【hibernate】<第二节>hibernate的一对多映射（基本类型）

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-configuration PUBLIC
 3         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 4         "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
 5 <hibernate-configuration>
 6     <session-factory>
 7     <!-- 基础配置（必须的配置） -->
 8         <!-- 配置数据库的驱动类 -->
 9         <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
10         <!-- 配置数据库的别名 -->
11         <!-- 什么是别名?大家都知道hibernate一个重要的优点是可以跨数据库使用，实现这点的原因就在这里，hibernate为每种常见的数据库都
12         实现了特定的sql语句，比如就分页来说，mysql就是limit语句，而oracle就是恶心的多个select嵌套在一起，但是hibernate本身不
13         能识别数据库的类型，在这里我们通过设置别名来告诉hibernate使用什么数据库的语句来实现
14         不同数据库的别名分别是什么？
15         hibernate的包里有一个是常用配置文件，从这里可以查到
16         Hiberante开发包__hibernate-distribution-3.6.0.Final-dist\hibernate-distribution-3.6.0.Final\project\etc\hibernate.properties
17          -->
18         <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
19         <!-- 配置数据库的url地址 -->
20         <property name="hibernate.connection.url">jdbc:mysql:///test</property>
21         <!-- 配置数据库的用户名 -->
22         <property name="hibernate.connection.username">root</property>
23         <!-- 配置数据库的密码 -->
24         <property name="hibernate.connection.password">root</property>
25         
26     <!-- 非必须配置 -->
27         <!-- 是否在控制台打印sql语句，建议开发时打开，发布后关闭 -->
28         <property name="show_sql">true</property>
29         <!-- 格式化控制台打印的sql语句 -->
30         <!--<property name="format_sql">true</property>  -->
31         <!-- hibernate有两种开发流程，一个是先在数据库里建好库，建好表，再写对应的实体类，与对应关系。另一种是按需求直接写实体类与对应关系，再通过hibernate自动
32         生成对应的数据库里的表。如果想自动生成表就要配置这个hbm2ddl.auto这个属性了，这个属性有好几个值，一般用update,其余的查文档吧
33          -->
34         <property name="hbm2ddl.auto">update</property>
35         
36     <!-- 添加映射文件 -->
37         <!-- <mapping resource="cn/kiwifly/entity/User.hbm.xml"/> -->
38     </session-factory>
39 </hibernate-configuration>

package cn.kiwifly.entity;

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

public class Department {

    private Integer id;
    private String name;
    private Set<Employee> employees = new HashSet<>();

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<Employee> getEmployees() {
        return employees;
    }

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

    public String toString() {
        return "Department [id=" + id + ", name=" + name + ", employees="
                + employees + "]";
    }

}

package cn.kiwifly.entity;

public class Employee {

    private Integer id;
    private String name;
    private Integer age;
    private Department department;

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String toString() {
        return "Employee [id=" + id + ", name=" + name + ", age=" + age
                + ", department=" + department.getName() + "]";
    }

}

<?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="cn.kiwifly.entity">
    <class name="Department" table="t_department">
        <id name="id" column="id" type="integer">
            <generator class="native" />
        </id>
        <property name="name" column="name" type="string"/>
        <set name="employees" table="t_employee" inverse="true">
            <key column="department_id" />
            <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://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cn.kiwifly.entity">
    <class name="Employee" table="t_employee">
        <id name="id" column="id" type="integer">
            <generator class="native" />
        </id>
        <property name="name" column="name" type="string" />
        <property name="age" column="age" type="integer" />
        <many-to-one name="department" column="department_id" class="Department" />
    </class>
</hibernate-mapping>