Categories
Java

Eclipse Workspace In Use Or Cannot Be Created

You may recieve the error message “Eclipse Workspace In Use Or Cannot Be Created” From Eclipse when trying to start up Eclipse, this typically means that Eclipse is already running.  If you have not started Eclipse, try to locate Eclipse in your operating systems task manager and kill it. You can also consider killing any java processes running if you cant find any Eclipse processes.

Categories
Java

HttpClient: Target host must not be null, or set in parameters

If you have the following code failing:

HttpGet httpget = new HttpGet(“www.host.com”);

Then the error is pretty easy to solve:
The problem is that you have not added a protocol to the URL, so change it to:

HttpGet httpget = new HttpGet(“http://www.host.com”);

And then it will work as wanted.

Categories
Java

java.util.concurrent.CopyOnWriteArrayList not found in java.net.URLClassLoader

Simply said: You are most likely trying to run a java app on a too old version of Java, try upgrading to java 1.6 and see if that helps.

Categories
Java

java.io.FileNotFoundException: no segments* file found (Solr)

You will receive that error from Solr when you (for example) have removed the index data, but not the index folder itself. Simply remote the folder that are supposed to contain the index data, and Solr will then recreate the folder, and the data when you start a indexing job. 🙂

Categories
Development Java

The hierarchy of the type Foo is inconsistent

You can get the error:

The hierarchy of the type *classname* is inconsistent

If you are trying to compile a class that requires another class not available. Normally due to compilation errors in the dependent classes. So fix the classes needed by the main class and try again.

Categories
Java

Hint: “org.apache.jasper.JasperException: java.lang.NumberFormatException”

Getting the exception “org.apache.jasper.JasperException: java.lang.NumberFormatException” when developing a JavaEE-app?

If you are basing yourself on data from a query, make shure that you are doing a SELECT against the table name and NOT the individual fields!

Categories
Java

A hint for the “Object foo is not a known entity type” errors from Glassfish

As a JavaEE-codemonkey you have perhaps noticed this error:

java.lang.IllegalArgumentException: Object: Ting@193c227 is not a known entity type.

This will occur when you have redeployed an app f.ex through Eclipse to Glassfish, the Glassfish server has not quite understood that it`s time to update its version, so what you need to do then is to simply restart the server (or domain).

Categories
Java Linux

One possible solution for Glassfish cluster node-agent startup problems

Just a quick hint for those of you who are experiencing problem with getting node-agents up and running in a Glassfish cluster.

If the problem is that the asadmin start-agent command simply times out/uses a long time to start, and even possibly returning a filenotfoundexception. The problem could be as simple as a firewall blocking traffic to/from the master-node. A quick way to check it is to simply disable the FW.

Note that if the master-node does not see the node-agent status, it is also caused by FW-issues, fix the FW and then restart the node-agent(s), then it all should work like a charm!