Develop Reference

Pubsub message with reactive panache monogodb failing to create ReactiveTransaction with session is null error

I have a quarkus project connecting to monogdb using reactive panache.
I would like my method to be wrapped in a transaction and my current code looks roughly as follows:
#Traced
#ApplicationScoped
#Startup
public class MyReceiver implements com.google.cloud.pubsub.v1.MessageRecevier {
#Override
#ActivateRequestContext
public void receiveMessage(PubsubMessage pubsubMessage, AckReplyConsumer ackReplyConsumer) {
try {
final String messageStr = pubsubMessage.getData().toStringUtf8();
final MyMessage messageContent = objectMapper.readValue(messageStr, getTypeReference());
handleMessage(messageContent).await().indefinitely();
ackReplyConsumer.ack();
} catch (Throwable ex) {
log.warn("{} Message ID: [{}] on [{}] ", ex.getMessage(), pubsubMessage.getMessageId(), subscriptionName);
ackReplyConsumer.nack();
}
}
public TypeReference<MyMessage> getTypeReference() {
return new TypeReference<>(){};
}
#ReactiveTransactional
public Uni<Void> handleMessage(MyMessage message) {
// code here is never reached
}
}
When i try to test my code however and get a message,
I am getting this error: java.lang.NullPointerException: Cannot invoke "org.hibernate.reactive.mutiny.Mutiny$Session.withTransaction(java.util.function.Function)" because "session" is null
And it happens when the code tries to go into handleMessage, so when the aspect for #ReactiveTransactional is being triggered
What can I look out for that is causing this cause I can't find anything that can be the source of the issue.

It seems at the moment, panache does not support transactions in mongodb which was the source of this issue.

Container Managed Transaction - Not marked for roll back

Bank.java
#Stateless
#Local
public class Bank implements IBank {
#EJB
IConfigBean iConfigBean;
#EJB
IDbs iDBS;
#EJB
IPosb iPosb;
#Override
public void doTransaction() {
System.out.println("--Bank Transaction Started--");
try {
Config config1 = getConfig(1);
iConfigBean.create(config1);
iDBS.doDBSTransaction();
Config config3 = getConfig(3);
iConfigBean.create(config3);
iPosb.doPOSBTransaction();
Config config5 = getConfig(5);
iConfigBean.create(config5);
} catch (Exception e) {
e.printStackTrace();
System.out.println("---Bank Exception--");
}
System.out.println("--Bank Transaction End--");
}
#Override
public Config getConfig(int inserttionOrderNo) {
Config config = new Config();
config.setType("EJBTransactionTESTING - " + inserttionOrderNo);
return config;
}
}
DBS.java
#Stateless
#Local
public class DBS implements IDbs {
#EJB
IConfigBean iConfigBean;
#Override
public void doDBSTransaction() {
System.out.println("--DBS Transaction Started--");
try {
Config config2 = getConfig(2);
iConfigBean.create(config2);
} catch (Exception e) {
e.printStackTrace();
System.out.println("--DBS Exception--");
}
System.out.println("--DBS Transaction End--");
}
#Override
public Config getConfig(int inserttionOrderNo) {
Config config = new Config();
config.setType("EJBTransactionTESTING - " + inserttionOrderNo);
return config;
}
}
POSB.java
#Stateless
#Local
public class POSB implements IPosb {
#EJB
IConfigBean iConfigBean;
#Override
public void doPOSBTransaction() {
System.out.println("--POSB Transaction Started--");
try {
Config config4 = getConfig(4);
iConfigBean.create(config4);
if (true) {
//For Test 1
//throw new NullPointerException();
}
} catch (Exception e) {
e.printStackTrace();
System.out.println("--POSB Exception--");
}
if (true) {
//For Test 2
// throw new NullPointerException();
}
System.out.println("--POSB Transaction End--");
}
#Override
public Config getConfig(int inserttionOrderNo) {
Config config = new Config();
config.setType("EJBTransactionTESTING - " + inserttionOrderNo);
return config;
}
}
I am new to Stack Overflow and Its my new question so correct me If I am wrong.
Environment is..
Windows 10
Java 1.8
Eclipse
Tomcat 8.5
EJB3
I have Three stateless bean, Please look at the Sequence Diagram of the Transaction flow.
I purposely making NullPointer Exception at two places during the transaction to know the difference and I have marked with Lightening Bold symbol in sequence diagram.
I am not using any #TransactionAttribute to any methods.
Test 1 - Null Pointer in Inside the try block (Lightening Bold symbol with Green)
When I start the testing, Got Null pointer exception and all the transaction are not marked for roll back and data also got inserted in db.
I can only see Null pointer exception in the console log.
Test 2 - Null Pointer in Outside the try - catch method (Lightening Bold symbol with Red)
When I start the testing, Got Null pointer exception plus EJBTransactionRolledbackException and all the transaction marked for roll back and no data inserted in db.
I can see NullPointer and EJBTransactionRolledback Exception in the console log.
Question here is,
Why EJB transaction is not marked for roll back If I made Null pointer inside try block
Why EJB transaction is roll back happens If I made null pointer outside try block
Thanks in advance.

Keep in mind EJB calls, all the "magic" made by container happens there, including transaction markup. It's possible due to the fact that EJB calls are not direct, but always go through proxy.
You have such calls in your code:
iPosb.doPOSBTransaction();
So, if unchecked exception (NPE for example) is thrown in this method and not caught - it's ultimately caught by container due to EJB proxy wrapping the call above. In this case transaction only could be rolled back.
Adding a call to a method of the same bean in your method (without using #EJB reference), does not change that:
#Override
public void doPOSBTransaction() {
try {
Config config4 = getConfig(4);
iConfigBean.create(config4);
if (true) {
newMethod();
}
} catch (Exception e) {
e.printStackTrace();
System.out.println("--POSB Exception--");
}
if (true) {
newMethod();
}
}
private void newMethod(){
throw new RuntimeException();
}
You can easily check that commit/rollback behaviour is just the same in this case, no matter that a method is added to call stack.
So the important thing you have to remember is that all container tricks work only on #EJB calls. So, for example, it's pointless to place transactional annotation on a private method - it won't be used ever.
Another important point is about checked exceptions. By default these do not cause transaction rollback indeed. But it's still possible to annotate your checked exception like below to make it rollback ongoing transaction:
#ApplicationException(rollback = true)

MQ Queue transaction not rolled back in a 2 phase transaction

I have an EJB timer (EJB 2.1) which has bean managed transaction.
The timer code calls a business method which deals with 2 resources in a single transaction. One is database and other one is MQ queue server.
Application server used is Websphere Application Server 7 (WAS). In order to ensure consistency across 2 resources (database and queue manager), we have enabled the option to support 2 phase commit in WAS. This is to ensure that in case of any exception during database operation, message posted in queue is rolled back along with database rollback and vice versa.
Below is the flow explained:
When timeout occurs in Timer code, startProcess() in DirectProcessor is called which is our business method. This method has a try block within which there is a method call to createPostXMLMessage() in the same class. This in turn has a call to another method postMessage() in class PostMsg.
The issue is when we encounter any database exception in createPostXMLMessage() method, the message posted earlier does not roll back although database part is successfully rolled back. Please help.
In ejb-jar.xml
<session id="Transmit">
<ejb-name>Transmit</ejb-name>
<home>com.TransmitHome</home>
<remote>com.Transmit</remote>
<ejb-class>com.TransmitBean</ejb-class>
<session-type>Stateless</session-type>
<transaction-type>Bean</transaction-type>
</session>
public class TransmitBean implements javax.ejb.SessionBean, javax.ejb.TimedObject {
public void ejbTimeout(Timer arg0) {
....
new DIRECTProcessor().startProcess(mySessionCtx);
}
}
public class DIRECTProcessor {
public String startProcess(javax.ejb.SessionContext mySessionCtx) {
....
UserTransaction ut= null;
ut = mySessionCtx.getUserTransaction();
try {
ut.begin();
createPostXMLMessage(interfaceObj, btch_id, dpId, errInd);
ut.commit();
}
catch (Exception e) {
ut.rollback();
ut=null;
}
}
public void createPostXMLMessage(ArrayList<InstrInterface> arr_instrObj, String batchId, String dpId,int errInd) throws Exception {
...
PostMsg pm = new PostMsg();
try {
pm.postMessage( q_name, final_msg.toString());
// database update operations using jdbc
}
catch (Exception e) {
throw e;
}
}
}
public class PostMsg {
public String postMessage(String qName, String message) throws Exception {
QueueConnectionFactory qcf = null;
Queue que = null;
QueueSession qSess = null;
QueueConnection qConn = null;
QueueSender qSender = null;
que = ServiceLocator.getInstance().getQ(qName);
try {
qConn = (QueueConnection) qcf.createQueueConnection(
Constants.QCONN_USER, Constants.QCONN_PSWD);
qSess = qConn.createQueueSession(true, Session.AUTO_ACKNOWLEDGE);
qSender = qSess.createSender(que);
TextMessage txt = qSess.createTextMessage();
txt.setJMSDestination(que);
txt.setText(message);
qSender.send(txt);
} catch (Exception e) {
retval = Constants.ERROR;
e.printStackTrace();
throw e;
} finally {
closeQSender(qSender);
closeQSession(qSess);
closeQConn(qConn);
}
return retval;
}
}

ThreadLocal and #Aspect annotation

I am using #Aspect to implement a retry logic(max_retries = 5) for database stale connection problems.In this Advice I have a ThreadLocal object which keep tracks of how many times logic has retried to get connection and it gets incremented whenever it cannot get connection so to avoid unlimited retries for stale connection issue, maximum number of retries is 5(constant).
But the problem I have is , in this #Aspect java class ThreadLocal never gets incremented and this is causing endlees loop in the code, which of course should not retry after maximun number of retries, but never reach that count and does not break out of while loop.
Please let me know if anybody had this problem with #Aspect and ThreadLcal object.
I will be happy to share the code.
private static ThreadLocal<Integer> retryCounter= new ThreadLocal<Integer>() {};
private static final String STALE_CONNECTION_EXCEPTION = "com.ibm.websphere.ce.cm.StaleConnectionException";
#Around("service")
public Object retryConnection(ProceedingJoinPoint pjp) throws Throwable {
if (staleConnectionException == null) {
return pjp.proceed();
}
Throwable exception = null;
retryCounter.set(new Integer(0));
while ( retryCounter.get() < MAX_TRIES) {
try {
return pjp.proceed();
}
catch (AppDataException he) {
exception = retry(he.getCause());
}
catch (NestedRuntimeException e) {
exception = retry(e);
}
}
if (exception != null) {
Logs.error("Stale connection exception occurred, no more retries left", this.getClass(), null);
logException(pjp, exception);
throw new AppDataException(exception);
}
return null;
}
private Throwable retry(Throwable e) throws Throwable {
if (e instanceof NestedRuntimeException && ((NestedRuntimeException)e).contains(staleConnectionException)) {
retryCounter.set(retryCounter.get()+1);
LogUtils.log("Stale connection exception occurred, retrying " + retryCounter.get() + " of " + MAX_TRIES, this.getClass());
return e;
}
else {
throw e;
}
}

As mentioned in the comments, not sure why you are using a thread local... but given that you are, what might be causing the infinite loop is recursive use of this aspect. Run it through a debugger or profile it to see if you are hitting the same aspect in a nested fashion.

To be honest, looking at your code, I think you would be better off not doing this at all, but rather just configure connection testing in your connection pool (assuming you are using one): http://pic.dhe.ibm.com/infocenter/wasinfo/v6r1/index.jsp?topic=/com.ibm.websphere.nd.multiplatform.doc/info/ae/ae/tdat_pretestconn.html

Block "finally" in a method that returns a value

I have a method, that connects to mail server, gets all the messages and returns these messages in an Array.
So this looks like this (pseudocode):
public Message[] getMessages() throws Exception {
try{
//Connection to mail server, getting all messages and putting them to an array
return Message[];
} finally {
CloseConnectionToMailServer(); //I don't need it anymore, I just need messages
}
}
I can put "return" instruction to "finally" block, but this disable potential Exception.
If I leave it as it is now, "return" can never be reached.
I think you caught the problem I ran at. How can I get all the messages I need, return an array with these messages and close connection to server in a delicate (in even "best practices") way?
Thank you in advance.

Your method is just fine. Even if you return from a try block finally block will be executed.
And your method must return a value :
public Message[] getMessages() throws Exception {
try{
//Connection to mail server, getting all messages and putting them to an array
return Message[];
} finally {
CloseConnectionToMailServer(); //I don't need it anymore, I just need messages
}
return null;
}

The 'standard' version (that I've seen) is
try {
doStuff()
} catch (Exception e) {
throw e;
} finally {
closeConnections();
}
return stuff;
I see no reason that shouldn't work for your code.
As a side note, if your code is a 'returns data' thing, I'd generally think it easier to make it a 'public Message[] getStuff() throws SQLException', then let the calling class handle the errors.

Why not this:
public Message[] getMessages() throws Exception {
Message = null;
try{
//Connection to mail server, getting all messages and putting them to an array
Message = Messages;
} finally {
CloseConnectionToMailServer(); //I don't need it anymore, I just need messages
return Message;
}
}