1.今天做一下Hibernate中实体类之间关联关系的笔记2.
2.首先说一下onetomany和manytoone，首先需要建立2个实体类，就拿员工和部门举例子吧，一个部门对应多个员工，一个员工只属于一个部门。
package com.icss.hibernate.map;
import java.util.HashSet;
import java.util.Set;
public class Department {
private Integer id;
private String name;
private Set<Employee> employees=new HashSet<Employee>();
@Override
public String toString() {
return "Department [id=" + id + ", name=" + name + ", employees="
+ employees + "]";
}
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;
}
}
Employee类
package com.icss.hibernate.map;
public class Employee {
private Integer id;
private String name;
private Department department;
@Override
public String toString() {
return "Employee [id=" + id + ", name=" + name + ", 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 Department getDepartment() {
return department;
}
public void setDepartment(Department department) {
this.department = department;
}
}
3.提供2个类对应的hbm文件，最重要的就是这个文件的配置了。
<?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.icss.hibernate.map">
<class name="Department" table="DEPARTMENT">
<id name="id" type="java.lang.Integer">
<column name="DEPARTMENT_ID" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="DEPARTMENT_NAME" />
</property>
<set name="employees" inverse="true">
<key column="departmentId"></key>
<one-to-many class="Employee"/>
</set>
<!--
映射多对一的关联关系。 使用 many-to-one 来映射多对一的关联关系
name: 多这一端关联的一那一端的属性的名字
class: 一那一端的属性对应的类名
column: 一那一端在多的一端对应的数据表中的外键的名字
-->
</class>
</hibernate-mapping>
Employee.hbm.xml文件
<?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.icss.hibernate.map">
<class name="Employee" table="EMPLYOEE">
<id name="id" type="java.lang.Integer">
<column name="EMPLYOEE_ID" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="USER_NAME" />
</property>
<many-to-one name="department" class="Department" column="departmentId"></many-to-one>
<!--
映射多对一的关联关系。 使用 many-to-one 来映射多对一的关联关系
name: 多这一端关联的一那一端的属性的名字
class: 一那一端的属性对应的类名
column: 一那一端在多的一端对应的数据表中的外键的名字
-->
</class>
</hibernate-mapping>
具体的里面的属性说明如图：
4.编写Hibernate.cfg,xml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 > <!-- 配置数据库信息 --> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <property name="connection.url">jdbc:mysql:///321</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.username">root</property> <property name="hibernate.connection.password">123</property> <!-- 其他配置 --> <property name="hibernate.show_sql">true</property> <property name="hibernate.format_sql">true</property> <!-- create：先删除，再创建 update：如果表不存在就创建，不一样就更新，一样就什么都不做。 create-drop：初始化时创建表，SessionFactory执行close()时删除表。 validate：验证表结构是否一致，如果不一致，就抛异常。 --> <property name="hbm2ddl.auto">update</property> <mapping resource="com/icss/hibernate/map/Department.hbm.xml"/> <mapping resource="com/icss/hibernate/map/Employee.hbm.xml"/> </session-factory> </hibernate-configuration>
5编写测试代码
package com.icss.hibernate.map;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.Before;
import org.junit.Test;
public class HibernateTest {
private SessionFactory sessionFactory;
private Session session;
private Transaction transaction;
@Before
public void init(){
Configuration configuration=new Configuration().configure();
sessionFactory =configuration.buildSessionFactory();
session=sessionFactory.openSession();
transaction=session.beginTransaction();
}
@Test
public void testSave() {
// 创建对象
Department department=new Department();
department.setName("研发部");
Department department2=new Department();
department2.setName("财务部");
Employee employee=new Employee();
employee.setName("张三");
Employee employee2=new Employee();
employee2.setName("李四111111");
//关联关系
employee.setDepartment(department);
employee2.setDepartment(department2);
// department.getEmployees().add(employee);
// department2.getEmployees().add(employee2);
//执行保存
session.save(department);
session.save(department2);
session.save(employee);
session.save(employee2);
session.getTransaction().commit();
session.close();
}
@Test
public void getUser(){
session = sessionFactory.openSession();
session.beginTransaction();
Department department=(Department) session.get(Department.class, 1);
System.out.println(department);
System.out.println(department.getEmployees());
session.getTransaction().commit();
session.close();
}
}
note：
Hibernate3.6
持久层的框架
添加环境：
1，jar包
2，配置文件
hibernate.cfg.xml
xxx.hbm.xml
使用Hibernate实现CRUD操作
// --- 准备
Configuration cfg = new Configuration().configure(); // hibernate.cfg.xml
SessionFactory sessionFactory = cfg.buildSessionFactory(); // 只需要一个
// --- 模板代码
Session session = sessionFactory.openSession();
Transaction tx = null;
try{
tx = session.beginTransaction();
// 操作
tx.commit();
}catch(Exception e){
tx.rollback();
throw e;
}finally{
session.close();
}
// --- 操作
Session中的方法：
save(Object)
--> insert into ..
update(Object)--> update ..
saveOrUpdate(Object)
delete(Object)--> delete ..
get(Class, id)--> select ...
createQuery(hql)--> select ..
主配置文件
1，数据库信息
方言、URL、驱动、用户名、密码
2，导入映射文件
3，其他配置
show_sql = true
hbm2ddl.auto = update
映射配置：
映射基础
类 -- 表
属性 -- 列
映射普通属性
name, type, column, length, not-null, ...
映射主键
主键生成略：native, uuid