我們談到關聯映射的多對多配置呢，有一種挺不好配置的，所以呢，就放到了這裡給大家參考
第一種：建立多對多雙向關聯 拆成兩個一對多
三個實體類
Employee
private Integer empno;
private String ename;
private Dept dept;
private Set<Project> projects=new HashSet<Project>(0);//集合 類 employee的屬性
private Set<ProEmp> pe=new HashSet<ProEmp>(0);
Project
private Integer proNo;//項目的編號 private String proName;//項目名稱 private Set<Employee> employees=new HashSet<Employee>(0);//集合 類 employee的屬性 private Set<ProEmp> pe=new HashSet<ProEmp>(0);
中間表
ProEmp
private Integer id;
private Project pro;
private Employee emp;
映射文件
Employee.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.three.entity">
<class name="Employee" table="Employee">
<id name="empno" column="empno">
<generator class="native"/>
</id>
<property name="ename" type="string" column="ename"/>
</class>
</hibernate-mapping>
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.three.entity">
<class name="Project" table="Project">
<id name="proNo" column="proNo">
<generator class="native"/>
</id>
<property name="proName" type="string" column="proName"/>
</class>
</hibernate-mapping>
ProEmp.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.three.entity">
<class name="ProEmp" table="ProEmp">
<id name="id" column="id">
<generator class="native"/>
</id>
<!-- 與員工關聯 -->
<many-to-one name="emp" column="empno" class="Employee"></many-to-one>
<!-- -與project關聯 -->
<many-to-one name="pro" class="Project" column="proNo"></many-to-one>
</class>
</hibernate-mapping>
大配置文件hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">
oracle.jdbc.driver.OracleDriver
</property>
<property name="connection.url">
jdbc:oracle:thin:@localhost:1521:orcl
</property>
<property name="connection.username">wgy</property>
<property name="connection.password">jpp</property>
<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>
<!-- SQL dialect --><!-- SQL 方言 -->
<property name="dialect">
org.hibernate.dialect.Oracle10gDialect
</property>
<!-- Enable Hibernate's automatic session context management -->
<!-- <property name="current_session_context_class">thread</property>
-->
<!-- Disable the second-level cache -->
<!-- <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
-->
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<!--序列化 -->
<property name="hbm2ddl.auto">create</property>
<!-- <property name="hbm2ddl.auto">update</property> -->
<!-- sql語句格式化 -->
<property name="format_sql">true</property>
<!-- 資源 -->
<<mapping resource="cn/three/entity/Dept.hbm.xml" />
<mapping resource="cn/three/entity/Employee.hbm.xml" />
<mapping resource="cn/three/entity/Project.hbm.xml" />
</session-factory>
</hibernate-configuration>
測試類看一下效果
package cn.main;
import org.hibernate.Session;
import cn.three.entity.ProEmp;
import cn.three.entity.Employee;
import cn.three.entity.Project;
import cn.util.HibernateUtil;
public class ThreeTest {
public static void main(String[] args) {
//三表一起
threeAddEmpAndProAndProEmp();
}
private static void threeAddEmpAndProAndProEmp() {
Session session = HibernateUtil.currentSession();
session.beginTransaction();
Employee emp=new Employee();
Project pro=new Project();
emp.setEname("李四");
pro.setProName("一號項目");
ProEmp pe=new ProEmp();
pe.setEmp(emp);
pe.setPro(pro);
session.save(pro);
session.save(emp);
session.save(pe);
session.getTransaction().commit();
HibernateUtil.closeSessio();
System.out.println("add ok");
}
}
第二種：不用拆成兩個一對多
只需要兩個映射文件，即可
Employee.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.entity">
<class name="Employee" table="Employee">
<id name="empno" column="empno">
<generator class="native"/>
</id>
<property name="ename" type="string" column="ename"/>
<!--多對一 -->
<many-to-one name="dept" column="deptNo" class="Dept"></many-to-one>
<!--多對多雙向關聯 -->
<set name="projects" inverse="true" table="proemp">
<key column="rempNo"></key>
<many-to-many class="Project" column="rproNo"></many-to-many>
</set>
</class>
</hibernate-mapping>
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.entity">
<class name="Project" table="Project">
<id name="proNo" column="proNo">
<generator class="native"/>
</id>
<property name="proName" type="string" column="proName"/>
<!--配置單向多對多關聯 -->
<!-- 映射project 類的employees的屬性 -->
<!--cascade="save-update":表名保存或更新project對象時，會級聯保存或更新與它關聯的Employee對象 -->
<set name="employees" table="proemp" cascade="save-update">
<key column="rproNo"></key>
<many-to-many class="Employee" column="rempNo"></many-to-many>
</set>
</class>
</hibernate-mapping>
測試類
private static void addProToEmpAndEmpToPro() {
Session session = HibernateUtil.currentSession();
session.beginTransaction();
Employee emp=new Employee();
Project pro=new Project();
emp.setEname("李四");
pro.setProName("一號項目");
pro.getEmployees().add(emp);
session.save(pro);
session.getTransaction().commit();
HibernateUtil.closeSessio();
System.out.println("add ok");
這樣就可以了，有問題在線解答！！！！！11111111
