Register default file formats on demand instead of at class init - #484
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Register default file formats on demand instead of at class init#484mattjala wants to merge 1 commit into
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…ation FileFormat's static initializer registered the default formats by instantiating each implementing class. Every implementing class is a subclass of FileFormat, so whenever a subclass was itself what triggered FileFormat's initialization, the JVM was already initializing that subclass on the same thread. Class.forName then returned immediately rather than waiting, and the instance was built from a class whose own static fields were still unassigned. This specifically became an issue for H4File, though it could easily have happend to NC2File or FitsFile instead. Registration now happens on the first call to a method that consults the list of supported formats. Those calls come from outside any class initialization, so Class.forName completes the subclass before the instance is built. The formats are also a table rather than four copies of the same block, and a format that fails to load no longer stops the ones after it. Fixes HDFGroup#481
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FileFormat's static initializer registered the default formats by instantiating each implementing class. Every implementing class is a subclass of FileFormat, so whenever a subclass was itself what triggered FileFormat's initialization, the JVM was already initializing that subclass on the same thread. Class.forName then returned immediately rather than waiting, and the instance was built from a class whose own static fields were still unassigned.
This specifically became an issue for H4File, though it could easily have happend to NC2File or FitsFile instead.
Registration now happens on the first call to a method that consults the list of supported formats. Those calls come from outside any class initialization, so Class.forName completes the subclass before the instance is built. The formats are also a table rather than four copies of the same block, and a format that fails to load no longer stops the ones after it.
Fixes #481