Fix: Add Apache Derby Nature in Eclipse does nothing

Tonight I had a strange issue with Eclipse: adding the Apache Derby nature to an Eclipse project wasn't working. Ordinarily, (provided that the Apache Derby Eclipse plugin is already installed) right-clicking a project and choosing Apache Derby->Add Apache Derby Nature to a project will do just that, enabling additional features such as starting or stopping the Derby network server.

This time, however, choosing that option appeared to do nothing. Rather than a menu full of commands, I was given only the option "Add Apache Derby Nature" in the Apache Derby context menu, which is what I had previously selected. I tried several times to add the nature in this manner, but to no avail.

The fix turned out to be simple. After grepping the directory of another project where I had successfully used Derby, I found that the change should have been reflected in my project's .project file.

The fix: if the Apache Derby nature isn't correctly added to a project through the Apache Derby menu, it can be done manually by editing the .project file (which is in the root directory the project). This is an XML file.

Find the <natures> node and add this line:

<nature>org.apache.derby.ui.derbyEngine</nature>

Here's how the entire <natures> node looks after the change in my project:



<natures>
<nature>org.eclipse.jem.workbench.JavaEMFNature</nature>
<nature>org.eclipse.wst.common.modulecore.ModuleCoreNature</nature>
<nature>org.eclipse.wst.common.project.facet.core.nature</nature>
<nature>org.eclipse.jdt.core.javanature</nature>
<nature>org.eclipse.wst.jsdt.core.jsNature</nature>
<nature>org.apache.derby.ui.derbyEngine</nature>
</natures>

Then, just save the file. Problem solved.

Getting Started with Eclipse

For about the last month I have been learning Java. Due to outside requirements, I have been using the BlueJ IDE for development. However today I decided to give Eclipse a try.

I installed version 3.2.2 from the Ubuntu repos and loaded a project I had just completed in BlueJ. It was then that I was greeted with a few errors regarding my code. The first of which was:

    Scanner cannot be resolved to a type

The line of code in question was:

    private Scanner userInput = new Scanner(System.in);

Strange, I thought, since I had made no changes to the code and had just compiled and run this project in BlueJ.

I first checked the installed version of Java:

    $ java -version
    java version "1.6.0_0"
    OpenJDK Runtime Environment (IcedTea6 1.4.1) (6b14-1.4.1-0ubuntu11)
    OpenJDK Client VM (build 14.0-b08, mixed mode, sharing)


    $ javac -version
    javac 1.6.0_0

Ok, everything looked good there. I checked the compiler settings in Eclipse and changed the compiler from 5.0 compliant to 6.0 compliant. No joy.

After some more digging I concluded that the issue was probably that Eclipse was not using the proper JRE. Sure enough, Eclipse was using version 1.5 at /usr/lib/jvm/java-1.5.0-gcj-4.3-1.5.0.0. I added another JRE entry pointing to /usr/lib/jvm/java-6-openjdk (which is what my BlueJ installation was already using) and voila! No more errors.

I guess I should look into cleaning up the multiple JRE's I have installed on this machine.

But first, back to exploring Eclipse!