2018.11.13 Hibernate 中数据库查询中的Criteria查询实例

Posted 2021-01-19 Legend

Criteria是面向对象的无语句查询

Demo.java

package com.legend.b_criteria;

import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;
import org.junit.jupiter.api.Test;

import com.legend.domain.Customer;
import com.legend.utils.HibernateUtils;

/**
 * 学习Criteria语法
 * @author qichunlin
 *
 */
public class Demo {
	//基本语法
	@Test 
	public void fun1() {
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		//--------------
		Criteria criteria = session.createCriteria(Customer.class);
		
		
		List<Customer> list = criteria.list();
		System.out.println(list);
		//--------------
		
		tx.commit();
		session.close();
		
	}
	
	//条件查询
	@Test
	public void fun2(){
		//
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		//--------------
		//创建Criteria 对象
		Criteria criteria = session.createCriteria(Customer.class);
		
		//添加Criteria的查询参数
		criteria.add(Restrictions.eq("cust_id", 1l));
		
		//获取查询的结果
		Customer c = (Customer) criteria.uniqueResult();
		System.out.println(c);
		//--------------
		
		//事务的提交
		tx.commit();
		session.close();
		
	
	}
	
	//分页查询
	//(当前页数-1)*每页条数
	@Test
	public void fun3() {
		//
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		//--------------
		//编写HQL语句
		Criteria criteria = session.createCriteria(Customer.class);
		
		criteria.setFirstResult(1);
		criteria.setMaxResults(2);
		
		List<Customer> list = criteria.list();
		System.out.println(list);
		//--------------
		
		tx.commit();
		session.close();
		
	}
	
	//排序检索
	@Test
	public void fun5() {
		//
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		//--------------
		Criteria criteria = session.createCriteria(Customer.class);
		
		criteria.addOrder(Order.desc("cust_id"));
		
		List<Customer> list = criteria.list();
		System.out.println(list);
		//--------------
		
		tx.commit();
		session.close();
		
	}
	
	//统计查询
	@Test
	public void fun6() {
		//
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		//--------------
		//编写HQL语句
		Criteria criteria = session.createCriteria(Customer.class);
		
		//设置查询目标
		criteria.setProjection(Projections.rowCount());
		//List list = query.list();
		List<Long> list = criteria.list();
		System.out.println(list);
		//--------------
		
		tx.commit();
		session.close();
		
	}
}

基本查询

统计查询

附上hibernate的额核心配置文件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">
<!-- 配置参数文件 -->
<hibernate-configuration>
	<session-factory>
		<!-- 
			#hibernate.dialect org.hibernate.dialect.mysqlDialect
			#hibernate.dialect org.hibernate.dialect.MySQLInnoDBDialect
			#hibernate.dialect org.hibernate.dialect.MySQLMyISAMDialect
			#hibernate.connection.driver_class com.mysql.jdbc.Driver
			#hibernate.connection.url jdbc:mysql:///test
			#hibernate.connection.username gavin
			#hibernate.connection.password
			配置mysql相关参数
		 -->
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.url">jdbc:mysql:///crm</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">123456</property>
		
		<!-- 配置mysql方言 -->
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
		
		<!-- 
			sql语句显示
			#hibernate.show_sql true
			# format SQL in log and console
			#hibernate.format_sql true
		
		 -->
		<property name="hibernate.format_sql">true</property>
		<property name="hibernate.show_sql">true</property>
		
		<!-- 
			## auto schema export
			#hibernate.hbm2ddl.auto create-drop
			#hibernate.hbm2ddl.auto create
			#hibernate.hbm2ddl.auto update
			#hibernate.hbm2ddl.auto validate
		 -->
		<property name="hibernate.hbm2ddl.auto">update</property>
		
		<!-- 
			设置数据库隔离级别
			## specify a JDBC isolation level
			#hibernate.connection.isolation 4
		 -->
		 <property name="hibernate.connection.isolation">4</property>
		
		<!-- 指定session与当前线程绑定 -->
		<property name="hibernate.current_session_context_class">thread</property>
		
		<!-- 配置映射文件加载 orm元数据 -->
		<mapping resource="com/legend/domain/Customer.hbm.xml"/>
		<mapping resource="com/legend/domain/LinkMan.hbm.xml" />
		<mapping resource="com/legend/domain/User.hbm.xml" />
		<mapping resource="com/legend/domain/Role.hbm.xml" />
		
		
	</session-factory>
</hibernate-configuration>	

传统的Criteria

离线的Criteria