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一：多对一单向关联
首先我们必须创建两个实体类
例如：Dept类
public class Dept { private Integer deptNo; private String dName; private String loc; private Set<Employee> emps=new HashSet<Employee>();
Employee类
public class Employee { private Integer empno; private String ename; private Dept dept;
现在我们可以在配置文件里面配置了
Dept.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="Dept" table="Dept"> <id name="deptNo" column="deptNo"> <generator class="native"/> </id> <property name="dName" type="string" column="dName"/> <property name="loc" type="string" column="loc"/> <!--cascade:级联 inverse：反转 --> <set name="emps" cascade="save-update" inverse="true" > <key column="deptNo"></key> <!--一对多 --> <one-to-many class="Employee"/> </set> </class> </hibernate-mapping>
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"/> <!--多对一 --> <many-to-one name="dept" column="deptNo" class="Dept"></many-to-one> <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>
到这里，一对多 和多对一的关联 配置已经完成！！
我们一起来看看测试类
// 添加数据 private static void addDeptAndEmployee() { Session currentSession = HibernateUtil.currentSession(); currentSession.beginTransaction(); Dept dept = new Dept(); //dept.setDeptNo(deptNo) dept.setdName("质管部22"); dept.setLoc("北京22"); Employee emp = new Employee(); emp.setEname("龙龙"); emp.setDept(dept);//建立dept 到employee 对象的 关联 currentSession.save(emp); currentSession.save(dept); currentSession.getTransaction().commit(); HibernateUtil.closeSessio(); System.out.println("add ok"); }
// 级联保存 cascade:级联 private static void addDeptAndEmployeeTocascade() { Session currentSession = HibernateUtil.currentSession(); currentSession.beginTransaction(); Dept dept = new Dept(); // dept.setDeptNo(deptNo) dept.setdName("质管部22"); dept.setLoc("北京22"); Employee emp = new Employee(); emp.setEname("龙龙"); // 建立Dept对象 和Employee 对象的 一对多 双向关系 emp.setDept(dept); dept.getEmps().add(emp);// currentSession.save(dept); currentSession.getTransaction().commit(); HibernateUtil.closeSessio(); System.out.println("add ok"); }
现在我们开始来看看多对多的关联
我们还是创建好实体类
例如：
Employee
public class Employee { private Integer empno; private String ename; private Dept dept; private Set<Project> projects=new HashSet<Project>(0);//集合 类 employee的属性
Project
public class Project { private Integer proNo;//项目的编号 private String proName;//项目名称 private Set<Employee> employees=new HashSet<Employee>(0);//集合 类 employee的属性
注意：我还在了Oracle 工具里面创建了 另外一个表proemp ，即 连接表，你看一下外键关系就可以知道了
create table proemp( rproNo number(6), rempNo number(6) ) alter table proemp add constraints FK_rproNo FOREIGN KEY(rproNo) REFERENCES Project(prono) alter table proemp add constraints FK_rempNo FOREIGN KEY(rempNo) REFERENCES employee(empNo)
然后来配置映射文件
单向 多对多关联
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"/> <!--多对一 --> <many-to-one name="dept" column="deptNo" class="Dept"></many-to-one> <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>
双向 多对多
<?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"/> <!--配置单向多对多关联 --> <!-- 映射project 类的employees的属性 --> <!--cascade="save-update":表名保存或更新project对象时，会级联保存或更新与它关联的Employee对象 --> <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>
我们一起来看看测试类
private static void addProToEmpAndEmpToPro() { Session session = HibernateUtil.currentSession(); session.beginTransaction(); Employee emp=new Employee(); Employee emp2=new Employee(); Project pro=new Project(); Project pro2=new Project(); emp.setEname("李四"); emp2.setEname("张三"); pro.setProName("一号项目"); pro2.setProName("二号项目"); pro.getEmployees().add(emp); pro.getEmployees().add(emp2); emp.getProjects().add(pro); emp.getProjects().add(pro2); pro2.getEmployees().add(emp); emp.getProjects().add(pro2); session.save(pro); session.save(pro2); HibernateUtil.closeSessio(); }
//保存Project 对象的同时还能保存 Employee对象 private static void addProToEmp() { Session session = HibernateUtil.currentSession(); session.beginTransaction(); Employee emp=new Employee(); Employee emp2=new Employee(); Project pro=new Project(); Project pro2=new Project(); emp.setEname("李四"); emp2.setEname("张三"); pro.setProName("一号项目"); pro2.setProName("二号项目"); pro.getEmployees().add(emp); pro.getEmployees().add(emp2); pro2.getEmployees().add(emp); session.save(pro); session.save(pro2); HibernateUtil.closeSessio(); }
就到这里了，有问题可以在线解答！！！！！！！！！！！！
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原文地址：http://www.cnblogs.com/whyhappy/p/5766777.html
