六、mybatis 第三方缓存之ehcache

一、概述：

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



4. 
   
5. 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
6. 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​​）；
7. config源文件中添加ehcache.xml
8. 对应的XXXMapper.xml中添加：

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

1. 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：

1 <?xml version="1.0" encoding="UTF-8"?>
 2 <ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 3  xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">
 4  <!-- 磁盘保存路径 -->
 5  <diskStore path="log/ehcache" />
 6  
 7  <defaultCache 
 8    maxElementsInMemory="1000" 
 9    maxElementsOnDisk="10000000"
10    eternal="false" 
11    overflowToDisk="true" 
12    timeToIdleSeconds="120"
13    timeToLiveSeconds="120" 
14    diskExpiryThreadIntervalSeconds="120"
15    memoryStoreEvictionPolicy="LRU">
16  </defaultCache>
17 </ehcache>
18

View Code

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：

1 void addEmp(Employee employee);
2 
3     Employee getEmpById(int

映射文件EmployeeMapper.xml

1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="dao.EmployeeMapper">
 6 <cache type="org.mybatis.caches.ehcache.EhcacheCache"></cache> 7 
 8     <insert id="addEmp" parameterType="entity.Employee" useGeneratedKeys="true" keyProperty="id">
 9         insert into tbl_employee(last_name,gender,email) values(
10         #{lastName},#{gender},#{email}
11         )
12     </insert>
13     
14     <select id="getEmpById" parameterType="Integer" resultType="entity.Employee">
15         select LAST_NAME AS
16         lastName,gender as gender,email as email from
17         tbl_employee where id =#{asdsdfsdf}
18     </select>
19 
20 </mapper>

junit测试类：

1 @Test
 2     public void test02() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         SqlSession openSession2 = null;
 6         try {
 7             InputStream inputStream = Resources.getResourceAsStream(resource);
 8             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 9             // 获取openSession 不会自动提交数据
10             openSession = sqlSessionFactory.openSession(true);
11             openSession2 = sqlSessionFactory.openSession(true);
12             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
13             Employee employee = mapper.getEmpByIdStepDis(1);
14             Employee employee1 = mapper.getEmpByIdStepDis(1);
15             System.out.println("测试一级缓存：" + employee);
16             System.out.println("测试一级缓存：" + employee1 + "," + (employee == employee1));
17 
18             EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);
19             Employee employee2 = mapper2.getEmpByIdStepDis(1);
20             System.out.println("sqlSession改变 一级缓存失效：" + employee2 + "," + (employee1 == employee2));
21             EmployeeMapper mapper23 = openSession2.getMapper(EmployeeMapper.class);
22             Employee employee23 = mapper23.getEmpByIdStepDis(2);
23             System.out.println("查询条件改变改变 一级缓存失效：" + employee23 + "," + (employee1 == employee23));
24 
25             Employee emp = new Employee();
26             emp.setLastName("Tom");
27             emp.setGender("男");
28             emp.setEmail("678@qq.com");
29             mapper23.addEmp(emp);
30             Employee employee4 = mapper23.getEmpByIdStepDis(2);
31             System.out.println("查询条件相同+sqlSession相同 一级缓存失效：" + employee23 + "," + (employee4 == employee23));
32 
33             Employee employee5 = mapper23.getEmpByIdStepDis(2);
34             openSession2.clearCache();
35             Employee employee6 = mapper23.getEmpByIdStepDis(2);
36             System.out.println("手动清楚缓存：" + (employee5 == employee6));
37         } catch (Exception e) {
38             // TODO: handle exception
39         } finally {
40             if (openSession != null) {
41                 openSession.close();
42             }
43 
44         }
45

View Code

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：

1 @Test
 2     public void test08() {
 3         String resource = "mybatis-config.xml";
 4         SqlSession openSession = null;
 5         SqlSession openSession2 = null;
 6         try {
 7             InputStream inputStream = Resources.getResourceAsStream(resource);
 8             SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 9             // 获取openSession 不会自动提交数据
10             openSession = sqlSessionFactory.openSession(true);
11             openSession2 = sqlSessionFactory.openSession(true);
12             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
13             EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);
14             Employee employee = mapper.getEmpById(1);
15 
16             System.out.println("测试二级缓存：" + employee);
17             openSession.close();
18             Employee employee1 = mapper2.getEmpById(1);
19             System.out.println("测试二级缓存：" + employee1 + "," + (employee == employee1));
20             openSession2.close();
21         } catch (Exception e) {
22             // TODO: handle exception
23         } finally {
24             if (openSession != null) {
25                 openSession.close();
26                 openSession2.close();
27             }
28 
29         }
30

View Code

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：

我从来不相信什么懒洋洋的自由。我向往的自由是通过勤奋和努力实现的更广阔的人生。 我要做一个自由又自律的人，靠势必实现的决心认真地活着。