1.在Mybatis的配置文件中开启二级缓存

开启缓存 ，为了查看Mybatis中查询的日志，添加 开启日志的配置。

2.领域类以及Dao

public class User implements Serializable{  private Integer userId;  private String userName;  private Date userBirthday;  private String userSex;  private String userAddress;  private List accounts;  省略get和set方法...... }import com.example.domain.User;import org.apache.ibatis.annotations.*;import org.apache.ibatis.mapping.FetchType;import java.util.List;@CacheNamespace(blocking = true)public interface UserDao {  /**   * 查找所有用户   * @return   */  @Select("select * from User")  @Results(id = "userMap",value = {@Result(id = true,column = "id",property = "userId"),      @Result(column = "username",property = "userName"),      @Result(column = "birthday",property = "userBirthday"),      @Result(column = "sex",property = "userSex"),      @Result(column = "address",property = "userAddress"),      @Result(column = "id",property = "accounts",many = @Many(select = "com.example.dao.AccountDao.findAccountByUid",fetchType = FetchType.LAZY))  })  List findAll();  /**   * 保存用户   * @param user   */  @Insert("insert into user(username,birthday,sex,address) values(#{username},#{birthday},#{sex},#{address})")  void saveUser(User user);  /**   * 更新用户   * @param user   */  @Update("update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} where id=#{id}")  void updateUser(User user);  /**   * 删除用户   * @param id   */  @Delete("delete from user where id=#{id}")  void deleteUser(Integer id);  /**   * 查询用户根据ID   * @param id   * @return   */  @Select("select * from user where id=#{id}")  @ResultMap(value = {"userMap"})  User findById(Integer id);  /**   * 根据用户名称查询用户   * @param name   * @return   *///  @Select("select * from user where username like #{name}")  @Select("select * from user where username like '%${value}%'")  List findByUserName(String name);  /**   * 查询用户数量   * @return   */  @Select("select count(*) from user")  int findTotalUser();}

3.在对应的Dao类上面增加注释以开启二级缓存　

@CacheNamespace(blocking = true)

4.测试

public class UserCacheTest {  private InputStream in;  private SqlSessionFactory sqlSessionFactory;  @Before  public void init()throws Exception{    in = Resources.getResourceAsStream("SqlMapConfig.xml");    sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);  }  @After  public void destory()throws Exception{    in.close();  }  @Test  public void testFindById(){    //第一查询    SqlSession sqlSession1 = sqlSessionFactory.openSession();    UserDao userDao1 = sqlSession1.getMapper(UserDao.class);    User user1 = userDao1.findById(41);    System.out.println(user1);    //关闭一级缓存    sqlSession1.close();    //第二次查询    SqlSession sqlSession2 = sqlSessionFactory.openSession();    UserDao userDao2 = sqlSession2.getMapper(UserDao.class);    User user2 = userDao2.findById(41);    System.out.println(user2);    sqlSession1.close();    System.out.println(user1 == user2);  }}

（1）未开启二级缓存时

（2）开启二级缓存时