#33 ExtensionMimeDetector not thread-safe

[Torsten Krah]

Using threads (and not using a "singleton" shared mime-util instance) the result is, that the Detector classes are not thread-safe at all - it seems its not possible to have more than "one" instance of a detector at different mime util instances because register/deregister does result in this failure:

java.util.ConcurrentModificationException: null
at java.util.Hashtable$Enumerator.next(Hashtable.java:1048) ~[na:1.6.0_20]
at eu.medsea.mimeutil.detector.ExtensionMimeDetector.initMimeTypes(ExtensionMimeDetector.java:291) ~[mime-util-2.1.3.jar:na]
at eu.medsea.mimeutil.detector.ExtensionMimeDetector.<init>(ExtensionMimeDetector.java:104) ~[mime-util-2.1.3.jar:na]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.6.0_20]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) ~[na:1.6.0_20]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.6.0_20]
at java.lang.reflect.Constructor.newInstance(Constructor.java:532) ~[na:1.6.0_20]
at java.lang.Class.newInstance0(Class.java:372) ~[na:1.6.0_20]
at java.lang.Class.newInstance(Class.java:325) ~[na:1.6.0_20]
at eu.medsea.mimeutil.MimeDetectorRegistry.registerMimeDetector(MimeUtil2.java:967) ~[mime-util-2.1.3.jar:na]
at eu.medsea.mimeutil.MimeUtil2.registerMimeDetector(MimeUtil2.java:222) [mime-util-2.1.3.jar:na]

Don't know the best solution yet - but what i expect is, that different instances does not interfere with each other - but actually this is whats happening - and if they share some code, this code should be thread-safe and should not result in "wrong" results compared to single threaded usage.

[Anonymous]

Add a synchronized block to the initMimeTypes method should do it. This may slow it down a little, but such problems as discribed will be gone.