一对多|多对一
一个分类对应多个商品，一个商品只属于一个分类
创建分类表 products用set装，set特点值不能够重复
package com.hibernate.domain;import java.util.HashSet;import java.util.Set;public class Category { ???private Integer cid; ???private String cname; ???private Set<Product> products = new HashSet<Product>(); ???????public Integer getCid() { ???????return cid; ???} ???public void setCid(Integer cid) { ???????this.cid = cid; ???} ???public String getCname() { ???????return cname; ???} ???public void setCname(String cname) { ???????this.cname = cname; ???} ???public Set<Product> getProducts() { ???????return products; ???} ???public void setProducts(Set<Product> products) { ???????this.products = products; ???}}创建商品表 category表示所属分类
package com.hibernate.domain;public class Product { ???private Integer pid; ???private String pname; ???private Category category; ???public Integer getPid() { ???????return pid; ???} ???public void setPid(Integer pid) { ???????this.pid = pid; ???} ???public String getPname() { ???????return pname; ???} ???public void setPname(String pname) { ???????this.pname = pname; ???} ???public Category getCategory() { ???????return category; ???} ???public void setCategory(Category category) { ???????this.category = category; ???}}配置映射关系
Category.hbm.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="com.hibernate.domain"> ???<class name="Category" table="Category"> ???????<id name="cid" column="cid"> ???????????<generator class="native"/> ???????</id> ???????<property name="cname"/> ???????<!--配置一对多关系 ???????set表示所有products ???????name 实体类中 商品集合属性 ???????--> ???????<set name="products"> ???????????<!--column 外键名 --> ???????????<key column="cpid"></key> ???????????<one-to-many class="Product"></one-to-many> ???????</set> ???</class></hibernate-mapping>
Product.hbm.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="com.hibernate.domain"> ???<class name="Product" table="Product"> ???????<id name="pid"> ???????????<generator class="native"/> ???????</id> ???????<property name="pname"/> ???????<!--配置多对一 所属分类 ???????name 分类属性 ???????class 分类全路径 ???????column 外键名称 要与 一对多设置的外键一样 ???????--> ???????<many-to-one name="category" class="Category" column="cpid"></many-to-one> ???</class></hibernate-mapping>
配置全局映射hibernate.cfg.xml
<mapping resource="com/hibernate/domain/Category.hbm.xml"></mapping><mapping resource="com/hibernate/domain/Product.hbm.xml"></mapping>
插入
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????Category category = new Category(); ???????????category.setCname("产品分类"); ???????????Product p1 = new Product(); ???????????p1.setPname("产品1"); ???????????p1.setCategory(category); ???????????Product p2 = new Product(); ???????????p2.setPname("产品2"); ???????????p2.setCategory(category); ???????????category.getProducts().add(p1); ???????????category.getProducts().add(p2); ???????????session.save(category); ???????????session.save(p1); ???????????session.save(p2); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}为已有分类追加商品
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????//获得已有分类对象 ???????????Category category = session.get(Category.class,1); ???????????Product p = new Product(); ???????????p.setCategory(category); ???????????p.setPname("小米电脑"); ???????????category.getProducts().add(p); ???????????session.save(p); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}移除分类下的商品 （将商品的外键设置为null 并没有删除）
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????//获得已有分类对象 ???????????Category category = session.get(Category.class,1); ???????????Product p = session.get(Product.class,2); ???????????category.getProducts().remove(p); ???????????p.setCategory(null); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}cascade级联操作
级联保存更新 只保存分类 自动把产品也保存
首先配置category.hbm.xml
<hibernate-mapping package="com.hibernate.domain"> ???<class name="Category" table="Category"> ??????... ???????<!--级联操作：cascade ???????????save-update：级联保存更新 ???????????delete:级联删除 ???????????all:save-update+delete --> ???????<set name="products" cascade="save-update"> ???????????<key column="cpid"></key> ???????????<one-to-many class="Product"></one-to-many> ???????</set> ???</class></hibernate-mapping>
编辑代码 只需要save 分类即可
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????Category category = new Category(); ???????????category.setCname("产品分类1"); ???????????Product p1 = new Product(); ???????????p1.setPname("产品11"); ???????????p1.setCategory(category); ???????????Product p2 = new Product(); ???????????p2.setPname("产品22"); ???????????p2.setCategory(category); ???????????category.getProducts().add(p1); ???????????category.getProducts().add(p2); ???????????session.save(category); ???????????//session.save(p1); ???????????//session.save(p2); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}级联删除 配置hbm.xml 为delete
<hibernate-mapping package="com.hibernate.domain"> ???<class name="Category" table="Category"> ???????。。。 ???????<!--级联操作：cascade ???????????save-update：级联保存更新 ???????????delete：级联删除 ???????????all：save-update+delete--> ???????<set name="products" cascade="delete"> ???????????<key column="cpid"></key> ???????????<one-to-many class="Product"></one-to-many> ???????</set> ???</class></hibernate-mapping>
编写删除代码 该分类下的产品都将被删除
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????Category category = session.get(Category.class,4); ???????????session.delete(category); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}cascade="all" 就是 添加 修改 删除时 不用save 商品 直接操作分类即可
在产品的配置文件中 也可以设置 many-to-one cascade="save-update" 操作时 就是不用操作分类表了
作用：简化操作，如果一定要用就用save-update，不要用delete。
inverse属性
关系维护，在保存时，两方都会维护外键关系，存在多余的维护关系语句。
上面保存分类和商品时 生成的sql语句如下：
Hibernate: ????insert ????into ???????Category ???????(cname) ????values ???????(?)Hibernate: ????insert ????into ???????Product ???????(pname, cpid) ????values ???????(?, ?)Hibernate: ????insert ????into ???????Product ???????(pname, cpid) ????values ???????(?, ?)Hibernate: ????update ???????Product ????set ???????cpid=? ????where ???????pid=?Hibernate: ????update ???????Product ????set ???????cpid=? ????where ???????pid=?
配置Category.hbm.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="com.hibernate.domain"> ???<class name="Category" table="Category"> ???????。。。 ???????<!-- inverse:配置关系是否维护 ???????????true:不维护 ???????????false：维护（默认值）--> ???????<set name="products" inverse="true"> ???????????<key column="cpid"></key> ???????????<one-to-many class="Product"></one-to-many> ???????</set> ???</class></hibernate-mapping>
修改配置文件后 重新运行程序 sql语句如下：
Hibernate: ????insert ????into ???????Category ???????(cname) ????values ???????(?)Hibernate: ????insert ????into ???????Product ???????(pname, cpid) ????values ???????(?, ?)Hibernate: ????insert ????into ???????Product ???????(pname, cpid) ????values ???????(?, ?)
inverse的作用就是 优化性能，此配置只能设置一的一方放弃维护关系，多的一方不可以放弃维护关系。
多对多
一个用户可以有很多角色，一个角色可以有很多用户。
使用中间表，至少两列，都是外键，分别引用其他两张表的主键
创建user表 set装role集合
package com.hibernate.domain;import java.util.HashSet;import java.util.Set;public class User { ???private Integer uid; ???private String uname; ???private Set<Role> roles = new HashSet<Role>(); ???public Integer getUid() { ???????return uid; ???} ???public void setUid(Integer uid) { ???????this.uid = uid; ???} ???public String getUname() { ???????return uname; ???} ???public void setUname(String uname) { ???????this.uname = uname; ???} ???public Set<Role> getRoles() { ???????return roles; ???} ???public void setRoles(Set<Role> roles) { ???????this.roles = roles; ???}}创建role表 set装user
package com.hibernate.domain;import java.util.HashSet;import java.util.Set;public class Role { ???private Integer rid; ???private String rname; ???private Set<User> users = new HashSet<User>(); ???public Integer getRid() { ???????return rid; ???} ???public void setRid(Integer rid) { ???????this.rid = rid; ???} ???public String getRname() { ???????return rname; ???} ???public void setRname(String rname) { ???????this.rname = rname; ???} ???public Set<User> getUsers() { ???????return users; ???} ???public void setUsers(Set<User> users) { ???????this.users = users; ???}}编写 User.hbm.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="com.hibernate.domain"> ???<class name="User" table="User"> ???????<id name="uid"> ???????????<generator class="native"/> ???????</id> ???????<property name="uname"/> ???????<!--多对多关系 ???????????table:中间表名 ???????--> ???????<set name="roles" table="User_Role"> ???????????<!--column 别人引入我的外键 uid --> ???????????<key column="uid"></key> ???????????<!--column 另外一方的外键 rid --> ???????????<many-to-many class="Role" column="rid"></many-to-many> ???????</set> ???</class></hibernate-mapping>
编写role.hbm.xml
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" ><hibernate-mapping package="com.hibernate.domain"> ???<class name="Role" table="Role"> ???????<id name="rid"> ???????????<generator class="native"/> ???????</id> ???????<property name="rname"/> ???????<set name="users" table="User_Role"> ???????????<key column="rid"></key> ???????????<many-to-many column="uid" class="User"></many-to-many> ???????</set> ???</class></hibernate-mapping>
最后写入全局配置中
<mapping resource="com/hibernate/domain/User.hbm.xml"></mapping><mapping resource="com/hibernate/domain/Role.hbm.xml"></mapping>
添加操作
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????User u1 = new User(); ???????????u1.setUname("武大郎"); ???????????User u2 = new User(); ???????????u2.setUname("武松"); ???????????Role r1 = new Role(); ???????????r1.setRname("卖烧饼"); ???????????Role r2 = new Role(); ???????????r2.setRname("武都头"); ???????????u1.getRoles().add(r1); ???????????u2.getRoles().add(r2); ???????????//武松帮大哥卖卖烧饼 ???????????u2.getRoles().add(r2); ???????????r1.getUsers().add(u1); ???????????r1.getUsers().add(u2); ???????????r2.getUsers().add(u2); ???????????session.save(u1); ???????????session.save(u2); ???????????session.save(r1); ???????????session.save(r2); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}虽然会插入数据成功 但是运行后会报错：could not execute statement（插入主键报错）,是因为双方都维护关系导致。
解决办法1： 去掉一方的维护关系
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????User u1 = new User(); ???????????u1.setUname("武大郎"); ???????????User u2 = new User(); ???????????u2.setUname("武松"); ???????????Role r1 = new Role(); ???????????r1.setRname("卖烧饼"); ???????????Role r2 = new Role(); ???????????r2.setRname("武都头"); ???????????u1.getRoles().add(r1); ???????????u2.getRoles().add(r2); ???????????//武松帮大哥卖卖烧饼 ???????????u2.getRoles().add(r2);// ???????????r1.getUsers().add(u1);// ???????????r1.getUsers().add(u2);// ???????????r2.getUsers().add(u2); ???????????session.save(u1); ???????????session.save(u2); ???????????session.save(r1); ???????????session.save(r2); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}解决办法2：
修改配置文件，选择一方不维护关系 加入节点inverse=true
<hibernate-mapping package="com.hibernate.domain"><class name="User" table="User"> ???<id name="uid"> ???????<generator class="native"/> ???</id> ???<property name="uname"/> ???<!--user一方 放弃维护 --> ???<set name="roles" table="User_Role" inverse="true"> ???????<key column="uid"></key> ???????<many-to-many class="Role" column="rid"></many-to-many> ???</set></class></hibernate-mapping>
然后把注释放开 ，运行 也不会报错了。
级联操作cascade
编辑user.hbm.xml配置文件
<hibernate-mapping package="com.hibernate.domain"><class name="User" table="User"> ???<id name="uid"> ???????<generator class="native"/> ???</id> ???<property name="uname"/> ???<!--user一方 放弃维护 --> ???<set name="roles" table="User_Role" inverse="true" cascade="save-update"> ???????<key column="uid"></key> ???????<many-to-many class="Role" column="rid"></many-to-many> ???</set></class></hibernate-mapping>
剩下联行save而已
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????User u1 = new User(); ???????????u1.setUname("武大郎"); ???????????User u2 = new User(); ???????????u2.setUname("武松"); ???????????Role r1 = new Role(); ???????????r1.setRname("卖烧饼"); ???????????Role r2 = new Role(); ???????????r2.setRname("武都头"); ???????????u1.getRoles().add(r1); ???????????u2.getRoles().add(r2); ???????????//武松帮大哥卖卖烧饼 ???????????u2.getRoles().add(r2); ???????????r1.getUsers().add(u1); ???????????r1.getUsers().add(u2); ???????????r2.getUsers().add(u2); ???????????session.save(u1); ???????????session.save(u2); ???????????//session.save(r1); ???????????//session.save(r2); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}只save一方，另一方自动save。
不建议使用 如果非要用就用save-update。
解除权限关系
public class Main { ???public static void main(String[] args) { ???????Session session = HibernateUtils.getCurrentSession(); ???????Transaction trans = session.beginTransaction(); ???????try { ???????????User u = session.get(User.class,2); ???????????//武松不想卖烧饼了 ???????????Role r = session.get(Role.class,1); ???????????r.getUsers().remove(u); ???????????trans.commit(); ???????} catch (Exception ex){ ???????????System.out.println(ex); ???????????trans.rollback(); ???????} ???}}Hibernate多表映射（三）
原文地址：https://www.cnblogs.com/baidawei/p/9063478.html