Why use link option when import file into eclipse project? - java

I know that there is the option to have links to source code under your src directory instead of having the source code files directly in your Eclipse project.
When is this case i.e. links for source code is best used?
I always found it more convenient to have the source code inside the Eclipse project

I can think of two possible use cases for this.
The first would be if you want to keep your source and IDE meta-data separate. For example it may be that some developers use Eclipse and some IntelliJ. In this case you would probably only want the source of the project to be stored in SCM, as otherwise, one set of developers are going to have to remove meta-data before importing the project. If they just link to the source, they can maintain there own meta-data for there IDE. Obviously this isn't an issue if everyone uses the same IDE.
The second use case would be dependencies. Say for example your working on two different projects A and B where A depends on B. If your not using a dependency management tool or willing to build and import the Jar from B to A each time you modify it, you could link to the source in B instead.
I'm sure there are plenty of other use cases floating around.

In addition to what Kingamajick mentions, you could have a structure that causes overly long path names.
Windows can only handle so much (256 characters? in older versions), and a deep package structure easily breaks that limit.
So, having your classes in a shallow directory near the top allows you to have your workspaces deeper down, and still leaves some room to wiggle.

Other scenarios; You have source code which is common for several OS:es, but the Eclipse projects are specific for each OS.
You can also create a form of linked resources that are relative to an environment variable. I've used that for situations where the version control system (ClearCase) adds user-specific catalognames.

Related

Is there any way to reorder projects in the package/project explorer in Eclipse?

I'm working on source code that is split across several projects with a specifically defined build order. I want to see the projects sorted by the build order so I can always tell which classes can be used in which projects. Does anyone know how to do this in Eclipse Kepler?
If you are not already using working sets in Eclipse, they provide a good way to organize your projects. The organization is single-level, rather than hierarchical, but you can group projects and then quicly select in the project explorer view settings whether you want the working sets to be shown or not. A potentially useful detail is that a project may be contained in multiple working sets, so that you can have multiple grouping criteria at the same time.
In your case, you could define a working set for each phase of your build, prefixing its name with a letter or number that would ensure its presentation in a specific order. Or you could define a working set for each set of projects with the same dependencies.
Alternatively, you might be able to just rename your projects appropriately. In many cases the project name itself is mostly cosmetic, although it is often used as a default in generated files.
In my opinion, however, the easiest way to "tell which classes can be used" is to just configure your project build paths correctly and let the editor do the rest. For me it is more natural not to use a class because it is not proposed for auto-completion or because any such use results in a compiler error, rather than explicitly checking the dependencies each and every time...
IMHO there is no such feature in eclipse. But you can use Resource Tagger plugin or Resource decorator plugin and filter the resources based on different conditions.

GWT refactoring: classes, modules, rename the whole project

I am writing here because of desperation caused by refactoring a GWT project.
My first try:
After I read all the praises of the refactoring tool from Eclipse ( I am using it as IDE) I simply right clicked on a module ( what a fool i was ) and use the refactoring option. My project became unusable.
First Conclusion:
Found out that I need to start with the classes and then go up and refactor a module at a time.
Second try:
Refactored some classes, worked fine until I messed something related to a ui.xml file. Project unusable!
Second Conclusion:
Be careful at the ui.xml files!
Third try:
Went pretty well, but I got ahead of myself and tried to remove some comments or replace class names in comments. Predictable result : project unusable!
Third Conclusion:
Try again!
Forth try:
Fail!
Fifth try:
Fail!
You get the picture.
Can someone experienced with GWT please offer some guidelines about the mystical realm of refactoring?
GWT has some rules based on naming conventions (e.g. the two interfaces for GWT-RPC, the *.ui.xml files and the class that uses them through UiBinder, the files related to ClientBundle or ImageBundle methods, the *.properties files for I18N), so failing to respect them when renaming/moving one class/file will break it.
GWT also sometimes references classes by name in non-Java files (#eval in the *.css of a CssResource, or in *.ui.xml files), non-Java portions of classes (JSNI) or string literals (e.g. in #ProxyForName and #ServiceName). Failing to update them all will break the build.
Because a tool makes it easy to refactor does not mean you should let it do it blindly: it's just a tool, you have to understand what it does and double-check it (hint: check the box in Eclipse that forces a preview before applying the refactoring) so it doesn't do too much or too few.

Is there any guideline of "What to share on Github" regarding RCP developments?

I recently started developing a plugin, which consist of several Eclipse Plugin-Projects. I use Maven/Yycho as a build tool and GitHub as version control system.
Now I was wondering what to push to my GitHub repositories. The POM files and Feature/Updatesites as well? It seems that this stuff is:
very User specific (the path are relative to the file structure on my computer)
do other developers need that stuff or should I give them the freedom of choosing their own build tools?
To clarify, I have right now 6 Eclipse projects:
*.plugin1
*.plugin1.tests
*.plugin2
*.releng
*.feature
*.p2updatesite
Would it be good practise to share everything? From my feeling I would say I will only share plugin1+tests & item # 2 (without the pom files) so that everyone can take care themselves about building.
You don't have to add to your repo:
anything that can easily be regenerated
anything with local paths specific to a user
Regarding building, ideally you should version at least a script able to generate the right pom, in order for a new contributor to be able to get going as fast as possible after cloning it.
If you can have config files with only relative paths (instead of absolute one), then you can include those, for others to use.
See for instance ".classpath and .project - check into version control or not?".

Identical Android apps with different package names

I have two Android apps that are identical except for the package name. This question has been asked before, and the recommendation was to refactor the package name as required, but I do not regard this as satisfactory. To my mind putting all the code in a source library would be preferable, but is there a better solution?
Putting the shared code in a Library Project is the recommended approach. See http://developer.android.com/guide/developing/projects/projects-eclipse.html#SettingUpLibraryProject
I take it the question is "How to I build both apps without duplication?" An easy answer: have your build system perform the duplication and package alteration for you. And one way to accomplish this even if you're used to letting Eclipse or ant handle everything in ways opaque to you:
make a temporary copy of your entire repository, with the original building only one of your apps.
make all the changes to the copy that will cause it to build your second app.
create a single .patch that expresses these changes.
have your build system perform step #1, apply the patch from step #3, and then reinvoke itself in the copy. "have your build system" means, write a script, add a target to a makefile (even if you normally avoid makefiles), add a target to ant, extend Eclipse, whatever.

Using serviceloader on android

I am very new to java and android development and to learn I am trying to start with an application to gather statistics and information like munin does. I am trying to be able to load "plugins" in my application. These plugins are already in the application but I don't want to have to invoke them all separately, but be able to iterate over them. I was trying to use serviceloader but could never get the META-INF/services into my apk. So I am wondering if it is possible to use serviceloader on android
Thanks
EDIT: I am asking about java.util.ServiceLoader, I think it should, but I can't figure out how to get my services folder into META-INF on the apk
There is an open bug report against this issue. See https://code.google.com/p/android/issues/detail?id=59658
The META-INF folder is deliberately excluded from the APK by ApkBuilder; the only comment in ApkBuilder.java is "we need to exclude some other folder (like /META-INF)" but there is no other explanation.
Even after adding META-INF with ant, you will still get in trouble if you want to use Proguard, which refuses to replace the content of META-INF/services/* files or rename them (that's another story, the author wants to keep Proguard agnostic).
However, people using maven may want to check https://github.com/pa314159/maven-android-plugin (the branch named "modified"), that tries to solve both issues. It is a fork from the original "android-maven-plugin" I modified one month ago for my own Android projects.
It also provides a patch for Proguard-4.7
Hope this helps, any feedback is welcome.
I've figured out a solution that may work for some situations. Instead of ServiceLoader, I'm using the org.openide.util.Lookup class / library that comes with NetBeans - it is a superset of ServiceLoader. It does not require NetBeans itself and seems to work ok with Eclipse. It is necessary to replace whatever ServiceLoader functionality you are using in your application with Lookup equivalents, and add the org-openide-util-lookup library. Then, you can just do something like this:
Lookup lookup = new ProxyLookup(Lookup.getDefault(),
Lookups.metaInfServices(myClass.getClassLoader(), "services/"));
And move your ServiceLoader files from META-INF/services/ to services/.
Note that, because of the ProxyLookup, this will continue to work on standard Java environments unchanged (i.e., in those cases it will continue to look in META-INF/services).
Here is a link to the documentation for the library: http://bits.netbeans.org/dev/javadoc/org-openide-util-lookup/org/openide/util/lookup/Lookups.html
UPDATE
After working with this for a couple of days, it seems to function well - I move between environments (standard Java and Android) and it works properly in each location. The primary downside is having to manually copy the files to the /services directory.
It is possible. You may want to check http://developer.android.com/reference/java/util/ServiceLoader.html
ServiceLoader is stuff from the Java language that is not really relevant on Android. I recommend not using it. If you just want to find a list of classes within your .apk to load, there are all kinds of ways to do this -- put in XMl file in res/xml that lists them, use reflection, annotations, etc.

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