The IBM Rational Application Developer 7 (RAD 7) IDE, based on Eclipse 3.3 doesn’t work out-of-the-box with Flex Builder 3. This is due to the IBM Java SDK using a different Xerces version then the one Flex Builder needs.

You’ll likely receive the following error:

java.lang.IllegalAccessError:
org.apache.xerces.util.XMLAttributesImpl$Attribute

Here is an easy guide to get you up and running quickly:

1. Install RAD7
2. Install Flex Builder 3
3. At the end of the install, the installer will complain about not being able to automatically setup an Extension Location. Be sure to execute the given instructions manually
4. Quit RAD7 if running
5. Edit the eclipse.ini file in c:\Program Files\IBM\SDP70 (directory where you installed RAD7)
6. Add the following line on a new line at the end of the file:

-Xbootclasspath/a:c:\progra~1\adobe\flexbu~1\sdks\3.0.0\lib\xercesImpl.jar

Restart RAD7 and open the Flex Development perspective to start developing the next-gen Flex app