Hibernate many2many映射关系

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多对多映射关系：

开发步骤：

JavaBean 映射文件测试

图片详解：

1.javaBean

Project.java

package cn.itcast.many2many;import java.util.HashSet;import java.util.Set;public class Project {private int proj_id;@Overridepublic String toString() {return "Project [proj_id=" + proj_id + ", proj_name=" + proj_name+ ", developers=" + developers + "]";}private String proj_name;private Set<Developer> developers=new HashSet<Developer>();public int getProj_id() {return proj_id;}public void setProj_id(int proj_id) {this.proj_id = proj_id;}public String getProj_name() {return proj_name;}public void setProj_name(String proj_name) {this.proj_name = proj_name;}public Set<Developer> getDevelopers() {return developers;}public void setDevelopers(Set<Developer> developers) {this.developers = developers;}}

Employee.java

package cn.itcast.many2many;import java.util.HashSet;import java.util.Set;public class Developer {@Overridepublic String toString() {return "Developer [d_id=" + d_id + ", d_name=" + d_name + ", projects="+ projects + "]";}private int d_id;private String d_name;private Set<Project> projects=new HashSet<Project>();public int getD_id() {return d_id;}public void setD_id(int d_id) {this.d_id = d_id;}public String getD_name() {return d_name;}public void setD_name(String d_name) {this.d_name = d_name;}public Set<Project> getProjects() {return projects;}public void setProjects(Set<Project> projects) {this.projects = projects;}}

2.配置文件

多对多的关系映射
1.映射的集合属性
2.属性对应的中间表
3.外键字段 projid
4.外键字段对应的中间表属性did
5.集合属性元素的类型

Project.hbm.xml

<?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="cn.itcast.many2many" auto-import="true"><class name="Project"><id name="proj_id"><generator class="native"></generator></id><property name="proj_name" column="proj_name" length="20" type="string"></property><!-- 多对多的关系映射1.映射的集合属性2.属性对应的中间表3.外键字段 projid4.外键字段对应的中间表属性did5.集合属性元素的类型 --> <set name="developers" table="t_relation" cascade="save-update" inverse="true"> <key column="projid"></key> <many-to-many class="Developer" column="did"></many-to-many> </set></class></hibernate-mapping>

Developer.hbm.xml

<?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="cn.itcast.many2many" auto-import="true"><class name="Developer"><id name="d_id"><generator class="native"></generator></id><property name="d_name" column="d_name" length="20" type="string"></property><!-- 这里配置的是多对多的关系映射 --> <set name="projects" table="t_relation"> <key column="did"></key> <many-to-many class="Project" column="projid"></many-to-many> </set></class></hibernate-mapping>

测试类：

package cn.itcast.many2many;import org.hibernate.Transaction;import org.hibernate.classic.Session;import org.junit.Test;import cn.itcast.utils.HibernateUtil;public class App {@Testpublic void test(){Session session = HibernateUtil.getSession();Transaction transaction = session.beginTransaction();//通过项目表维护员工表//1.项目表Project proj=new Project();proj.setProj_name("OA项目");Project proj2=new Project();proj2.setProj_name("ERP系统");//2.员工表Developer dev_lwk=new Developer();dev_lwk.setD_name("李卫康");Developer dev_hw=new Developer();dev_hw.setD_name("韩玮");Developer  dev_ccs=new Developer();dev_ccs.setD_name("程崇树");//3.关系proj.getDevelopers().add(dev_lwk);proj.getDevelopers().add(dev_hw);proj2.getDevelopers().add(dev_lwk);proj2.getDevelopers().add(dev_ccs);session.save(proj);session.save(proj2);transaction.commit();session.close();}}

运行测试得到的数据库表：

t_relation的外键

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