Hibernate关联关系映射[通俗易懂]

<class name=”Person”> <id name=”id” column=”personId”> <generator class=”native”/> </id> <join table=”PersonAddress” optional=”true”> <key column=”personId” unique=”true”/> <many-to-one name=”address” column=”addressId” not-null=”true” unique=”true”/> </join> </class> <class name=”Address”> <id name=”id” column=”addressId”> <generator class=”native”/> </id> </class>

<?xml version=”1.0″ encoding=”utf-8″?> <!DOCTYPE hibernate-mapping PUBLIC “-//Hibernate/Hibernate Mapping DTD 3.0//EN” “http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd”> <!– Mapping file autogenerated by MyEclipse Persistence Tools –> <hibernate-mapping> <class name=”com.morris.hql.entity.Department” table=”DEPARTMENT” schema=”SCOTT”> <id name=”deptid” type=”java.lang.String”> <column name=”DEPTID” length=”20″ /> <generator class=”assigned” /> </id> <property name=”deptname” type=”java.lang.String”> <column name=”DEPTNAME” length=”20″ not-null=”true” /> </property> <set name=”employees” inverse=”true”> <key> <column name=”DEPTID” length=”20″ /> </key> <one-to-many class=”com.morris.hql.entity.Employee” /> </set> </class> </hibernate-mapping>

<?xml version=”1.0″ encoding=”utf-8″?> <!DOCTYPE hibernate-mapping PUBLIC “-//Hibernate/Hibernate Mapping DTD 3.0//EN” “http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd”> <!– Mapping file autogenerated by MyEclipse Persistence Tools –> <hibernate-mapping> <class name=”com.morris.hql.entity.Employee” table=”EMPLOYEE” schema=”SCOTT”> <id name=”empid” type=”java.lang.String”> <column name=”EMPID” length=”20″ /> <generator class=”assigned” /> </id> <many-to-one name=”department” class=”com.morris.hql.entity.Department” fetch=”select”> <column name=”DEPTID” length=”20″ /> </many-to-one> <property name=”empname” type=”java.lang.String”> <column name=”EMPNAME” length=”20″ not-null=”true” /> </property> </class> </hibernate-mapping>

<class name=”Person”> <id name=”id” column=”personId”> <generator class=”native”/> </id> <set name=”addresses” table=”PersonAddress”> <key column=”personId”/> <many-to-many column=”addressId” class=”Address”/> </set> </class> <class name=”Address”> <id name=”id” column=”addressId”> <generator class=”native”/> </id> </class>

public void addDeptEmp(Department dept, Employee emp) { Session session = HibernateSessionFactory.getSession(); Transaction transaction = null; try { transaction = session.beginTransaction(); dept.getEmployees().add(emp); emp.setDepartment(dept); session.save(dept); transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } finally { if (session != null) { session.close(); } } }

Hibernate: select employee_.EMPID, employee_.DEPTID as DEPTID0_, employee_.EMPNAME as EMPNAME0_ from SCOTT.EMPLOYEE employee_ where employee_.EMPID=? Hibernate: insert into SCOTT.DEPARTMENT (DEPTNAME, DEPTID) values (?, ?) Hibernate: insert into SCOTT.EMPLOYEE (DEPTID, EMPNAME, EMPID) values (? , ? , ? )

public void deleteDeptEmp(Department dept, Employee emp) { Session session = HibernateSessionFactory.getSession(); Transaction transaction = null; try { transaction = session.beginTransaction(); session.delete(dept); transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } finally { if (session != null) { session.close(); } } }

Hibernate: select department0_.DEPTID as DEPTID1_1_, department0_.DEPTNAME as DEPTNAME1_1_, employees1_.DEPTID as DEPTID3_, employees1_.EMPID as EMPID3_, employees1_.EMPID as EMPID0_0_, employees1_.DEPTID as DEPTID0_0_, employees1_.EMPNAME as EMPNAME0_0_ from SCOTT.DEPARTMENT department0_ left outer join SCOTT.EMPLOYEE employees1_ on department0_.DEPTID=employees1_.DEPTID where department0_.DEPTID=? Hibernate: delete from SCOTT.EMPLOYEE where EMPID=? Hibernate: delete from SCOTT.DEPARTMENT where DEPTID=?

public void updateDeptEmp() { Session session = HibernateSessionFactory.getSession(); Transaction transaction = null; try { transaction = session.beginTransaction(); Department dept = (Department) session.load(Department.class, “5”); Employee emp = (Employee) session.load(Employee.class, “1001”); dept.setDeptname(“就业部“); emp.setEmpname(“a”); session.update(dept); session.update(emp); transaction.commit(); } catch (Exception e) { if (transaction != null) { transaction.rollback(); } e.printStackTrace(); } finally { if (session != null) { session.close(); } } }

Hibernate: select department0_.DEPTID as DEPTID1_1_, department0_.DEPTNAME as DEPTNAME1_1_, employees1_.DEPTID as DEPTID3_, employees1_.EMPID as EMPID3_, employees1_.EMPID as EMPID0_0_, employees1_.DEPTID as DEPTID0_0_, employees1_.EMPNAME as EMPNAME0_0_ from SCOTT.DEPARTMENT department0_ left outer join SCOTT.EMPLOYEE employees1_ on department0_.DEPTID=employees1_.DEPTID where department0_.DEPTID=? Hibernate: select employee0_.EMPID as EMPID0_0_, employee0_.DEPTID as DEPTID0_0_, employee0_.EMPNAME as EMPNAME0_0_ from SCOTT.EMPLOYEE employee0_ where employee0_.EMPID=? Hibernate: update SCOTT.DEPARTMENT set DEPTNAME=? where DEPTID=? Hibernate: update SCOTT.EMPLOYEE set DEPTID=?, EMPNAME=? where EMPID=?

public Employee queryEmployeeById(String id){ Session session = HibernateSessionFactory.getSession(); Employee employee = null; try { employee = (Employee) session.load(Employee.class, id); System.out.println(employee.getEmpname()); } finally { if (session != null) { session.close(); } } return employee; }

Hibernate: select employee0_.EMPID as EMPID0_0_, employee0_.DEPTID as DEPTID0_0_, employee0_.EMPNAME as EMPNAME0_0_ from SCOTT.EMPLOYEE employee0_ where employee0_.EMPID=? Hibernate: select department0_.DEPTID as DEPTID1_0_, department0_.DEPTNAME as DEPTNAME1_0_ from SCOTT.DEPARTMENT department0_ where department0_.DEPTID=? a