如何使用注释创建hibernate组合键 [英] How to create hibernate composite key using annotations

问题描述

我试图使用 hibernate annotations 将数据插入到 MySQL数据库表中，该表没有主键定义。然而事实是这个表的2个字段在表中是唯一的，我可以使用hibernate注释来实现相同的功能吗？

这是我的代码..

  @Entity 
 @Table（name =RolesMenuItems）
 public class RolesMenuItems {
 
 @Column（name =RoleID）
 private String roleID; 
 
 @Column（name =MenuItemID）
 private String menuItemID; 
 / * setter getter methods * / 
} 
  

解决方案您可以使用 @Embeddeble 和 @EmbeddedId 创建一个组合键并将其与您的实体。例如：

  @Embeddable 
 public class RolesMenu {
 @Column（name =RoleID） 
私人字符串roleID; 
 
 @Column（name =MenuItemID）
 private String menuItemID; 
 $ b $ // getter，setter方法
} 
 
 @Entity 
 @Table（name =RolesMenuItems）
 public class RolesMenuItems { 
 
 @EmbeddedId 
私人RolesMenu roleMenu; 
 
 setter getter methods 
 
 code> 

然后在您的Java代码中使用 RolesMenuItems 以通常方式保存实体。

http://docs.jboss.org/hibernate/annotations/3.5/reference/en/html_single / b d0e535

编辑：
坚持实体：

  RolesMenu roleMenu = new RolesMenu（）; 
 roleMenu.setRoleID（...）; 
 roleMenu.setMenuItemID（...）; 
 
 RolesMenuItems roleItem = new RolesMenuItems（）; 
 roleItem.setRoleMenu（roleMenu）; 
 
 em.persist（roleItem）; 
  

I am trying to use hibernate annotations to insert data to a MySQL database table which doesn't have a primary key defined.

However the fact is 2 fields of that table together are unique in the table.how can i achieve the same using hibernate annotation?.

here is my code..

 @Entity
 @Table(name = "RolesMenuItems")
    public class RolesMenuItems {

       @Column(name = "RoleID")
       private String roleID;

       @Column(name = "MenuItemID")
       private String menuItemID;
  /*setter getter methods */
 }

解决方案

You can use @Embeddeble and @EmbeddedId to create a composite key and map it with your Entity. For example:

@Embeddable
public class RolesMenu {
    @Column(name = "RoleID")
    private String roleID;

    @Column(name = "MenuItemID")
    private String menuItemID;

    //getter, setter methods
}

 @Entity
 @Table(name = "RolesMenuItems")
 public class RolesMenuItems {

     @EmbeddedId
     private RolesMenu roleMenu;

  /*setter getter methods */
 }

Then use RolesMenuItems in your Java code to persist entities in usual way.

Reference: http://docs.jboss.org/hibernate/annotations/3.5/reference/en/html_single/#d0e535

Edit: To persist the entity:

RolesMenu roleMenu = new RolesMenu();
roleMenu.setRoleID(...);
roleMenu.setMenuItemID(...);

RolesMenuItems roleItem = new RolesMenuItems();
roleItem.setRoleMenu( roleMenu );

em.persist(roleItem);

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