Hibernate4Step7

本着应用的目的快速学习Hibernate4框架

• Hibernate查询

前面的话

本节主要介绍：

本节主要讲解Hibernate4的查询方式，主要包括如下：

1. 导航对象图查询方式
2. OID查询方式
3. 本地SQL查询方式
4. HQL查询方式
5. QBC（Query By Criteria）查询方式

一、导航对象图查询方式

比如说学生和班级有多对一关系，在查询学生的时候，通过学生端把所有的班级查询出来。

二、OID查询方式

比如说get()/load()方法获取数据。

三、本地SQL查询方式

比如说用的MySQL数据库，那么就根据MySQL的SQL语法进行查询。

如果说用的Oracle数据库，那么就用的Oracle语法进行查询。

本地SQL查询方式的一个缺陷就是不能跨数据库，如果换了个数据库，可能就要重新编写新的SQL代码

四、HQL查询方式

HQL（Hibernate Query Language）是面向对象的查询语言；是使用最广的查询方式。

五、QBC查询方式

QBC（Query By Criteria）是Hibernate提供的一套用于查询的接口，可以根据这套接口进行查询。

JUnitTest

package cn.codeforgod.test;


import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.criterion.Criterion;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Restrictions;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import cn.codeforgod.model.Student;
import cn.codeforgod.util.HibernateUtil;

public class StudentTest{

	private SessionFactory sessionFactory = HibernateUtil.getSessionFactory();

	private Session session;

	private Transaction transaction;

	@Before
	public void setUp() throws Exception	{
	
		session = sessionFactory.openSession();
		transaction = session.beginTransaction();
	}

	@After
	public void tearDown() throws Exception	{
	
		transaction.commit();
		session.close();
		sessionFactory.close();
	}
	
	// 使用本地化SQL进行普通查询
	@Test
	public void testSQLQuery1() throws Exception	{
	
		String sql = "select * from t_student";
		List<Student> studentList = (List<Student>) session.createSQLQuery(sql).addEntity(Student.class).list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 本地化SQL进行带条件的查询
	@Test
	public void testSQLQuery2() throws Exception	{
	
		String sql = "select * from t_student where studentName like :studentName and studentAge = :studentAge";
		Query query = session.createSQLQuery(sql).addEntity(Student.class);
		query.setString("studentName", "张%");
		query.setInteger("studentAge", 14);
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL进行普通查询
	@Test
	public void testHQLQuery1() throws Exception	{
	
		String hql = "from Student";
		Query query = session.createQuery(hql);
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL进行带条件的查询
	@Test
	public void testHQLQuery2() throws Exception	{
	
		String hql = "from Student where name like :studentName and age = :studentAge";
		Query query = session.createQuery(hql);
		query.setString("studentName", "张%");
		query.setInteger("studentAge", 14);
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL进行带条件的查询
	@Test
	public void testHQLQuery3() throws Exception	{
	
		String hql = "from Student where name like :studentName and age = :studentAge";
		Query query = session.createQuery(hql);
		query.setString("studentName", "张%");
		query.setInteger("studentAge", 14);
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL进行创建别名的查询
	@Test
	public void testHQLQuery4() throws Exception	{
	
		String hql = "from Student s where s.name like :studentName and s.age = :studentAge";
		Query query = session.createQuery(hql);
		query.setString("studentName", "张%");
		query.setInteger("studentAge", 14);
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL进行普通查询并对结果以按照age降序排序
	@Test
	public void testHQLQuery5() throws Exception	{
	
		String hql = "from Student order by age desc";
		Query query = session.createQuery(hql);
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL进行分页查询
	@Test
	public void testHQLQuery6() throws Exception	{
	
		String hql = "from Student";
		Query query = session.createQuery(hql);
		query.setFirstResult(0);	// 从何开始 limit 0,2
		query.setMaxResults(2);		// 共有几条
		List<Student> studentList = query.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用HQL查询单个对象
	@Test
	public void testHQLQuery7() throws Exception	{
	
		String hql = "from Student";
		Query query = session.createQuery(hql);
		query.setFirstResult(2);
		query.setMaxResults(1);
		Student student = (Student) query.uniqueResult();
		System.out.println(student);
	}
	
	// 使用QBC进行普通查询
	@Test
	public void testQBCQuery1() throws Exception	{
	
		Criteria criteria = session.createCriteria(Student.class);
		List<Student> studentList = criteria.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用QBC进行带条件查询&单个结果
	@Test
	public void testQBCQuery2() throws Exception	{
	
		Criteria criteria = session.createCriteria(Student.class);
		Criterion c1 = Restrictions.like("name", "张%");
		Criterion c2 = Restrictions.eq("age", 14);
		criteria.add(c1);
		criteria.add(c2);
		Student student = (Student) criteria.uniqueResult();
		System.out.println(student);
	}
	
	// 使用QBC进行普通查询并对结果以按照age降序排序
	@Test
	public void testQBCQuery3() throws Exception	{
	
		Criteria criteria = session.createCriteria(Student.class);
		criteria.addOrder(Order.desc("age"));
		List<Student> studentList = criteria.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
	
	// 使用QBC进行分页查询
	@Test
	public void testQBCQuery4() throws Exception	{
	
		Criteria criteria = session.createCriteria(Student.class);
		criteria.setFirstResult(0);
		criteria.setMaxResults(2);
		List<Student> studentList = criteria.list();
		for (Student student : studentList)
		{
			System.out.println(student);
		}
	}
}