I have a plain Java project (not a plugin project) which I want to add to a classpath of a eclipse plugin which I am developing. But in web projects I can add that project as a build path and it works fine. But I tried same thing in eclipse plugin, I am able to compile successfully, but at run time I am getting java.lang.ClassNotFoundException.
I know OSGi quite well and I know how to add OSGi into an classpath (using export-packages) but what I want is to add Standard, non-osgi project into an classpath, so that I wont' get runtime errors. Is there anyway I can achieve this?
I can export project as a jar file or make it as a plugin project and it would work fine. But that's not my option currently because, still that API is in pre-alpha stage, and there would be lot of changes going on. So I am trying to avoid pain of exporting it as jar file everytime. Is there any option for me other than this?
I have a similar situation: I want non-OSGi Maven dependencies integrated into the classpath of my plugin. I succeeded with a roundabout solution, which I think is the best I could get.
I have a build step outside of Eclipse where I copy the class files of the dependency into the plugin's lib folder. The lib folder is specified in MANIFEST.MF as an entry in Bundle-ClassPath and (here comes the hack) as a source folder in build.properties. That was the only way to make the plugin work both when launched from within Eclipse and when exported.
Related
I'm trying to find more information on how eclipse handles Running a project.
I want to understand it more because I have an issue I'm currently having where apache-poi .jar files which have been included into the classpath of my project will work properly when the project is ran through eclipse, but will not be detected when going to the same projects folder and running the main jar file to start the program.
It gives me the error: java.lang.NoClassDefFoundError: org/apache/poi/ss/usermodel/Cell (although sometimes instead of Cell, it's Sheet)
What could I consult to understand what is going on here, and possibly solve this issue?
Your NoClassDefFoundError indicates that the library was not available while running the jar.
This depends upon how you are exporting your project into the jar file.
If you're using eclipse to do so, you can:
Export->Java->Runnable Jar to create a jar that includes its dependencies
Make sure to check Package required libraries into generated JAR.
This will make all your jars (in build path including apache-poi.jar) as a part of the final jar.
It runs from eclipse because libraries are on the build path of the eclipse which makes them available in the classpath.
I have a Java project that depends on a 3-rd party component. This component is available both as a jar and as a Maven/Ant project. One option for me is to simply add the jar as a library. However, I prefer to add the source code into my project since I may need to slightly modify their source code to better suit my needs.
What's the right way to do it in Eclipse?
My main project has a simple structure: src/ and lib/. The external component also has a standard structure: src/, test/, build/, target/, pom.xml, build.xml. So do I need to copy piece by piece (like contents of one src/ into the other src/), in which case what goes where? Or do I somehow copy it all at once? Or smth else?
The best way would be if you use maven on your projet for dependency management. This way, if you have the other projects open in eclipse, your project will resolve them as local projects, but if you don't, maven will try to fetch the jars from the configured nexus repository.
This way, you avoid having to manually configure your Eclipse projects. Maven will be able to configure your project anywhere you want to build it, not having to manually configure dependency resolution.
Import both the projects into eclipse. Add the reference of 3pp jar project to your project as a reference by clicking on Add on build path option. While delivering it as output there will be a dependency to the 3pp jar project. So either deliver it as separate jar and add it to classpath while executing your project else you have to copy the entire source files into your project and deliver it test complete jar.
Making a jar will be handled by eclipse itself.
I am currently using eclipse for working with Java. Additionaly I use git to synchronize my project between my laptop and my desktop PC.
The problem is now the following: I added external JARs to the project (Slick-Util, LWJGL).
But the path to each library is another on each device. So everytime I start working on the other device, I have to change the path to the jar files and the javadocs.
The libraries are all stored in my eclipse workspace. So the libraries and the projects are all in the same folder. And this folder is also commited with git.
Is there a way to change the eclipse settings (or do something else) so I do not have to change the path to the libraries and javadocs everytime?
I already googled and searched for it, but I could not find something about it.
Just don't add the libraries' jars to git. There are multiple build tools for java, which manage dependencies for you - you just state the libraries you're going to use, and the build tool downloads it for you at build time.
I would recommend Gradle, but Maven is also a very popular choice.
In gradle, you would create a file build.gradle, and define your dependencies in it:
apply plugin: 'eclipse'
apply plugin: 'java'
repositories {
mavenCentral()
}
dependencies {
compile 'org.lwjgl.lwjgl:lwjgl:2.9.0'
compile 'org.lwjgl.lwjgl:lwjgl_util:2.9.0'
}
Then you would run gradle eclipse from the command line - that would add the libraries you use to the classpath in eclipse. And when you want to compile and package your project you would run gradle build from the command line. You should read about it if you're going to use it, what I describe may not be exactly what you need.
Also, there are instructions for using LWJGL with maven.
add jar files to a lib folder inside your project like this : D:\Workspace\myproject\lib\your-jar-file.jar
then go to your projects build path select libraries tab and click on add jars and NOT add external jars this way your jar files path will be relative to your project
EDIT :
I highly recommend to use a build tool as Kiril Raychev described.
it will look a bit confusing to start with but after a while and after a normal growth in your application that will lead to using different frameworks, controlling and managing dependencies and their conflicts without a build tool will literally kill you.
You can simply use -f flag on add command.
git add -f test.jar
And, then commit and push to your repo.
Up until now i usually use svn so i'm not entirely sure how it works out in git, but have you tried to store the JARs in the lib folder of the project they are used in? (Eclipse displays the lib folder so you can easiely add them to the buildpath with a right click on the library in the package explorer.)
That way the relative location/path of the libraries to the project should stay the same. Furthermore if you plan to pack the project into a JAR later you ship the libraries inside that JAR without having to worry whether the user of that file even has them on his computer.
PS: Looks like i'm a minute too late. Dave basically said the same thing.
I am working on a Hadoop project in Eclipse that depends on another one of my projects; I've included the other project in my build path, but when I export the dependent project, it only contains the classes from that same project.
Ordinarily, this would not be a problem, as I could just link the other project with the -cp flag, but Hadoop requires you to pass the jar as an argument, meaning that all of my dependencies must be inside that jar.
Is there a way, in Eclipse, to automatically build and include classes from projects that you depend on?
Thanks.
You coud use Ant to automatically build, test and export. It needs some time learning it, but its worth.
There are possible tasks (fileset, zipgroupfileset, copy) to include files, jars (unzipped) or anything into the final jar. By this way you definitly know whats inside your distribution jar and you don't need an eclipe installation running.
I suggest you take a look at maven as a build tool. You define the dependencies and build steps for each of your projects in files called pom files. The maven plugins for Eclipse (the m2e plugins) can take the configuration in the pom file and setup your Eclipse build paths and project description so that you can access the classes in your other project in Eclipse. Maven can also create a jar for you that has the classes from both projects (a "jar-with-dependencies").
In maven terms, your two projects are called "artifacts" with one having a dependency on the other.
The one downside to maven (and the cause for many negative comments about maven) is an initially steep learning curve that can be frustrating. What you're trying to do, however, is very straightforward and I expect you can find a number of examples showing you exactly what you want to do.
The first step, and that's what my answer is about, is to take a look at maven. It may seem overly complex, but it can scale to handle just about any build configuration you need as your hadoop apps get more and more complex.
You can export a project as a Runnable jar, which can be useful if you want a single jar, with dependencies included.
Select the Project. File > Export. Select the Java section. Select Runnable JAR file.
See related answer:
Eclipse: How to build an executable jar with external jar?
The issue is as follows:
I have a 3rd party Eclipse plug-in installed and running
The above Eclipse plug-in provides an "extension point" of sorts - a source for a class I can extend/rewrite and replace in the plug-in lib directory (I am not saying it's a great idea, but necessity makes us do things we are not proud of - in-house development has its quirks)
The idea here is to envelop any such change in an external JAR (created by us) so that any change in code wouldn't require us to restart Eclipse to "refresh" the "extension point" class during development.
Eventually, a plugin/bundle will be created and placed as a dependency on the original plugin - so that installing and using that plug-in would actually, you know, work.
Question is - can I somehow add what is basically an external JAR file to Eclipse Application debug/run configuration?
Normally, adding JAR to classpath tab would work for regular Java application debugging/running. Eclipse Application however, doesn't have that tab.
So far the efforts (failed, perhaps due to some stupid syntax error or whatnot) included:
Adding the JAR as a dependency to Bundle-ClassPath: of the plug-in as C:\test.jar
Adding the JAR to the system's CLASSPATH variable
None of that made any difference - the code in the "extension point" that refers to a class in the JAR file fails - exception that boils down to:
Caused by: java.lang.ClassNotFoundException: test.Test
at org.eclipse.osgi.internal.loader.BundleLoader.
findClassInternal(BundleLoader.java:506)
Any pointer/help/criticism would be greatly appreciated.
Update
Apparently putting the JAR in the lib directory of the plug-in and updating the MANIFEST file doesn't work (not that it would help me - since such a solution would require a "refresh", which I am trying to avoid in the first place), so I must be doing something fundamentally wrong.
Does that make any sense or did I miss something in one of those attempts?
I have included an external JAR file to my Eclipse application.....not to the debug/run configurations but to the application itself.
What we did was to wrap the plugin into it's own java project. We are using maven for our build, so the pom.xml lists the dependency as the .jar file (which we put into a lib directory in the project). The manifest.mf file exports the needed classes. My application plugins have a dependency on this project. When I debug/run the application in the workbench I just make sure that this library project is included.
I'm not sure this answers your question completely or not....but I hope it helps.
A first guess based on some assumptions:
You are developing an extension to an 3rd party extension point 'foo'. Your application is a Eclipse Application, that you start via a run configuration. You need to create a new plugin 'foo-extension' which implements the extension point. You have to add the new plugin as a plugin dependency to your application. This way it will be available in the project class path, as well as in the 'Plugin-Ins' tab of your run configuration. Select the new project and when you start your application the extension will be available with the latest change.