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背景介绍
1，最近有一个大数据量插入的操作入库的业务场景，须要先做一些其余批改操作，而后在执行插入操作，因为插入数据可能会很多，用到多线程去拆分数据并行处理来进步响应工夫，如果有一个线程执行失败，则全副回滚。
2，在 spring 中能够应用 @Transactional 注解去管制事务，使出现异常时会进行回滚，在多线程中，这个注解则不会失效，如果主线程须要先执行一些批改数据库的操作，当子线程在进行解决出现异常时，主线程批改的数据则不会回滚，导致数据谬误。
3，上面用一个简略示例演示多线程事务。
专用的类和办法
/**
* 均匀拆分 list 办法.
* @param source
* @param n
* @param <T>
* @return
*/
public static <T> List<List<T>> averageAssign(List<T> source,int n){List<List<T>> result=new ArrayList<List<T>>();
int remaider=source.size()%n;
int number=source.size()/n;
int offset=0;// 偏移量
for(int i=0;i<n;i++){
List<T> value=null;
if(remaider>0){value=source.subList(i*number+offset, (i+1)*number+offset+1);
remaider--;
offset++;
}else{value=source.subList(i*number+offset, (i+1)*number+offset);
}
result.add(value);
}
return result;
}
/** 线程池配置
* @version V1.0
*/
public class ExecutorConfig {private static int maxPoolSize = Runtime.getRuntime().availableProcessors();
private volatile static ExecutorService executorService;
public static ExecutorService getThreadPool() {if (executorService == null){synchronized (ExecutorConfig.class){if (executorService == null){executorService = newThreadPool();
}
}
}
return executorService;
}
private static ExecutorService newThreadPool(){
int queueSize = 500;
int corePool = Math.min(5, maxPoolSize);
return new ThreadPoolExecutor(corePool, maxPoolSize, 10000L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(queueSize),new ThreadPoolExecutor.AbortPolicy());
}
private ExecutorConfig(){}
}
/** 获取 sqlSession
* @author 86182
* @version V1.0
*/
@Component
public class SqlContext {
@Resource
private SqlSessionTemplate sqlSessionTemplate;
public SqlSession getSqlSession(){SqlSessionFactory sqlSessionFactory = sqlSessionTemplate.getSqlSessionFactory();
return sqlSessionFactory.openSession();}
}举荐一个 Spring Boot 基础教程及实战示例：https://github.com/javastacks/spring-boot-best-practice
示例事务不胜利操作
/**
* 测试多线程事务.
* @param employeeDOList
*/
@Override
@Transactional
public void saveThread(List<EmployeeDO> employeeDOList) {
try {
// 先做删除操作, 如果子线程出现异常, 此操作不会回滚
this.getBaseMapper().delete(null);
// 获取线程池
ExecutorService service = ExecutorConfig.getThreadPool();
// 拆分数据, 拆分 5 份
List<List<EmployeeDO>> lists=averageAssign(employeeDOList, 5);
// 执行的线程
Thread []threadArray = new Thread[lists.size()];
// 监控子线程执行结束, 再执行主线程, 要不然会导致主线程敞开, 子线程也会随着敞开
CountDownLatch countDownLatch = new CountDownLatch(lists.size());
AtomicBoolean atomicBoolean = new AtomicBoolean(true);
for (int i =0;i<lists.size();i++){if (i==lists.size()-1){atomicBoolean.set(false);
}
List<EmployeeDO> list = lists.get(i);
threadArray[i] = new Thread(() -> {
try {
// 最初一个线程抛出异样
if (!atomicBoolean.get()){throw new ServiceException("001","出现异常");
}
// 批量增加,mybatisPlus 中自带的 batch 办法
this.saveBatch(list);
}finally {countDownLatch.countDown();
}
});
}
for (int i = 0; i <lists.size(); i++){service.execute(threadArray[i]);
}
// 当子线程执行结束时, 主线程再往下执行
countDownLatch.await();
System.out.println("增加结束");
}catch (Exception e){log.info("error",e);
throw new ServiceException("002","出现异常");
}finally {connection.close();
}
}数据库中存在一条数据：
Spring Boot 根底就不介绍了，举荐下这个实战教程：
https://github.com/javastacks/spring-boot-best-practice
// 测试用例
@RunWith(SpringRunner.class)
@SpringBootTest(classes = { ThreadTest01.class, MainApplication.class})
public class ThreadTest01 {
@Resource
private EmployeeBO employeeBO;
/**
* 测试多线程事务.
* @throws InterruptedException
*/
@Test
public void MoreThreadTest2() throws InterruptedException {
int size = 10;
List<EmployeeDO> employeeDOList = new ArrayList<>(size);
for (int i = 0; i<size;i++){EmployeeDO employeeDO = new EmployeeDO();
employeeDO.setEmployeeName("lol"+i);
employeeDO.setAge(18);
employeeDO.setGender(1);
employeeDO.setIdNumber(i+"XX");
employeeDO.setCreatTime(Calendar.getInstance().getTime());
employeeDOList.add(employeeDO);
}
try {employeeBO.saveThread(employeeDOList);
System.out.println("增加胜利");
}catch (Exception e){e.printStackTrace();
}
}
}测试后果：
能够发现子线程组执行时，有一个线程执行失败，其余线程也会抛出异样，然而主线程中执行的删除操作，没有回滚，@Transactional注解没有失效。
应用 sqlSession 管制手动提交事务
@Resource
SqlContext sqlContext;
/**
* 测试多线程事务.
* @param employeeDOList
*/
@Override
public void saveThread(List<EmployeeDO> employeeDOList) throws SQLException {// 获取数据库连贯, 获取会话(外部自有事务)
SqlSession sqlSession = sqlContext.getSqlSession();
Connection connection = sqlSession.getConnection();
try {
// 设置手动提交
connection.setAutoCommit(false);
// 获取 mapper
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
// 先做删除操作
employeeMapper.delete(null);
// 获取执行器
ExecutorService service = ExecutorConfig.getThreadPool();
List<Callable<Integer>> callableList = new ArrayList<>();
// 拆分 list
List<List<EmployeeDO>> lists=averageAssign(employeeDOList, 5);
AtomicBoolean atomicBoolean = new AtomicBoolean(true);
for (int i =0;i<lists.size();i++){if (i==lists.size()-1){atomicBoolean.set(false);
}
List<EmployeeDO> list = lists.get(i);
// 应用返回后果的 callable 去执行,
Callable<Integer> callable = () -> {
// 让最初一个线程抛出异样
if (!atomicBoolean.get()){throw new ServiceException("001","出现异常");
}
return employeeMapper.saveBatch(list);
};
callableList.add(callable);
}
// 执行子线程
List<Future<Integer>> futures = service.invokeAll(callableList);
for (Future<Integer> future:futures) {
// 如果有一个执行不胜利, 则全副回滚
if (future.get()<=0){connection.rollback();
return;
}
}
connection.commit();
System.out.println("增加结束");
}catch (Exception e){connection.rollback();
log.info("error",e);
throw new ServiceException("002","出现异常");
}finally {connection.close();
}
}
// sql
<insert id="saveBatch" parameterType="List">
INSERT INTO
employee (employee_id,age,employee_name,birth_date,gender,id_number,creat_time,update_time,status)
values
<foreach collection="list" item="item" index="index" separator=",">
(#{item.employeeId},
#{item.age},
#{item.employeeName},
#{item.birthDate},
#{item.gender},
#{item.idNumber},
#{item.creatTime},
#{item.updateTime},
#{item.status}
)
</foreach>
</insert>数据库中一条数据：
测试后果：抛出异样，
删除操作的数据回滚了，数据库中的数据仍旧存在，阐明事务胜利了。
胜利操作示例：
@Resource
SqlContext sqlContext;
/**
* 测试多线程事务.
* @param employeeDOList
*/
@Override
public void saveThread(List<EmployeeDO> employeeDOList) throws SQLException {// 获取数据库连贯, 获取会话(外部自有事务)
SqlSession sqlSession = sqlContext.getSqlSession();
Connection connection = sqlSession.getConnection();
try {
// 设置手动提交
connection.setAutoCommit(false);
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
// 先做删除操作
employeeMapper.delete(null);
ExecutorService service = ExecutorConfig.getThreadPool();
List<Callable<Integer>> callableList = new ArrayList<>();
List<List<EmployeeDO>> lists=averageAssign(employeeDOList, 5);
for (int i =0;i<lists.size();i++){List<EmployeeDO> list = lists.get(i);
Callable<Integer> callable = () -> employeeMapper.saveBatch(list);
callableList.add(callable);
}
// 执行子线程
List<Future<Integer>> futures = service.invokeAll(callableList);
for (Future<Integer> future:futures) {if (future.get()<=0){connection.rollback();
return;
}
}
connection.commit();
System.out.println("增加结束");
}catch (Exception e){connection.rollback();
log.info("error",e);
throw new ServiceException("002","出现异常");
// throw new ServiceException(ExceptionCodeEnum.EMPLOYEE_SAVE_OR_UPDATE_ERROR);
}
}测试后果：
数据库中数据：
删除的删除了，增加的增加胜利了，测试胜利。
版权申明：本文为 CSDN 博主「weixin_43225491」的原创文章，遵循 CC 4.0 BY-SA 版权协定，转载请附上原文出处链接及本申明。原文链接：https://blog.csdn.net/weixin_43225491/article/details/117705686
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