初识Hibernate(三)之多表关系维护
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关系型数据库中常见的三种关系
- 一对多关系(最常见)
- 多对多关系
- 一对一关系(很少见)
Hibernate也提供了三种关系的维护,简化操作.
多一对多关系及简单CURD
测试用例 : 简易的客户联系人对应关系
客户表 :
CREATE TABLE `cst_customer` ( `cust_id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '客户编号(主键)', `cust_name` varchar(32) NOT NULL COMMENT '客户名称(公司名称)', `cust_user_id` bigint(32) DEFAULT NULL COMMENT '负责人id', `cust_create_id` bigint(32) DEFAULT NULL COMMENT '创建人id', `cust_source` varchar(32) DEFAULT NULL COMMENT '客户信息来源', `cust_industry` varchar(32) DEFAULT NULL COMMENT '客户所属行业', `cust_level` varchar(32) DEFAULT NULL COMMENT '客户级别', `cust_linkman` varchar(64) DEFAULT NULL COMMENT '联系人', `cust_phone` varchar(64) DEFAULT NULL COMMENT '固定电话', `cust_mobile` varchar(16) DEFAULT NULL COMMENT '移动电话', PRIMARY KEY (`cust_id`)) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;联系人表 :
CREATE TABLE `cst_linkman` ( `lkm_id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '联系人编号(主键)', `lkm_name` varchar(16) DEFAULT NULL COMMENT '联系人姓名', `lkm_cust_id` bigint(32) NOT NULL COMMENT '客户id', `lkm_gender` char(1) DEFAULT NULL COMMENT '联系人性别', `lkm_phone` varchar(16) DEFAULT NULL COMMENT '联系人办公电话', `lkm_mobile` varchar(16) DEFAULT NULL COMMENT '联系人手机', `lkm_email` varchar(64) DEFAULT NULL COMMENT '联系人邮箱', `lkm_qq` varchar(16) DEFAULT NULL COMMENT '联系人qq', `lkm_position` varchar(16) DEFAULT NULL COMMENT '联系人职位', `lkm_memo` varchar(512) DEFAULT NULL COMMENT '联系人备注', PRIMARY KEY (`lkm_id`), KEY `FK_cst_linkman_lkm_cust_id` (`lkm_cust_id`), CONSTRAINT `FK_cst_linkman_lkm_cust_id` FOREIGN KEY (`lkm_cust_id`) REFERENCES `cst_customer` (`cust_id`) ON DELETE NO ACTION ON UPDATE NO ACTION) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;关系型数据库中对应关系 :
Java中实体对应关系 :
实体Customer:
package com.tangbaobao.domain;import java.util.HashSet;import java.util.Set;/** * @author 唐学俊 * @version 创建时间：2017年11月8日 下午8:52:20 * */public class Customer { /* * CREATE TABLE `cst_customer` ( `cust_id` BIGINT(32) NOT NULL AUTO_INCREMENT * COMMENT '客户编号(主键)', `cust_name` VARCHAR(32) NOT NULL COMMENT '客户名称(公司名称)', * `cust_source` VARCHAR(32) DEFAULT NULL COMMENT '客户信息来源', `cust_industry` * VARCHAR(32) DEFAULT NULL COMMENT '客户所属行业', `cust_level` VARCHAR(32) DEFAULT * NULL COMMENT '客户级别', `cust_linkman` VARCHAR(64) DEFAULT NULL COMMENT '联系人', * `cust_phone` VARCHAR(64) DEFAULT NULL COMMENT '固定电话', `cust_mobile` * VARCHAR(16) DEFAULT NULL COMMENT '移动电话', PRIMARY KEY (`cust_id`) ) * ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8; */ 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> linkMen = new HashSet<LinkMan>(); public Set<LinkMan> getLinkMen() { return linkMen; } public void setLinkMen(Set<LinkMan> linkMen) { this.linkMen = linkMen; } 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 + "]"; }}实体LinkMan:
package com.tangbaobao.domain;/*** @author 唐学俊* @version 创建时间：2017年11月21日 下午7:25:45* */public class LinkMan {/* CREATE TABLE `cst_linkman` ( `lkm_id` bigint(32) NOT NULL AUTO_INCREMENT COMMENT '联系人编号(主键)', `lkm_name` varchar(16) DEFAULT NULL COMMENT '联系人姓名', `lkm_cust_id` bigint(32) NOT NULL COMMENT '客户id', `lkm_gender` char(1) DEFAULT NULL COMMENT '联系人性别', `lkm_phone` varchar(16) DEFAULT NULL COMMENT '联系人办公电话', `lkm_mobile` varchar(16) DEFAULT NULL COMMENT '联系人手机', `lkm_email` varchar(64) DEFAULT NULL COMMENT '联系人邮箱', `lkm_qq` varchar(16) DEFAULT NULL COMMENT '联系人qq', `lkm_position` varchar(16) DEFAULT NULL COMMENT '联系人职位', `lkm_memo` varchar(512) DEFAULT NULL COMMENT '联系人备注', PRIMARY KEY (`lkm_id`), KEY `FK_cst_linkman_lkm_cust_id` (`lkm_cust_id`), CONSTRAINT `FK_cst_linkman_lkm_cust_id` FOREIGN KEY (`lkm_cust_id`) REFERENCES `cst_customer` (`cust_id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;*/ private Long lkm_id; private Character lkm_gender; private String lkm_name ; private String lkm_phone; private String lkm_mobile; private String lkm_email; private String lkm_qq; private String lkm_position; private String lkm_memo; private Customer customer; public Customer getCustomer() { return customer; } public void setCustomer(Customer customer) { this.customer = customer; } public Long getLkm_id() { return lkm_id; } public void setLkm_id(Long lkm_id) { this.lkm_id = lkm_id; } public Character getLkm_gender() { return lkm_gender; } public void setLkm_gender(Character lkm_gender) { this.lkm_gender = lkm_gender; } public String getLkm_name() { return lkm_name; } public void setLkm_name(String lkm_name) { this.lkm_name = lkm_name; } public String getLkm_phone() { return lkm_phone; } public void setLkm_phone(String lkm_phone) { this.lkm_phone = lkm_phone; } public String getLkm_mobile() { return lkm_mobile; } public void setLkm_mobile(String lkm_mobile) { this.lkm_mobile = lkm_mobile; } 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_position() { return lkm_position; } public void setLkm_position(String lkm_position) { this.lkm_position = lkm_position; } public String getLkm_memo() { return lkm_memo; } public void setLkm_memo(String lkm_memo) { this.lkm_memo = lkm_memo; } @Override public String toString() { return "LinkMan [lkm_id=" + lkm_id + ", lkm_gender=" + lkm_gender + ", lkm_name=" + lkm_name + ", lkm_phone=" + lkm_phone + ", lkm_mobile=" + lkm_mobile + ", lkm_email=" + lkm_email + ", lkm_qq=" + lkm_qq + ", lkm_position=" + lkm_position + ", lkm_memo=" + lkm_memo + "]"; }}实体LinkMan映射文件 LinkMan.hbm.xml配置文件:
<?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="com.tangbaobao.domain"> <class name="LinkMan" table="cst_linkman"> <id name ="lkm_id"> <generator class="native"></generator> </id> <property name="lkm_gender"></property> <property name="lkm_name"></property> <property name="lkm_phone"></property> <property name="lkm_mobile"></property> <property name="lkm_email"></property> <property name="lkm_qq"></property> <property name="lkm_position"></property> <property name="lkm_memo"></property> <many-to-one name="customer" class="Customer" column="lkm_cust_id" ></many-to-one> </class> </hibernate-mapping>注意 : 配置文件中需要配置
<many-to-onename="customer" //对应的属性名class="Customer"//对应的实体类的全包名column="lkm_cust_id" //外键></many-to-one>实体Customer映射文件 Customer.hbm.xml配置文件:
<?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"> <!-- 配置表与实体对象的关系 --> <!-- package属性:填写一个包名.在元素内部凡是需要书写完整类名的属性,可以直接写简答类名了. --><hibernate-mapping package="com.tangbaobao.domain" > <class name="Customer" table="cst_customer" > <id name="cust_id" > <!-- generator:主键生成策略(明天讲) --> <generator class="native"></generator> </id> <property name="cust_name" column="cust_name" > <!-- <column name="cust_name" sql-type="varchar" ></column> --> </property> <property name="cust_source" column="cust_source" ></property> <property name="cust_industry" column="cust_industry" ></property> <property name="cust_level" column="cust_level" ></property> <property name="cust_linkman" column="cust_linkman" ></property> <property name="cust_phone" column="cust_phone" ></property> <property name="cust_mobile" column="cust_mobile" ></property> <set name ="linkMen" > <key column="lkm_cust_id"></key> <one-to-many class ="LinkMan"/> </set> </class></hibernate-mapping>注意: 需配置一对多关系
<set name ="linkMen" >//向关联的属性 <key column="lkm_cust_id"></key>//外键 <one-to-many class ="LinkMan"/>//对应的实体类</set>简单的多表CURD
package com.tangbaobao.test;import java.util.Set;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import com.tangbaobao.domain.Customer;import com.tangbaobao.domain.LinkMan;import com.tangbaobao.utils.HibernateUtils;/*** @author 唐学俊* @version 创建时间：2017年11月21日 下午8:05:21* */public class Test1 { @Test //建立连接 public void fun() { //获取session对象 Session session = HibernateUtils.getSession(); //开启事务 Transaction tx = session.beginTransaction(); //新建客户对象 Customer customer = new Customer(); customer.setCust_name("糖糖工作室"); //新建联系人对象 LinkMan linkMan1 = new LinkMan(); linkMan1.setLkm_name("唐学俊"); LinkMan linkMan2 = new LinkMan(); linkMan2.setLkm_name("唐丽"); //设置一对多关系 customer.getLinkMen().add(linkMan1); customer.getLinkMen().add(linkMan2); //设置多对一关系 linkMan1.setCustomer(customer); linkMan2.setCustomer(customer); //持久化到数据库 session.save(customer); session.save(linkMan2); session.save(linkMan1); //提交事务 tx.commit(); //关闭资源 HibernateUtils.closeAll(); } //为联系人添加客户 @Test public void fun2() { //获取session对象 Session session = HibernateUtils.getSession(); //开启事务 Transaction tx = session.beginTransaction(); //新建联系人 LinkMan linkMan = new LinkMan(); linkMan.setLkm_name("唐宝宝"); //将联系人与客户关联 Customer customer = session.get(Customer.class, 1L); customer.getLinkMen().add(linkMan); linkMan.setCustomer(customer); //持久化数据 session.save(customer); session.save(linkMan); //提交事务 tx.commit(); //关闭资源 HibernateUtils.closeAll(); } //将联系人与客户取消关联 @Test public void fun3() { //获取session对象 Session session = HibernateUtils.getSession(); //开启事务 Transaction tx = session.beginTransaction(); Customer customer = session.get(Customer.class,1L); LinkMan linkMan = session.get(LinkMan.class, 5L); //移除数据 customer.getLinkMen().remove(customer); linkMan.setCustomer(null); //持久化数据 session.save(customer); session.save(linkMan); //提交事务 tx.commit(); //关闭资源 HibernateUtils.closeAll(); }}多表级联的简单操作
什么是级联操作?
级联操作就是根据主外键的关系,只需在关联的一方保存属性即可将两方关系都持久化到数据库
级联操作解决什么问题?
如果有n个关系,每次都要用session.save()来持久化,这样增加了代码的冗余性,而且增大工作量
实体映射配置文件需要增加 cascade 属性
<?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"> <!-- 配置表与实体对象的关系 --> <!-- package属性:填写一个包名.在元素内部凡是需要书写完整类名的属性,可以直接写简答类名了. --><hibernate-mapping package="com.tangbaobao.domain" > <!-- class元素: 配置实体与表的对应关系的 name: 完整类名 table:数据库表名 --> <class name="Customer" table="cst_customer" > <!-- id元素:配置主键映射的属性 name: 填写主键对应属性名 column(可选): 填写表中的主键列名.默认值:列名会默认使用属性名 type(可选):填写列(属性)的类型.hibernate会自动检测实体的属性类型. 每个类型有三种填法: java类型|hibernate类型|数据库类型 not-null(可选):配置该属性(列)是否不能为空. 默认值:false length(可选):配置数据库中列的长度. 默认值:使用数据库类型的最大长度 --> <id name="cust_id" > <!-- generator:主键生成策略(明天讲) --> <generator class="native"></generator> </id> <!-- property元素:除id之外的普通属性映射 name: 填写属性名 column(可选): 填写列名 type(可选):填写列(属性)的类型.hibernate会自动检测实体的属性类型. 每个类型有三种填法: java类型|hibernate类型|数据库类型 not-null(可选):配置该属性(列)是否不能为空. 默认值:false length(可选):配置数据库中列的长度. 默认值:使用数据库类型的最大长度 --> <property name="cust_name" column="cust_name" > <!-- <column name="cust_name" sql-type="varchar" ></column> --> </property> <property name="cust_source" column="cust_source" ></property> <property name="cust_industry" column="cust_industry" ></property> <property name="cust_level" column="cust_level" ></property> <property name="cust_linkman" column="cust_linkman" ></property> <property name="cust_phone" column="cust_phone" ></property> <property name="cust_mobile" column="cust_mobile" ></property> <!-- 级联操作 1.save-update 2.delete 3.all --> <set name ="linkMen" cascade="save-update" > <key column="lkm_cust_id"></key> <one-to-many class ="LinkMan" /> </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="com.tangbaobao.domain"> <class name="LinkMan" table="cst_linkman"> <id name ="lkm_id"> <generator class="native"></generator> </id> <property name="lkm_gender"></property> <property name="lkm_name"></property> <property name="lkm_phone"></property> <property name="lkm_mobile"></property> <property name="lkm_email"></property> <property name="lkm_qq"></property> <property name="lkm_position"></property> <property name="lkm_memo"></property> <many-to-one name="customer" class="Customer" column="lkm_cust_id" cascade="save-update"></many-to-one> </class> </hibernate-mapping>级联操作多表CURD
package com.tangbaobao.test;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import com.tangbaobao.domain.Customer;import com.tangbaobao.domain.LinkMan;import com.tangbaobao.utils.HibernateUtils;/*** @author 唐学俊* @version 创建时间：2017年11月21日 下午8:45:19* 级联操作*/public class Test2 { @Test //级联操作增加联系人 public void fun() { //获取session对象 Session session = HibernateUtils.getSession(); //开启事务 Transaction tx = session.beginTransaction(); //新建客户对象 Customer customer = new Customer(); customer.setCust_name("糖糖工作室"); //新建联系人对象 LinkMan linkMan1 = new LinkMan(); linkMan1.setLkm_name("唐学俊"); LinkMan linkMan2 = new LinkMan(); linkMan2.setLkm_name("唐丽"); //设置一对多关系 customer.getLinkMen().add(linkMan1); customer.getLinkMen().add(linkMan2); //设置多对一关系 linkMan1.setCustomer(customer); linkMan2.setCustomer(customer); //持久化到数据库//前提Cusotomer.hbm.xml已经配置了cascade session.save(customer); //提交事务 tx.commit(); //关闭资源 HibernateUtils.closeAll(); } @Test //级联操作删除联系人 public void fun2() { //获取session对象 Session session = HibernateUtils.getSession(); //开启事务 Transaction tx = session.beginTransaction(); //获取客户 Customer customer = session.get(Customer.class, 1L); //删除客户 session.delete(customer); //提交事务 tx.commit(); //关闭资源 HibernateUtils.closeAll(); } @Test //级联保存联系人对应客户 public void fun3() { //获取session对象 Session session = HibernateUtils.getSession(); //开启事务 Transaction tx = session.beginTransaction(); //新建客户对象 Customer customer = new Customer(); customer.setCust_name("图图工作室"); //新建联系人对象 LinkMan linkMan1 = new LinkMan(); linkMan1.setLkm_name("唐学俊"); LinkMan linkMan2 = new LinkMan(); linkMan2.setLkm_name("唐丽"); //设置一对多关系 customer.getLinkMen().add(linkMan1); customer.getLinkMen().add(linkMan2); //设置多对一关系 linkMan1.setCustomer(customer); linkMan2.setCustomer(customer); //持久化到数据库//前提Cusotomer.hbm.xml已经配置了cascade session.save(linkMan1); session.save(linkMan2); //提交事务 tx.commit(); //关闭资源 HibernateUtils.closeAll(); }}设置inverse属性优化Hibernate持久化效率
出现问题
在生成LInkMan表时已经加入了外键;
但是下面有多了两次更新外键操作,这是Customer又维护了一次,降低了Hibernate的性能.
解决办法:
Hibernate 在关联属性中为我我们提供了inverse属性;是否维护外键
inverse: false:维护
inverse:true:不维护
配置:
<set name ="linkMen" inverse="true"> <key column="lkm_cust_id"></key> <one-to-many class ="LinkMan" /></set>测试结果:
总结
Hibernate中一对多关系中操作主要有以下:
- 配置多表关系
- 配置级联属性,简化多表操作;cascade
- 配置是否维护外键,提高性能inverse
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