Hibernate HQL示例一:基本配置及测试查询
Hibernate Hql查询：
大小写敏感，如：from Student 指的是从Student对象中查询。
示例：
第一步创建数据库hibernate
第二步运行ExportDB.java生成表结构。
第三步运行InitData.java生成数据。
第四步进行其它测试。
工具类代码：
package com.bjsxt.hibernate;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
public class ExportDB {
public static void main(String[] args) {
//读取配置文件
Configuration cfg = new Configuration().configure();
//创建SchemaExport对象
SchemaExport export = new SchemaExport(cfg);
//创建数据库表
export.create(true,true);
}
}package com.bjsxt.hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtils {
private static SessionFactory factory;
private HibernateUtils() {}
static {
Configuration cfg = new Configuration().configure();
factory = cfg.buildSessionFactory();
}
public static SessionFactory getSessionFactory() {
return factory;
}
public static Session getSession() {
return factory.openSession();
}
public static void closeSession(Session session) {
if (session != null) {
if (session.isOpen()) {
session.close();
}
}
}
}package com.bjsxt.hibernate;
import java.util.Set;
public class Classes {
private int id;
private String name;
private Set students;
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 Set getStudents() {
return students;
}
public void setStudents(Set students) {
this.students = students;
}
}package com.bjsxt.hibernate;
import java.util.Date;
public class Student {
private int id;
private String name;
private Date createTime;
private Classes classes;
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 Classes getClasses() {
return classes;
}
public void setClasses(Classes classes) {
this.classes = classes;
}
public Date getCreateTime() {
return createTime;
}
public void setCreateTime(Date createTime) {
this.createTime = createTime;
}
}Classes.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> <class name="com.bjsxt.hibernate.Classes" table="t_classes"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <!-- <set name="students" cascade="all" order-by="id"> --> <set name="students" inverse="true"> <key column="classid"/> <one-to-many class="com.bjsxt.hibernate.Student"/> </set> </class> </hibernate-mapping>
Student.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> <class name="com.bjsxt.hibernate.Student" table="t_student"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <property name="createTime"/> <many-to-one name="classes" column="classid"/> <filter name="idfilter" condition="id < :myid"/> </class> <query name="searchStudents"><![CDATA[ select s from Student s where s.id < ? ]]> </query> <filter-def name="idfilter"> <filter-param name="myid" type="integer"/> </filter-def> </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.url"> jdbc:mysql://127.0.0.1/hibernate </property> <property name="hibernate.connection.driver_class"> com.mysql.jdbc.Driver </property> <property name="hibernate.connection.username">root</property> <property name="hibernate.connection.password">super</property> <property name="dialect"> org.hibernate.dialect.MySQLDialect </property> <property name="show_sql">true</property> <mapping resource="com/bjsxt/hibernate/Classes.hbm.xml"/> <mapping resource="com/bjsxt/hibernate/Student.hbm.xml"/> </session-factory> </hibernate-configuration>
上面文件创建完成之后，运行ExportDB.java
数据库中创建两个表格：t_classes,t_student
表结构如下：
mysql> desc t_classes; +-------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(255) | YES | | NULL | | +-------+--------------+------+-----+---------+----------------+ 2 rows in set (0.00 sec) mysql> desc t_student; +------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(255) | YES | | NULL | | | createTime | datetime | YES | | NULL | | | classid | int(11) | YES | MUL | NULL | | +------------+--------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec)
为了作测试生成数据类InitData.java如下：
package com.bjsxt.hibernate;
import java.text.SimpleDateFormat;
import java.util.Date;
import org.hibernate.Session;
public class InitData {
public static void main(String[] args) {
Session session = HibernateUtils.getSession();
try {
session.beginTransaction();
for(int i=0; i<10; i++){
Classes classes = new Classes();
classes.setName("班级"+i);
session.save(classes);
for(int j=0; j<10; j++){
Student student = new Student();
student.setName("班级"+i+"的学生"+j);
student.setCreateTime(randomDate("2007-01-01","2007-03-01"));
//在内存中建立由student指向classes的引用
student.setClasses(classes);
session.save(student);
}
}
for(int i=0; i<5; i++){
Classes classes = new Classes();
classes.setName("无学生班级"+i);
session.save(classes);
}
for(int i=0; i<10; i++){
Student student = new Student();
student.setName("无业游民"+i);
session.save(student);
}
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
} finally{
HibernateUtils.closeSession(session);
}
}
/**
* 获取随机日期
* @param beginDate 起始日期，格式为：yyyy-MM-dd
* @param endDate 结束日期，格式为：yyyy-MM-dd
* @return
*/
private static Date randomDate(String beginDate,String endDate){
try {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
Date start = format.parse(beginDate);
Date end = format.parse(endDate);
if(start.getTime() >= end.getTime()){
return null;
}
long date = random(start.getTime(),end.getTime());
return new Date(date);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
private static long random(long begin,long end){
long rtn = begin + (long)(Math.random() * (end - begin));
if(rtn == begin || rtn == end){
return random(begin,end);
}
return rtn;
}
}以下开始做测试：
测试类1：SimpleObjectQueryTest.java
package com.bjsxt.hibernate;
import java.util.Iterator;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import junit.framework.TestCase;
/**
* 对象查询的基本测试
* @author Administrator
*
*/
public class SimpleObjectQueryTest extends TestCase {
public void testQuery1() {
Session session = null;
try {
session = HibernateUtils.getSession();
//可以忽略select语句
List students = session.createQuery("from Student").list();
for (Iterator iter = students.iterator();iter.hasNext();) {
//返回值是Student对象
Student student = (Student)iter.next();
System.out.println(student.getName());
}
}catch(Exception e) {
e.printStackTrace();
}finally {
HibernateUtils.closeSession(session);
}
}
public void testQuery2() {
Session session = null;
try {
session = HibernateUtils.getSession();
//可以忽略select语句,表可以加别名
List students = session.createQuery("from Student s").list();
for (Iterator iter = students.iterator();iter.hasNext();) {
//返回值是Student对象
Student student = (Student)iter.next();
System.out.println(student.getName());
}
}catch(Exception e) {
e.printStackTrace();
}finally {
HibernateUtils.closeSession(session);
}
}
public void testQuery3() {
Session session = null;
try {
session = HibernateUtils.getSession();
//可以忽略select语句,表可以加别名
List students = session.createQuery("from Student as s").list();
for (Iterator iter = students.iterator();iter.hasNext();) {
//返回值是Student对象
Student student = (Student)iter.next();
System.out.println(student.getName());
}
}catch(Exception e) {
e.printStackTrace();
}finally {
HibernateUtils.closeSession(session);
}
}
public void testQuery4() {
Session session = null;
try {
session = HibernateUtils.getSession();
//使用select关键字时，必须定义别名
List students = session.createQuery("select s from Student s").list();
for (Iterator iter = students.iterator();iter.hasNext();) {
//返回值是Student对象
Student student = (Student)iter.next();
System.out.println(student.getName());
}
}catch(Exception e) {
e.printStackTrace();
}finally {
HibernateUtils.closeSession(session);
}
}
public void testQuery5() {
Session session = null;
try {
session = HibernateUtils.getSession();
//不支持select * ....这样的HQL查询语句
List students = session.createQuery("select * from Student").list();
for (Iterator iter = students.iterator();iter.hasNext();) {
//返回值是Student对象
Student student = (Student)iter.next();
System.out.println(student.getName());
}
}catch(Exception e) {
e.printStackTrace();
}finally {
HibernateUtils.closeSession(session);
}
}
}上面测试中得到的结论：
做查询时，可以忽略select语句； 表可以加别名； 使用select关键字时，必须定义别名； 不支持select * ....这样的HQL查询语句