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hibernate 多对一
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1，部门和员工：多对一
Department.hbm.xml
<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.maple.hibernate.domain"> <class name="Department"> <id name="id"> <generator class="native" /> </id> <property name="name" /> </class></hibernate-mapping>
Employee.hbm.xml
<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.maple.hibernate.domain"> <class name="Employee"> <id name="id"> <generator class="native" /> </id> <property name="name" /> <many-to-one name="depart" column="depart_id"/> </class></hibernate-mapping>
hibernate.cfg.xml
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration> <session-factory> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/test</property> <property name="hibernate.connection.username">root </property> <property name="hibernate.connection.password">root </property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <property name="hibernate.hbm2ddl.auto">create</property> <property name="show_sql">true</property> <mapping resource="com/maple/hibernate/domain/Department.hbm.xml"/> <mapping resource="com/maple/hibernate/domain/Employee.hbm.xml"/> </session-factory></hibernate-configuration>
Department.java
package com.maple.hibernate.domain;public class Department { private int id; private String name; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }
Employee.java
package com.maple.hibernate.domain;public class Employee { private int id; private String name; private Department depart; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Department getDepart() { return depart; } public void setDepart(Department depart) { this.depart = depart; } }
测试代码
package com.maple.hibernate;import org.hibernate.Hibernate;import org.hibernate.Session;import org.hibernate.Transaction;import com.maple.hibernate.domain.Department;import com.maple.hibernate.domain.Employee;public class Many2One { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub add(); //System.out.println("ff"); Employee emp=query(1); System.out.println("ffff depart name:"+emp.getDepart().getName());//如果在query方法中没有 } static Employee query(int employeeid){ Session s=null; try{ s=HibernateUtil.getSession(); Employee emp=(Employee) s.get(Employee.class, employeeid); Hibernate.initialize(emp.getDepart());//若无，main中打印语句出错// System.out.println("depart name:"+emp.getDepart().getName());//可以 return emp; }finally{ if(s!=null){ s.close(); } } } static Department add(){ Session s=null; Transaction tx=null; try{ s=HibernateUtil.getSession(); Department depart=new Department(); depart.setName("software"); Employee emp=new Employee(); emp.setDepart(depart); emp.setName("aaa"); tx=s.beginTransaction(); s.save(depart); //如果放下面，employee会多出一条更新语句 s.save(emp); tx.commit(); return depart; }finally{ if(s!=null){ s.close(); } } }}
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hibernate 多对一
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