I want to intercept ClassLoader's loadClass method. In order to show the process of loading class by ClassLoader. But I don't know the working principle of aspectj. It can modify the source code of the JDK?
You could just use a debugger and step through the process in order to understand it.
AspectJ can weave aspects into existing class files during compilation (CTW, compile-time weaving) or during class-loading (LTW, load-time weaving).
LTW does not work for JDK classes because those classes are always loaded before the weaving agent. So you have a bootstrapping problem there.
What you can do, however, is to apply CTW to the class files in e.g. rt.jar from your JRE/JDK distribution, zip the woven class files into another JAR and replace the original one with it. Then if you start the JVM with aspectjrt.jar on the boot classpath, you see the aspects in action. I have done that before and it works. But really, this is not what AspectJ was designed for. But you asked, so I told you. It is a very advanced topic though, and I doubt that it is the road you should take as a complete AspectJ greenhorn - no offense meant.
Update: Because I have been asked this question so often, I created a little demo project showing how to weave aspects into the JRE/JDK. I still do not think it makes sense to use it under normal circumstances, but what the heck: Why do people climb the Mount Everest? Because it exists. ;-)
Related
I have several project setups in very different languages. For example an android project.
Whenever I want to create a new android project I copy that project, rename everything I need to rename and I have a ready to go project with which I start working.
Since this is very time consuming and I am sure this can be automated I thought about creating a tool that does this for me, but then I thought there are probably thousand solutions out there, which solve the exact same problem already, I am just not aware of.
So my question is, do you know of any tools like this? The requirements I see are, that it has to be os, language, IDE independent and it must support a command line interface. Ideally with less setup effort.
You should try Telosys (https://www.telosys.org) a lightweight code generator that is able to generate any kind of langage with any kind of framework.
This tool is quite simple, free and Open Source.
It provides a Command Line Interface (so it can be used with any environment/IDE).
It is usualy used to boostrap a project and to generated all the repetitive code (CRUD, Controllers, unit tests, HTML pages, etc)
See also :
https://modeling-languages.com/telosys-tools-the-concept-of-lightweight-model-for-code-generation/
https://www.slideshare.net/lguerin/telosys-project-booster-paris-open-source-summit-2019
I am using the autoreload-server example which is working great for reloading namespaces on changes to the .clj files using ns-tracker.
https://github.com/pedestal/samples/blob/master/auto-reload-server/dev/dev.clj
However, it is not picking up changes to enlive templates in the resources/public dir. I've added my template paths to the vector in defn watch:
`([] (watch ["src" "resources" "resources/public" "public"]))`
As well as this in the namespaces that use enlive deftemplate:
(net.cgrand.reload/auto-reload *ns*)
However this does not work. My assumption is ns-tracker only works for clj files, and that I am using the enlive reload feature incorrectly.
Is anyone using enlive and have this figured out, or have any ideas to try?
I was hoping that Enlive Issue #6: Auto-reloading of templates was solved in early December 2013 in version 1.1.5 by this commit. But, in my testing, I cannot confirm that it is a fix. I might be doing something wrong.
A note: the example you cite, I think, dates from the pre-0.2.0 tooling changes for Pedestal. I could be wrong, but I think you'd be better off following the current documentation, not that sample file.
Pedestal's 'hello world' service app's key suggestions (which may change) are:
Use ns-tracker to figure out which namespaces to reload.
add :resource-paths ["config", "resources"] to project.clj so that Enlive can find your static HTML resources.
These steps are not enough to cause a change to a resource to trigger a reload, because ns-tracker will not pay attention to :resource-paths. Here are the details:
ns-tracker relies on clojure.tools.namespace.find/find-clojure-sources-in-dir.
clojure.tools.namespace.find/find-clojure-sources-in-dir
When you think about it, you can see why ns-tracker doesn't pick up resources; they aren't Clojure namespaces. In my opinion, this is coherent design decision, given the name, ns-tracker.
Still, pragmatically, it is clear that from the point of view of Pedestal that we do want to reload when a resource changes.
Now, let me add another thing. From a tooling perspective, let's say you do setup a watch on the resources directory. Even so, it is not easy to identify, in a granular fashion, which specific Clojure namespaces will be impacted. One resource may be used as a defsnippet by multiple deftemplate's. Therefore, one resource change can affect multiple Clojure namespaces. Strings pointing to resources might even be constructed dynamically. So, figuring out the exact minimal set of namespaces to reload may be impossible in the general case.
All of this said, it should be 'easy' and safe enough to reload all Clojure namespaces whenever a resource changes.
So, in summary, I have not solved this problem myself, but hopefully what I've explained above will help move the ball forward.
I could not find a working solution off the shelf, so I ended up writing a small ring wrapper that does the job, see https://github.com/kolov/enlive-reload
I've been looking into using Mercurial for version management and wanted to try it out. I'm planning on doing a project on my own to help me learn C++ coming from Java and thought it would be a good idea to try version management with it. It would probably be a game or some sort of simple application, not sure with a GUI or not.
The problem is I don't know much about version management. When in a project is a good time to make the repository? Should I just do it right away? How often should I make commits?
I'll be using Netbeans for my development since it seems to be pretty good, also has Mercurial controls built in, but what should I set in the .hgignore for my project? I assume the repository would be the whole folder Netbeans creates but what should I make it ignore?
Bonus questions: I'll be using Bitbucket for hosting/backup, should I make the project public? Why/why not? Also would that make it open source? Should I bother with attaching a license? Because I have no idea how the licenses work and such. Then again, I sincerely doubt I'll be making anything anyone will want to copy too badly.
On repos:
You should use a VCS repository as soon as possible. Not only does it allow for off-site backups, but it allows you to track changes. To find out when a bug was introduced.
Having a VCS, particularly a distributed VCS like Mercurial, will change the way you code. You won't have to be careful not to break things, because you always have the old version that you can revert to. If, after a few weeks or months, you decide that a particular course of development was a bad idea, you can rewind all the way back to some prior point.
You should generally commit either every day, or every time you finish a task. Like, you might have a 4-hour task of "write this class and get it working". You commit after that. When you're done for the day, you commit. I wouldn't suggest committing in a non-compiling state, though, so you should try to stop for the day only when everything still builds.
As for ignoring, you should ignore things you don't intend to commit. Things that you wouldn't want in the repo. Generated files, temporary files, the stuff that you wouldn't need.
What should be in the repo is 100% of the information necessary to build the project from scratch (minus external dependencies).
On licenses:
I would say that it is very rude to put up a public repository without some kind of license attached. Without a license, that means that anyone even pulling from the repo (which is what you're inviting by making it public) is a violation of your copyright without direct, explicit permission from you.
So either look at how copyright works and pick a license to release your stuff under, or keep your repos private.
The instant you conceive of it, usually. There is no penalty for putting everything you have into a VCS right away, and who knows, you may want that super-duper prototype version later on down the road. Unless you're going to be checking in large media files (don't), my answer is: right now.
As for how often to commit, that's a personal preference. I use git, and as far as I'm concerned there is no problem with checking in every time you make some unit of significant change. The more snapshots along the way you have, the easier it becomes to track down bugs later on.
Your .hgignore is up to you. You need to decide what to version and what not to. As a rule of thumb, any files generated during compilation probably shouldn't be checked in.
Also, if you release it to the public, please attach a license. It doesn't matter what it is, but it makes all the bosses and lawyers in the world happy when they know what they can and can't do with your code. Finally, please don't release something to the public unless you think someone else will benefit from it. The internet already suffers from information overload.
Commit early, and commit often.
With distributed VCS like hg or git there's really no reason not to start a repo before you even write any code. If you decide to scrap your project, you can always delete your repo before you post it to whatever hosting site you're using. The more often you commit, the easier it will be to hone in on where you messed up later on (you will).
Stuff to put in your ignore file would be build files and anything that your IDE generates periodically, like user preferences and tag caches. You don't want to foist your preferences on someone else and you don't want to have to create a commit every time you change the position of a window in the IDE. What's in the repo should be the minimum that someone would need to be able to work on your project.
If you're just doing a small project to learn, then I wouldn't worry about licenses or having a private repo. You can always add a license later. Alternatively, just pick a permissive license and go with it.
Based on my experience with git, I would recommend the following:
Create repository along with project.
Commit as often as you can with detailed comments
When you want to test a new idea - create a branch. If the idea is successful, merge your code to the master branch. If the idea is not successful, you can just discard the branch. Probably this is the most important idea.
Put the names of object files, executables and editor backup files in the ignore list.
Does someone know if there is a way to pack everything-application related into one (single) exe-file?
My product is fully written in C++, has a lot of external plugins (dll) and some external data packages. It should be accessible using the network and without installation (launch in one click).
Are there some tools to make something like virtual filesystem and unpack everything application-related to memory?
Or probably I have to somehow (manually) integrate all the dlls and the data? Is this possible?
Thank you
Try an .msi file, or ClickOnce deployment (assuming Windows, assuming at least VS 2005).
Edit: Based on a comment below, I don't know in general if you can do exactly what you are asking with an arbitary set of DLLs. You can include, say, Microsoft Foundation Classes statically rather than dynamically. But the distributor of a DLL may not want to allow complete incorporation into your code. Even if you could, you might be running against license agreements and the like.
Not sure if that's what you want but UPX is made to generate a single exe from an application made of several ones : http://upx.sourceforge.net/
However if you want a virtual folder system, maybe you just need to use PhysicsFS ? http://icculus.org/physfs/
Anyway your question is not really clear...
Let me first say I am aware of this faq for Mach-II, which discusses using application specific mappings as a third option when:
locating the framework in the server root is not possible and
creating a server wide mapping to the Mach-II framework directory is impossible
Using application specific mappings would also work for other ColdFusion frameworks with similar requirements (ColdSpring). Here is my issue however: my (I should say "their") production servers are all running ColdFusion MX7, and application specific mappings were introduced in ColdFusion 8. I most likely will be unable to do option 1 or 2 because they involve creating server wide changes that could conflict with other applications (I don't have a final word on this but I am preparing for that to be the case).
That said, is there anybody out there who was in similar bind and has done an option 4, in any ColdFusion version, or with any similar framework? The only option 4 I can think of is modifying the entire framework to change this hardcoded path, and even if that worked it would be time consuming and risky. I'm fairly sure that if there was a simple modification or other simple solution it would already be included in the framework (maybe it's included in version 1.8 of Mach-II and I don't know about it yet).
Any thoughts on solving this problem or even unorthodox setups with libraries that have specific path requirements would be appreciated. Any thoughts from Team Mach-II would especially appreciated...we're on the same team here Matt! ;-)
EDIT
Apparently, the ColdBox framework includes a refactor.xml ANT task which includes a target that refactors the ColdBox code to use a different absolute path as a base along with several other useful refactoring targets. So problem solved for ColdBox users.
Looking at the build.xml for Mach-II (1.6 and 1.8) I don't see any target in there that would allow me to refactor the code. I thought about creating a feature request ticket for such a task for Mach-II but frankly I don't think creating such an ANT task is a big priority for the MachII team since the need really only relates to either
a) users of ColdFusion versions below 8
b) someone who wants to use multiple Mach-II versions in the same application, a use I doubt they want to support
The ColdSpring code I have doesn't come with any ANT tasks at all, although I do have unit tests, and I bet if I poked around the SVN I'd find a few build scripts.
Using Ant tasks to refactor and retest the code, or the simpler (and sort of cop out) solution of creating a separate ColdFusion instance for the application are the best answers I've been able to come up with. I don't need this application to exist in the shared scope of other applications, so my first solution is going to be to try and get a dedicated CF instance for this application.
I'm also going to look at the ColdBox refactor.xml ANT task however and see if I can modify it to work generically to recognize and refactor CFC references with modified absolute paths. If I complete this task I'll be sure to post the code somewhere and edit create an answer to link to it. If anybody else wants to take a crack at that or help me out with it feel free.
Until then I'll leave this question open and see if someone comes up with a better solution.
Fusebox is not so strict, I think.
In XML mode (maybe I call this not 100% correcly, just mean using the Application.cfm) it's just proper include in index.cfm, something like:
<cfinclude template="fusebox5/fusebox5.cfm" />
In non-XML mode it will need proper extending in the root Application.cfc:
<cfcomponent extends="path.to.fusebox5.Application" output="false">
All you need is to know the path.
Perhaps you could create a symbolic link and let the operating system resolve the issue for you?
I've been playing with FW/1 lately, and while it may look like you need to add a mapping and extend org.corfield.framework, you can actually move the framework.cfc file into your web root and just extend="framework". It's dead simple, and gets you straight into a great framework with no mess and very little overhead.
It should be as simple as dropping the 'MachII' folder at the root of your domain (i.e. example.com/MachII). No mappings are required to use Mach-II if you just deploy at the root of the domain of your website.
Also:
Please file a ticket for the ANT task you mentioned in your question. Team Mach-II would love to have this issue logged:
Enter a new ticket on the Mach-II Trac
If you want to tackle an ANT task for us, we can get stuff like this incorporated into the builds faster than waiting to for a Team member to work on the ticket. Code submissions from the community are welcome and appreciated.
We don't keep an eye on Stack Overflow very often so we invite you to join our official community group at called "Mach-II for ColdFusion" at Google Groups. The Google Group is the best place to ask questions or comments like this if you want feedback from the Team.