Hibernateday06 QBC(Query by Criteria)

QBC (Query by Criteria)由hibernate提供的更具面向对象的查询方式，
    能够支持运行时动态查询语句
 在Hibernate使用QBC的步骤
   1.通过session.createCriteria()获得Criteria实例
   2.使用工具类Restrictions(Expression早起版本)追加查询条件
   3.调用uniqueResult()或者list()获得结果

排序使用Order类
Projection 提供聚合函数的方法

 

1.提供实体类Dept.java和Employee.java

package com.jsu.hb.pojo;

import java.util.HashSet;
import java.util.Set;

public class Dept {
	private Integer id;
	private String dname;
	private String dno;
	private Set<Employee> emps = new HashSet<Employee>();
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getDname() {
		return dname;
	}
	public void setDname(String dname) {
		this.dname = dname;
	}
	public String getDno() {
		return dno;
	}
	public void setDno(String dno) {
		this.dno = dno;
	}
	public Set<Employee> getEmps() {
		return emps;
	}
	public void setEmps(Set<Employee> emps) {
		this.emps = emps;
	}
	
}

 Employee.java

package com.jsu.hb.pojo;

import java.util.Date;

public class Employee {
	private Integer id;
	private String name;
	private Date birthday;
	private String email;
	private double salary;
	private Dept dept;
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	
	public String getEmail() {
		return email;
	}
	public void setEmail(String email) {
		this.email = email;
	}
	public double getSalary() {
		return salary;
	}
	public void setSalary(double salary) {
		this.salary = salary;
	}
	public Dept getDept() {
		return dept;
	}
	public void setDept(Dept dept) {
		this.dept = dept;
	}
	
}

 2.建表

create  table g_dept(
	t_id integer primary key,
	t_dname varchar2(20),
	t_dno varchar2(20)
)

create table g_employee(
	t_id integer primary key,
	t_name varchar2(25),
	t_birthday date,
	t_salary number(12,2),
	t_email varchar2(50),
	d_id integer references g_dept(t_id)
)

insert into g_dept(t_id,t_dname,t_dno) values (1,'dev','001');
insert into g_dept(t_id,t_dname,t_dno) values (2,'train','002');
insert into g_dept(t_id,t_dname,t_dno) values (3,'market','003');
insert into g_dept(t_id,t_dname,t_dno) values (4,'game','004');

insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id) 
values (1,'bobs',to_date('2012-1-11','yyyy-mm-dd'),'bobs@b',100.0,1);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (2,'scott',to_date('2010-10-11','yyyy-mm-dd'),'scott@b',300.0,1);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (3,'tiger',to_date('2008-2-11','yyyy-mm-dd'),'tiger@b',400.0,2);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (4,'lucy',to_date('2009-3-11','yyyy-mm-dd'),'lucy@b',600.0,2);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (5,'lily',to_date('2012-4-11','yyyy-mm-dd'),'lily@b',1000.0,3);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (6,'tom',to_date('2001-10-11','yyyy-mm-dd'),'tom@b',700.0,3);
insert into g_employee(t_id,t_name,t_birthday,t_email,t_salary,d_id)
values (7,'black',to_date('2001-10-11','yyyy-mm-dd'),'black@b',200.0,null);

commit

 3.提供映射文件query.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  package="com.jsu.hb.pojo">
	<class name="Dept" table="g_dept">
		<id name="id" column="t_id">
			<generator class="increment"></generator>
		</id>
		<property name="dname" column="t_dname"></property>
		<property name="dno" column="t_dno"></property>
		<!-- 关系属性 -->
		<set name="emps" cascade="all" inverse="true">
			<key column="d_id"></key>
			<one-to-many class="Employee"></one-to-many>
		</set>
	</class>
	<class name="Employee" table="g_employee">
		<id name="id" column="t_id">
			<generator class="increment"></generator>
		</id>
		<property name="name" column="t_name"></property>
		<property name="birthday" column="t_birthday" type="java.util.Date"></property>
		<property name="email" column="t_email"></property>
		<property name="salary" column="t_salary"></property>
		<!-- 双向关系是添加关系属性 -->
	   <many-to-one name="dept" class="Dept" cascade="save-update" column="d_id"></many-to-one>
	</class>
</hibernate-mapping>

 4.在hibernate.cfg.xml中对映射文件进行注册

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory> 
		<!-- show_sql:是否显示hibernate执行的SQL语句，默认为false -->
		<property name="show_sql">true</property>
		<!-- show_sql:是否显示hibernate执行格式化输出的SQL语句，默认为false -->
		<property name="format_sql">true</property>
		<!-- 配置与数据库连接的参数 -->
		<property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
		<property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:oracle</property>
		<property name="connection.username">scott</property>
		<property name="connection.password">tiger</property>
		<!-- 2.自身属性相关的配置
			dialect:方言
			hibernate根据dialect的配置进行特定数据性能方面的调优
		 -->
		<property name="dialect">org.hibernate.dialect.Oracle9iDialect</property>
		<mapping resource="com/jsu/hb/pojo/query.hbm.xml"></mapping>
	</session-factory>
</hibernate-configuration>

 5.提供工具类HibernateUtil.java

 

package com.jsu.hb.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {
	private static SessionFactory sf;
	private static ThreadLocal<Session> tl= new ThreadLocal<Session>();
	static{
		try{
				Configuration cfg = new Configuration();
				cfg.configure();
				sf=cfg.buildSessionFactory();
		}catch(Exception e){
			e.printStackTrace();
		}
	}
	public static Session openSession(){
		return sf.openSession();
	}
	public static Session getCurrentSession(){
		Session session = tl.get();//先从储存的线程中查找
		if(session==null){
			session=openSession();
			tl.set(session);
			return session;
		}
		return session;
	}
}

 6.提供测试类TestQBC.java

public class TestQBC {

	public void testQbc() {
		Session session = HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		// hql:from Employee
		Criteria cir = session.createCriteria(Employee.class);
		cir.add(Restrictions.eq("name", "haoren"));// 加入 name='haoren ' 的条件
		Employee e = (Employee) cir.uniqueResult();// 获得单个结果
		System.out.println(e.getName() + "  " + e.getSalary());
		tx.commit();
	}

	// 为员工的工资排序
	public void testOrder() {
		Session session = HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		// hql:from Employee
		Criteria cir = session.createCriteria(Employee.class);
		cir.add(Expression.between("salary", 100.0, 400.0));
		cir.addOrder(Order.asc("salary"));
		List<Employee> emps = cir.list();
		for (Employee e : emps) {
			System.out.println(e.getName() + " : " + e.getSalary());
		}
		tx.commit();

	}

	// 员工表的平均工资

	public void testAvg() {
		Session session = HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		// hql:from Employee
		Criteria cir = session.createCriteria(Employee.class);
		cir.setProjection(Projections.avg("salary"));
		Double d = (Double) cir.uniqueResult();
		System.out.println(d);
		tx.commit();
	}

	// 部门号为1的所有员工
	@Test
	public void testDept() {
		Session session = HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		// hql:from Employee
		Criteria cir = session.createCriteria(Employee.class);
		Criteria ciradd = cir.createCriteria("dept");// employee对象的关系属性的名称
		ciradd.add(Expression.eq("id", 1));
		List<Employee> emps = cir.list();
		for (Employee e : emps) {
			System.out.println(e.getName() + "   " + e.getDept().getId());
		}
		tx.commit();
	}
}