一：多對一單向關聯
首先我們必須創建兩個實體類
例如：Dept類
public class Dept {
private Integer deptNo;
private String dName;
private String loc;
private Set<Employee> emps=new HashSet<Employee>();
Employee類
public class Employee {
private Integer empno;
private String ename;
private Dept dept;
現在我們可以在配置文件裡面配置了
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:級聯 inverse：反轉 -->
<set name="emps" cascade="save-update" inverse="true" >
<key column="deptNo"></key>
<!--一對多 -->
<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"/>
<!--多對一 -->
<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>
到這裡，一對多 和多對一的關聯 配置已經完成！！
我們一起來看看測試類
// 添加數據
private static void addDeptAndEmployee() {
Session currentSession = HibernateUtil.currentSession();
currentSession.beginTransaction();
Dept dept = new Dept();
//dept.setDeptNo(deptNo)
dept.setdName("質管部22");
dept.setLoc("北京22");
Employee emp = new Employee();
emp.setEname("龍龍");
emp.setDept(dept);//建立dept 到employee 對象的 關聯
currentSession.save(emp);
currentSession.save(dept);
currentSession.getTransaction().commit();
HibernateUtil.closeSessio();
System.out.println("add ok");
}
// 級聯保存 cascade:級聯
private static void addDeptAndEmployeeTocascade() {
Session currentSession = HibernateUtil.currentSession();
currentSession.beginTransaction();
Dept dept = new Dept();
// dept.setDeptNo(deptNo)
dept.setdName("質管部22");
dept.setLoc("北京22");
Employee emp = new Employee();
emp.setEname("龍龍");
// 建立Dept對象 和Employee 對象的 一對多 雙向關系
emp.setDept(dept);
dept.getEmps().add(emp);//
currentSession.save(dept);
currentSession.getTransaction().commit();
HibernateUtil.closeSessio();
System.out.println("add ok");
}
現在我們開始來看看多對多的關聯
我們還是創建好實體類
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 類 employee的屬性
Project
public class 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
注意：我還在了Oracle 工具裡面創建了 另外一個表proemp ，即 連接表，你看一下外鍵關系就可以知道了
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)
然後來配置映射文件
單向 多對多關聯
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>
<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>
雙向 多對多
<?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>
我們一起來看看測試類
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("張三");
pro.setProName("一號項目");
pro2.setProName("二號項目");
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 對象的同時還能保存 Employee對象
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("張三");
pro.setProName("一號項目");
pro2.setProName("二號項目");
pro.getEmployees().add(emp);
pro.getEmployees().add(emp2);
pro2.getEmployees().add(emp);
session.save(pro);
session.save(pro2);
HibernateUtil.closeSessio();
}
就到這裡了，有問題可以在線解答！！！！！！！！！！！！
