/**
* Deletes a topic, including all of its messages and TopicUsers
*
* @param topic The topic to delete
* @param userRequestingDeletion The user who requested the topic be deleted
* @throws AccessDeniedException
*/
public void deleteTopic(JMSTopic topic, JMSUser userRequestingDeletion)
throws AccessDeniedException {
if (userRequestingDeletion.equals(topic.getOwner())) {
// If the topic does not contain null fields
if (isValidTopic(topic)) {
try {
Transaction transaction = TransactionHelper.getTransaction(10000l);
space.takeIfExists(topic, transaction, 3000l);
deleteAllTopicUsers(topic, transaction);
MessageService.getMessageService().deleteAllTopicMessages(topic, transaction);
// Writes a JMSTopicDeleted object so listeners know the
// topic
// has been removed
space.write(new JMSTopicDeleted(topic), transaction, 1000l * 60l);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
}
} else {
System.err.println(
"Attempted to delete topic with on or more null fields. "
+ "Due to how JavaSpaces work, this will delete one at random and is not allowed.");
}
} else {
throw new AccessDeniedException("Only the topic's owner can delete the topic");
}
}
/**
* Writes a topic to the JavaSpace
*
* @param topic
* @throws Exception
*/
public Lease createTopic(JMSTopic topic)
throws DuplicateEntryException, InvalidAttributeValueException, RemoteException,
TransactionException {
Transaction transaction = TransactionHelper.getTransaction(3000);
Lease lease = null;
try {
// If the topic is valid (non-null name, base name, and ID)
if (isValidTopic(topic)) {
// If the topic does not already exist in the space
if (!topicExistsInSpace(topic, transaction)) {
// Write it to the space and commit the transaction
lease = space.write(topic, transaction, Lease.FOREVER);
transaction.commit();
} else {
// Otherwise it's a duplicate, so throw an exception
throw new DuplicateEntryException(
"Failed to create topic. Topic baseName or id matches with an existing topic.");
}
} else {
// Otherwise the Topic object is invalid, so throw an exception
throw new InvalidAttributeValueException(
"Topic being creates is invalid (one or more fields null)");
}
} catch (DuplicateEntryException
| InvalidAttributeValueException
| RemoteException
| TransactionException e) {
// If anything in the try block throws an error, abort the
// transaction before rethrowing the error
if (transaction != null) {
try {
transaction.abort();
} catch (Exception e1) {
System.err.println("Failed to abort transaction");
e1.printStackTrace();
}
}
throw e;
}
return lease;
}
/**
* Removes a given user from a given topic
*
* @param topic The topic to remove the user from
* @param user The user to remove from the topic
*/
public void removeTopicUser(JMSTopic topic, JMSUser user) {
try {
Transaction transaction = TransactionHelper.getTransaction();
boolean removed = false;
JMSTopicUser template = new JMSTopicUser(topic, user);
// If the space is in a bad state and has duplicate users in a
// topic, this while loop ensures they are all removed
while (space.takeIfExists(template, transaction, 1000) != null) {
removed = true;
}
// Put a JMSTopicUserRemoved object in the space so listeners can
// pick them up and remove them from other user's lists
if (removed) {
JMSTopicUserRemoved removedTopicUser =
new JMSTopicUserRemoved(template.getTopic(), template.getUser());
// Writes the JMSTopicUserRemoved with a 60 second lease, so
// listeners have 60 seconds to act on it
space.write(removedTopicUser, transaction, 1000l * 60l);
}
transaction.commit();
} catch (RemoteException
| UnusableEntryException
| TransactionException
| InterruptedException e) {
System.err.println(
"Failed to remove user from topic. "
+ "User ID: '"
+ user.getId().toString()
+ "' && Topic ID: '"
+ topic.getId().toString()
+ "'");
e.printStackTrace();
}
}
/**
* Adds a given user to a given topic.
*
* @param topic The topic to add the user to
* @param user The user to add to the topic
*/
public Lease addTopicUser(JMSTopic topic, JMSUser user) {
JMSTopicUser topicUser = new JMSTopicUser(topic, user);
Lease lease = null;
try {
Transaction transaction = TransactionHelper.getTransaction();
// Only add the TopicUser if it isn't already in there...
if (space.readIfExists(topicUser, transaction, 1000) == null) {
lease = space.write(topicUser, transaction, Lease.FOREVER);
}
transaction.commit();
} catch (RemoteException
| UnusableEntryException
| TransactionException
| InterruptedException e) {
System.err.println("Failed to add user to topic");
e.printStackTrace();
}
return lease;
}