JPA-二级缓存

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com</groupId>
    <artifactId>jpa</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.14</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.4.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-jpamodelgen</artifactId>
            <version>5.4.1.Final</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <!-- 指定jdk -->
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

persistence.xml

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
             version="2.2">
    <persistence-unit name="jpaname">

        <!-- 实体类 -->
        <class>com.jpa.yingshe.Customer</class>

        <properties>
            <!-- 数据库信息 -->
            <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://192.168.8.136/jpa?useSSL=false"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="root"/>

            <!-- 配置 hibernate 属性 -->
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>
        </properties>
    </persistence-unit>
</persistence>

Customer

package com.jpa.yingshe;

import javax.persistence.*;

@Table(name = "JPA_CUTOMERS")
@Entity
public class Customer {

    private Integer id;
    private String lastName;

    private String email;

    public Customer() {
    }

    public Customer(String lastName) {
        this.lastName = lastName;
    }

    @GeneratedValue(strategy = GenerationType.AUTO)
    @Id
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Column(name = "LAST_NAME", length = 50, nullable = false)
    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

测试

先看JPA自带的一级缓存

package jpa.test;

import com.jpa.yingshe.Customer;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

public class JPAyingshe {
    private EntityManagerFactory entityManagerFactory;
    private EntityManager entityManager;
    private EntityTransaction transaction;

    @Before
    public void init() {
        entityManagerFactory = Persistence.createEntityManagerFactory("jpaname");
        entityManager = entityManagerFactory.createEntityManager();
        transaction = entityManager.getTransaction();
        transaction.begin();
    }

    @After
    public void destroy() {
        transaction.commit();
        entityManager.close();
        entityManagerFactory.close();
    }

    @Test
    public void testFirstLevelCache() {
        Customer customer1 = entityManager.find(Customer.class, 1);
        Customer customer2 = entityManager.find(Customer.class, 1);
    }
}

中间关闭会话再试试

@Test
public void testFirstLevelCache() {
    Customer customer1 = entityManager.find(Customer.class, 1);
    
    transaction.commit();
    entityManager.close();

    entityManager = entityManagerFactory.createEntityManager();
    transaction = entityManager.getTransaction();
    transaction.begin();

    Customer customer2 = entityManager.find(Customer.class, 1);
}

配置二级缓存，让关闭会话后也只发送一次查询

 添加 ehcache 依赖

<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-ehcache</artifactId>
    <version>5.4.1.Final</version>
</dependency>
<dependency>
    <groupId>org.ehcache</groupId>
    <artifactId>ehcache</artifactId>
    <version>3.6.3</version>
</dependency>

添加 ehcache.xml 配置

<ehcache>
    <diskStore path="./target/tmp"/>
    
    <defaultCache
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="120"
        timeToLiveSeconds="120"
        overflowToDisk="true"
        />
    
    <cache name="sampleCache1"
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="300"
        timeToLiveSeconds="600"
        overflowToDisk="true"
        />

    <cache name="sampleCache2"
        maxElementsInMemory="1000"
        eternal="true"
        timeToIdleSeconds="0"
        timeToLiveSeconds="0"
        overflowToDisk="false"
        /> -->
</ehcache>

修改 persistence.xml 配置

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd"
             version="2.2">
    <persistence-unit name="jpaname" transaction-type="RESOURCE_LOCAL">

        <!-- 配置使用什么 ORM 产品来作为 JPA 的实现 -->
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <!-- 实体类 -->
        <class>com.jpa.yingshe.Customer</class>

        <!--
        配置二级缓存的策略
        ALL：所有的实体类都被缓存
        NONE：所有的实体类都不被缓存.
        ENABLE_SELECTIVE：标识 @Cacheable(true) 注解的实体类将被缓存
        DISABLE_SELECTIVE：缓存除标识 @Cacheable(false) 以外的所有实体类
        UNSPECIFIED：默认值，JPA 产品默认值将被使用
        -->
        <shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>

        <properties>
            <!-- 数据库信息 -->
            <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:mysql://192.168.8.136/jpa?useSSL=false"/>
            <property name="javax.persistence.jdbc.user" value="root"/>
            <property name="javax.persistence.jdbc.password" value="root"/>

            <!-- 配置 hibernate 属性 -->
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.hbm2ddl.auto" value="update"/>

            <!-- 二级缓存相关 -->
            <property name="hibernate.cache.use_second_level_cache" value="true"/>
            <property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.internal.EhcacheRegionFactory"/>
            <property name="hibernate.cache.use_query_cache" value="true"/>
        </properties>
    </persistence-unit>
</persistence>

修改实体类，添加缓存注解

@Cacheable
@Table(name = "JPA_CUTOMERS")
@Entity
public class Customer {

    private Integer id;

查询

@Test
public void testSecondLevelCache() {
    Customer customer1 = entityManager.find(Customer.class, 1);

    transaction.commit();
    entityManager.close();

    entityManager = entityManagerFactory.createEntityManager();
    transaction = entityManager.getTransaction();
    transaction.begin();

    Customer customer2 = entityManager.find(Customer.class, 1);
}

项目结构

 

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