I'm not sure if what I'm asking is possible, but I would like to do the following:
When a file is created in a certain folder (Windows), my program should respond. I'd like to let Windows call a callback method when a file is created.
Another option is of course just use a loop and constantly check if a new file is in the folder, but I'd like to know it instantly, so a callback method would be much more efficient.
Is this possible? The language is not important, although Java is preferred.
With Java nio 2 (available in Java 1.7 +), you can "watch" a directory and get notified when that directory changes.
The method proposed in the tutorial linked above uses the WatchService API.
Commons IO contains a FileAlterationListener wich has a onDirectoryChangemethod. Can be an alternative if Java 1.7 is not available.
If you are not bound to Java, then you could use very convenient FileSystemWatcher in C# or VisualBasic. It will allow you to watch all kinds of events which can occur in folder and it's quite easy to implement it.
Related
I'm trying to read a .qm translation files with Java.
.qm files are binary files. I don't have access to the .ts files.
And I don't find much info on these .qm files.
How are they structured ?
Regards,
There's no documentation that I know of, but if you look at QTranslator::load you should be able to follow the format of the QM file.
You will probably need to reimplement QTranslator in Java, as you need not only the ability to load the files, but also to extract and apply translations in Qt fashion.
As per request of OP:
You could use those files by using the Qt libraries and JNI. By using the translator in a c++ dll you can translate strings easily. However, you cannot extract the files or list the contained translations. But if all you need is the actual translation, this solution should work.
I cannot give a real example, because I only now how it works in theory, I haven't tried it, because it's not trivial. But if you are eager to try it out, the general idea would be:
Create a C++ dll and build it against QtCore. The easiest way is to download Qt from their website qt.io. You can for example create a default library project with QtCreator. Note: Besides Qt5Core.dll, Qt requires other libraries to correctly run. They are all included in the installation, but once you deploy your application, those of course have to be includes as well.
Include JNI to the C++ project and link against it. if you're new to this, here is a nice tutorial: Java Programming Tutorial
Create your wrapper methods. Methods in cpp you can call from java that take java strings, convert them to QString, translate them with QTranslator and convert them back.
Load the library in Java and execute those methods
Important:
First, I don't know how java handles dll dependencies. If you encounter errors while loading the dll, it's probably because dependencies of your dll are not present. Second, Qt typically requires a QCoreApplication running in the main thread for most of it's operations. I tested the translator without such an app, and it worked. So apparently for translations only the app is not required. However, depending on what you do in your dll, I think this is important to know.
If you need more details, feel free to ask.
i need to detect if a class relies on another class programatically,to detect inappropriate intimacy code smell(i want to analyze other java programs ,using my program).Any directions on
how to achieve this will be a great help.
And
How to identify all the objects created in a java program?
How to identify all the called methods in a java program?
Any help would be appreciated.
You might want to use what's already there instead of building something yourself. Especially if you're not very familiar with the internals of Java and the JVM.
Have a look at JDepend: http://clarkware.com/software/JDepend.html
Use a profiler as JConsole or VisualVM. With the use of profilers you can pretty much see everything that happens at runtime.
One way i think of is using logger, Put some log statement in the construct and in the methods you want to monitor. So through logs you can find out the objects created and methods accessed
I have found very useful the ObjectWeb asm-all Java bytecode manipulation and analysis library, also known as asm-all.jar
It allows you to convert any *.jar application into equivalent XML file. You can fully inspect the application structure, change it in the XML format and convert back into *.jar file
In order to use the XML files you'll need to understand what it contains. Oracle's The Java® Virtual Machine Specification is very good reference to start with
BTW: one thing you can do with this tool is to instrument the bytecode so that it creates runtime profiling information - which methods were called and by whom (as suggested by #upog)
Is there any mechanism to get and set the file/directory permissions?
For example, I want to show the permisssions of a file in a shell way:
-rwxr-xr--
Is it possible to do this using Java?
I know that there are some methods in the File class to know if the file canExecute, canRead and canWrite, but AFAIK this info is for the current user only. I need to know the whole octal number, for example 755, so I need to get it from the user, from group and from others.
I know that Java7 brings Posix operations, but how could do this using a smaller JRE?
I would like not to use a command like ls, or chmod.
If you can use external libraries, there are several:
JPosix
Posix for java
jnr-posix
If an entire library seems a hassle, creating a JNI wrapper that calls the lstat C function and returns the access mode takes you about 10 minutes. Here's a tutorial that creates such a wrapper for the isatty and ttyname functions.
As you say, in Java7, the JVM supports it, so you have a guarantee that this can be done portably in all OSs (because the JVM implementation takes care of it). Under Java7, you'd have to use a native library per OS you want to support. This is potentially even dirtier than executing chmod
Eclipse allows to get all references to a function. I'd like to go further and know if anyone knows of a tool or script that would do this recursively ie from a function it would produce the list of different possible function stacks to access to it.
I am looking for this to make sure all the impacts of a change are captured in the spaghetti old legacy code I am looking at the moment. Thanks.
Try eclipse's Call Hierarchy.
It's CTRL-ALT-H on Windows, CTRL-OPTION-H on OS X.
(Hotkeys for eclipse 3.x, I have yet to use eclipse 4)
Its called the Call Hierarchy and you can open it with Ctrl+Alt+H
http://www.javaprogrammingforums.com/java-jdk-ide-tutorials/19-list-shortcuts-key-eclipse.html
I am currently writing a program in JAVA that examines the behavior of external executable. One of the requirements is to observe the file operations of the external executable in real time (check if the executable creates/ deletes/modifies any file). I tried to find a suitable API in java to help me do this though it was not possible to find one. I have found the Class FileAlterationObserver which is not suitable for my program since you have to specify manually all the directories you want to monitor.
I was wondering if any of you knows a good API to use?
Thanks for your time in advance.
Without java, you could use the linux lsof command to list the open files in the system. Alternatively, and with Java, you can use libnotify, but you will need to specify the folders. I can't see any other way of doing this with pure java.
EDIT #Keppil linked you to the file change notification API that looks way more suitable than libjnotify. I wasn't aware it existed!