Using jarIndex for Hibench, there is an unexpected behavior with the exception
"Exception in thread "main"
org.apache.hadoop.fs.UnsupportedFileSystemException: No FileSystem for scheme
"hdfs"".
After investigating it, it is related to the usage of ServiceLoader with
JarIndex.
The below stack shows the issue with JDK11:
getResource:1016, URLClassPath$JarLoader (jdk.internal.loader)
getResource:937, URLClassPath$JarLoader (jdk.internal.loader)
findResource:912, URLClassPath$JarLoader (jdk.internal.loader)
next:341, URLClassPath$1 (jdk.internal.loader)
hasMoreElements:351, URLClassPath$1 (jdk.internal.loader)
hasNext:355, BuiltinClassLoader$1 (jdk.internal.loader)
hasMoreElements:363, BuiltinClassLoader$1 (jdk.internal.loader)
next:3032, CompoundEnumeration (java.lang)
hasMoreElements:3041, CompoundEnumeration (java.lang)
nextProviderClass:1203, ServiceLoader$LazyClassPathLookupIterator (java.util)
hasNextService:1221, ServiceLoader$LazyClassPathLookupIterator (java.util)
hasNext:1265, ServiceLoader$LazyClassPathLookupIterator (java.util)
hasNext:1300, ServiceLoader$2 (java.util)
hasNext:1385, ServiceLoader$3 (java.util)
The below API tries to get all the resources with the same name.
public Enumeration<URL> findResources(final String name,
final boolean check)
```
After using JarIndex, URLClassPath.findResources only returns 1 URL.
It is the same as the description in JDK-6957241.
The issue still exists in JDK18.
Root cause:
public Enumeration<URL> findResources(final String name,
final boolean check) {
return new Enumeration<>() {
private int index = 0;
private URL url = null;
private boolean next() {
if (url != null) {
return true;
} else {
Loader loader;
while ((loader = getLoader(index++)) != null) {
url = loader.findResource(name, check);
if (url != null) {
return true;
}
}
return false;
}
}
...
};
}
With the JarIndex, there is only one loader which is corresponding to the jar
with the index due to the implementation in JarLoader.getResource(final String
name, boolean check, Set<String> visited).
Loaders corresponding to other jar packages will not appear in this while.
So it only returns 1 instance.
To solve the issue, I change the implementation "private boolean next()".
If the loader has index, traverse the index and get all the resource from the
loader.
-------------
Commit messages:
- solve Whitespace error
- 6957241: ClassLoader.getResources() returns only 1 instance when using jar
indexing
Changes: https://git.openjdk.java.net/jdk/pull/5316/files
Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5316&range=00
Issue: https://bugs.openjdk.java.net/browse/JDK-6957241
Stats: 769 lines in 8 files changed: 763 ins; 0 del; 6 mod
Patch: https://git.openjdk.java.net/jdk/pull/5316.diff
Fetch: git fetch https://git.openjdk.java.net/jdk pull/5316/head:pull/5316
PR: https://git.openjdk.java.net/jdk/pull/5316
