一对多
一对多的实体 多对一的实体
需要使用set集合用于保存对象 需要一对多实体的对象
set<对象> 变量名 对象 变量名
package domain;
import java.util.HashSet;
import java.util.Set;
public class Customer {
public Set<LinkMan> getLinkMans() {
return linkMans;
}
public void setLinkMans(Set<LinkMan> linkMans) {
this.linkMans = linkMans;
}
private Long cust_id;
private String cust_name;
private String cust_source;
private String cust_industry;
private String cust_level;
private String cust_linkman;
private String cust_phone;
private String cust_mobile;
private Set<LinkMan> linkMans = new HashSet<LinkMan>();
public Customer() {
super();
}
public Customer(String cust_name,Long cust_id) {
super();
this.cust_id = cust_id;
this.cust_name=cust_name;
}
public Long getCust_id() {
return cust_id;
}
public void setCust_id(Long cust_id) {
this.cust_id = cust_id;
}
public String getCust_name() {
return cust_name;
}
public void setCust_name(String cust_name) {
this.cust_name = cust_name;
}
public String getCust_source() {
return cust_source;
}
public void setCust_source(String cust_source) {
this.cust_source = cust_source;
}
public String getCust_industry() {
return cust_industry;
}
public void setCust_industry(String cust_industry) {
this.cust_industry = cust_industry;
}
public String getCust_level() {
return cust_level;
}
public void setCust_level(String cust_level) {
this.cust_level = cust_level;
}
public String getCust_linkman() {
return cust_linkman;
}
public void setCust_linkman(String cust_linkman) {
this.cust_linkman = cust_linkman;
}
public String getCust_phone() {
return cust_phone;
}
public void setCust_phone(String cust_phone) {
this.cust_phone = cust_phone;
}
public String getCust_mobile() {
return cust_mobile;
}
public void setCust_mobile(String cust_mobile) {
this.cust_mobile = cust_mobile;
}
@Override
public String toString() {
return "Customer [cust_id=" + cust_id + ", cust_name=" + cust_name + "]";
}
}
package domain;
public class LinkMan {
@Override
public String toString() {
return "LinkMan [lkm_id=" + lkm_id + ", lkm_name=" + lkm_name + ", lkm_gender=" + lkm_gender + ", lkm_phone="
+ lkm_phone + ", lkm_email=" + lkm_email + ", lkm_qq=" + lkm_qq + ", lkm_mobile=" + lkm_mobile
+ ", lkm_memo=" + lkm_memo + ", lkm_postion=" + lkm_postion + ", customer=" + customer + "]";
}
private Long lkm_id;
private String lkm_name;
private Character lkm_gender;
private String lkm_phone;
private String lkm_email;
private String lkm_qq;
private String lkm_mobile;
private String lkm_memo;
private String lkm_postion;
private Customer customer;
public Long getLkm_id() {
return lkm_id;
}
public void setLkm_id(Long lkm_id) {
this.lkm_id = lkm_id;
}
public String getLkm_name() {
return lkm_name;
}
public void setLkm_name(String lkm_name) {
this.lkm_name = lkm_name;
}
public Character getLkm_gender() {
return lkm_gender;
}
public void setLkm_gender(Character lkm_gender) {
this.lkm_gender = lkm_gender;
}
public String getLkm_phone() {
return lkm_phone;
}
public void setLkm_phone(String lkm_phone) {
this.lkm_phone = lkm_phone;
}
public String getLkm_email() {
return lkm_email;
}
public void setLkm_email(String lkm_email) {
this.lkm_email = lkm_email;
}
public String getLkm_qq() {
return lkm_qq;
}
public void setLkm_qq(String lkm_qq) {
this.lkm_qq = lkm_qq;
}
public String getLkm_mobile() {
return lkm_mobile;
}
public void setLkm_mobile(String lkm_mobile) {
this.lkm_mobile = lkm_mobile;
}
public String getLkm_memo() {
return lkm_memo;
}
public void setLkm_memo(String lkm_memo) {
this.lkm_memo = lkm_memo;
}
public String getLkm_postion() {
return lkm_postion;
}
public void setLkm_postion(String lkm_postion) {
this.lkm_postion = lkm_postion;
}
public Customer getCustomer() {
return customer;
}
public void setCustomer(Customer customer) {
this.customer = customer;
}
}
orm元数据的表达就是
<!-- 集合,一对多关系,在配置文件中配置 -->
<!--
name属性:集合属性名
column属性: 外键列名
class属性: 与我关联的对象完整类名
-->
<set name="linkMans" >
<key column="lkm_cust_id"></key>
<one-to-many class="LinkMan"/>
</set>
多对一
<many-to-one name="customer" column="lkm_cust_id" class="Customer" ></many-to-one>
配置号xml后即可开始操作
public void func1() {
Session sesion = HibernateUtils.openSession();
Transaction tx = sesion.beginTransaction();
//--------------------------------------
Customer c = new Customer();
c.setCust_name("as");
LinkMan linkman = new LinkMan();
linkman.setLkm_name("sss");
LinkMan linkman2 = new LinkMan();
linkman2.setLkm_name("ccc");
//一对多
c.getLinkMans().add(linkman);
c.getLinkMans().add(linkman2);
//多对一
linkman.setCustomer(c);
linkman2.setCustomer(c);
sesion.save(c);
/*设置级联 不需要下面两行代码*/
sesion.save(linkman);
sesion.save(linkman2);
//--------------------------------------
tx.commit();
sesion.close();
}
这时候可以设置级联操作 就可以只写一边save了、 cascade属性
//一对多
<!-- 级联操作: cascade save-update: 级联保存更新 delete:级联删除 all:save-update+delete 级联操作: 简化操作.目的就是为了少些两行代码. --> <set name="linkMans" cascade="save-update" inverse="true" lazy="true" fetch="select"> <key column="lkm_cust_id"></key> <one-to-many class="LinkMan"/> </set>
//多对一
<many-to-one name="customer" column="lkm_cust_id" class="Customer" cascade="save-update"></many-to-one>
保存时.两方都会维护外键关系.关系维护两次,重复了.
显然只需要一端在维护关系
//一对多
<!-- inverse属性: 配置关系是否维护. true: 放弃维护关系 false(默认值): 维护关系 inverse属性: 性能优化.提高关系维护的性能. 原则: 无论怎么放弃,总有一方必须要维护关系. 一对多关系中: 一的一方放弃.也只能一的一方放弃.多的一方不能放弃. -->
<set name="linkMans" cascade="save-update" inverse="true" lazy="true" fetch="select"> <key column="lkm_cust_id"></key> <one-to-many class="LinkMan"/> </set>
//多对一
<many-to-one name="customer" column="lkm_cust_id" class="Customer" cascade="save-update"></many-to-one>
多对多
实体1 实体2
需要使用set集合用于保存对象 需要使用set集合用于保存对象
set<对象> 变量名 set<对象> 变量名
package domain;
import java.util.HashSet;
import java.util.Set;
public class User {
@Override
public String toString() {
return "User [user_id=" + user_id + ", user_code=" + user_code + ", user_name=" + user_name + ", user_password="
+ user_password + ", user_state=" + user_state + ", roles=" + roles + "]";
}
public String getUser_name() {
return user_name;
}
public void setUser_name(String user_name) {
this.user_name = user_name;
}
public Set<Role> getRoles() {
return roles;
}
public void setRoles(Set<Role> roles) {
this.roles = roles;
}
private Long user_id;
private String user_code;
private String user_name;
private String user_password;
private Character user_state;
private Set<Role> roles = new HashSet<Role>();
public Long getUser_id() {
return user_id;
}
public void setUser_id(Long user_id) {
this.user_id = user_id;
}
public String getUser_code() {
return user_code;
}
public void setUser_code(String user_code) {
this.user_code = user_code;
}
public String getUser_password() {
return user_password;
}
public void setUser_password(String user_password) {
this.user_password = user_password;
}
public Character getUser_state() {
return user_state;
}
public void setUser_state(Character user_state) {
this.user_state = user_state;
}
}
package domain;
import java.util.HashSet;
import java.util.Set;
public class Role {
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
public Long getRole_id() {
return role_id;
}
public void setRole_id(Long 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_memo() {
return role_memo;
}
public void setRole_memo(String role_memo) {
this.role_memo = role_memo;
}
private Long role_id;
private String role_name;
private String role_memo;
private Set<User> users = new HashSet<User>();
}
orm元数据
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="domain" >
<class name="Role" table="sys_role" >
<id name="role_id" >
<!-- generator:主键生成策略(明天讲) -->
<generator class="native"></generator>
</id>
<property name="role_name"></property>
<property name="role_memo"></property>
<!-- 使用inverse属性
true: 放弃维护外键关系
false(默认值):维护关系
结论: 将来在开发中,如果遇到多对多关系.一定要选择一方放弃维护关系.
一般谁来放弃要看业务方向. 例如录入员工时,需要为员工指定所属角色.
那么业务方向就是由员工维护角色. 角色不需要维护与员工关系.角色放弃维护
-->
<set name="users" table="sys_user_role" inverse="true">
<key column="role_id"></key>
<many-to-many class="User" column="user_id"></many-to-many>
</set>
</class>
</hibernate-mapping>
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="domain" >
<class name="User" table="sys_user" >
<id name="user_id" >
<generator class="native"></generator>
</id>
<property name="user_name" ></property>
<property name="user_code" ></property>
<property name="user_password"></property>
<property name="user_state"></property>
<!-- 多对多描述 -->
<!-- 多对多关系表达 -->
<!--
name: 集合属性名
table: 配置中间表名
key
|-column:外键,别人引用"我"的外键列名
class: 我与哪个类是多对多关系
column:外键.我引用比人的外键列名
-->
<!-- cascade级联操作:
save-update: 级联保存更新
delete:级联删除
all:级联保存更新+级联删除
结论: cascade简化代码书写.该属性使不使用无所谓. 建议要用只用save-update.
如果使用delete操作太过危险.尤其在多对多中.不建议使用.
-->
<set name="roles" table="sys_user_role" cascade="save-update">
<key column="user_id"></key>
<many-to-many class="Role" column="role_id"></many-to-many>
</set>
</class>
</hibernate-mapping>
操作多对多
public class demo3 {
public void function1() {
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//--------------------------------------
User user1 = new User();
User user2 = new User();
user1.setUser_name("user1");
user2.setUser_name("user2");
Role role1 = new Role();
Role role2 = new Role();
role1.setRole_name("role1");
role2.setRole_name("role2");
user1.getRoles().add(role1);
user1.getRoles().add(role2);
user2.getRoles().add(role1);
user2.getRoles().add(role2);
role1.getUsers().add(user1);
role1.getUsers().add(user2);
role2.getUsers().add(user1);
role2.getUsers().add(user2);
session.save(user1);
session.save(user2);
session.save(role1);
session.save(role2);
//--------------------------------------
tx.commit();
session.close();
}
@Test
public void function3() {
Session session = HibernateUtils.openSession();
Transaction tx = session.beginTransaction();
//--------------------------------------
//删除关系
User user = session.get(User.class, 1l);
Role role1 = session.get(Role.class, 1l);
Role role2 = session.get(Role.class, 2l);
Role role3 = session.get(Role.class, 3l);
user.getRoles().remove(role1);
user.getRoles().remove(role2);
user.getRoles().remove(role3);
//session.save(user);
//--------------------------------------
tx.commit();
session.close();
}
}
多对多 使用inverse属性 只允许一方维护关系
原文：https://www.cnblogs.com/hywhyme/p/11628899.html