Mybatis中缓存

SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        CacheMapper mapper = sqlSession.getMapper(CacheMapper.class);
        Emp emp1 = mapper.getEmpByEid(1);
        System.out.println(emp1);
        Emp emp2 = mapper.getEmpByEid(1);
        System.out.println(emp2);

 可以看到只访问了一次数据库（因为只有一条sql语句记录）

SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        CacheMapper mapper1 = sqlSession.getMapper(CacheMapper.class);
        CacheMapper mapper2 = sqlSession.getMapper(CacheMapper.class);
        Emp emp1 = mapper1.getEmpByEid(1);
        Emp emp2 = mapper2.getEmpByEid(1);
        System.out.println(emp1);
        System.out.println(emp2);

 一样的结果

 SqlSession sqlSession1 = SqlSessionUtils.getSqlSession();
        SqlSession sqlSession2 = SqlSessionUtils.getSqlSession();
        CacheMapper mapper = sqlSession1.getMapper(CacheMapper.class);
        Emp emp1 = mapper.getEmpByEid(1);
        CacheMapper mapper1 = sqlSession2.getMapper(CacheMapper.class);
        Emp emp2 = mapper1.getEmpByEid(1);
        System.out.println(emp1);
        System.out.println(emp2);

 可以看到访问了2次数据库，因为我们创建了两个sqlSession

因此可以看到一级缓存的范围在同一个sqlSession下。

在中间增加一个添加操作

 SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        CacheMapper mapper = sqlSession.getMapper(CacheMapper.class);
        Emp emp1 = mapper.getEmpByEid(1);
        System.out.println(emp1);
        int result = mapper.insertEmp(new Emp(null, "ab", 21, "女", "ab@qq.com"));
        System.out.println(result);
        Emp emp2 = mapper.getEmpByEid(1);
        System.out.println(emp2);

 可以看到访问了三次，说明一级缓存失效了。

  try {
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
            SqlSession sqlSession1 = sqlSessionFactory.openSession(true);
            CacheMapper mapper1 = sqlSession1.getMapper(CacheMapper.class);
            Emp emp1 = mapper1.getEmpByEid(1);
            System.out.println(emp1);
            sqlSession1.close();
            SqlSession sqlSession2 = sqlSessionFactory.openSession();
            CacheMapper mapper2 = sqlSession2.getMapper(CacheMapper.class);
            Emp emp2 = mapper2.getEmpByEid(1);
            System.out.println(emp2);


        } catch (IOException e) {
            e.printStackTrace();
        }
    }

 一个SqlSessionFactory建立了sqlSession1和sqlSession2

注意当缺sqlSession1.close()或是sqlSession1.commit() 不会实现二级缓存，不满足条件c