hibernate关联映射之一对多&多对一

package loaderman.b_one2Many;import java.util.HashSet;import java.util.Set;public class Dept { ???private int deptId; ???private String deptName; ???// 【一对多】 部门对应的多个员工 ???private Set<Employee> emps = new HashSet<Employee>(); ???public int getDeptId() { ???????return deptId; ???} ???public void setDeptId(int deptId) { ???????this.deptId = deptId; ???} ???public String getDeptName() { ???????return deptName; ???} ???public void setDeptName(String deptName) { ???????this.deptName = deptName; ???} ???public Set<Employee> getEmps() { ???????return emps; ???} ???public void setEmps(Set<Employee> emps) { ???????this.emps = emps; ???}}

package loaderman.b_one2Many;public class Employee { ???private int empId; ???private String empName; ???private double salary; ???// 【多对一】员工与部门 ???private Dept dept; ???public int getEmpId() { ???????return empId; ???} ???public void setEmpId(int empId) { ???????this.empId = empId; ???} ???public String getEmpName() { ???????return empName; ???} ???public void setEmpName(String empName) { ???????this.empName = empName; ???} ???public double getSalary() { ???????return salary; ???} ???public void setSalary(double salary) { ???????this.salary = salary; ???} ???public Dept getDept() { ???????return dept; ???} ???public void setDept(Dept dept) { ???????this.dept = dept; ???}}

package loaderman.b_one2Many;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(Dept.class) ???????????????.addClass(Employee.class) ??// 测试时候使用 ???????????????.buildSessionFactory(); ???} ???// 保存， 部门方 【一的一方法操作】 ???@Test ???public void save() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 部门对象 ???????Dept dept = new Dept(); ???????dept.setDeptName("应用开发部"); ???????// 员工对象 ???????Employee emp_zs = new Employee(); ???????emp_zs.setEmpName("张三"); ???????Employee emp_ls = new Employee(); ???????emp_ls.setEmpName("李四"); ???????// 关系 ???????dept.getEmps().add(emp_zs); ???????dept.getEmps().add(emp_ls); ???????// 保存 ???????session.save(emp_zs); ???????session.save(emp_ls); ???????session.save(dept); // 保存部门，部门下所有的员工 ???????session.getTransaction().commit(); ???????session.close(); ???????/* ????????* ?结果 ????????* ?Hibernate: insert into t_employee (empName, salary, dept_id) values (?, ?, ?) ???????????Hibernate: insert into t_employee (empName, salary, dept_id) values (?, ?, ?) ???????????Hibernate: insert into t_dept (deptName) values (?) ???????????Hibernate: update t_employee set deptId=? where empId=? ???维护员工引用的部门的id ???????????Hibernate: update t_employee set deptId=? where empId=? ????????*/ ???} ???// 【推荐】 保存， 部员方 【多的一方法操作】 ???@Test ???public void save2() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 部门对象 ???????Dept dept = new Dept(); ???????dept.setDeptName("综合部"); ???????// 员工对象 ???????Employee emp_zs = new Employee(); ???????emp_zs.setEmpName("张三"); ???????Employee emp_ls = new Employee(); ???????emp_ls.setEmpName("李四"); ???????// 关系 ???????emp_zs.setDept(dept); ???????emp_ls.setDept(dept); ???????// 保存 ???????session.save(dept); // 先保存一的方法 ???????session.save(emp_zs); ???????session.save(emp_ls);// 再保存多的一方，关系会自动维护(映射配置完) ???????session.getTransaction().commit(); ???????session.close(); ???????/* ????????* ?结果 ????????* ?Hibernate: insert into t_dept (deptName) values (?) ???????????Hibernate: insert into t_employee (empName, salary, dept_id) values (?, ?, ?) ???????????Hibernate: insert into t_employee (empName, salary, dept_id) values (?, ?, ?) ???????????少生成2条update ?sql ????????*/ ???}}

package loaderman.b_one2Many;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;import org.junit.Test;public class App2_get { ???private static SessionFactory sf; ???static { ???????sf = new Configuration() ???????????????.configure() ???????????????.addClass(Dept.class) ???????????????.addClass(Employee.class) ??// 测试时候使用 ???????????????.buildSessionFactory(); ???} ???@Test ???public void get() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 通过部门方，获取另外一方// ???????Dept dept = (Dept) session.get(Dept.class, 1);// ???????System.out.println(dept.getDeptName());// ???????System.out.println(dept.getEmps());// 懒加载 ???????// 通过员工房，获取另外一方 ???????Employee emp = (Employee) session.get(Employee.class, 1); ???????System.out.println(emp.getEmpName()); ???????System.out.println(emp.getDept().getDeptName()); ???????session.getTransaction().commit(); ???????session.close(); ???}}

package loaderman.b_one2Many;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;import org.junit.Test;public class App3_inverse { ???private static SessionFactory sf; ???static { ???????sf = new Configuration() ???????????????.configure() ???????????????.addClass(Dept.class) ???????????????.addClass(Employee.class) ??// 测试时候使用 ???????????????.buildSessionFactory(); ???} ???// 1. 保存数据 ???@Test ???public void save() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 部门对象 ???????Dept dept = new Dept(); ???????dept.setDeptName("应用开发部"); ???????// 员工对象 ???????Employee emp_zs = new Employee(); ???????emp_zs.setEmpName("张三"); ???????Employee emp_ls = new Employee(); ???????emp_ls.setEmpName("李四"); ???????// 关系 ???????dept.getEmps().add(emp_zs); ???????dept.getEmps().add(emp_ls); ?// inverse=true, ?不会设置关联。 ???????// ????????????????此时的关联应该通过员工方维护。 ???????// 保存 ???????session.save(emp_zs); ???????session.save(emp_ls); ???????session.save(dept); // 保存部门，部门下所有的员工 ???????session.getTransaction().commit(); ???????session.close(); ???} ???//2. 是否设置inverse，对获取数据的影响？ ??无. ???@Test ???public void get() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????Dept dept = (Dept) session.get(Dept.class, 1); ???????System.out.println(dept.getDeptName()); ???????System.out.println(dept.getEmps()); ???????session.getTransaction().commit(); ???????session.close(); ???} ???// 3. 是否设置inverse，对解除关联关系影响？ ???// inverse=false， ?可以解除关联 ???// inverse=true， ?当前方(部门)没有控制权，不能解除关联关系(不会生成update语句,也不会报错) ???// ???@Test ???public void removeRelation() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 获取部门 ???????Dept dept = (Dept) session.get(Dept.class, 2); ???????// 解除关系 ???????dept.getEmps().clear(); ???????session.getTransaction().commit(); ???????session.close(); ???} ???//3. 是否设置inverse属性，在删除数据中对关联关系的影响? ???// inverse=false, 有控制权， 可以删除。先清空外键引用，再删除数据。 ???// inverse=true, ?没有控制权: 如果删除的记录有被外键引用，会报错，违反主外键引用约束！ ???// ????????????????????????????如果删除的记录没有被引用，可以直接删除。 ???@Test ???public void deleteData() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 查询部门 ???????Dept dept = (Dept) session.get(Dept.class, 8); ???????session.delete(dept); ???????session.getTransaction().commit(); ???????session.close(); ???} ???@Test ???public void bak() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????session.getTransaction().commit(); ???????session.close(); ???}}

package loaderman.b_one2Many;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;import org.junit.Test;public class App4_cascade { ???private static SessionFactory sf; ???static { ???????sf = new Configuration() ???????????????.configure() ???????????????.addClass(Dept.class) ???????????????.addClass(Employee.class) ??// 测试时候使用 ???????????????.buildSessionFactory(); ???} ???// 级联保存 ???@Test ???public void save() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????// 部门对象 ???????Dept dept = new Dept(); ???????dept.setDeptName("财务部"); ???????// 员工对象 ???????Employee emp_zs = new Employee(); ???????emp_zs.setEmpName("张三"); ???????Employee emp_ls = new Employee(); ???????emp_ls.setEmpName("李四"); ???????// 关系 ???????dept.getEmps().add(emp_zs); ???????dept.getEmps().add(emp_ls); ???????// 保存// ???????session.save(emp_zs);// ???????session.save(emp_ls); ???????session.save(dept); // 需要设置级联保存； 保存部门，部门下所有的员工 ???????session.getTransaction().commit(); ???????session.close(); ???} ???// 级联删除 ???@Test ???public void delete() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????Dept dept = (Dept) session.get(Dept.class,7); ???????session.delete(dept); // 级联删除 ???????session.getTransaction().commit(); ???????session.close(); ???} ???@Test ???public void bak() { ???????Session session = sf.openSession(); ???????session.beginTransaction(); ???????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.b_one2Many"> ???????<class name="Dept" table="t_dept"> ???????<id name="deptId"> ???????????<generator class="native"></generator> ???????</id> ???????????<property name="deptName" length="20"></property> ???????????????<!-- ????????????一对多关联映射配置 ?（通过部门管理到员工） ???????????Dept 映射关键点： ???????????1. ?指定 映射的集合属性： "emps" ???????????2. ?集合属性对应的集合表： "t_employee" ???????????3. ?集合表的外键字段 ??"t_employee. dept_id" ???????????4. ?集合元素的类型 ???????????????????????inverse=false ?set集合映射的默认值； 表示有控制权 ????????--> ????????<set name="emps" cascade="save-update,delete" table="t_employee" inverse="true"> ??<!-- table="t_employee" --> ?????????????<key column="dept_id"></key> ?????????????<one-to-many class="Employee"/> ????????</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.b_one2Many"> ???????<class name="Employee" table="t_employee"> ???????<id name="empId"> ???????????<generator class="native"></generator> ???????</id> ???????????<property name="empName" length="20"></property> ???????<property name="salary" type="double"></property> ???????????????<!-- ????????????多对一映射配置 ???????????Employee 映射关键点： ???????????1. ?映射的部门属性 ?： ?dept ???????????2. ?映射的部门属性，对应的外键字段: dept_id ???????????3. ?部门的类型 ????????--> ????????<many-to-one name="dept" column="dept_id" class="Dept"></many-to-one> ????????????</class> ???</hibernate-mapping>