一、在mybatis中ExecutorType的使用
1.Mybatis内置的ExecutorType有3种,默认的是simple,该模式下它为每个语句的执行创建一个新的预处理语句,单条提交sql;而batch模式重复使用已经预处理的语句,
并且批量执行所有更新语句,显然batch性能将更优;
2.但batch模式也有自己的问题,比如在Insert操作时,在事务没有提交之前,是没有办法获取到自增的id,这在某型情形下是不符合业务要求的;
在测试中使用simple模式提交10000条数据,时间为18248 毫秒,batch模式为5023 ,性能提高70%;
public void mybatisBatch() { SqlSession session = getSqlSessionFactory().openSession(); try { DeptMapper deptMapper = (DeptMapper) session.getMapper(DeptMapper.class); long start =System.currentTimeMillis(); for (int i = 0; i <10000 ; i++) { SysDept dept=new SysDept(UUID.randomUUID().toString().substring(1,6), 1, new Date(), new Date(), 1); deptMapper.saveSysDept(dept); } long end =System.currentTimeMillis(); System.out.println("耗时:"+(end-start)); //ExecutorType.BATCH 批量耗时耗时:2134 //单条操作耗时 耗时:8584 } catch (Exception e) { e.printStackTrace(); } finally { session.commit(); session.close(); } } public void saveDeptBatchOne() { SqlSession session = getSqlSessionFactory().openSession(); try { DeptMapper deptMapper = (DeptMapper) session.getMapper(DeptMapper.class); long start =System.currentTimeMillis(); List<SysDept> deptList=new ArrayList<SysDept>(); for (int i = 0; i <100000 ; i++) { SysDept dept=new SysDept(UUID.randomUUID().toString().substring(1,6), 1, new Date(), new Date(), 1); deptList.add(dept); if(i%500==0){ deptMapper.saveDeptBatch(deptList); deptList.clear(); } } deptMapper.saveDeptBatch(deptList); long end =System.currentTimeMillis(); System.out.println("耗时:"+(end-start)); //非BATCH批量耗时 耗时:938 } catch (Exception e) { e.printStackTrace(); } finally { session.commit(); session.close(); } } public void saveDeptBatchTwo() { //设置ExecutorType.BATCH原理:把SQL语句发个数据库,数据库预编译好,数据库等待需要运行的参数,接收到参数后一次运行,ExecutorType.BATCH只打印一次SQL语句,多次设置参数步骤, SqlSession session = getSqlSessionFactory().openSession(ExecutorType.BATCH); try { DeptMapper deptMapper = (DeptMapper) session.getMapper(DeptMapper.class); long start =System.currentTimeMillis(); List<SysDept> deptList=new ArrayList<SysDept>(); for (int i = 0; i <100000; i++) { SysDept dept=new SysDept(UUID.randomUUID().toString().substring(1,6), 1, new Date(), new Date(), 1); deptList.add(dept); if(i%500==0){ deptMapper.saveDeptBatch(deptList); deptList.clear(); } } deptMapper.saveDeptBatch(deptList); long end =System.currentTimeMillis(); System.out.println("耗时:"+(end-start)); //BATCH批量耗时 耗时:822 } catch (Exception e) { e.printStackTrace(); } finally { session.commit(); session.close(); } }
二、在mybatis+spring中ExecutorType的使用
1、在spring配置文件中添加批量执行的SqlSessionTemplate
<!--配置一个可以进行批量执行的sqlSession -->
<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
<constructor-arg name="sqlSessionFactory" ref="sqlSessionFactoryBean"></constructor-arg>
<constructor-arg name="executorType" value="BATCH"></constructor-arg>
</bean>
2、service中获取批量添加的SqlSession
public class DeptService { private DeptMapper deptMapper; private SqlSession sqlSession; public List<Dept> addDept(){ //executorType=BATCH 添加操作 DeptMapper mapper = sqlSession.getMapper(DeptMapper.class); return mapper.saveDept(Dept); } }
三、$和#的区别
#{}:可以获取map中的值或者pojo对象属性的值; ${}:可以获取map中的值或者pojo对象属性的值; select * from tbl_employee where id=${id} and last_name=#{lastName} Preparing: select * from tbl_employee where id=2 and last_name=? 区别: #{}:是以预编译的形式,将参数设置到sql语句中;PreparedStatement;防止sql注入 ${}:取出的值直接拼装在sql语句中;会有安全问题;