Consider the following code:
// BundleContext bc ...
final ServiceReference[] refs =
bc.getServiceReferences( SomeType.class.getName(),
"(foo=bar)" );
if ( null != refs )
for ( ServiceReference ref: refs ) {
final SomeType st = (SomeType) bc.getService( ref );
try {
if ( null != st )
return st.use( 42 );
} catch (NullPointerException ignored) {
// Ignore it, as the service went away.
} finally {
bc.ungetService( ref );
}
}
Here we grab all known ServiceReferences for a given object class and
filter, walk the set, and attempt to call on the first valid
reference.
We attempt to catch a NPE that might arise from the "st.use( 42 )"
call if the object referenced by "st" were to disappear immediately
after the null check but before we could call call its use() method.
Several questions:
o Could this NPE actually arise here, or is "st" pinned in memory by
the reference we're holding to it?
o Is the preceding null test then spurious?
o Should I bother with BundleContext.ungetService() if
BundleContext.getService() had returned null?
--
Steven E. Harris
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