I got a little problem. I want to use hibernate in an eclipse rcp. (i'm new to osgi and eclipse rcp). So I added the jar into the plugin-project folder and the build path and the bundle build path, but when I try to use hibernate from my bundle, it crashes with a ClassNotFoundException.
What is the proper way to do this?
Pls look at eclipse buddy policy. This might help you if you are facing class not getting loaded because of osgi classloading.
Hibernate, and many other classic Java programs (ab)use dynamic class loading to to connect the different parts. They classes they use are read from a file and then loaded with Class.forName. This is fundamentally not-modular since these classes are by definition implementation classes, which should be hidden.
Since OSGi is a modularity framework it puts fences around a module (a bundle) and refuses to load anything that is not properly exported and imported. So if Hibernate does its Class.forName it will run right into this fence, as it should be to get the advantages of modularity.
Eclipse Buddy policy is like a huge hole in this fence, moving things back tot he bad old classpath: linear search. With a buddy policy, Eclipse will just start searching if there is a class somewhere that has that name. Since this ignores versions, you can no longer rely on proper version handling. The good news is that it works most of the time. The bad news is that you loose privacy and when it does not work you get weird errors.
With Hibernate, only solution is to not use the text file setup but use the API and give Hibernate the actual classes. In those cases Hibernate will use the class loader of those classes and that works. In OSGi, as long as you follow the Java language rules there are no problems.
To handle the kind of problems that class loading hacks address OSGi uses services.
Related
we have some dependent/common jars of the plugin which we are currently placing in .lib of ContentNavigator application and referring the same in build.xml of ContentNavigator. while we placed the jars in local and tried to give the local path in build.xml it didn't worked out.Can anyone suggest what is the recommended way of doing it?
I've applied the following approaches:
Embed/extract all the content(.class files) of the dependency-jars within the navigator plugin. While the upside is that you have a nice bundle containing all your dependency-classes, it might cause some problems with signed jar's. Or on files that are duplicate amongst your dependencies.
Make use of the "Shared Library" concept. You basically "attach" jar's to the classloader of your server/JVM, Application(ear) or module(war). In your case you would probably attach the shared-library to the navigator.ear, allowing all plugins to access the dependencies you register as a sharedlibrary. One huge downside is (in my experience) that you need to reboot websphere every time you update one of the library-jars.
A third option is to move the functionality out of your ICN Plugin, and let another EAR/EJB do the work (and reference to it from the plugin using a jndi lookup).
I personally prefer option 3 because it's the cleanest way to bundle your functionality&dependencies in an EAR. But option 2 will be a good call when libraries are truely common and won't be updated often.
p.s. In your question you mention the build aspect of your software as well (e.g. "how to correctly reference the dependencies"). You might want to look into the concepts of "dependency management" (using Ant, IVY is a good choice, but i would suggest moving to Maven, or Gradle)
Considering that I am developing an end-user software program (as an uberjar) I am wondering what my options are to make it possible for the user to download a plugin and load that during runtime.
The plugin(s) should come compiled and without source code, so sth. like load is not an option.
What existing libraries (or ways of Java...?) exist to build this on?
EDIT: If you are not sure I would also be satisfied with a way that costs a reboot/-start of the main-program. However, what is important is that the source-code won't be included in any JAR file (neither main application nor plugin-jars, see :omit-source of Leiningen documentation).
To add a jar during runtime, use pomegranate which lets you add a .jar file to the classpath. Plugins of your software should be regular Clojure libs that follow certain conventions that you need to establish:
Make them provide (e. g. in an edn) a symbol to an object implementing a constructor/destructor mechanism such as the Lifecycle protocol in Stuart Sierras component library. In runtime, require and resolve that symbol, start the resulting object and hand it over to rest your programs plugin coordination facilities.
Provide a public API in your program that allows the plugins to interact with it in ways that you coordinate asynchronously e. g. with clojure.core.async (don't let one plugin block the entire program).
Make sure that the plugins have a coordinated way to expose their functionality to each other only if they desire so to enable a high degree of modularity among your plugins. Make sure that your plugin loader is capable of detecting dependencies among plugins and is capable of loading and unloading them in the right order.
I've not tried it myself, but you should in theory be able to get OSGi to work with Clojure.
There's a Clojure / OSGi integration library here:
https://github.com/aav/clojure.osgi
If I were to attempt to role my own solution, I would try using tools.namespace to load and unload plugins. I'm not entirely sure it will work, but it's certainly in the right direction. I think one key piece is that the plugin jars will have to be "installed" in a location that's already on the classpath.
Again, this is only the start of one possible solution. I haven't tried doing this.
We have a J2EE application that we deploy to eg. tomcat. We use MagicDraw to model and generate our modelcode. We are currently looking at alternatives to MagicDraw.
I have previously used EMF:
http://www.eclipse.org/modeling/emf/
but that was inside an RCP application (handling dependencies through P2, maven/tycho).
Just a quick glance at the mvnrepository does not give too many results (of course we could upload necessary dependencies manually to our own )
http://mvnrepository.com/search.html?query=emf
How well does EMF work in a non RCP/OSGi application and are there any examples out there to get started?
A few resources I found:
http://www.fosslc.org/drupal/content/emf-large-scale-modeling-outside-eclipse
http://www.eclipsezone.com/eclipse/forums/t57389.html
It's not entirely clear if you are asking for a way to define models outside of an RCP app or if you simply want to work with the generated models.
It's relatively easy to work with emf from a regular Java or Java EE application. If you look for the keyword 'standalone' in the EMF FAQ you will find some useful information.
I have an exported Eclipse Java Project in my server and I want to be able to compile the project and use ASTParser with JDT.
I'm able to compile the project using BatchCompiler, however it runs on console and gives me PrintWriters instead of an array of problems and errors. Also I want to be able to use proposals in Eclipse and BatchCompiler didn't built for this purpose.
Therefore I tried to use ASTParser, it can be used with either char[] or ICompilationUnit. CompletionProposalCollector and org.eclipse.jdt.internal.compiler.Compiler.Compiler needs ICompilationUnit so I have to create an ICompilationUnit which only can be created by an IJavaProject (https://dl.dropboxusercontent.com/u/10773282/2012/eclipse_workspace.pdf) in order to be able to use these features.
It seems the only way to create IJavaProject is to use ResourcesPlugin.getWorkspace(), however it returns java.lang.IllegalStateException: Workspace is closed. on my computer and it seems the reason is that the program that I coded is not an Eclipse plug-in.
Is there any way to create IJavaProject without Eclipse environment?
From the comments, it looks like you are trying to do more than just parsing, you actually want to get some form of content assist.
I'm afraid that you're asking for too much. There is no simple way to get the power and flexibility of JDT outside of a running Eclipse instance (believe me, I've tried). There's no simple way, but if you are brave and strong willed, you can one of try following:
Run a headless Eclipse on your server that works on top of an actual workspace. This would be the easiest to implement, but would be the most resource intensive and least flexible way of doing things.
Use the jdt core jar, and create alternate implementations of the IResource hierarchy, and the parts of JFace that are used by the the parser and the CompletionEngine. This would likely be the most feature-rich way to go, but also the most brittle. I can't guarantee that this would work as you may need to create some very complex stubs for internal Eclipse non-API classes.
Avoid the CompletionEngine and the ASTParser entirely and just use the batch compiler. You would then need to provide an alternate implementation of org.eclipse.jdt.internal.compiler.env.INameEnvironment. This implementation would be able to find types, files, and compilation units in your actual project structure. You'd need to reimplement support for content assist, but this would most likely work reasonably well.
I am actually fairly interested in doing something like this (but I lack the time to do it). If you are seriously considering creating a headless JDT that can run on a server, feel free to ask for more information. I am quite familiar with JDT internals.
I've had a similar problem. Here is how to use ASTParser without Eclipse (it just needs the core JDT JAR on the classpath): http://blog.pdark.de/2010/11/05/using-eclipse-to-parse-java-code/
Is there a way within Eclipse (MyEclipse specifically) to have code assist functionality within a JSF (or XHTML, or JSP, etc) file where I am attempting to access managed bean properties?
See section 8.1.2.1.2.2. Content Assist Based on Project Data # http://docs.jboss.org/tools/2.0.0.GA/jsf/en/html/jbds_editors.html for clarification.
The docs you referenced are a perfect way to achieve way you need. Contrary to what its name may suggest, JBossTools is universally useable without the need to deploy to JBoss or otherwise have any JBoss specific things in your code.
The only thing is that MyEclipse, being a massively modified Eclipse, will probably not work together with JBossTools (but actually it is supposed to offer exactly this kind of functionality already).