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https://issues.apache.org/jira/browse/SIS-193?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Desruisseaux updated SIS-193:
------------------------------------
Labels: JDK9 (was: )
> Remove the workaround for ServiceLoader bug
> -------------------------------------------
>
> Key: SIS-193
> URL: https://issues.apache.org/jira/browse/SIS-193
> Project: Spatial Information Systems
> Issue Type: Task
> Components: Referencing
> Reporter: Martin Desruisseaux
> Priority: Minor
> Labels: JDK9
>
> As of 1.8.0_31-b13, {{java.util.ServiceLoader}} does not support usage of a
> second {{Iterator}} in the middle of a previous iteration. The following Java
> code provides two simple tests with a {{ServiceLoader}} iterating over two
> elements.
> {code:java}
> import java.util.Iterator;
> import java.util.ServiceLoader;
> public class ServiceLoaderTest {
> public static class I1 extends ServiceLoaderTest {} // A dummy provider.
> public static class I2 extends ServiceLoaderTest {} // An other provider.
> public static void main(String[] args) {
> test1();
> test2();
> }
> private static void test1() {
> System.out.println();
> System.out.println("---- TEST 1 ----");
> ServiceLoader<ServiceLoaderTest> loader =
> ServiceLoader.load(ServiceLoaderTest.class);
> Iterator<ServiceLoaderTest> it1 = loader.iterator();
> System.out.println("it1.hasNext() = " + it1.hasNext());
> System.out.println("it1.next() = " + it1.next());
> Iterator<ServiceLoaderTest> it2 = loader.iterator();
> System.out.println("it2.hasNext() = " + it2.hasNext());
> System.out.println("it2.next() = " + it2.next());
> System.out.println("it1.hasNext() = " + it1.hasNext());
> System.out.println("it1.next() = " + it1.next());
> System.out.println("it2.hasNext() = " + it2.hasNext()); // Expected
> "true" here, but get "false".
> }
> private static void test2() {
> System.out.println();
> System.out.println("---- TEST 2 ----");
> ServiceLoader<ServiceLoaderTest> loader =
> ServiceLoader.load(ServiceLoaderTest.class);
> Iterator<ServiceLoaderTest> it1 = loader.iterator();
> System.out.println("it1.hasNext() = " + it1.hasNext());
> System.out.println("it1.next() = " + it1.next());
> Iterator<ServiceLoaderTest> it2 = loader.iterator();
> System.out.println("it1.hasNext() = " + it1.hasNext());
> System.out.println("it2.hasNext() = " + it2.hasNext());
> System.out.println("it1.next() = " + it1.next());
> System.out.println("it2.next() = " + it2.next()); //
> ConcurrentModificationException here.
> }
> }
> {code}
> The second test throws the following exception:
> {noformat}
> Exception in thread "main" java.util.ConcurrentModificationException
> at
> java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:711)
> at
> java.util.LinkedHashMap$LinkedEntryIterator.next(LinkedHashMap.java:744)
> at
> java.util.LinkedHashMap$LinkedEntryIterator.next(LinkedHashMap.java:742)
> at java.util.ServiceLoader$1.next(ServiceLoader.java:479)
> at test.ServiceLoaderTest.test2(ServiceLoaderTest.java:47)
> at test.ServiceLoaderTest.main(ServiceLoaderTest.java:12)
> {noformat}
> The workaround applied in Apache SIS has been to add a {{LazySet}} internal
> class which wraps an {{Iterable}} and caches its values. But this is a little
> bit unfortunate since {{ServiceLoader}} already caches its values.
> {{ServiceLoader}} is probably going to be significantly rewritten in JDK9 as
> a side effect of the Jigsaw project. So we should revisit if our {{LazySet}}
> workaround is still needed on a JDK9 branch.
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