I am cleaning up the DataReaders in an old .NET 1.1 project that I inherited.
The previous developer coded the data-access-layer in such a way that most of the DAL methods returned SqlDataReaders (thus leaving it up to the caller to properly call the .Close() or .Dispose() methods).
I have come across a situation, though, where a caller is not catching the returned SqlDataReader (and therefore is not disposing of it properly). See the code below:
Data Access Method:
Public Shared Function UpdateData() As SqlDataReader
...
drSQL = cmdSQL.ExecuteReader(CommandBehavior.CloseConnection)
Return drSQL
End Function
Calling code:
...
DataAccessLayer.UpdateData()
...
As you can see, the calling method does not receive/catch the returned SqlDataReader. So what happens? Is that SqlDataReader still out there and open? Or does it automatically get garbage collected since nothing is addressing it?
I couldn't think of a way to debug and test this. If anybody has any ideas or suggestions that would be great.
i believe that it will get closed but not until the garbage-collector gets 'round to it, which may not be for a very long time...
Related
Firstly i would like to apologize if i could not find anything about what i would like to describe that really solved my problems. This does not mean that i fully searched in the site. Although i have been spending too much time (days). I am also new on here (in the sense that i never wrote/replied to SO users). And i am sorry for my possible english errors.
I have to say i am new to Java EE.
I am working on WildFly 14, using MySQL.
I am now focusing on a JPA problem.
I have a uniqueness constraint. I am doing tests and while performing the uniqueness violation test, from the data source level i get a MySQLIntegrityConstraintViolationException, and that's ok. I have the problem in that the persist() method does not let me catch the exception (i even put Throwable in the clause, but nothing..). I strongly, strictly, need to catch that, in order to manage a crucial procedure (that, indirectly contains the call to .remove()) in my work's code.
By the way, trying to write that exception, the system does not show me the window of the suggested classes/annotations/etc, suggesting me just to create the class "MySQLIntegrityConstraintViolationException". Doesn't working on WildFly, using MySQL, suffice, for having the suggestions?
Not finding the solution, i decided to change: instead of using persist(), i decided to use .createNativeQuery() in which i put as parameter a String describing an insertion in the db. It seems working. Indeed it works (signals uniqueness violation (ok!), does not execute the TRY block code (ok!) and goes into CATCH block (ok!)). But, again, the exception/error is not clear.
Also, when in the code i enter the piece of code that is in charge of managing the catching and then executing what's inside (and i have a .remove(), inside), it raises the exception:
"Transaction is required to perform this operation (either use a transaction or extended persistence context)" --> this referring to my entityManager.remove() execution..
Now i cannot understand.. should not JPA/JTA manage automatically the transactions?
Moreover, trying, later, to put entityManager.getTransaction().begin() (and commit()), it gives me the problem of having tried to manage manually transactions when instead i couldn't.. seems an endless loop..
[edit]: i am working in CMT context, so i am allowed to work with just EntityManager and EntityManagerFactory. I have tried with entityManager.getTransaction().begin() and entityManager.getTransaction().commit() and it hasn't worked.
[edit']: .getTransaction (EntityTransaction object) cannot be used in CMT context, for this reason that didn't work.
[edit'']: i have solved the transaction issue, by means of the transaction management suited for the CMT context: JTA + CMT requires us to manage the transactions with a TRY-CATCH-FINALLY block, in whose TRY body it is needed to put the operation we want to perform on the database and in whose FINALLY body it is needed to put the EntityManager object closing (em.close()). Though, as explained above, i have used em.createNativeQuery(), that, when failing, throws catchable (catchable in my app) exceptions; i would really need to do a roll-back (usage of .createNativeQuery() is temporary) in my work code and use the .persist() method, so i need to know what to do in order to be able to catch that MySQLIntegrityConstraintViolationException.
Thanks so much!
IT SEEMS i have solved the problem.
Rolling back to the use of .persist() (so, discarding createNativeQuery()), putting em.flush() JUST AFTER em.persist(my_entity_object) has helped me, in that, once the uniqueness constraint is violated (see above), the raised exception is now catchable. With the catchable exception, I can now do as described at the beginning of the post.
WARNING: I remind you of the fact that i am new to JavaEE-JPA-JTA. I have been "lucky" because, since my lack of knowledge, i put that instruction (em.flush()) by taking a guess (i don't know how i could think of that). Hence, I would not be able to explain the behaviour; I would appreciate, though, any explanation of what could have happen, of how and when the method flush() is used, and so on and so forth..
Thanks!
If I have a function call that returns true or false as the condition of an if statement, do I have to worry about Swift forking my code for efficiency?
For example,
if (resourceIsAvailable()) { //execute code }
If checking for the resource is computationally expensive, will Xcode wait or attempt to continue on with the code?
Is this worth using a completion handler?
What if the resource check must make a database call?
Good question.
First off... can a function be used? Absolutely.
Second... should it be used?
A lot of that depends on the implementation of the function. If the function is known (to the person who wrote it) to take a long time to complete then I would expect that person to deal with that accordingly.
Thankfully with a lot of iOS things like that are taken out of the hands of the developer (mostly). CoreData and Network requests normally come with a completion handler. So any function that uses them would also need to be async and have a completion handler.
There is no fixed rule for this. My best advice would be...
If you can see the implementation of the function then try to work out what it’s doing.
If you can’t then give it a go. You could even use the time profiler in Xcode profiler to determine how long it is taking to complete.
The worst that could happen is you find it is slow and then change it for something else.
So the issue I'm having only recently started after an update to the Lync client somewhere around version 15.0.4849.1000. The issue revolves around app sharing conferences, which I have working fine still in 2016 SFB and anything prior to 15.0.4849.1000.
The core issue as far as I can tell deals with Modality.BeginConnect, the passed in callback does not get called. Although, I have had it get called when I'm debugging, stepping through the code and hitting breakpoints, etc. So that leads me to think that normally maybe something's not getting initialized in time, or some sort of race condition, but I haven't been able to pin down exactly what makes it function correctly in that case.
EDIT: I just realized another exception occurs during the call to BeginConnect:
A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in Microsoft.Lync.Model.dll
Additional information: Exception from HRESULT: 0x80F10083
And that HRESULT translates to: "The operation is disabled by capability". What in the world does that mean?
The odd thing is (or seems odd to me) that even though the callback is never called, I do receive a ModalityStateChanged event for ModalityState.Connected...
So if you have any ideas what would perhaps cause that, please share!
I don't think these this is related, but a call to this:
m_aeConversationWnd = AutomationElement.FromHandle(m_ConversationWindow.Handle);
shortly before calling BeginConnect, fails with the exception:
A first chance exception of type 'System.ArgumentException' occurred in UIAutomationClientsideProviders.dll
Additional information: Value does not fall within the expected range.
I have inherited a perl project that I am having a problem testing. There are existing tests, and one of them uses the Test::MockObject->fake_module function. This test passes now. However, if I add a use (or use_ok) for an additional testing module (which also works ok in different tests), I am getting the following:
No mocked subs for loaded module 'IO::File'
In the test in question we have this:
my $io_file_mock = Test::MockObject->new();
$io_file_mock->set_isa('IO::File', 'IO::Handle');
$io_file_mock->set_true('flush', 'print');
$io_file_mock->fake_module('IO::File');
$io_file_mock->fake_new('IO::File');
I see in the documentation for MockObject->fake_module that this is written:
If you use fake_module() to mock a module that already exists in memory -- one you've loaded elsewhere perhaps, but do not pass any subroutines to mock, this method will throw an exception. This is because if you call the constructor later on, you probably won't get a mock object back and you'll be confused.
Not sure I understand this message and how I can make my test work.
Can anyone please help me?
Thanks
Solved in the comments:
I was able to solve my problem by putting the above code in a separate BEGIN block before the BEGIN block that calls my use_ok calls. Is there any problem with that? - Mark
A BEGIN code block is executed as soon as possible, that is, the moment it is completely defined, even before the rest of the containing file (or string) is parsed.
If the use_ok method that was failing is in a BEGIN block and it depended other variables, then those dependent variables would need to be initialized in a BEGIN block as well or they would be temporarily undef when use_ok was called.
For more information read: BEGIN, UNITCHECK, CHECK, INIT and END
I am trying to write unit tests for a bit of code involving Events. Since I need to raise an event at will, I've decided to rely upon RhinoMocks to do so for me, and then make sure that the results of the events being raised are as expected (when they click a button, values should change in a predictable manner, in this example, the height of the object should decrease)
So, I do a bit of research and realize I need an Event Raiser for the event in question. Then it's as simple as calling eventraiser.Raise(); and we're good.
The code for obtaining an event raiser I've written as is follows (written in C#) (more or less copied straight off the net)
using (mocks.Record())
{
MyControl testing = mocks.DynamicMock<MyControl>();
testing.Controls.Find("MainLabel",false)[0].Click += null;
LastCall.IgnoreArguments();
LastCall.Constraints(Rhino.Mocks.Constraints.Is.NotNull());
Raiser1 = LastCall.GetEventRaiser();
}
I then test it as In playback mode.
using (mocks.Playback())
{
MyControl thingy = new MyControl();
int temp=thingy.Size.Height;
Raiser1.Raise();
Assert.Greater(temp, thingy.Size.Height);
}
The problem is, when I run these tests through NUnit, it fails. It throws an exception at the line testing.Controls.Find("MainLabel",false)[0].Click += null; which complains about trying to add null to the event listener. Specifically, "System.NullReferenceException: Object Reference not set to an instance of the Object"
Now, I was under the understanding that any code under the Mocks.Record heading wouldn't actually be called, it would instead create expectations for code calls in the playback. However, this is the second instance where I've had a problem like this (the first problem involved classes/cases that where a lot more complicated) Where it appears in NUnit that the code is actually being called normally instead of creating expectations. I am curious if anyone can point out what I am doing wrong. Or an alternative way to solve the core issue.
I'm not sure, but you might get that behaviour if you haven't made the event virtual in MyControl. If methods, events, or properties aren't virtual, then I don't think DynamicMock can replace their behaviour with recording and playback versions.
Personally, I like to define interfaces for the classes I'm going to mock out and then mock the interface. That way, I'm sure to avoid this kind of problem.