Hibernate投影查询

叁歲伎倆 2022-05-24 10:48 212阅读 0赞

##### 【例】雇员信息表 #####

雇员表结构

![20180525165344180][]

雇员信息

![20180525165354801][]

##### 第一步：创建雇员类 #####

package com.dwx.models;
    import java.util.Date;
    public class Employee {
    	private int id;
    	private String emp_id;
    	private String emp_name;
    	private String emp_sex;
    	private Date emp_birth;
    	private String emp_job;
    	private double emp_salary;
    	public int getId() {
    		return id;
    	}
    	public void setId(int id) {
    		this.id = id;
    	}
    	public String getEmp_id() {
    		return emp_id;
    	}
    	public void setEmp_id(String emp_id) {
    		this.emp_id = emp_id;
    	}
    	public String getEmp_name() {
    		return emp_name;
    	}
    	public void setEmp_name(String emp_name) {
    		this.emp_name = emp_name;
    	}
    	public String getEmp_sex() {
    		return emp_sex;
    	}
    	public void setEmp_sex(String emp_sex) {
    		this.emp_sex = emp_sex;
    	}
    	public Date getEmp_birth() {
    		return emp_birth;
    	}
    	public void setEmp_birth(Date emp_birth) {
    		this.emp_birth = emp_birth;
    	}
    	public String getEmp_job() {
    		return emp_job;
    	}
    	public void setEmp_job(String emp_job) {
    		this.emp_job = emp_job;
    	}
    	public double getEmp_salary() {
    		return emp_salary;
    	}
    	public void setEmp_salary(double emp_salary) {
    		this.emp_salary = emp_salary;
    	}
    }

##### 第二步：配置Employee.hbm.xml #####

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
    <hibernate-mapping>
    	<class name="com.dwx.models.Employee" table="employee">
    		<id name="id"><generator class="native"></generator></id>
    		<property name="emp_id"></property>
    		<property name="emp_name"></property>
    		<property name="emp_sex"></property>
    		<property name="emp_birth"></property>
    		<property name="emp_job"></property>
    		<property name="emp_salary"></property>
    	</class>
    </hibernate-mapping>

##### 第三步：配置hibernate.cfg.xml #####

<?xml version='1.0' encoding='UTF-8'?>
    <!DOCTYPE hibernate-configuration PUBLIC
              "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
              "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
    
    <hibernate-configuration>
    
    <session-factory>
    	<property name="myeclipse.connection.profile">test</property>
    	<property name="dialect">
    		org.hibernate.dialect.MySQLDialect
    	</property>
    	<property name="connection.password">root</property>
    	<property name="connection.username">root</property>
    	<property name="connection.url">
    		jdbc:mysql://localhost:3306/student
    	</property>
    	<property name="connection.driver_class">
    		com.mysql.jdbc.Driver
    	</property>
    	<property name="show_sql">true</property>
    	<mapping resource="com/dwx/models/Employee.hbm.xml" />
    
    </session-factory>
    
    </hibernate-configuration>

##### 第四步：创建测试类 #####

package com.dwx.models;
    import java.util.Iterator;
    import java.util.List;
    import org.hibernate.Query;
    import org.hibernate.Session;
    import org.hibernate.Transaction;
    public class Test {
    	public static void main(String[] args) {
    		Session session=null;
    		Transaction tx=null;
    		try{
    			session=HibernateSessionFactory.getSession();
    			String hql="from Employee";
    			Query query=session.createQuery(hql);
    			List list=query.list();
    			Iterator it=list.iterator();
    			while(it.hasNext()){
    				Employee emp=(Employee)it.next();
    				System.out.println(emp.getEmp_id()+" "+emp.getEmp_name()+" "+emp.getEmp_sex()+
    						emp.getEmp_birth()+" "+emp.getEmp_job()+" "+emp.getEmp_salary());
    			}
    		}catch(Exception e){
    			e.printStackTrace();
    		}finally{
    			HibernateSessionFactory.closeSession();
    		}
    	}
    
    }

查询所有雇员信息

session=HibernateSessionFactory.getSession();
    			String hql="from Employee";
    			Query query=session.createQuery(hql);
    			List list=query.list();
    			Iterator it=list.iterator();
    			while(it.hasNext()){
    				Employee emp=(Employee)it.next();
    				System.out.println(emp.getEmp_id()+" "+emp.getEmp_name()+" "+emp.getEmp_sex()+
    						emp.getEmp_birth()+" "+emp.getEmp_job()+" "+emp.getEmp_salary());
    			}

运行结果：

![20180525170137160][]

查询雇员部分信息

session=HibernateSessionFactory.getSession();
    			String hql="select emp.emp_id,emp.emp_name from Employee emp";
    			Query query=session.createQuery(hql);
    			List list=query.list();
    			Iterator it=list.iterator();
    			while(it.hasNext()){
    				Object [] object=(Object[])it.next();
    				System.out.println(object[0]+" "+object[1]);
    			}

运行结果：

![20180525171155950][]

对查询结果进行排序

session=HibernateSessionFactory.getSession();
    			String hql="from Employee emp order by emp.id desc";
    			Query query=session.createQuery(hql);
    			List list=query.list();
    			Iterator it=list.iterator();
    			while(it.hasNext()){
    				Employee emp=(Employee)it.next();
    				System.out.println(emp.getId()+" "+emp.getEmp_id()+" "+emp.getEmp_name()+" "+emp.getEmp_sex()+
    						emp.getEmp_birth()+" "+emp.getEmp_job()+" "+emp.getEmp_salary());
    			}

运行结果：

![20180525171740593][]

[20180525165344180]: /images/20220524/948573aaebc14e0a8d5643aecc60caaf.png
[20180525165354801]: /images/20220524/2081c6d4fe8942bdb88378cb84a8eeda.png
[20180525170137160]: /images/20220524/5ecc338b568243ca8ba5fcbcc955a2e7.png
[20180525171155950]: /images/20220524/e9b22a668fde40a3b34ba124ec4a165e.png
[20180525171740593]: /images/20220524/1fd53447d81a4c3a8c55189f8fac1e3e.png