Re: (Server-side) AutoBeans and thread-safety
On Tuesday, February 24, 2015 at 6:56:50 PM UTC+1, Andreas Kohn wrote:
I understand that autobean's are actually parsed lazily, so for me this
looks like a concurrency issue somewhere inside the autobeans framework
itself. I didn't see any notes about sharing autobeans between threads in
the documentation, so:
1. Should it be possible to share them, or is additional synchronization
in the application code needed?
2. Instead of synchronizing all accesses, would it be enough to force a
full parse run of the autobean before making it visible to other threads?
3. Is this problem only affecting server-side code, or would similar
issues also be possible in client-side code? (I'm suspecting: It depends
on the browser's implementation of JS?)
Regarding the second question: I did not manage to reproduce the issue by
using this additional code:
AutoBeanUtils.getAutoBean(delegate).accept(new AutoBeanVisitor() { /*
Nothing */ });
Small update here: I was able to get my test to break again even after
using the #accept() idea, by using a Map property in the bean, and
iterating over its entry set. So my conclusion here: using autobeans on the
server side without external synchronization and careful coding is
dangerous.
I've now worked around this issue by copying the contents of the bean into
a separate class that implements the bean interface as well. In my case I
do not need the ability to modify the contents, so I didn't bother working
out how I'd get my copy serialized into JSON again.
Regards,
--
Andreas
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(Server-side) AutoBeans and thread-safety
Hi,
I hope this is the right forum to also ask questions about the Autobeans
framework, if not please do redirect me!
We're using autobeans both in client code and server code, and so far
things work nicely except in one situation: sometimes parsing autobeans
simply fails with a stack trace similar to this:
java.lang.NullPointerException
at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.makeProxy(
ProxyAutoBean.java:105)
at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.createShim(
ProxyAutoBean.java:393)
at com.google.web.bindery.autobean.vm.impl.ProxyAutoBean.as(ProxyAutoBean.
java:222)
at com.google.web.bindery.autobean.vm.impl.ShimHandler.maybeWrap(ShimHandler
.java:113)
at com.google.web.bindery.autobean.vm.impl.ShimHandler.invoke(ShimHandler.
java:91)
at com.sun.proxy.$Proxy368.get(Unknown Source)
at com.google.web.bindery.autobean.shared.impl.SplittableSimpleMap$1$1$1.
init(SplittableSimpleMap.java:90)
at com.google.web.bindery.autobean.shared.impl.SplittableSimpleMap$1$1.next(
SplittableSimpleMap.java:86)
at com.google.web.bindery.autobean.shared.impl.SplittableSimpleMap$1$1.next(
SplittableSimpleMap.java:76)
at sun.reflect.GeneratedMethodAccessor89.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(
DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.web.bindery.autobean.vm.impl.ShimHandler.invoke(ShimHandler.
java:85)
at com.sun.proxy.$Proxy347.next(Unknown Source)
at XXX.function(XXX.java:...)
When dumping the contents of the bean at that point everything looks
proper, and it can be parsed just fine in an isolated unit test. After some
more investigation I managed to reproduce this and other similar
exceptions: it seems to happen when multiple threads access a recently
created autobean proxy.
I understand that autobean's are actually parsed lazily, so for me this
looks like a concurrency issue somewhere inside the autobeans framework
itself. I didn't see any notes about sharing autobeans between threads in
the documentation, so:
1. Should it be possible to share them, or is additional synchronization in
the application code needed?
2. Instead of synchronizing all accesses, would it be enough to force a
full parse run of the autobean before making it visible to other threads?
3. Is this problem only affecting server-side code, or would similar issues
also be possible in client-side code? (I'm suspecting: It depends on the
browser's implementation of JS?)
Regarding the second question: I did not manage to reproduce the issue by
using this additional code:
AutoBeanUtils.getAutoBean(delegate).accept(new AutoBeanVisitor() { /*
Nothing */ });
Regards,
--
Andreas
--
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