Category Archives: Eclipse

Eclipse won’t start after Windows shutdown

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My laptop unexpectedly shutdown when I had Eclipse open. After rebooting I could not start Eclipse. Instead it kept crashing with the message “An error has occurred. See the log file …” Looking at the log file I saw errors related to the Perforce plugin.

java.lang.NoClassDefFoundError
        at org.eclipse.ui.internal.themes.ThemeElementHelper.installFont(ThemeElementHelper.java:101)

org.osgi.framework.BundleException: Exception in org.eclipse.core.internal.compatibility.PluginActivator.start() of bundle com.perforce.team.ui.
        at org.eclipse.osgi.framework.internal.core.BundleContextImpl.startActivator(BundleContextImpl.java:1010)
Caused by: java.lang.ExceptionInInitializerError
        at com.perforce.team.ui.PerforceUIPlugin.initializeDefaultPreferences(PerforceUIPlugin.java:284)

I saw a post about this problem which referred to another post for a solution. Basically the post suggests that stale plugin cache information is causing the problem and suggests starting Eclipse with the -clean argument. After doing this I was successfully able to launch Eclipse.

Eclipse Serial Version UID Bug

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Currently there is a bug with Eclipse and generating the serial version UID. When attempting to generate a serial version UID you will see a dialogue window which says “Computing serial version ID….” and “Starting virtual machine…”. Unfortunately this hangs and you are forced to kill your Eclipse IDE. I started seeing this bug after installing some JDBC plugins and the GEF plugin, I’m not sure if it’s related to that. I tried disabling the plugins but I still see the problem. Before I wasn’t having this problem.

I noticed that I haven’t encountered this problem on other installations of Eclipse, even w/ the JDBC plugins, so could just be that I have a bad build of Eclipse.

JDBC Plugins for Eclipse

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I was previously using DbVisualizer to query and update my Oracle databases and was not completely satisfied with it. I actually prefer PhpMyAdmin but that only works with MySQL.

Since I use Eclipse so much for development I decided to look for a JDBC plugin that is at least as good as DbVisualizer. My goal is to have in one workspace access to my database as well as my source and configuration files.

I went to EclipsePlugins and downloaded the three highest rated JDBC plugins, all which happen to be free (in some cases just for non-commercial use).

  1. DBEdit
  2. QuantumDB
  3. SQLExplorer

I installed DBEdit 1.0.3_1, Quantum DB 3.0.1 (which requires GEF, I installed 3.1.1), SQLExplorer 2.2.4.

Setup was quite simple with DBEdit, just add the JDBC driver to the CLASSPATH, give it the JDBC URL and connect. Setup was almost as simple with Quantum DB though it asks you for the components of the JDBC URL instead of the URL directly. I couldn’t figure out how to setup SQLExplorer within five minutes so I gave up.

DBEdit and Quantum DB have similar interfaces and both are similar to DbVisualizer though Quantum DB’s appealed to me a little more. However Quantum DB’s interface responded much more quickly and querying of tables was much faster. DBEdit has a nice feature, which I did not completely test, of inline editing of cell values which seems quite powerful.

Because of Quantum DB’s speed and responsiveness I am going to continue to use that as my primary JDBC plugin but I will also keep DBEdit on the side to use for its inline editing but also in case I find Quantum DB does something in an unintuitive manner.

Update: Since I posted this less than a month ago I found DBEdit much more useful than Quantum DB. It’s inline editing, inserting feature, and other editing features really make it powerful. Also its filter, scrolling through result sets, etc. are great. I highly recommend DBEdit.

Import A Project Into Eclipse

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When I get someone’s Eclipse project I always ended up recreating the project. Now I won’t need to do that anymore since I learned about the Import feature.

  1. Go to File > Import…
  2. Select Existing Projects into Workspace
  3. Select the root directory of the project
  4. Press Finish and watch Eclipse wonderfully recreate the project.

Serial Version UID

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It is simple to make a class serializable, just have it implement the java.io.Serializable interface. However it is not easy to support the serialized form forever.

One issue is the serial version UID. Every serializable class has a unique identification number associated with it. If you do not specify the identification number explicitly by declaring a private static final long field named serialVersionUID, the system automatically generates it by applying a complex deterministic procedure to the class… If you change [the class] in any way … the automatically generated serial version UID changes. If you fail to declare an explicit serial version UID, compatibility will be broken.

Bloch, Joshua. Effective Java. p. 214

To generate the serial version UID for a class use the serialver tool which comes with the Java SDK. The serialver tool returns the serial version UID for one or more classes.

Example:

$ serialver -classpath 'build;C:/foo/classes.jar' com.bar.FooMessage

or

> serialver -classpath build;C:\foo\classes.jar com.bar.FooMessage

An even easier way to generate the serial version UID is to use the Eclipse IDE. If your class implements the java.io.Serializable interface and it does not have a serial version UID then Eclipse will give a warning about this next to the class name. If you click on the warning you can choose the option “Add generated serial version ID.”

Note, currently there is a bug with Eclipse and generating the serial version UID. When attempting to generate a serial version UID you will see a dialogue window which says “Computing serial version ID….” and “Starting virtual machine…”. Unfortunately this hangs and you are forced to kill your Eclipse IDE. I started seeing this bug yesterday after installing some JDBC plugins and the GEF plugin, I’m not sure if it’s related to that. I tried disabling the plugins but I still see the problem. Before I wasn’t having this problem.