Mybatis 的三种执行器
作者：互联网
在企业开发中, 对数据库的批量操作, 是一个非常常见的操作, Mybatis提供了批量执行器, 来支持批量操作.
1. Mybatis sql执行器
Mybatis 支持全局修改执行器, 参数名为: defaultExecutorType. 但是笔者并不推荐这种方式,笔者建议在获取sqlSession对象时设置.
Mybatis 共有三种执行器:
- SIMPLE: 默认的执行器, 对每条sql进行预编译->设置参数->执行等操作
- BATCH: 批量执行器, 对相同sql进行一次预编译, 然后设置参数, 最后统一执行操作
- REUSE: REUSE 执行器会重用预处理语句（prepared statements
1.1 局部设置
在获取sqlSession时设置, 需要注意的时, 如果选择的是批量执行器时, 需要手工提交事务.
// 获取指定执行器的sqlSession SqlSession sqlSession = sqlSessionFactory.openSession(ExecutorType.BATCH) // 获取批量执行器时, 需要手动提交事务 sqlSession.commit();
1.2 全局配置
可在全局配置文件中配置, 但是笔者不推荐这种方式, 了解即可.
<settings>
<setting name="defaultExecutorType" value="BATCH" />
</settings>
2. 三种执行器测试
对于单挑sql执行, 不同的执行器没有太大的差异, 所以笔者使用批量插入操作来测试不同执行器的不同行为方式.
需要特别注意的时, 当选择批量执行器时, 纵使在获取sqlSession时, 设置了自动提交事务, 也需要手动提交事务
2.1 映射文件
为保证测试条件尽可能一致, 笔者写里一个清空表的方法, 在每个测试用例执行之前, 先清空表.
<mapper namespace="org.zongf.learn.mybatis3.l01.mapper.StudentMapper">
<!-- 清空表中数据, 同时重置自增序列从0开始 -->
<delete id="clear">
truncate table t_student
</delete>
<!-- 新增 -->
<insert id="save" useGeneratedKeys="true" keyProperty="id">
insert into t_student values (null , #{name}, #{age}, #{sex}, #{birth})
</insert>
</mapper>
2.2 测试用例
public class TestStudentMapper {
// 批量保存方法
private void batchSave(StudentMapper mapper) {
// 初始化10000个对象
List<StudentPO> list = new ArrayList<>();
for (int i = 0; i < 10000; i++) {
list.add(new StudentPO("zhangsan_" + i, "M",20 + i % 10, LocalDate.now()));
}
// 批量执行
long start = System.currentTimeMillis();
for (StudentPO studentPO : list) {
mapper.save(studentPO);
}
long end = System.currentTimeMillis();
// 输出执行耗时
System.out.println("耗时:" + (end - start) + " ms!");
}
// 每次执行前,请空表
@Before
public void setUp(){
StudentMapper studentMapper = SqlSessionUtil.getMapper(StudentMapper.class);
studentMapper.clear();
}
// 默认执行器
@Test
public void test_SIMPLE(){
// 获取自动提交事务的Maper
StudentMapper mapper = SqlSessionUtil.getMapperAutoTx(StudentMapper.class);
// 执行批量保存
batchSave(mapper);
}
// 重用预编译执行器
@Test
public void test_REUSE(){
// 获取批量保存sqlSession
SqlSession sqlSession = SqlSessionUtil.openSession(ExecutorType.REUSE, true);
// 获取Mapper 对象
StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
// 执行批量保存
batchSave(mapper);
}
// 批量执行器
@Test
public void test_BATCH(){
// 获取批量保存sqlSession
SqlSession sqlSession = SqlSessionUtil.openSession(ExecutorType.BATCH, true);
// 获取Mapper 对象
StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
// 执行批量保存
batchSave(mapper);
sqlSession.commit();
}
}
3. 批量测试日志分析
从测试结果可以看出, 在做批量操作时, 使用批量执行器, 性能会有很大的提升.
3.1 SIMPLE 方式
从执行日志可以看出, 每次插入操作, 都会执行编译, 设置参数, 执行sql操作.
[2019-06-13 11:30:38:812][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Preparing: insert into t_student values (null , ?, ?, ?, ?) [2019-06-13 11:30:38:819][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_0(String), 20(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:30:38:824][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <== Updates: 1 [2019-06-13 11:30:38:827][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Preparing: insert into t_student values (null , ?, ?, ?, ?) [2019-06-13 11:30:38:828][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_1(String), 21(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:30:38:832][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <== Updates: 1 [2019-06-13 11:30:38:833][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Preparing: insert into t_student values (null , ?, ?, ?, ?) [2019-06-13 11:30:38:839][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_2(String), 22(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:30:38:841][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <== Updates: 1 ... 耗时:21575 ms!
3.2 REUSE 方式
从执行日志可以看出, 只有第一次插入操作, 执行了sql编译步骤, 对其它插入操作执行了设置参数, 执行sql的操作.
[2019-06-13 11:31:11:752][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Preparing: insert into t_student values (null , ?, ?, ?, ?) [2019-06-13 11:31:11:757][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_0(String), 20(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:31:11:759][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <== Updates: 1 [2019-06-13 11:31:11:761][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_1(String), 21(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:31:11:764][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <== Updates: 1 [2019-06-13 11:31:11:776][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_2(String), 22(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:31:11:778][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- <== Updates: 1 ... 耗时:19322 ms!
3.3 BATCH
从执行日志可以看出, 只对第一次插入操作执行了sql编译操作, 对其它插入操作仅执行了设置参数操作, 最后统一执行.
[2019-06-13 11:31:29:270][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Preparing: insert into t_student values (null , ?, ?, ?, ?) [2019-06-13 11:31:29:276][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_0(String), 20(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:31:29:277][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_1(String), 21(Integer), M(String), 2019-06-13(Date) [2019-06-13 11:31:29:277][main][DEBUG][o.z.l.m.l.mapper.StudentMapper.save]- ==> Parameters: zhangsan_2(String), 22(Integer), M(String), 2019-06-13(Date) ... 耗时:835 ms!
参考：https://blog.csdn.net/zongf0504/article/details/100104029
标签：执行器,mapper,13,06,StudentMapper,三种,11,Mybatis,2019 来源： https://www.cnblogs.com/Vincent-yuan/p/15491674.html