hibernate5二级缓存配置

hibernate默认有一个一级缓存，就是默认的Session缓存，当我们做了一次查询，hibernate会把这个结果缓存起来，叫做一级缓存，当我们接着在这个Session会话里面再做一次同样条件的查询，hibernate不会再次查询数据库，而是直接在一级缓存中获取结果并返回。一级缓存是内置的，他也不能被卸载。一级缓存是指在同一个Session会话内的查询做的缓存，如果跨了Session，或者当前Session关闭，重新开启了一个新的Session，这时候一级缓存是失效的。

二级缓存是一个可插拔的缓存，可有可无，如果你配置了，他就有，没有配置就没有。二级缓存的实现，默认是用ehcache,需要增加一个配置文件ehcache.xml，如下所示：

<?xml version="1.0" encoding="utf-8" ?>
<ehcache>
    <diskStore path="java.io.tmpdir"/>
    <defaultCache 
      maxElementsInMemory="10000"
      eternal="false"
      timeToIdleSeconds="120"
      timeToLiveSeconds="120"
      overflowToDisk="true" 
     />
</ehcache>

实体类如下：

BaseEntity.java

package com.xxx.hibernate.domain;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;
@MappedSuperclass
public class BaseEntity {
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	protected Integer id;
	@Column(name="modifydate")
	protected Date modifyDate;
	@Column(name="createdate")
	protected Date createDate;
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public Date getModifyDate() {
		return modifyDate;
	}
	public void setModifyDate(Date modifyDate) {
		this.modifyDate = modifyDate;
	}
	public Date getCreateDate() {
		return createDate;
	}
	public void setCreateDate(Date createDate) {
		this.createDate = createDate;
	}
}

User.java

package com.xxx.hibernate.domain;
import javax.persistence.Entity;
import javax.persistence.Table;

import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;
@Table(name="xx_user")
@Entity
@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)
public class User extends BaseEntity{
	private String name;
	private int age;
	private String email;
	private String mobile;
	private String password;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getEmail() {
		return email;
	}
	public void setEmail(String email) {
		this.email = email;
	}
	public String getMobile() {
		return mobile;
	}
	public void setMobile(String mobile) {
		this.mobile = mobile;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	@Override
	public String toString() {
		return "user:[id="+id+",name="+name+",age="+age+
				",email="+email+",mobile="+mobile+"]";
	}
}

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="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql:///hibernate?useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=false</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.pool_size">20</property>
        <property name="dialect">org.hibernate.dialect.MySQL57InnoDBDialect</property>
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <property name="hbm2ddl.auto">update</property>
        <property name="hibernate.cache.use_second_level_cache">true</property>
        <property name="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
        <property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property>
        <property name="hibernate.cache.use_query_cache">true</property>
        <mapping class="com.xxx.hibernate.domain.User"/>
   </session-factory>
</hibernate-configuration>

测试类代码：

package com.xxx.hibernate.test;
import java.util.Date;
import java.util.List;

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

import com.xxx.hibernate.domain.User;
public class HibernateAppTest {
	
	private static SessionFactory sessionFactory;
	private static final ThreadLocal<Session> session = new ThreadLocal<Session>();
	
	static{
		try {
			Configuration cfg = new Configuration().configure();
			sessionFactory = cfg.buildSessionFactory();
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	public static Session getSession(){
		Session sess = session.get();
		if(sess==null){
			sess = sessionFactory.openSession();
			session.set(sess);
		}
		return sess;
	}
	
	public static void closeSession(){
		Session sess = session.get();
		if(sess!=null){
			sess.close();
		}
		session.set(null);
		sessionFactory.close();
	}
	
	public static void add(String name,int age,String email,String mobile,String password){
		User user = new User();
		user.setName(name);
		user.setAge(age);
		user.setEmail(email);
		user.setMobile(mobile);
		user.setPassword(password);
		user.setCreateDate(new Date());
		user.setModifyDate(new Date());
		//
		Session sess = getSession();
		Transaction tx = sess.beginTransaction();
		sess.save(user);
		tx.commit();
		closeSession();
	}
	
	public static void search(Integer id){
		Session sess = getSession();
		User user = sess.get(User.class, id);
		if(user!=null)
			System.out.println(user);
	}
	
	public static void testDefaultCache(){
		long start = System.currentTimeMillis();
		search(2);
		long end = System.currentTimeMillis();
		System.out.println("it takes "+(end-start)+" .");
		//======================
		start = System.currentTimeMillis();
		search(2);
		end = System.currentTimeMillis();
		System.out.println("it takes "+(end-start)+" .");
		
		start = System.currentTimeMillis();
		search(1);
		end = System.currentTimeMillis();
		System.out.println("it takes "+(end-start)+" .");
		
		closeSession();
	}
	
	@SuppressWarnings("unchecked")
	public static void testL2Cache(){
		Session sess = sessionFactory.openSession();
		List<User> list = sess.createQuery("from User").setCacheable(true).list();
		for(User user:list){
			System.out.println(user);
		}
		sess.close();
		System.out.println("=======================分割线======================");
		Session sess2 = sessionFactory.openSession();
		list = sess2.createQuery("from User").setCacheable(true).list();
		for(User user:list){
			System.out.println(user);
		}
		sess2.close();
		closeSession();
	}
	
	public static void main(String[] args) {
		//add("xxx", 18, "[email protected]", "15902020509", "123456");
		//add("aaa", 33, "[email protected]", "15902020520", "123456");	
		//testDefaultCache();
		testL2Cache();
	}
}

运行testL2Cache()方法，打印关键信息如下：

第一次查询，打印了sql语句，说明从数据库中做了查询，第二次查询，直接使用了二级缓存，因此，并没有打印sql语句。这个结果说明hibernate二级缓存配置正确并且生效了。

hibernate5二级缓存配置

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