• Hibernate的双向关联。
      对象之间可以相互读取。
      
      双向只针对读取的操作。对于增、删除、改的操作没有任何影响。

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 案例 ： 实现双向多对多

• MenuBean.java

package bean;import java.io.Serializable;import java.util.HashSet;import java.util.Set;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.JoinTable;import javax.persistence.ManyToMany;import javax.persistence.Table;@Entity@Table(name = "menu")public class MenuBean implements Serializable {    @Id    private Integer menuid;    private String menuname;    @ManyToMany    @JoinTable(name = "role_menu",  //指定数据库中的中间表    joinColumns = @JoinColumn(name = "menu_id"),  //设置当前实体在中间表中的映射，也就是说在中间表中有一个字段叫menu_id，使它指向当前表的主键这里是menuid     inverseJoinColumns = @JoinColumn(name = "roleid")  //设置对方实体在中间中的映射，也就是说在中间表中有一个字段roleid，使它指向对方表的主键。     )    private Set
     
       roleSet = new HashSet
      
       ();    public MenuBean(Integer menuid, String menuname) {        super();        this.menuid = menuid;        this.menuname = menuname;    }    public MenuBean() {        super();        // TODO Auto-generated constructor stub    }    public Integer getMenuid() {        return menuid;    }    public void setMenuid(Integer menuid) {        this.menuid = menuid;    }    public String getMenuname() {        return menuname;    }    public void setMenuname(String menuname) {        this.menuname = menuname;    }    public Set
       
         getRoleSet() {        return roleSet;    }    public void setRoleSet(Set
        
          roleSet) {        this.roleSet = roleSet;    }}
        
       
      
     

• RoleBean.java

package bean;import java.io.Serializable;import java.util.HashSet;import java.util.Set;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.JoinTable;import javax.persistence.ManyToMany;import javax.persistence.Table;@Entity@Table(name = "role")public class RoleBean implements Serializable {    @Id    private Integer role_id;    private String role_name;    private String role_remark;    @ManyToMany    @JoinTable(name = "role_menu",     joinColumns = @JoinColumn(name = "roleid"),     inverseJoinColumns = @JoinColumn(name = "menu_id"))    private Set
     
       menuSet = new HashSet
      
       ();    public RoleBean(Integer role_id, String role_name, String role_remark) {        super();        this.role_id = role_id;        this.role_name = role_name;        this.role_remark = role_remark;    }    public RoleBean() {        super();        // TODO Auto-generated constructor stub    }    public Integer getRole_id() {        return role_id;    }    public void setRole_id(Integer role_id) {        this.role_id = role_id;    }    public String getRole_name() {        return role_name;    }    public void setRole_name(String role_name) {        this.role_name = role_name;    }    public String getRole_remark() {        return role_remark;    }    public void setRole_remark(String role_remark) {        this.role_remark = role_remark;    }    public Set
       
         getMenuSet() {        return menuSet;    }    public void setMenuSet(Set
        
          menuSet) {        this.menuSet = menuSet;    }}
        
       
      
     

• 添加到总配置文件即可实现。