Mybatis-18-Cache in action Mybatis 缓存实战

老马啸西风2016年7月27日大约 8 分钟

Mybatis 缓存实战

数据准备

建表脚本

db.sql

CREATE DATABASE mybatis
  DEFAULT CHARACTER SET utf8
  COLLATE utf8_general_ci;

USE mybatis;

init.sql

DROP TABLE IF EXISTS `user`;
CREATE TABLE user (
  id        BIGINT(20) PRIMARY KEY AUTO_INCREMENT NOT NULL
  COMMENT '主键, 自增',
  username  VARCHAR(64)                           NOT NULL
  COMMENT '用户名',
  password  VARCHAR(128)                          NOT NULL
  COMMENT '密码',
  `created_time` timestamp NULL,
  `updated_time` timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

  UNIQUE INDEX `username_UNIQUE` (`username`)
)
  COMMENT '用户表';

INSERT INTO `user` (username, password, created_time, updated_time) VALUES (
  'ryo', '123456', NOW(), NOW()
);

DROP TABLE IF EXISTS `role`;
CREATE TABLE role (
  id          BIGINT(20) PRIMARY KEY AUTO_INCREMENT NOT NULL
  COMMENT '主键,自增',
  name        VARCHAR(64)                           NOT NULL
  COMMENT '角色名称',
  code        VARCHAR(64)                           NOT NULL
  COMMENT '角色代码',
  description VARCHAR(128)                          NULL DEFAULT ''
  COMMENT '角色说明',
  `created_time` timestamp NULL,
  `updated_time` timestamp DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

  INDEX `name`(`name`),
  UNIQUE INDEX `code_UNIQUE`(`code`)
)
  COMMENT '角色表';

INSERT INTO `role` (name, code, description, created_time, updated_time) VALUES (
  '管理员', 'admin', '这个系统里天下第一', NOW(), NOW()
);

开启测试

测试代码地址

mybatis 配置

mybatis-config.xml

其他配置省略。

测试一

条件

一级缓存开启 + localCacheScope=SESSION

测试代码

在同一个 SqlSession 执行两次相同条件的查询。

@Test
public void timesQueryTest() {
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    User user = new User();
    user.setId(1L);
    System.out.println("初次 " + userMapper.selectOne(user));
    System.out.println("再次 " + userMapper.selectOne(user));
}

测试结果

实际上只执行了一次。第二次直接使用缓存的结果。

2018-09-08 13:04:04.109  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 - ==>  Preparing: SELECT ID,USERNAME,PASSWORD,created_time,updated_time FROM uSER WHERE ID = ? 
2018-09-08 13:04:04.133  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 - ==> Parameters: 1(Long)
2018-09-08 13:04:04.150  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 -   Preparing: SELECT ID,USERNAME,PASSWORD,created_time,updated_time FROM uSER WHERE ID = ? 
2018-09-08 13:14:29.127  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 - ==> Parameters: 1(Long)
2018-09-08 13:14:29.143  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 -   Preparing: INSERT INTO uSER ( ID,USERNAME,PASSWORD,created_time,updated_time ) VALUES( ?,?,?,?,? ) 
2018-09-08 13:14:29.151  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.insert:145 - ==> Parameters: null, new(String), 123456(String), null, null
2018-09-08 13:14:29.157  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.insert:145 -   Executing: SELECT LAST_INSERT_ID() 
2018-09-08 13:14:29.161  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.insert!selectKey:145 -   Preparing: SELECT ID,USERNAME,PASSWORD,created_time,updated_time FROM uSER WHERE ID = ? 
2018-09-08 13:14:29.162  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 - ==> Parameters: 1(Long)
2018-09-08 13:14:29.164  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectOne:145 -   Preparing: SELECT ID,USERNAME,PASSWORD,created_time,updated_time FROM uSER WHERE ID = ? 
2018-09-08 14:12:36.485  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:12:36.503  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectByPrimaryKey:145 -   Preparing: UPDATE uSER SET PASSWORD = ? WHERE ID = ? 
2018-09-08 14:12:36.544  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.updateByPrimaryKeySelective:145 - ==> Parameters: new 99507(String), 1(Long)
2018-09-08 14:12:36.548  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.updateByPrimaryKeySelective:145 -   Preparing: SELECT ID,USERNAME,PASSWORD,created_time,updated_time FROM uSER WHERE ID = ? 
2018-09-08 14:12:36.549  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:12:36.550  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.UserMapper.selectByPrimaryKey:145 -  一级缓存 -> 数据库。

## 二级缓存配置

- 全局开启配置

```xml

在 xml 文件中配置

在 MyBatis 的映射 XML 中配置 cach e或者 cache-ref 。

cache-ref代表引用别的命名空间的Cache配置，两个命名空间的操作使用的是同一个Cache。

实验一

场景

两个 session，第一个不提交

代码

@Test
public void queryTest() {
    final Long roleKey = 1L;
    SqlSession firstSqlSession = sqlSessionFactory.openSession(true);
    SqlSession secondSqlSession = sqlSessionFactory.openSession(true);
    RoleMapper firstMapper = firstSqlSession.getMapper(RoleMapper.class);
    RoleMapper secondMapper = secondSqlSession.getMapper(RoleMapper.class);

    System.out.println("firstUserMapper 查询：" + firstMapper.selectByPrimaryKey(roleKey));
    System.out.println("secondUserMapper 查询：" + secondMapper.selectByPrimaryKey(roleKey));
}

日志

查询了两次。第二次查询并没有命中缓存。

2018-09-08 14:29:55.104  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - ==>  Preparing: SELECT ID,NAME,CODE,DESCRIPTION,created_time,updated_time FROM rOLE WHERE ID = ? 
2018-09-08 14:29:55.125  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:29:55.142  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 -   Preparing: SELECT ID,NAME,CODE,DESCRIPTION,created_time,updated_time FROM rOLE WHERE ID = ? 
2018-09-08 14:29:55.161  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:29:55.163  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 -   Preparing: SELECT ID,NAME,CODE,DESCRIPTION,created_time,updated_time FROM rOLE WHERE ID = ? 
2018-09-08 14:33:27.380  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:33:27.398  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 -   Preparing: SELECT ID,NAME,CODE,DESCRIPTION,created_time,updated_time FROM rOLE WHERE ID = ? 
2018-09-08 14:40:48.734  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:40:48.750  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 -   Preparing: UPDATE rOLE SET DESCRIPTION = ? WHERE ID = ? 
2018-09-08 14:40:48.796  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.updateByPrimaryKeySelective:145 - ==> Parameters: 新的描述哈哈哈(String), 1(Long)
2018-09-08 14:40:48.797  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.updateByPrimaryKeySelective:145 -   Preparing: SELECT ID,NAME,CODE,DESCRIPTION,created_time,updated_time FROM rOLE WHERE ID = ? 
2018-09-08 14:40:48.807  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - ==> Parameters: 1(Long)
2018-09-08 14:40:48.808  DEBUG [main] com.github.houbb.mybatis.learn.cache.mapper.RoleMapper.selectByPrimaryKey:145 - <==      Total: 1
secondUserMapper 查询：Role{id=1, name='管理员', code='admin', description='新的描述哈哈哈', createdTime=Sat Sep 08 04:37:10 CST 2018, updatedTime=Sat Sep 08 06:39:51 CST 2018}

备注

mybatis 缓存不适应于多表关联的场景。

可以再一个表的缓存中，引用另一个关联表的 cache 即可。

参考资料

mybatis

聊聊 MyBatis 缓存机制

源码解读 MyBatis 的缓存

贡献者

binbin.hou