svn co <JBoss AS sources> jboss
cd jboss
mvn dependency:sources

SRC_DIR=~/tmp/jboss-mvn-src
mkdir -p SRC_DIR
cd ~/.m2/repository/org/jboss
find . -name *-sources.jar -exec cp {} SRC_DIR \;

cd SRC_DIR
for i in `ls`; do mkdir $i.dir; cd $i.dir; jar -xf ../$i; cd ..; done;

# Now search it however you want... e.g.:
find . -name *.java -exec grep -H xb.builder.useUnorderedSequence {} \;