hibernate关联映射之多对多

package loaderman.c_many2many;import java.util.HashSet;import java.util.Set;/** * 开发人员 * * */public class Developer { ???private int d_id; ???private String d_name; ???// 开发人员，参数的多个项目 ???private Set<Project> projects = new HashSet<Project>(); ???public int getD_id() { ???????return d_id; ???} ???public void setD_id(int dId) { ???????d_id = dId; ???} ???public String getD_name() { ???????return d_name; ???} ???public void setD_name(String dName) { ???????d_name = dName; ???} ???public Set<Project> getProjects() { ???????return projects; ???} ???public void setProjects(Set<Project> projects) { ???????this.projects = projects; ???}}

package loaderman.c_many2many;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;import org.junit.Test;public class App1_save { ???private static SessionFactory sf; ???static { ???????sf = new Configuration() ???????????????.configure() ???????????????.addClass(Project.class) ???????????????.addClass(Developer.class) ??// 测试时候使用 ???????????????.buildSessionFactory(); ???} ???// 1. 多对多，保存 ?【只能通过一方维护另外一方，不能重复维护！】 ???@Test ???public void save() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????/* ????????* 模拟数据： ???????????电商系统（曹吉，王春） ???????????OA系统（王春，老张） ????????*/ ???????// 创建项目对象 ???????Project prj_ds = new Project(); ???????prj_ds.setPrj_name("电商系统"); ???????Project prj_oa = new Project(); ???????prj_oa.setPrj_name("OA系统"); ???????// 创建员工对象 ???????Developer dev_cj = new Developer(); ???????dev_cj.setD_name("曹吉"); ???????Developer dev_wc = new Developer(); ???????dev_wc.setD_name("王春"); ???????Developer dev_lz = new Developer(); ???????dev_lz.setD_name("老张"); ???????// 关系 【项目方】 ???????prj_ds.getDevelopers().add(dev_cj); ???????prj_ds.getDevelopers().add(dev_wc); // 电商系统（曹吉，王春） ???????prj_oa.getDevelopers().add(dev_wc); ???????prj_oa.getDevelopers().add(dev_lz); // OA系统（王春，老张） ???????// 保存// ???????session.save(dev_cj);// ???????session.save(dev_wc);// ???????session.save(dev_lz); ???????session.save(prj_ds); ???????session.save(prj_oa); ??// 必须要设置级联保存 ???????session.getTransaction().commit(); ???????session.close(); ???} ???@Test ???public void bak() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????session.getTransaction().commit(); ???????session.close(); ???}}

package loaderman.c_many2many;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;import org.junit.Test;public class App2_inverse { ???private static SessionFactory sf; ???static { ???????sf = new Configuration() ???????????????.configure() ???????????????.addClass(Project.class) ???????????????.addClass(Developer.class) ??// 测试时候使用 ???????????????.buildSessionFactory(); ???} ???// 多对多 ???//1. 设置inverse属性，对保存数据影响? ???// 有影响。 ???// inverse=false ，有控制权，可以维护关联关系； 保存数据的时候会把对象关系插入中间表； ???// inverse=true, ?没有控制权， 不会往中间表插入数据。 ???@Test ???public void save() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????/* ????????* 模拟数据： ???????????电商系统（曹吉，王春） ???????????OA系统（王春，老张） ????????*/ ???????// 创建项目对象 ???????Project prj_ds = new Project(); ???????prj_ds.setPrj_name("电商系统"); ???????Project prj_oa = new Project(); ???????prj_oa.setPrj_name("OA系统"); ???????// 创建员工对象 ???????Developer dev_cj = new Developer(); ???????dev_cj.setD_name("曹吉"); ???????Developer dev_wc = new Developer(); ???????dev_wc.setD_name("王春"); ???????Developer dev_lz = new Developer(); ???????dev_lz.setD_name("老张"); ???????// 关系 【项目方】 ???????prj_ds.getDevelopers().add(dev_cj); ???????prj_ds.getDevelopers().add(dev_wc); // 电商系统（曹吉，王春） ???????prj_oa.getDevelopers().add(dev_wc); ???????prj_oa.getDevelopers().add(dev_lz); // OA系统（王春，老张） ???????// 保存// ???????session.save(dev_cj);// ???????session.save(dev_wc);// ???????session.save(dev_lz); ???????session.save(prj_ds); ???????session.save(prj_oa); ??// 必须要设置级联保存 ???????session.getTransaction().commit(); ???????session.close(); ???} ???//2 .设置inverse属性， 对获取数据影响？ ?无 ???@Test ???public void get() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????Project prj = (Project) session.get(Project.class, 1); ???????System.out.println(prj.getPrj_name()); ???????System.out.println(prj.getDevelopers()); ???????session.getTransaction().commit(); ???????session.close(); ???} ???//3. 设置inverse属性， 对解除关系影响？ ???// 有影响。 ???// inverse=false ,有控制权， 解除关系就是删除中间表的数据。 ???// inverse=true, 没有控制权，不能解除关系。 ???@Test ???public void removeRelation() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????Project prj = (Project) session.get(Project.class, 7); ???????prj.getDevelopers().clear(); ???????session.getTransaction().commit(); ???????session.close(); ???} ???//3. 设置inverse属性，对删除数据的影响? ???// inverse=false, 有控制权。 先删除中间表数据，再删除自身。 ???// inverse=true, 没有控制权。 如果删除的数据有被引用，会报错！ 否则，才可以删除 ???@Test ???public void deleteData() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????Project prj = (Project) session.get(Project.class, 1); ???????session.delete(prj); ???????session.getTransaction().commit(); ???????session.close(); ???}}

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC ????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="loaderman.c_many2many"> ???????<class name="Developer" table="t_developer"> ???????<id name="d_id"> ???????????<generator class="native"></generator> ???????</id> ???????????<property name="d_name" length="20"></property> ???????????????<!-- ????????????多对多映射配置： 员工方 ???????????????name ?指定映射的集合属性 ???????????????table 集合属性对应的中间表 ???????????????key ??指定中间表的外键字段(引用当前表t_developer主键的外键字段) ???????????????many-to-many ???????????????????column 指定外键字段对应的项目字段 ???????????????????class ?集合元素的类型 ????????--> ???????<set name="projects" table="t_relation"> ???????????<key column="did"></key> ???????????<many-to-many column="prjId" class="Project"></many-to-many> ???????</set> ????????????????????</class> ???</hibernate-mapping>

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC ????"-//Hibernate/Hibernate Mapping DTD 3.0//EN" ???"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="loaderman.c_many2many"> ???????<class name="Project" table="t_project"> ???????<id name="prj_id"> ???????????<generator class="native"></generator> ???????</id> ???????????<property name="prj_name" length="20"></property> ???????<!-- ????????????多对多映射: ???????????1. ?映射的集合属性： “developers” ???????????2. ?集合属性，对应的中间表： “t_relation” ???????????3. 外键字段: ?prjId ???????????4. 外键字段，对应的中间表字段: ?did ???????????5. ??集合属性元素的类型 ????????--> ????????<set name="developers" table="t_relation" cascade="save-update" inverse="true"> ????????????<key column="prjId"></key> ????????????<many-to-many column="did" class="Developer"></many-to-many> ????????</set> ????????????</class> ???</hibernate-mapping>

package loaderman.c_many2many;import java.util.HashSet;import java.util.Set;/** * 项目 * * @author Jie.Yuan * */public class Project { ???private int prj_id; ???private String prj_name; ???// 项目下的多个员工 ???private Set<Developer> developers = new HashSet<Developer>(); ???public int getPrj_id() { ???????return prj_id; ???} ???public void setPrj_id(int prjId) { ???????prj_id = prjId; ???} ???public String getPrj_name() { ???????return prj_name; ???} ???public void setPrj_name(String prjName) { ???????prj_name = prjName; ???} ???public Set<Developer> getDevelopers() { ???????return developers; ???} ???public void setDevelopers(Set<Developer> developers) { ???????this.developers = developers; ???}}