HQL查询对象实战详解

雨点打透心脏的1/2处 2022-02-24 01:18 216阅读 0赞

1.项目结构及目标数据库：  
![百度百度百度][20190402170248466.png]  
![百度百度百度][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29MZW5nWXVlSHVu_size_16_color_FFFFFF_t_70]  
2.hql配置文件：

<?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">
    
    <hibernate-configuration>
    	<session-factory>
    
    		
    		<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
    		<property name="connection.url">jdbc:oracle:thin:@localhost:orcl</property>
    		<property name="connection.username">scott</property>
    		<property name="connection.password">tiger</property>
    
    		
    		<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
    
    		
    		<property name="show_sql">true</property>
    
    		
    		<property name="hbm2ddl.auto">update</property>
    		<property name="format_sql">true</property>
    
    		
    		<mapping resource="hbm/Emp.hbm.xml" />
    		<mapping resource="hbm/Dept.hbm.xml" />
    
    	</session-factory>
    </hibernate-configuration>

映射文件

<?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>
    	<class name="com.hxzy.hql.entity.Emp" table="emp"
    		lazy="true" select-before-update="true">
    		
    		
    		<id name="empno" column="empno" type="java.lang.Integer">
    			<generator class="increment" />
    		</id>
    		
            
    		<property name="ename" column="ename" type="java.lang.String"/>
    		<property name="deptno" column="deptno" type="java.lang.Integer" />
    		<property name="job" column="job" type="java.lang.String" />
    		<property name="mgr" column="mgr" type="java.lang.String" />
    		<property name="hiredate" column="hiredate" type="java.lang.Integer" />
    		<property name="sal" column="sal" type="java.lang.Integer" />
    		<property name="comm" column="comm" type="java.lang.Integer" />
    		
    	</class>	
    </hibernate-mapping>

3.对象  
public class Emp \{  
private int empno;  
private String ename;  
private int deptno;  
private String job;  
private int mgr;  
private String hiredate;  
private int sal;  
private String comm;

/**
     * emp构造方法(empno,ename,deptno)
     * */
    public Emp(int empno, String ename, int deptno) {
    	super();
    	this.deptno = deptno;
    	this.empno = empno;
    	this.ename = ename;
    }
    。。。

4.查询代码：  
dao层：

public class EmpDaoImpl {
    	private static SessionFactory sessionFactory;
        private static Session session;
        private static Transaction transaction;
    	
    	/**
    	 * 获取session
    	 * */
    	public Session getSession() {
    		Configuration cfg = new Configuration().configure();//启动配置
    		sessionFactory = cfg.buildSessionFactory();//创建会话工厂
    		session = sessionFactory.openSession();//开启会话
    		return session;
    	}
    	
    	/**
    	 * 关闭资源
    	 * */
    	 public void destory(){
    	        if(session!=null){//关闭会话
    	            session.close();
    	        }
    	        if(sessionFactory!=null){//销毁会话工厂
    	            sessionFactory.close();
    	        }
    	    }
    	 
    	/**
    	 * select all
    	 * */
    	public List<Emp> getEmpList(){
    		Session session = getSession();//获取会话
    		transaction = session.beginTransaction();//开启事务
    		List<Emp> empList = new ArrayList<Emp>();
    		String hql = "select new com.hxzy.hql.entity.Emp(emp.empno,emp.ename,emp.deptno) from Emp emp ";
    		try {
    			Query query = session.createQuery(hql);//创建hql query
    			empList = query.list();//查出结果集并接收
    			transaction.commit();//提交事务
    		}catch(Exception e) {
    			e.printStackTrace();//输出异常信息
    			transaction.rollback();//有异常则回滚
    		}finally {
    			destory();//关闭资源
    		}
    		return empList;
    	}
    
    }

测试：

@Test
    	public void tet() {
    		EmpDaoImpl empDaoImpl = new EmpDaoImpl();
    		List<Emp> empList = empDaoImpl.getEmpList();
    		System.out.println(" deptno\tempno\tename");
    		for(Emp e: empList) {
    			System.out.println(e.getDeptno()+"\t"+e.getEmpno()+"\t"+e.getEname());
    		}
    	}

5.结果：  
![百度百度百度][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29MZW5nWXVlSHVu_size_16_color_FFFFFF_t_70 1]  
参考文档：[https://download.csdn.net/download/olengyuehun/11082672][https_download.csdn.net_download_olengyuehun_11082672]  
参考资料：[https://blog.csdn.net/oLengYueHun/article/details/88974387][https_blog.csdn.net_oLengYueHun_article_details_88974387]

[20190402170248466.png]: /images/20220224/c0d933174bbc45beafc7a7971a500ab3.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29MZW5nWXVlSHVu_size_16_color_FFFFFF_t_70]: /images/20220224/0ce9984aa26049769eb90cbc36ecf0c1.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29MZW5nWXVlSHVu_size_16_color_FFFFFF_t_70 1]: /images/20220224/e9df64b13714440cb6d83ed91c5bf4a0.png
[https_download.csdn.net_download_olengyuehun_11082672]: https://download.csdn.net/download/olengyuehun/11082672
[https_blog.csdn.net_oLengYueHun_article_details_88974387]: https://blog.csdn.net/oLengYueHun/article/details/88974387