` public void itemClick(ItemClickEvent evt) { // TODO Auto-generated method stub super.itemClick(evt); if (StringUtils.equals("itg_pctestitem", evt.ge Read More
posted @ 2021-03-03 14:24 周世元ISO8859-1 Views(1) Comments(0) Diggs(0) Edit
1.group_concat的使用 2.合并结果集 3.自连接(使用场景:需要查出当前用户和它上一级用户的信息,他们俩根据parentid关联且在同一张表) 4.向上取整和向下取整 Read More
posted @ 2020-12-02 10:47 周世元ISO8859-1 Views(34) Comments(0) Diggs(0) Edit
MyBatis Plus 自动类型转换之TypeHandler 数据库表里有ids字段,存放的都是主键id,逗号分隔。 model里面是Set集合装Integer类型的 ids 用MyBatis的TypeHandler做自动类型转换 分三步: 1.实体类需要加个注解 @TableName(autoR Read More
posted @ 2020-11-18 17:45 周世元ISO8859-1 Views(296) Comments(0) Diggs(0) Edit
深拷贝和浅拷贝的区别 深拷贝和浅拷贝最根本的区别在于是否真正获取一个对象的复制实体,而不是引用。 假设B复制了A,修改A的时候,看B是否发生变化: 如果B跟着也变了,说明是浅拷贝,拿人手短!(修改堆内存中的同一个值) 如果B没有改变,说明是深拷贝,自食其力!(修改堆内存中的不同的值) 浅拷贝(sha Read More
posted @ 2020-11-17 16:25 周世元ISO8859-1 Views(39) Comments(0) Diggs(0) Edit
![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015113211878-1744703605.png) ![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015113230489-1822973748.png) Read More
posted @ 2020-10-15 11:33 周世元ISO8859-1 Views(45) Comments(0) Diggs(0) Edit
![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015112749800-1208490778.png) Read More
posted @ 2020-10-15 11:28 周世元ISO8859-1 Views(110) Comments(0) Diggs(0) Edit
![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015110419005-1337871847.png) Read More
posted @ 2020-10-15 11:04 周世元ISO8859-1 Views(98) Comments(0) Diggs(0) Edit
![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015105401160-632129031.png) ![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015105416719-1938983599.png) ![](https://i Read More
posted @ 2020-10-15 10:55 周世元ISO8859-1 Views(109) Comments(0) Diggs(0) Edit
![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015104042113-774150909.png) ![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015104103479-1520115518.png) ![](https://i Read More
posted @ 2020-10-15 10:43 周世元ISO8859-1 Views(169) Comments(0) Diggs(0) Edit
![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015103100924-697467373.png) ![](https://img2020.cnblogs.com/blog/1472232/202010/1472232-20201015103149800-1633265446.png) ![](https://i Read More
posted @ 2020-10-15 10:32 周世元ISO8859-1 Views(67) Comments(0) Diggs(0) Edit