SCB-1011 Added a NPE check in TransactionAspect

omega/omega-transaction/src/main/java/org/apache/servicecomb/pack/omega/transaction/TransactionAspect.java

@@ -55,7 +55,10 @@ Object advise(ProceedingJoinPoint joinPoint, Compensable compensable) throws Thr
     if (transactionContext != null) {
       populateOmegaContext(context, transactionContext);
     }
-
+    // SCB-1011 Need to check if the globalTxId transaction is null to avoid the message sending failure
+    if (context.globalTxId() == null) {
+      throw new OmegaException("Cannot find the globalTxId from OmegaContext. Please using @SagaStart to start a global transaction.");
+    }
     String localTxId = context.localTxId();
     context.newLocalTxId();
     LOG.debug("Updated context {} for compensable method {} ", context, method.toString());

omega/omega-transaction/src/test/java/org/apache/servicecomb/pack/omega/transaction/TransactionAspectTest.java

@@ -22,6 +22,7 @@
 import static org.hamcrest.core.IsInstanceOf.instanceOf;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
@@ -142,6 +143,17 @@ public void setNewLocalTxIdCompensableWithTransactionContext() throws Throwable
     assertThat(omegaContext.localTxId(), is(transactionLocalTxId));
   }
 
+  @Test
+  public void globalTxIsNotSet() throws Throwable {
+    omegaContext.setGlobalTxId(null);
+    try {
+      aspect.advise(joinPoint, compensable);
+      fail("Expect exception here");
+    } catch (OmegaException ex) {
+      assertThat(ex.getMessage(), is("Cannot find the globalTxId from OmegaContext. Please using @SagaStart to start a global transaction."));
+    }
+  }
+
   @Test
   public void newLocalTxIdInCompensable() throws Throwable {
     aspect.advise(joinPoint, compensable);