[OpenJDK 2D-Dev] [9] request for review: 8068749: Restrict javax.imageio.spi.ServiceRegistry to ImageIO types

[Stuart Marks]

Hi all,

Please review this following code and API change:

Bug:
	https://bugs.openjdk.java.net/browse/JDK-8068749

Webrev:
	http://cr.openjdk.java.net/~smarks/reviews/8068749/webrev.0/

The change is to be pushed into the jdk9/client forest.

The background is that this is a "preparation for Jigsaw" bug. The 
javax.imageio.spi.ServiceRegistry class was introduced long ago in order to load 
Image I/O service providers; in fact it was also fully general service loading 
mechanism, capable of loading providers for arbitrary service types. This latter 
function has been superseded by java.util.ServiceLoader (introduced in JDK 6), 
although iio.SR can still be used for general purpose service provider loading.

In JDK 9, Jigsaw modularization will require additional work, and use of new, 
modular APIs, to implement general purpose service loading. Loading of specific 
APIs -- which is the primary use case for iio.SR -- is considerably simpler. 
Given that general purpose service loading is now handled by j.u.SL, we wish to 
remove general purpose support from iio.SR and restrict its use to loading only 
Image I/O related service providers.

This change adds explicit checks in iio.SR to restrict the service types to the 
known set of Image I/O interfaces, and it will throw IAE if asked to load a 
provider for any other service type. Use of iio.SR to load Image I/O providers 
will continue to work unchanged.

This is clearly an incompatible change. I've done some internet searching, and 
use of iio.SR to load Image I/O providers is quite common. I was able to find 
one use of iio.SR to load a non Image I/O provider, but the project where this 
occurred migrated to j.u.SL several years ago. Based on this, we believe the 
impact of this change to be small.

s'marks