日志
1.日志工厂
如果一个数据库的操作，出现了异常，我们需要排错。日志就是最好的工具。
日志工厂：SLF4JLOG4J(掌握）LOG4J2JDK_LOGGINGCOMMONS_LOGGING==STDOUT_LOGGING（掌握）==NO_LOGGING
2.分页
减少数据的处理量
Limit分页
select * from user limit 2,2
从第三个开始，查找两个。如果只有一个参数0~n
使用myBatis实现分页。
1.接口
//分页List<User> getUserByLimit(Map<String,Integer> map);
2.Mapper.xml
<select id="getUserByLimit" parameterType="map" resultType="user">select * from mybatis.user limit #{startIndex},#{pageSize}</select>3.测试
public void getTest(){SqlSession sqlSession = MybatisUtils.getSqlSession();UserMapper mapper = sqlSession.getMapper(UserMapper.class);HashMap<String, Integer> map = new HashMap<String, Integer>();map.put("startIndex",1);map.put("pageSize",2);List<User> user = mapper.getUserByLimit(map);for (User user1 : user) {System.out.println(user);}sqlSession.close();}
RowBounds分页
1.接口
List<User> getUserByRowBounds();
2.xml文件
<select id="getUserByRowBounds" resultType="user">select * from mybatis.user</select>
3.测试
public void rowBoundsTest(){SqlSession sqlSession = MybatisUtils.getSqlSession();RowBounds rowBounds = new RowBounds(2, 2);List<User> userList;userList = sqlSession.selectList("dao.UserMapper.getUserByRowBounds",null,rowBounds);for (User user : userList) {System.out.println(user);}sqlSession.close();}
