Configuring fast-swap in WebLogic fails, with a "BEA_HOME environment variable is null" AsserionError

In WebLogic 10.3.0, I tried adding

<fast-swap> 
    <enabled>true</enabled> 
</fast-swap> 

to my weblogic.xml configuration fil开发者_如何学编程e. (<fast-swap>true</fast-swap>, as specified in the instructions here, throws an XML error, instead. Most examples that I've found cite the method I've posted above as the One True Way. )

Unfortunately, the weblogic.servlet.internal.WebAppModule.loadFastSwapClassloader throws an error:

"java.lang.AssertionError: BEA_HOME environment variable is null"

The BEA_HOME environment variable is set! I can't imagine what might be going wrong.