（七）mybatis批量操作，分页插件

首先使用方式很简单：

SqlSession sqlSession = sessionFactory.openSession(ExecutorType.BATCH);

批量操作核心：改变执行sql的方式，改为BATCH

那么原因是什么呢？

首先普通方式是插入一条数据，就搭建一个sql语句，然后传入参数，执行sql，但是BATCH方式，预编译一次，我们将sql语句的框架先搭建好，之后每次执行的时候，只需要给里面填，并不需要再次搭建sql语句。

通过控制台日志输出也可以看的出来：

这是BATCH方式的批量插入的：

EBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - Committing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@52851b44]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@52851b44]
DEBUG [main] - Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@52851b44]
DEBUG [main] - Returned connection  to pool.

Process finished with exit code 

这是不使用BATCH

EBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - ==>  Preparing: insert into student ( name, loves ) values ( ?, ? )
DEBUG [main] - ==> Parameters: 温鸿飞(String), dsadsa(String)
DEBUG [main] - <==    Updates:
DEBUG [main] - Committing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1852a3ff]
DEBUG [main] - Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1852a3ff]
DEBUG [main] - Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@1852a3ff]
DEBUG [main] - Returned connection  to pool.

Process finished with exit code 

可以看到预编译了很多次。

分页插件：PageHelper，

很简单，下载jar包或者在maven之中直接导入，

查询时加入这句话，

PageHelper.startPage(pageNum,pageSize);

之后正常查询，就会返回相应页数的信息，当然还有其他很多细节的，看官网就行：https://pagehelper.github.io/docs/howtouse/

常用这两种：

1.比如获取当前页，总数据量，总页码等，

获取PageHelper.startPage(pageNum,pageSize);   的返回值，Page<Object> 之后通过各种get方法即可获取，

2.当然也可以获取第一页，最后一页，使用pageinfo

PageInfo<classname> xx = new PageInfo<>(list);