六、mybatis 第三方缓存之ehcache

一、概述：

1. 下载地址：https://github.com/mybatis/ehcache-cache
2. 目录结构：　

   

    

3. lib文件夹中添加jar包：ehcache-core-2.6.8.jar　　mybatis-ehcache-1.0.3.jar　　slf4j-api-1.6.1.jar　　slf4j-simple-1.6.1.jar
4. 全局配置文件mybatis-config.xml:开启缓存（开启方法同五、mybatis两级缓存中使用步骤中的配置文件）；
5. config源文件中添加ehcache.xml
6. 对应的XXXMapper.xml中添加：

   <cache type="org.mybatis.caches.ehcache.EhcacheCache"></cache>

    

7. 引用缓存：例如DepartmentMapper.xml 引用 EmployeeMapper.xml中的缓存：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="dao.DepartmentMapper">
    <!-- 引用缓存：namespace:指定和哪个名称空间下的缓存一样 -->
    <cache-ref namespace="dao.EmployeeMapper" />
    <select id="getDepartmentById"
        resultType="introduction.Department">
        SELECT * FROM TBL_DEPARTMENT WHERE ID= #{id}
    </select>
</mapper>

 

二、ehcache.xml

1.ehcache.xml文件：

<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">
 <!-- 磁盘保存路径 -->
 <diskStore path="log/ehcache" />
 
 <defaultCache 
   maxElementsInMemory="1000" 
   maxElementsOnDisk="10000000"
   eternal="false" 
   overflowToDisk="true" 
   timeToIdleSeconds="120"
   timeToLiveSeconds="120" 
   diskExpiryThreadIntervalSeconds="120"
   memoryStoreEvictionPolicy="LRU">
 </defaultCache>
</ehcache>
 

2.ehcache.xm属性说明

• diskStore：指定数据在磁盘中的存储位置。
• defaultCache：当借助CacheManager.add("demoCache")创建Cache时，EhCache便会采用<defalutCache/>指定的的管理策略

以下属性是必须的：

• maxElementsInMemory - 在内存中缓存的element的最大数目 
• maxElementsOnDisk - 在磁盘上缓存的element的最大数目，若是0表示无穷大
• eterna- 设定缓存的elements是否永远不过期。如果为true，则缓存的数据始终有效，如果为false那么还要根据timeToIdleSeconds，timeToLiveSeconds判断
• overflowToDisk - 设定当内存缓存溢出的时候是否将过期的element缓存到磁盘上

以下属性是可选的：

• timeToIdleSeconds - 当缓存在EhCache中的数据前后两次访问的时间超过timeToIdleSeconds的属性取值时，这些数据便会删除，默认值是0,也就是可闲置时间无穷大
• timeToLiveSeconds - 缓存element的有效生命期，默认是0.,也就是element存活时间无穷大
•  diskSpoolBufferSizeMB 这个参数设置DiskStore(磁盘缓存)的缓存区大小.默认是30MB.每个Cache都应该有自己的一个缓冲区.
• diskPersistent - 在VM重启的时候是否启用磁盘保存EhCache中的数据，默认是false。
• diskExpiryThreadIntervalSeconds - 磁盘缓存的清理线程运行间隔，默认是120秒。每个120s，相应的线程会进行一次EhCache中数据的清理工作
• memoryStoreEvictionPolicy - 当内存缓存达到最大，有新的element加入的时候， 移除缓存中element的策略。默认是LRU（最近最少使用），可选的有LFU（最不常使用）和FIFO（先进先出）

三、实例验证：

 1.一级缓存实例验证：

接口文件EmployeeMapper.java：

void addEmp(Employee employee);

    Employee getEmpById(int id);

映射文件EmployeeMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
  "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="dao.EmployeeMapper">
<cache type="org.mybatis.caches.ehcache.EhcacheCache"></cache>

    <insert id="addEmp" parameterType="entity.Employee" useGeneratedKeys="true" keyProperty="id">
        insert into tbl_employee(last_name,gender,email) values(
        #{lastName},#{gender},#{email}
        )
    </insert>
    
    <select id="getEmpById" parameterType="Integer" resultType="entity.Employee">
        select LAST_NAME AS
        lastName,gender as gender,email as email from
        tbl_employee where id =#{asdsdfsdf}
    </select>

</mapper>

junit测试类：

@Test
    public void test02() {
        String resource = "mybatis-config.xml";
        SqlSession openSession = null;
        SqlSession openSession2 = null;
        try {
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            // 获取openSession 不会自动提交数据
            openSession = sqlSessionFactory.openSession(true);
            openSession2 = sqlSessionFactory.openSession(true);
            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
            Employee employee = mapper.getEmpByIdStepDis(1);
            Employee employee1 = mapper.getEmpByIdStepDis(1);
            System.out.println("测试一级缓存：" + employee);
            System.out.println("测试一级缓存：" + employee1 + "," + (employee == employee1));

            EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);
            Employee employee2 = mapper2.getEmpByIdStepDis(1);
            System.out.println("sqlSession改变 一级缓存失效：" + employee2 + "," + (employee1 == employee2));
            EmployeeMapper mapper23 = openSession2.getMapper(EmployeeMapper.class);
            Employee employee23 = mapper23.getEmpByIdStepDis(2);
            System.out.println("查询条件改变改变 一级缓存失效：" + employee23 + "," + (employee1 == employee23));

            Employee emp = new Employee();
            emp.setLastName("Tom");
            emp.setGender("男");
            emp.setEmail("678@qq.com");
            mapper23.addEmp(emp);
            Employee employee4 = mapper23.getEmpByIdStepDis(2);
            System.out.println("查询条件相同+sqlSession相同 一级缓存失效：" + employee23 + "," + (employee4 == employee23));

            Employee employee5 = mapper23.getEmpByIdStepDis(2);
            openSession2.clearCache();
            Employee employee6 = mapper23.getEmpByIdStepDis(2);
            System.out.println("手动清楚缓存：" + (employee5 == employee6));
        } catch (Exception e) {
            // TODO: handle exception
        } finally {
            if (openSession != null) {
                openSession.close();
            }

        }
    }

运行结果：

测试一级缓存：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=Department [id=1, departmentName=null]]

测试一级缓存：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=Department [id=1, departmentName=null]],true

sqlSession改变 一级缓存失效：Employee [id=1, lastName=joy33333, email=joy52112225@iclound.com, gender=女, dept=Department [id=1, departmentName=null]],false

查询条件改变改变 一级缓存失效：Employee [id=2, lastName=joy2x22222, email=joy2x22222, gender=男, dept=null],false

查询条件相同+sqlSession相同 一级缓存失效：Employee [id=2, lastName=joy2x22222, email=joy2x22222, gender=男, dept=null],false

手动清楚缓存：false

2.二级缓存实例验证：

接口文件EmployeeMapper.java：同1级缓存实例验证

映射文件EmployeeMapper.xml：同1级缓存实例验证

junit测试类：

@Test
    public void test08() {
        String resource = "mybatis-config.xml";
        SqlSession openSession = null;
        SqlSession openSession2 = null;
        try {
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            // 获取openSession 不会自动提交数据
            openSession = sqlSessionFactory.openSession(true);
            openSession2 = sqlSessionFactory.openSession(true);
            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
            EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);
            Employee employee = mapper.getEmpById(1);

            System.out.println("测试二级缓存：" + employee);
            openSession.close();
            Employee employee1 = mapper2.getEmpById(1);
            System.out.println("测试二级缓存：" + employee1 + "," + (employee == employee1));
            openSession2.close();
        } catch (Exception e) {
            // TODO: handle exception
        } finally {
            if (openSession != null) {
                openSession.close();
                openSession2.close();
            }

        }
    }

运行结果：

测试二级缓存：Employee [id=null, lastName=joy33333, email=joy52112225@iclound.com, gender=女]

测试二级缓存：Employee [id=null, lastName=joy33333, email=joy52112225@iclound.com, gender=女],true

四、缓存文件查看：