Hibernate 一对多双向映射及乐观锁使用
Hibernate 一对多双向映射及乐观锁使用在“Hibernate关联关系映射实例速查”一文中，通过myeclipse5.5，快速做出了Hibernate各种映射的示例。时隔快一年了，但是还是有博友向我索要工程源码，很遗憾的是已经找不到了。但找到一了一个测试代码：对双向关联和乐观锁的测试。其实映射类型很多，搞清楚一对多，基本上所有的映射就搞明白了，一对一也是一对多的特例而已，多对多也可以转换为一对多和多对一，并且实际中很少用到多对多。
还是老规矩，因为是测试，代码几乎全部是myeclipse生成的，我稍作了修改。并且应博友“阿飞”的留言，我做了详细的注释。
例子两部分：
1、一对多双向映射：模型是“班级－学生”模型。两个实体分别是Tclass和Student。
2、乐观锁的是使用，版本分别使用递增整数和时间戳。两个实体分别是Foo和Bar。
Tclass实体及其映射：
public class Tclass implements java.io.Serializable {
// Fields
private Long cid;
private String cname;
private Set students = new HashSet(0);
// Constructors
// Property accessors
.......
public String toString() {
return "Tclass{" +
"cid=" + cid +
", cname='" + cname + '\'' +
'}';
}
}
<hibernate-mapping>
<class name="stu.one2many.pojo.Tclass" table="tclass">
<id name="cid" type="java.lang.Long">
<column name="cid"/>
<generator class="native"/>
</id>
<property name="cname" type="java.lang.String">
<column name="cname" length="24" not-null="true"/>
</property>
<!-- set元素属性说明：
name="students" 设置表示多个学生的变量名；
inverse="true" 关系控制反转,不掌握主控权,表示Tclass不控制与Student关联关系，而是将这种关联控制的权利转给Student。
cascade="all" 表示级联操作，操作班级的时候，对班级关联的学生也做同样的操作。
lazy="true" 查询班级的时候，延迟查询班级下的学生。
-->
<set name="students" inverse="true" cascade="all" lazy="true">
<key>
<!--
name="fk_cid" 指定关联的外键列；
not-null="true" 说明这个外间列不能为空，多余的。
-->
<column name="fk_cid" not-null="true"/>
</key>
<!-- 指定所关联的类 -->
<one-to-many class="stu.one2many.pojo.Student"/>
</set>
</class>
</hibernate-mapping>
Student实体及其映射
public class Student implements java.io.Serializable {
// Fields
private Long sid;
private Tclass tclass;
private String sname;
// Constructors
// Property accessors
.......
public String toString() {
return "Student{" +
"sid=" + sid +
", sname='" + sname + '\'' +
'}';
}
}
<hibernate-mapping>
<class name="stu.one2many.pojo.Student" table="student">
<id name="sid" type="java.lang.Long">
<column name="sid" />
<generator class="native" />
</id>
<!-- 表示多个Student关联一个Tclass -->
<!--
name="tclass" 关联的成员变量名;
class="stu.one2many.pojo.Tclass" 表示所关联的类;
fetch="select" 查询策略,有两个选项select和join,
select表示通过外联接来进行查询,查询速度稍慢,但消耗资源少;
join表示通过内连接来查询,速度快,但消耗资源多.
-->
<many-to-one name="tclass"
class="stu.one2many.pojo.Tclass"
fetch="select">
<!-- 指定关联的外键列 -->
<column name="fk_cid" not-null="true" />
</many-to-one>
<property name="sname" type="java.lang.String">
<column name="sname" length="24" not-null="true" />
</property>
</class>
</hibernate-mapping>
测试班级学生模型：
public class Test {
/**
* @param args
*/
public static void main(String[] args) {
testSave();
// testDeleteTclass();
}
public static void testSave() {
Tclass c = new Tclass();
c.setCname("某班级");
Student s1 = new Student();
Student s2 = new Student();
s1.setSname("张三");
s1.setTclass(c);
s2.setSname("李四");
s2.setTclass(c);
c.getStudents().add(s1);
c.getStudents().add(s2);
Session session = HibernateSessionFactory.getSession();
Transaction tx = session.beginTransaction();
session.save(c);
tx.commit();
session.close();
}
public static void testUpdateClass() {
System.out.println("----------------正在调用testUpdateClass()----------------");
Session session = HibernateSessionFactory.getSession();
Tclass c = (Tclass) session.load(Tclass.class, Long.valueOf(1L));
System.out.println(c);
c.setCname("班级更名");
session.beginTransaction().commit();
}
public static void testUpdateStudent() {
System.out.println("----------------正在调用testUpdateStudent()----------------");
Session session = HibernateSessionFactory.getSession();
Tclass c = (Tclass) session.load(Tclass.class, Long.valueOf(3L));
Student s = (Student) session.load(Student.class, Long.valueOf(2L));
s.setSname("学生改名换姓-王八");
s.setTclass(c);
System.out.println(c);
System.out.println(s);
session.beginTransaction().commit();
System.out.println(s);
System.out.println(s.getTclass());
}
public static void testDeleteStudent() {
System.out.println("----------------正在调用testDelete()----------------");
Session session = HibernateSessionFactory.getSession();
Student s = (Student) session.load(Student.class, Long.valueOf(5L));
System.out.println(s);
System.out.println(s.getTclass());
session.delete(s);
session.beginTransaction().commit();
}
public static void testDeleteTclass() {
System.out.println("----------------正在调用testDelete()----------------");
Session session = HibernateSessionFactory.getSession();
Tclass c = (Tclass) session.load(Tclass.class, Long.valueOf(3L));
System.out.println(c);
session.delete(c);
session.beginTransaction().commit();
}
public static void testQueryClass() {
System.out.println("----------------正在调用testQueryClass()----------------");
Session session = HibernateSessionFactory.getSession();
Tclass c = (Tclass) session.load(Tclass.class, new Long("1"));
System.out.println(c);
System.out.println(c.getStudents());
}
public static void testQueryStudent() {
System.out.println("----------------正在调用testQueryStudent()----------------");
Session session = HibernateSessionFactory.getSession();
Student s = (Student) session.load(Student.class, new Long("1"));
System.out.println(s);
System.out.println(s.getTclass());
}
}
下面是乐观锁的使用：
1、基于整数的版本控制
Foo实体和映射文件
public class Foo implements java.io.Serializable {
// Fields
private Long pid;
private Integer version;
private String name;
// Constructors
// Property accessors
.......
public String toString() {
return "Foo{" +
"pid=" + pid +
", version=" + version +
", name='" + name + '\'' +
'}';
}
}
<hibernate-mapping>
<class name="stu.one2many.pojo.Foo" table="foo"
optimistic-lock="version">
<id name="pid" type="java.lang.Long">
<column name="pid" />
<generator class="native" />
</id>
<!-- 版本控制字段必须在id后配置 -->
<version name="version" type="java.lang.Integer">
<column name="version" />
</version>
<property name="name" type="java.lang.String">
<column name="name" length="24" not-null="true" />
</property>
</class>
</hibernate-mapping>
测试：
public class TestFoo {
/**
* @param args
*/
public static void main(String[] args) {
testSave();
}
public static void testSave(){
Foo foo1 = new Foo("foo1");
Session session = HibernateSessionFactory.getSession();
session.save(foo1);
session.beginTransaction().commit();
session.close();
}
}
2、基于时间戳的版本控制
public class Bar implements java.io.Serializable, Comparable {
// Fields
private Long id;
private Date timestamp;
private String name;
// Constructors
// Property accessors
.......
public String toString() {
return "Bar{" +
"id=" + id +
", timestamp=" + timestamp +
", name='" + name + '\'' +
'}';
}
/**
* 排序接口方法实现，为了能对查询结果按照id的大小进行排序
* @param o 排序对象
* @return 比较值
*/
public int compareTo(Object o) {
Bar bar = (Bar) o;
Long res = this.id - bar.getId();
return res.intValue();
}
}
<hibernate-mapping>
<class name="stu.one2many.pojo.Bar" table="bar" optimistic-lock="version">
<id name="id" type="java.lang.Long">
<column name="id" />
<generator class="native" />
</id>
<version name="timestamp" type="java.util.Date">
<column name="timestamp" length="0" not-null="true" />
</version>
<property name="name" type="java.lang.String">
<column name="name" length="24" not-null="true" />
</property>
</class>
</hibernate-mapping>
public class TestBar {
public static void main(String args[]) {
testUpdateBar();
testQueryBar();
}
public static void testSaveBar() {
Bar bar = new Bar("bar");
Session session = HibernateSessionFactory.getSession();
session.save(bar);
session.beginTransaction().commit();
session.close();
}
public static void testQueryBar() {
Session session = HibernateSessionFactory.getSession();
String hql = "from Bar";
Query query = session.createQuery(hql);
List<Bar> barList = query.list();
Collections.sort(barList);
for (Bar bar : barList) {
System.out.println(bar.getId() + ":\t" + bar.getTimestamp().getTime());
}
session.close();
}
public static void testUpdateBar() {
Session session = HibernateSessionFactory.getSession();
String hql = "from Bar";
Query query = session.createQuery(hql);
List<Bar> barList = query.list();
for (Bar bar : barList) {
bar.setName("newBar");
}
session.beginTransaction().commit();
session.close();
}
}
public class TestStack {
public static void main(String args[]){
test();
}
public static voidtest(){
Stack stack = new Stack();
String s1= "1";
String s2="2";
String s3= "3";
String s4= "4";
stack.push(s1);
stack.push(s2);
stack.push(s3);
stack.push(s4);
for(;!stack.isEmpty();){
System.out.println(stack.pop());
}
//for语句先判断是否符合条件,然后确定是否执行循环
for(int i=0;i>10;i--){
System.out.println(">>> "+i);
}
}
}
下面是SessionFactory工具和hibernate配置文件：
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
/**
* Configures and provides access to Hibernate sessions, tied to the
* current thread of execution.Follows the Thread Local Session
* pattern, see {@link http://hibernate.org/42.html }.
*/
public class HibernateSessionFactory {
/**
* Location of hibernate.cfg.xml file.
* Location should be on the classpath as Hibernate uses
* #resourceAsStream style lookup for its configuration file.
* The default classpath location of the hibernate config file is
* in the default package. Use #setConfigFile() to update
* the location of the configuration file for the current session.
*/
private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
privatestatic Configuration configuration = new Configuration();
private static org.hibernate.SessionFactory sessionFactory;
private static String configFile = CONFIG_FILE_LOCATION;
static {
try {
configuration.configure(configFile);
sessionFactory = configuration.buildSessionFactory();
} catch (Exception e) {
System.err
.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
private HibernateSessionFactory() {
}
/**
* Returns the ThreadLocal Session instance.Lazy initialize
* the <code>SessionFactory</code> if needed.
*
*@return Session
*@throws HibernateException
*/
public static Session getSession() throws HibernateException {
Session session = (Session) threadLocal.get();
if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
session = (sessionFactory != null) ? sessionFactory.openSession()
: null;
threadLocal.set(session);
}
return session;
}
/**
*Rebuild hibernate session factory
*
*/
public static void rebuildSessionFactory() {
try {
configuration.configure(configFile);
sessionFactory = configuration.buildSessionFactory();
} catch (Exception e) {
System.err
.println("%%%% Error Creating SessionFactory %%%%");
e.printStackTrace();
}
}
/**
*Close the single hibernate session instance.
*
*@throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);
if (session != null) {
session.close();
}
}
/**
*return session factory
*
*/
public static org.hibernate.SessionFactory getSessionFactory() {
return sessionFactory;
}
/**
*return session factory
*
* session factory will be rebuilded in the next call
*/
public static void setConfigFile(String configFile) {
HibernateSessionFactory.configFile = configFile;
sessionFactory = null;
}
/**
*return hibernate configuration
*
*/
public static Configuration getConfiguration() {
return configuration;
}
}
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools. -->
<hibernate-configuration>
<session-factory>
<property name="connection.username">root</property>
<property name="connection.url">
jdbc:mysql://localhost:3306/testdb
</property>
<property name="dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="myeclipse.connection.profile">
com.mysql.jdbc.Driver
</property>
<property name="connection.password">leizhimin</property>
<property name="connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="show_sql">true</property>
<!--<property name="format_sql">true</property>-->
<property name="hbm2ddl.auto">create</property>
<mapping resource="stu/one2many/pojo/Tclass.hbm.xml" />
<mapping resource="stu/one2many/pojo/Student.hbm.xml" />
<mapping resource="stu/one2many/pojo/Foo.hbm.xml"></mapping>
<mapping resource="stu/one2many/pojo/Bar.hbm.xml" />
</session-factory>
</hibernate-configuration>
数据库用的是mysql5，sql脚本我导出了一份如下：
/*
SQLyog Enterprise - MySQL GUI v6.5
MySQL - 5.0.45-community-nt : Database - testdb
*********************************************************************
*/
/*!40101 SET NAMES utf8 */;
/*!40101 SET SQL_MODE=''*/;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
create database if not exists testdb;
USE testdb;
/*Table structure for table bar */
DROP TABLE IF EXISTS bar;
CREATE TABLE bar (
id bigint(20) NOT NULL auto_increment,
timestamp datetime NOT NULL,
name varchar(24) NOT NULL,
PRIMARY KEY(id)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;
/*Table structure for table foo */
DROP TABLE IF EXISTS foo;
CREATE TABLE foo (
pid bigint(20) NOT NULL auto_increment,
version int(11) NOT NULL,
name varchar(24) NOT NULL,
PRIMARY KEY(pid)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;
/*Table structure for table student */
DROP TABLE IF EXISTS student;
CREATE TABLE student (
sid bigint(20) NOT NULL auto_increment,
fk_cid bigint(20) NOT NULL,
sname varchar(24) NOT NULL,
PRIMARY KEY(sid),
KEY FK8FFE823B3AA29689 (fk_cid),
CONSTRAINT FK8FFE823B3AA29689 FOREIGN KEY (fk_cid) REFERENCES tclass (cid)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=gbk;
/*Table structure for table tclass */
DROP TABLE IF EXISTS tclass;
CREATE TABLE tclass (
cid bigint(20) NOT NULL auto_increment,
cname varchar(24) NOT NULL,
PRIMARY KEY(cid)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gbk;
/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
具体测试运行的结果运行下即可看到。
源码压缩包太大4M多，我删除了所有引用的包。使用的是hibernate3.1
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