【技术分享】多线程事务怎么回滚？
一 场景介绍
1，最近有一个大数据量插入的操作入库的业务场景，需要先做一些其他修改操作，然后在执行插入操作，由于插入数据可能会很多，用到多线程去拆分数据并行处理来提高响应时间，如果有一个线程执行失败，则全部回滚。
2，在spring中可以使用@Transactional注解去控制事务，使出现异常时会进行回滚，在多线程中，这个注解则不会生效，如果主线程需要先执行一些修改数据库的操作，当子线程在进行处理出现异常时，主线程修改的数据则不会回滚，导致数据错误。
二 代码演示
- 线程池配置类
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(){
}
}
- sqlSession工具类
@Component
public class SqlContext {
@Resource
private SqlSessionTemplate sqlSessionTemplate;
public SqlSession getSqlSession(){
SqlSessionFactory sqlSessionFactory = sqlSessionTemplate.getSqlSessionFactory();
return sqlSessionFactory.openSession();
}
}
- 拆分list工具类
/**
* 平均拆分list方法.
* @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;
}
- 多线程使用手动提交事务实现事务回滚
操作失败
@Resource
SqlContext sqlContext;
/**
* 测试多线程事务.
* @param employeeDOList
*/
@Override
public void saveThread(List<EmployeeDO> employeeDOList) throws SQLException {
// 获取数据库连接,获取会话(内部自有事务)
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);
//使用返回结果的callable去执行,
Callable<Integer> callable = () -> {
//让最后一个线程抛出异常
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) {
//如果有一个执行不成功,则全部回滚
if (future.get()<=0){
connection.rollback();
return;
}
}
connection.commit();
System.out.println("添加完毕");
}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>
操作成功
@Resource
SqlContext sqlContext;
/**
* 测试多线程事务.
* @param employeeDOList
*/
@Override
public void saveThread(List<EmployeeDO> employeeDOList) throws SQLException {
// 获取数据库连接,获取会话(内部自有事务)
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("添加完毕");
}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);
}
}
