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Eclipse Java Build Path Jar Library classes not found even if available in jar

Recently I wanted to add the nebula shelf to my eclipse plugin. Therefore I added the org.eclipse.nebula.widgets.pshelf.source_1.1.0.201701302244.jar the build path of my eclipse project.
Sadly eclipse can't find the class files inside of the jar, even after cleaning and rebuilding the whole project.
Picture:
Checking the same jar file with jd-gui results in:
Picture:
I exported the *.java files with jd-gui and copied them to my project. Using this method my project built successfully and worked as expected.
Can someone tell me how I can use the jar file without exporting all of the java files manually? Thanks for your help! :-)

Do not use source jars. You can tell eclipse while debugging to use the source jar.
Add the jar to build path: right click on jar -> build path -> add to build path

Don't try to add Eclipse plugins directly to the build path of another plugin as it won't work.
Instead add the plugin to your target platform or import it in to your workspace.
Then add the plugin to your plugin's Dependencies. In the MANIFEST.MF editor you do this on the 'Dependencies' tab in the 'Required Plug-ins' list.

Moving from NetBeans to eclipse, can't seem to find generated java files

I have been developing in NetBeans, I am exploring changing over to eclipse.
We have a set of directories for the modules in our project; we have scripts that check things out of Subversion and do other things with that directory tree, and we have NetBeans access the sources, etc., from that directory tree.
All our modules are built, etc., with Maven. All of this works fine from within NetBeans.
I have successfully imported all the projects into eclipse (File / Import / Maven), but evidently something is different in the handling of "generated sources". We have some castor-generated files in one module, and jaxb-generated files in another. The generated files in both cases are not found by the compiler, and therefore these modules have compile errors.
Maven is configured to generate the Java classes which cannot be found; maven clean deletes them and maven compiler:compile puts them back. But in eclipse those java files cannot be found for compiling other classes, but in NetBeans they can.
I tried deleting the generated java files, then rebuilding in eclipse; the java files were regenerated in generated-sources, but still cannot be found by the compiler when it comes time to compile (or syntax-highlight) my code.
It sort of looks like a classpath issue, but we don't set the classpath in NetBeans for a maven project. How should I configure things in eclipse so the generated class files are found?

In Eclipse in the Package Explorer right click the project folder which contains the missing files. Goto "Build Path >" then "Configure Build Path...". Properties for your project folder will open.
Click on the "Source" tab. Then click on the "Add Folder..." on the left. A source folder selector box opens, here select your folder which contains the auto generated sources. Normally it will be in the target directory. Then press ok. If this will not work, try one directory deeper or less deep.
If there is no target directory, build the project folder with maven on a shell.
The generated-sources directory will be stored in the .classpath file in your project folder.
HTH.

how to make .jar file in Eclipse MARS

I'm learning Hadoop under VMware now.(win7, 64) Due to some reason, I can't convert a .java file to .jar file under virtual machine, so I tried to create .jar file under Eclipse.
I'm currently using Eclipse MARS(4.5.1). I need to download something about fat jar, but I can't find it online.
My colleague copied his Eclipse software to me. It is already installed, so I copied the whole package. It is Eclipse Kepler. So I am running two Eclipse software on my computer now. will this cause some problem? (I saved projects seperately)
I can do the convert .jar file thing correctly on Eclipse Kepler now. But I still want to use MARS and delete the extra Eclipse.
thank you !

What you're looking for is the "Fat JAR" eclipse plugin.
Fat jar is a jar which contains all the classes used by the project including their referenced dependencies.
The plugin can enable the creation of such a jar.
In your case, however, Eclipse "Mars" & Eclipse "Kepler" include this functionality. The trick is to get to it...
Here's what you do in order to export a Fat JAR:
Right-click on the required Project and select "Export..." --> "Runnable JAR file".
Select the option which extracts libraries and specify the destination JAR file.
Launch configuration is used to execute this JAR with a predefined "Main" class (this is the "Runnable" part...) using "java -jar file.jar".
If you don't plan to - it won't matter.
(Optional) You can also "Save as ANT script" which, well..., generates XML ant script as well.

select project
select Export
Expand the Java node and select JAR file. Click Next
In the JAR File Specification page, select the resources that you want to export in the Select the resources to export field
.
Select the appropriate checkbox to specify whether you want to Export generated class files and resources or Export Java source
or go to http://www.codejava.net/ides/eclipse/how-to-create-jar-file-in-eclipse

Can you import a non-archive project directory in Eclipse?

I read this article which shows how to import/export projects in Eclipse (although it seems a little outdated and I'm using 3.7 Indigo).
To export a project, you go to File >> Export and it creates some kind of "project archive" file on the local file system. You could then email it to someone else, who could then import the archive as a new project or into an existing project.
But what if you don't have an "archive" file to begin with?!? What if you just have the project files and directories but without all the Eclipse-metatdata (.project file, etc.)? Is there anyway to tell Eclipse to look at, say:
/home/myuser/some/path/to/project/root/
src/main/java
SomeObject.java
build.xml
...and get it to read that as a new Java project?

Try the steps below:
Create a Java Project in Eclipse as below:
Load the project contents from your file system as below:
Hope this works for you.

.project and .classpath files are the base of the project structure. Without a .project file Eclipse won't recognize your project. The .classpath is important too but that one changes between environments. Should you use the files from another environment you'll have to reconfigure some settings.
Rather than emailing code, I suggest you use a Version Control system and, also, some Eclipse plugins. SVN + Subclipse for example.
If you trully want to send the project to another person just send him the project's folder and import it as an existing project by doing right click on the project explorer and selecting Import > Existing Project into workspace.

Creating and using custom JAR in Android project

I am trying to create and use jar file in an Android project under Eclipse. I have tried various methods without any success. Here are the steps:
Create jar file from the source files jar -cf lib.jar *.java
Copy jar file to libs folder
Right click, Build Path->Add to Build path
Now, compiler gives unresolved symbols if I try to use a class from the jar file?
Can someone please let me know correct method to create and use an external jar file for the Android project under eclipse.

This worked fine for me:
1)Place Jars in assets folder.
2)Right click on project name.
3)Select properties.
4)Select Java build path.
5) Select Libraries.
6) Click Add Jars.