMISSION_MENU_GROUP")
public class MenuGroup implements AccessPermission,IntOrderable{
        /**菜单所包含的菜单节点*/
	private List<MenuNode> menuNodes = new ArrayList<MenuNode>();

    @OneToMany(mappedBy="menuGroup")
	@LazyCollection(LazyCollectionOption.FALSE)
	public List<MenuNode> getMenuNodes() {
		return menuNodes;
	}
     //略
}

@Entity
@Table(name = "PERMISSION_MENU_NODE")
public class MenuNode implements AccessPermission,IntOrderable{

      /**企业会员部门*/
	private List<EnterpriseDept> enterpriseDepartments=new ArrayList<EnterpriseDept>();

     /**菜单所在组*/
	private MenuGroup menuGroup;

	@ManyToMany
	@JoinTable(
			name = "PERMISSION_MENUNODE_ENTER_DEPT", 
			joinColumns = { 
					@JoinColumn(name = "MENU_NODE_ID") 
					}, 
			inverseJoinColumns = { 
					@JoinColumn(name = "ENTERPRISE_DEPARTMENT_ID")
					})
	@LazyCollection(LazyCollectionOption.FALSE)
	public List<EnterpriseDept> getEnterpriseDepartments() {
		return enterpriseDepartments;
	}


	@ManyToOne
	@JoinColumn(name = "MENU_GROUP_ID",nullable=false)
	public MenuGroup getMenuGroup() {
		return menuGroup;
	}


     //略
}

@Entity
@Table(name = "ENTERPRISE_DEPT")
public class EnterpriseDept extends BasicDept{

     //略

}

@MappedSuperclass
public abstract class BasicDept implements java.io.Serializable, ValueObject<BasicDept>,Identityable{

    protected String id;


    @Id
    @Column(length = 32)
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    public String getId() {
	return id;
    }

    //略
}