Hi KL
On 31/01/12 00:10, K Fung wrote:
Hi everyone,
I have a question about the technique described at
http://cxf.547215.n5.nabble.com/Cannot-obtain-UriInfo-in-isWriteable-for-custom-providers-td5023534.html.
Wouldn't it be possible to run into a race condition involving the injected
variables?
Per section 4.1 JAX-RS specification, "By default a single instance of each
provider class is instantiated for each JAX-RS application". This means
that any instance variable injection (e.g., such as those done by @Context)
may be overwritten by the next thread that uses that provider. To put it
even more succinctly...
1. A single instance of MyJSONProvider has been instantiated by the CXF
JAX-RS framework
2. Request one reaches MyJSONProvider and CXF injects A into
context. Request one is in the MyJSONProivder.isWriteable method.
3. Request two reaches MyJSONProvider and CXF injects B into the context.
Request two is in the MyJSONProvider.writeTo method.
4. Request one resumes. It sees "B" in the context instead of "A" :(
Is there a way within CXF to allow a provider to be created for each
request? Alternatively, can variables be injected in a provider in a
thread-safe way (perhaps using ThreadLocal)?
Currently all the providers (as opposed to root resource classes which
can have various lifecycles) are treated as singletons by CXF.
But the contexts are thread-safe, the providers get the thread-safe
proxies injected early at the init time...
I should also mention that we're not afraid of getting into modifying CXF
JAX-RS internals. So if we need to implement something within CXF, we could
give that a whirl too.
Sounds good indeed :-)
thanks, Sergey
Thanks in advance!
Cheers,
kl
--
Sergey Beryozkin
Talend Community Coders
http://coders.talend.com/
Blog: http://sberyozkin.blogspot.com
