hibernate5二级缓存配置

╰+攻爆jí腚メ 2021-12-19 15:39 277阅读 0赞

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&characterEncoding=utf-8&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, "xxx@hibernate.cn", "15902020509", "123456");
    		//add("aaa", 33, "aaa@hibernate.cn", "15902020520", "123456");	
    		//testDefaultCache();
    		testL2Cache();
    	}
    }

运行testL2Cache()方法，打印关键信息如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlaW5pZmk_size_16_color_FFFFFF_t_70][]

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。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZlaW5pZmk_size_16_color_FFFFFF_t_70]: /images/20211219/02ee3b5dcae14a81aa0facb7f662d5a5.png