descriptiion:
  noclassfound exception thrown up while previewing report on jboss.

test build:
birt2.5.2 v20100115-0630

step to reproduce:

1. deploy birt runtime to jboss4.2.2
2. preview a report using sampledb

error log:
caused by: java.lang.noclassdeffounderror: could not initialize class org.apache.derby.jdbc.embeddeddriver
	at java.lang.class.forname0(native method)
	at java.lang.class.forname(class.java:247)
	at org.eclipse.birt.report.data.oda.sampledb.sampledbjdbcconnectionfactory.getderbydriver(sampledbjdbcconnectionfactory.java:132)
	at org.eclipse.birt.report.data.oda.sampledb.sampledbjdbcconnectionfactory.getconnection(sampledbjdbcconnectionfactory.java:80)
	at org.eclipse.birt.report.data.oda.jdbc.jdbcdrivermanager.doconnect(jdbcdrivermanager.java:239)
	at org.eclipse.birt.report.data.oda.jdbc.jdbcdrivermanager.getconnection(jdbcdrivermanager.java:212)
	at org.eclipse.birt.report.data.oda.jdbc.connection.connectbyurl(connection.java:234)
	at org.eclipse.birt.report.data.oda.jdbc.connection.open(connection.java:160)
	at org.eclipse.datatools.connectivity.oda.consumer.helper.odaconnection.open(odaconnection.java:239)
	at org.eclipse.birt.data.engine.odaconsumer.connectionmanager.openconnection(connectionmanager.java:165)
	at org.eclipse.birt.data.engine.executor.datasource.newconnection(datasource.java:190)
	at org.eclipse.birt.data.engine.executor.datasource.open(datasource.java:178)
	at org.eclipse.birt.data.engine.impl.datasourceruntime.openodidatasource(datasourceruntime.java:208)
	at org.eclipse.birt.data.engine.impl.queryexecutor.opendatasource(queryexecutor.java:396)
websphere has the same issue.
this is a derby bug. 
http://issues.apache.org/jira/browse/derby-3887

to fix this bug we have disabled derby jmx.
this bug is fixed in derby 10.5.3.0. we will upgrade derby version to 10.5.3.0 in next birt version.
reproduce in birt runtime build v20100129-0630
fixed.
verified in v20100201-0630