五分鐘教你手寫 SpringBoot 本地事務管理實現

MethodA() {
 MethodB()；
 MethodC();
}

 // 以下代碼省略部分內容
 public Object invoke(MethodInvocation invocation) throws Throwable {
  // 獲取事務調用的目標方法
  Class<?> targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);
  // 執行帶事務調用
  return invokeWithinTransaction(invocation.getMethod(), targetClass, invocation::proceed);
 }

 // 以下代碼省略部分內容
 protected Object invokeWithinTransaction(Method method, @Nullable Class<?> targetClass, final InvocationCallback invocation) throws Throwable {
  Object retVal;
  try {
   // 調用真正的方法體
   retVal = invocation.proceedWithInvocation();
  }
  catch (Throwable ex) {
   // 如果出現異常，執行事務異常處理
   completeTransactionAfterThrowing(txInfo, ex);
   throw ex;
  }
  finally {
   // 最後做一下清理工作，主要是緩存和狀態等
   cleanupTransactionInfo(txInfo);
  }
  // 如果沒有異常，直接提交事務
  commitTransactionAfterReturning(txInfo);
  return retVal;
 }

 // 以下代碼省略部分內容
 protected void completeTransactionAfterThrowing(@Nullable TransactionInfo txInfo, Throwable ex) {
  // 判斷是否需要回滾，判斷的邏輯就是看有沒有聲明事務屬性，同時判斷是不是在目前的這個異常中執行回滾
  if (txInfo.transactionAttribute != null && txInfo.transactionAttribute.rollbackOn(ex)) {
   // 執行回滾
   txInfo.getTransactionManager().rollback(txInfo.getTransactionStatus());
  }
  else {
   // 否則不需要回滾，直接提交即可
   txInfo.getTransactionManager().commit(txInfo.getTransactionStatus());
  }
 }

 @Override
 protected void doRollback(DefaultTransactionStatus status) {
  DataSourceTransactionObject txObject = (DataSourceTransactionObject) status.getTransaction();
  Connection con = txObject.getConnectionHolder().getConnection();
  if (status.isDebug()) {
   logger.debug("Rolling back JDBC transaction on Connection [" + con + "]");
  }
  try {
   // 調用jdbc的 rollback進行回滾事務
   con.rollback();
  }
  catch (SQLException ex) {
   throw new TransactionSystemException("Could not roll back JDBC transaction", ex);
  }
 }

  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-aop</artifactId>
  </dependency>
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-jdbc</artifactId>
  </dependency>

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface MyTransaction {
 // 指定異常回滾
 Class<? extends Throwable>[] rollbackFor() default {};
}

@Component
public class DataSourceConnectHolder {

 @Autowired
 private DataSource dataSource;
 /**
  * 線程綁定對象
  */
 ThreadLocal<Connection> resources = new NamedThreadLocal<>("Transactional resources");

 public Connection getConnection() {
  Connection con = resources.get();
  if (con != null) {
   return con;
  }
  try {
   con = dataSource.getConnection();
   // 為瞭體現事務，全部設置為手動提交事務
   con.setAutoCommit(false);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  resources.set(con);
  return con;
 }

 public void cleanHolder() {
  Connection con = resources.get();
  if (con != null) {
   try {
    con.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
  }
  resources.remove();
 }
}

@Aspect
@Component
public class MyTransactionAopHandler {
 
 @Autowired
 private DataSourceConnectHolder connectHolder;
 
 Class<? extends Throwable>[] es;

 // 攔截所有MyTransaction註解的方法
 @org.aspectj.lang.annotation.Pointcut("@annotation(你的包路徑.MyTransaction)")
 public void Transaction() {

 }

 @Around("Transaction()")
 public Object TransactionProceed(ProceedingJoinPoint proceed) throws Throwable {
  Object result = null;
  Signature signature = proceed.getSignature();
  MethodSignature methodSignature = (MethodSignature) signature;
  Method method = methodSignature.getMethod();
  if (method == null) {
   return result;
  }
  MyTransaction transaction = method.getAnnotation(MyTransaction.class);
  if (transaction != null) {
   es = transaction.rollbackFor();
  }
  try {
   result = proceed.proceed();
  } catch (Throwable throwable) {
   // 異常處理
   completeTransactionAfterThrowing(throwable);
   throw throwable;
  }
  // 直接提交
  doCommit();
  return result;
 }

 /**
  * 執行回滾，最後關閉連接和清理線程綁定
  */
 private void doRollBack() {
  try {
   connectHolder.getConnection().rollback();
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   connectHolder.cleanHolder();
  }

 }

 /**
  * 執行提交，最後關閉連接和清理線程綁定
  */
 private void doCommit() {
  try {
   connectHolder.getConnection().commit();
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   connectHolder.cleanHolder();
  }
 }

 /**
  * 異常處理，捕獲的異常是目標異常或者其子類，就進行回滾，否則就提交事務。
  */
 private void completeTransactionAfterThrowing(Throwable throwable) {
  if (es != null && es.length > 0) {
   for (Class<? extends Throwable> e : es) {
    if (e.isAssignableFrom(throwable.getClass())) {
     doRollBack();
    }
   }
  }
  doCommit();
 }

}

@Service
public class MyTransactionTest {

 @Autowired
 private DataSourceConnectHolder holder;

 // 一個事務中執行兩個sql插入
 @MyTransaction(rollbackFor = NullPointerException.class)
 public void saveTest(int id) {
  save(id, "白菜Java自習室");
  save(id + 10, "白菜Java自習室");
  throw new RuntimeException();
 }

 // 執行sql
 private void save(int id, String value) {
  String sql = "insert into test values(?,?)";
  Connection connection = holder.getConnection();
  PreparedStatement stmt = null;
  try {
   stmt = connection.prepareStatement(sql);
   stmt.setInt(1, id);
   stmt.setString(2, value);
   stmt.executeUpdate();
  } catch (SQLException e) {
   e.printStackTrace();
  }
 }

}