Hibernate查询缓存

一级，二级缓存都是对整个实体进行缓存，它不会缓存普通属性。如果想对普通属性进行缓存，那我们就需要使用查询缓存。但是在多数情况下查询缓存不能提高应用程序的性能，反而降低了应用程序的性能。如果经常使用相同的查询语句，且查询参数也相同，这个时候使用查询缓存才能起到好的效果。

1.配置查询缓存

   <property name="hibernate.cache.use_query_cache">true</property>2.实例演示

package cn.codeWang.entity;

import javax.persistence.Cacheable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity(name = “person”)
@Cacheable
//选择缓存策略
@org.hibernate.annotations.Cache(usage =CacheConcurrencyStrategy.READ_ONLY)
public class Person {
@Id
@GeneratedValue
private int id;
private String name;
private String sex;
private String department;

public Person() {}public Person(String name, String sex, String department) {    super();    this.name = name;    this.sex = sex;    this.department = department;}public String getName() {    return name;}public String getSex() {    return sex;}public String getDepartment() {    return department;}

}

<diskStore path="java.io.tmpdir"/><defaultCache    maxElementsInMemory="10000"    eternal="false"    timeToIdleSeconds="120"    timeToLiveSeconds="120"    overflowToDisk="true"    /><!-- Sample cache named sampleCache1    This cache contains a maximum in memory of 10000 elements, and will expire    an element if it is idle for more than 5 minutes and lives for more than    10 minutes.    If there are more than 10000 elements it will overflow to the    disk cache, which in this configuration will go to wherever java.io.tmp is    defined on your system. On a standard Linux system this will be /tmp"    --><cache name="cn.codeWang.entity.Person"    maxElementsInMemory="10000"    eternal="false"    timeToIdleSeconds="300"    timeToLiveSeconds="600"    overflowToDisk="true"    /><!-- Place configuration for your caches following -->

3.同一个session使用两条相同的查询语句

@Test
public void testQuery(){

    List<Person> list=session.createQuery("from person").setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    }     list=session.createQuery("from person").setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    } }

控制台输出结果：
Hibernate:
select
person0_.id as id1_0_0_,
person0_.department as departme2_0_0_,
person0_.name as name3_0_0_,
person0_.sex as sex4_0_0_
from
person person0_
where
person0_.id=?
姓名=凯耐
姓名=凯耐

4.不同session使用两条相同的查询语句

@Test
public void testQuery(){

    List<Person> list=session.createQuery("from person").setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    }     //第二次获得session对象     session = sessionFactory.openSession();      list=session.createQuery("from person").setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    } }

控制台输出结果：
Hibernate:
select
person0_.id as id1_0_0_,
person0_.department as departme2_0_0_,
person0_.name as name3_0_0_,
person0_.sex as sex4_0_0_
from
person person0_
where
person0_.id=?
姓名=凯耐
姓名=凯耐

5.同一个session使用两条不同的查询语句

@Testpublic void testQuery(){    List<Person> list=session.createQuery("from person").setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    }     list=session.createQuery("from person where id=:xx").setParameter("xx",2).setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    } }

控制台输出结果：

Hibernate:
select
person0_.id as id1_0_0_,
person0_.department as departme2_0_0_,
person0_.name as name3_0_0_,
person0_.sex as sex4_0_0_
from
person person0_
where
person0_.id=?
姓名=凯耐
姓名=凯耐

6.不同session使用两条不同的查询语句

@Test
public void testQuery(){

    List<Person> list=session.createQuery("from person").setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    }     //第二次获得session对象     session = sessionFactory.openSession();      list=session.createQuery("from person where id=:xx").setParameter("xx",2).setCacheable(true).list();    for(Person p:list){        System.out.println(p.getName());    } }

控制台输出结果：

Hibernate:
select
person0_.id as id1_0_0_,
person0_.department as departme2_0_0_,
person0_.name as name3_0_0_,
person0_.sex as sex4_0_0_
from
person person0_
where
person0_.id=?
姓名=凯耐
姓名=凯耐

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