hibernate之初学一对多和多对一配置及使用

按查询及存取速率来说的一对多用的相对多对一少一些，这里只写主要配置文件的代码

首先是hibernate的配置文件

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/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:///webproject</property>
<property name="hibernate.connection.username">root</property>            
<property name="hibernate.connection.password">123456</property>            
<property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">create</property>
<mapping resource="com/shaoxin/entity/Dept.hbm.xml"/>
<mapping resource="com/shaoxin/entity/Employee.hbm.xml"/>
</session-factory>
</hibernate-configuration>

一对多的配置文件代码，很明显使用到了set集合

<?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="com.shaoxin.entity">
<class name="Dept" table="dept">
<id name="deptid" column="deptid">
<generator class="native"></generator>
</id>
<property name="deptName" column="deptname"></property><!--
            一对多设置外键方式，class代表外键类型
--><set name="setEmployees" table="employee">
<key column="dept_id"></key>
<one-to-many class="Employee"/>
</set>
</class>
</hibernate-mapping>

对应的实体类：

package com.shaoxin.entity;

import java.util.HashSet;
import java.util.Set;

public class Dept {
private int deptid;
private String deptName;
private Set<Employee> setEmployees = 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> getSetEmployees() {
return setEmployees;
    }

public void setSetEmployees(Set<Employee> setEmployees) {
this.setEmployees = setEmployees;
    }

}

多对一的配置文件代码，很明显是一个对象类型

<?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="com.shaoxin.entity">
<class name="Employee"  table="employee">
<id name="employeeid" column="employeeid">
<generator class="native"></generator>
</id>
<property name="employeeName" column="employeename"/><!--
            多对一创建外键方式：属性分别为：外键对应的表，外键字段，外键类型
--><many-to-one name="dept" column="dept_id" class="Dept"></many-to-one>
</class>
</hibernate-mapping>

对应的实体类

package com.shaoxin.entity;

public class Employee {
private int employeeid;
private String employeeName;
private Dept dept;

public int getEmployeeid() {
return employeeid;
    }

public void setEmployeeid(int employeeid) {
this.employeeid = employeeid;
    }

public String getEmployeeName() {
return employeeName;
    }

public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
    }

public Dept getDept() {
return dept;
    }

public void setDept(Dept dept) {
this.dept = dept;
    }

}

测试这两个存储方式

package com.shaoxin.entity;

import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.classic.Session;
import org.junit.Test;

public class TestMany2Many {
static SessionFactory sf;
static {
        sf = new Configuration().configure().buildSessionFactory();
    }

    @Test
public void testOne2Many() throws Exception {
        Session openSession = sf.openSession();
        Transaction beginTransaction = openSession.beginTransaction();
        Employee empzs = new Employee();
        Employee empls = new Employee();
        empls.setEmployeeName("李四");
        empzs.setEmployeeName("张三");
        Dept dept = new Dept();
        dept.getSetEmployees().add(empls);
        dept.getSetEmployees().add(empzs);
        dept.setDeptName("应用开发");
        openSession.save(empls);
        openSession.save(empzs);
        openSession.save(dept);
        beginTransaction.commit();
        openSession.close();
    }

    @Test
public void testMany2One() throws Exception {
        Session openSession = sf.openSession();
        Transaction beginTransaction = openSession.beginTransaction();
        Employee empzs = new Employee();
        Employee empls = new Employee();
        Dept dept = new Dept();
        dept.setDeptName("应用开发");
        empls.setEmployeeName("李四");
        empzs.setEmployeeName("张三");
        empls.setDept(dept);
        empzs.setDept(dept);
        openSession.save(dept);
        openSession.save(empls);
        openSession.save(empzs);
        beginTransaction.commit();
        openSession.close();
    }
}