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前置

什么是一级缓存: mybatis 默认开启一级缓存, SQLSession会话缓存, 每个SQLSession都会有各自的缓存
以下会演示一级缓存生效/失效的场景
项目地址: https://gitee.com/xmaxm/test-code/blob/master/chaim-cache/chaim-mybatis-cache/chaim-mybatis-cache-one/README.md

相关缓存文章

Mybatis的一级缓存
Mybatis的二级缓存 (默认方式)
Mybatis的二级缓存 (Redis方式)
Mybatis的二级缓存 (ehcache方式)

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生效

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场景一

测试一级缓存生效, 默认开启, 需要保证在同一个 SqlSession (可使用 @Transactional 保持其同一个会话)
使用mybatis plus方法

@Transactional
public void queryingLevelCache() {
    LambdaQueryWrapper<SysUser> queryWrapper = new LambdaQueryWrapper<>();
    queryWrapper.select(SysUser::getUsername, SysUser::getPhone, SysUser::getId);
    queryWrapper.last("limit 1");
    SysUser sysUsers = sysUserMapper.selectOne(queryWrapper);
    log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

    SysUser user = sysUserMapper.selectOne(queryWrapper);
    log.info("查询成功, 观察日志, id: {}", user.getId());
}

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场景二

测试一级缓存生效, 默认开启, 需要保证在同一个 SqlSession (可使用 @Transactional 保持其同一个会话)
使用自定义SQL

    @Transactional
    public void queryingLevelCache(Integer integer) {
        SysUser sysUsers = sysUserMapper.selectHandwritingSql();
        log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

        SysUser user = sysUserMapper.selectHandwritingSql();
        log.info("查询成功, 观察日志, id: {}", user.getId());
    }

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失效

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场景一

测试一级缓存失效: 当两次查询存在之间, 存在增删改的情况

public void queryingLevelCacheFail() {
        LambdaQueryWrapper<SysUser> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.select(SysUser::getUsername, SysUser::getPhone, SysUser::getId);
        queryWrapper.last("limit 1");
        SysUser sysUsers = sysUserMapper.selectOne(queryWrapper);
        log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

        SysUser sysUser = SysUser.builder()
                .username("潇潇")
                .email("gmail.com")
                .phone("000123")
                .password("123456")
                .sex(1)
                .state(0)
                .salt(1234)
                .build();
        sysUserMapper.insert(sysUser);
        log.info("观察新增日志, id: {}", sysUsers.getPassword());

        SysUser user = sysUserMapper.selectOne(queryWrapper);
        log.info("查询成功, 观察日志, id: {}", user.getId());
    }

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场景二

测试一级缓存失效: 当两次查询的方式不一样, 使用mybatis的方法, 以及自定义SQL
同理, 当查询的条件以及查询的内容不一致时也会失效

 public void queryingLevelCacheFail(Integer integer) {
        LambdaQueryWrapper<SysUser> queryWrapper = new LambdaQueryWrapper<>();
        queryWrapper.select(SysUser::getUsername, SysUser::getPhone);
        queryWrapper.last("limit 1");
        SysUser sysUsers = sysUserMapper.selectOne(queryWrapper);
        log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

        SysUser user = sysUserMapper.selectHandwritingSql();
        log.info("查询成功, 观察日志, id: {}", user.getId());
    }

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场景三

测试一级缓存失效: 手动清除缓存

@Override
public void queryingLevelCacheFail(String string) {
    SysUser sysUsers = sysUserMapper.selectHandwritingSql();
    log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

    sqlSession.clearCache();

    SysUser user = sysUserMapper.selectHandwritingSql();
    log.info("查询成功, 观察日志, id: {}", user.getId());
}

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场景四

测试一级缓存失效: 去除@Transactional, 使其不在同一个 SqlSession

@Override
public void queryingLevelCacheFail(Boolean blo) {
    SysUser sysUsers = sysUserMapper.selectHandwritingSql();
    log.info("查询成功, 观察日志, id: {}", sysUsers.getId());
    
    SysUser user = sysUserMapper.selectHandwritingSql();
    log.info("查询成功, 观察日志, id: {}", user.getId());
}

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场景五

测试一级缓存失效:
xml配置: flushCache=“true”
注解方式SQL配置: @Options(flushCache = Options.FlushCachePolicy.TRUE)
同理还可以全局配置: 禁用mybatis一级缓存: mybatis-plus.configuration.local-cache-scope: statement. 默认开始 session

@Override
public void queryingLevelCacheFail(Long lon) {
    SysUser sysUsers = sysUserMapper.selectHandwritingSqlFail();
    log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

    SysUser user = sysUserMapper.selectHandwritingSqlFail();
    log.info("查询成功, 观察日志, id: {}", user.getId());

    log.info("-----------自义定SQL的两种失效方式-----------------");

    sysUsers = sysUserMapper.selectHandwritingSqlFail2();
    log.info("查询成功, 观察日志, id: {}", sysUsers.getId());

    user = sysUserMapper.selectHandwritingSqlFail2();
    log.info("查询成功, 观察日志, id: {}", user.getId());
}

<select id="selectHandwritingSqlFail" resultType="com.chaim.mybatis.cache.one.entitys.SysUser" flushCache="true">
    SELECT username,phone,id FROM sys_user limit 1
</select>

@Options(flushCache = Options.FlushCachePolicy.TRUE)
@Select("SELECT username,phone,id FROM sys_user limit 1")
SysUser selectHandwritingSqlFail2();