hibernate检索

检索策略

类级别检索策略：
	lazy：默认是true，表示懒加载
		     若为false，则是直接加载
		     >>若使用get方法：则lazy不起作用，都会直接发送sql语句
		     >>若使用load方法：则会进行懒加载，直到访问对象的非id属性时才会select语句
set标签中的检索策略： <set name="set" table="ORDERS" inverse="true" lazy="true" batch-size="3" fetch="join">
	lazy：默认是true，表示懒加载
			>>用set属性时才查询
		     若为false
		    >>查询Customer时，连发两条select语句，第一句查Customer，第二句查set
		     若为extra，则表示增强懒加载，尽可能延迟初始化的时机，
		     		  比如size（）时	select
								        count(ORDER_ID) 
								    from
								        ORDERS 
								    where
								        CUSTOMER_ID =?
	batch-size:批量处理用来为延迟检索策略或立即检索策略设定批量检索的数量.（extra增强懒加载不适用） 
			     批量检索能减少 SELECT 语句的数目, 提高延迟检索或立即检索的运行性能. 
			     	一次处理两个时
			      	select
				        set0_.CUSTOMER_ID as CUSTOMER3_0_1_,
				        set0_.ORDER_ID as ORDER_ID1_1_1_,
				        set0_.ORDER_ID as ORDER_ID1_1_0_,
				        set0_.ORDER_DESC as ORDER_DE2_1_0_,
				        set0_.CUSTOMER_ID as CUSTOMER3_1_0_ 
				    from
				        ORDERS set0_ 
				    where
				        set0_.CUSTOMER_ID in (
				            ?, ?
				        )	
			     若为增强懒加载，则不起作用
	fetch:默认是select：就是正常，简单的select查询
	
		  当 fetch 属性为 “subselect” 时
			1.假定 Session 缓存中有 n 个 orders 集合代理类实例没有被初始化, 
			  Hibernate 能够通过带子查询的 select 语句, 来批量初始化 n 个 orders 集合代理类实例
			2.batch-size 属性将被忽略
			3.子查询中的 select 语句为查询 CUSTOMERS 表 OID 的 SELECT 语句
		  
		  当 fetch 属性为 “join” 时:
			1.检索 Customer 对象时, 会采用迫切左外连接(通过左外连接加载与检索指定的对象关联的对象)
			     策略来检索所有关联的 Order 对象
			2.lazy 属性将被忽略
			3.Query 的list() 方法会忽略映射文件中配置的迫切左外连接检索策略, 而依旧采用延迟加载策略
 <many-to-one>和<one-to-one>同上		  
	
	

检索方法

1.HQL

package jiansuo_jiben;

import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class TestHQL {
	private SessionFactory sessionFactory;
	private Session session;
	private Transaction transaction;
	
	@Before
	public void before(){
		Configuration configuration = new Configuration().configure();
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties())
																		.buildServiceRegistry();
		sessionFactory = configuration.buildSessionFactory(serviceRegistry);
		session  = sessionFactory.openSession();
		transaction = session.beginTransaction();
	}

	@After
	public void after(){
		transaction.commit();
		session.close();
		sessionFactory.close();
	}

	@Test
	public void test() {
		Query query = session.createQuery("FROM Employee where salary >= :sal and"
				+ " department = :dep order by salary asc");
		
		Department d = new Department();
		d.setId(1);
		query.setInteger("sal", 500).setEntity("dep", d);
		
		List<Employee> es = query.list();
		System.out.println(es);
		Iterator<Employee> it = es.iterator();
		while(it.hasNext()){
			System.out.println(it.next().getName());
		}
	}

	@Test
	public void testPageQuery() {//分页查询
		Query q = session.createQuery("FROM Employee ORDER BY salary desc");
		
		int pageNo = 1;//第几页，从1开始
		int pageSize = 3;//每页几条记录
		
		
		q.setFirstResult( (pageNo-1) * pageSize );//设置第一条记录的位置
		q.setMaxResults(pageSize);//设置每页的记录条数
		
		List<Employee> es = q.list();
		for(Employee e:es){
			System.out.println(e);
		}
	}
	@Test
	public void testNameQuery() {//命名查询，在hbm.xml文件中写hql
//<query name="minSalaryAsDepartment"><![CDATA[SELECT min(e.salary) FROM Employee e GROUP BY e.department]]></query>
		Query q = session.getNamedQuery("minSalaryAsDepartment");//引用
		
//		Department dep = new Department();
//		dep.setId(2);
//		
//		q.setEntity("dep", dep);
		
		List<Integer> mins = q.list();
		System.out.println(mins);
	}
	@Test
	public void testFieldQuery() {//字段查询,要用对应的构造方法,也可不封装
		String hql = "SELECT new Employee(e.salary,e.name,e.department) FROM Employee e WHERE e.department = :dep";
		
		Department dep = new Department();
		dep.setId(1);
		
		Query q = session.createQuery(hql);
		q.setEntity("dep", dep);
		
		List<Employee> os = q.list();
		
		for(Employee o:os){
			System.out.println(o);
		}
	}
	@Test
	public void test_baobiao_Query() {//报表查询，使用对应的方法
		String hql = "SELECT min(e.salary),max(e.salary) FROM Employee e WHERE e.salary>100 GROUP BY e.department";
		
		
		Query q = session.createQuery(hql);
		
		List<Object[]> os = q.list();
		
		for(Object[] o:os){
			System.out.println(Arrays.asList(o));
		}
	}
}

2.QBC

package jiansuo_jiben;

import java.sql.SQLException;
import java.util.Iterator;
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.cfg.Configuration;
import org.hibernate.criterion.Conjunction;
import org.hibernate.criterion.Disjunction;
import org.hibernate.criterion.MatchMode;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;
import org.hibernate.jdbc.Work;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class TestQBC_SQL_Cache {
	private SessionFactory sessionFactory;
	private Session session;
	private Transaction transaction;
	
	@Before
	public void before(){
		Configuration configuration = new Configuration().configure();
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties())
																		.buildServiceRegistry();
		sessionFactory = configuration.buildSessionFactory(serviceRegistry);
		session  = sessionFactory.openSession();
		transaction = session.beginTransaction();
	}

	@After
	public void after(){
		transaction.commit();
		session.close();
		sessionFactory.close();
	}
	
	@Test
	public void testQBC4(){
		Criteria criteria = session.createCriteria(Employee.class);
		
		//1. 添加排序
		criteria.addOrder(Order.asc("salary"));
		criteria.addOrder(Order.desc("name"));
		
		//2. 添加翻页方法
		int pageSize = 5;
		int pageNo = 3;
		List<Employee> es = criteria.setFirstResult((pageNo - 1) * pageSize)
		        .setMaxResults(pageSize)
		        .list();
		for(Employee e:es){
			System.out.println(e);
		}
	}
	
	@Test
	public void testQBC3(){//跟报表查询差不多
		Criteria criteria = session.createCriteria(Employee.class);
		
		//统计查询: 使用 Projection 来表示: 可以由 Projections 的静态方法得到
		criteria.setProjection(Projections.max("salary"));
		
		System.out.println(criteria.uniqueResult()); //50000
	}
	
	@Test
	public void testQBC2(){
		Criteria criteria = session.createCriteria(Employee.class);
		
		//1. AND: 使用 Conjunction 表示
		//Conjunction 本身就是一个 Criterion 对象
		//且其中还可以添加 Criterion 对象
		Conjunction conjunction = Restrictions.conjunction();
		conjunction.add(Restrictions.like("name", "a", MatchMode.ANYWHERE));
		Department dept = new Department();
		dept.setId(80);
		conjunction.add(Restrictions.eq("department", dept));
		System.out.println(conjunction); 
		
		//2. OR
		Disjunction disjunction = Restrictions.disjunction();
		disjunction.add(Restrictions.le("salary", 6000));
		disjunction.add(Restrictions.isNull("name"));
		
		System.out.println(disjunction);
		
		criteria.add(disjunction);
		criteria.add(conjunction);
		
		criteria.list();
	}
	
	@Test
	public void testQBC(){
		//1. 创建一个 Criteria 对象
		Criteria criteria = session.createCriteria(Employee.class);
		
		//2. 添加查询条件: 在 QBC 中查询条件使用 Criterion 来表示
		//Criterion 可以通过 Restrictions 的静态方法得到
		criteria.add(Restrictions.eq("email", "SKUMAR"));
		criteria.add(Restrictions.gt("salary", 5000F));
		
		//3. 执行查询
		Employee employee = (Employee) criteria.uniqueResult();
		System.out.println(employee); 
	}
}

3.本地SQL

package jiansuo_jiben;

import java.sql.SQLException;
import java.util.Iterator;
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.cfg.Configuration;
import org.hibernate.criterion.Conjunction;
import org.hibernate.criterion.Disjunction;
import org.hibernate.criterion.MatchMode;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;
import org.hibernate.jdbc.Work;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class TestQBC_SQL_Cache {
	private SessionFactory sessionFactory;
	private Session session;
	private Transaction transaction;
	
	@Before
	public void before(){
		Configuration configuration = new Configuration().configure();
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties())
																		.buildServiceRegistry();
		sessionFactory = configuration.buildSessionFactory(serviceRegistry);
		session  = sessionFactory.openSession();
		transaction = session.beginTransaction();
	}

	@After
	public void after(){
		transaction.commit();
		session.close();
		sessionFactory.close();
	}
	
	@Test
	public void testHQLUpdate(){
		String hql = "DELETE FROM Department d WHERE d.id = :id";
		
		session.createQuery(hql).setInteger("id", 280)
		                        .executeUpdate();
	}
	
	@Test
	public void testNativeSQL(){
		String sql = "INSERT INTO gg_department VALUES(?, ?)";
		Query query = session.createSQLQuery(sql);
		
		query.setInteger(0, 280)
		     .setString(1, "ATGUIGU")
		     .executeUpdate();
	}
}