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Posted to dev@felix.apache.org by GitBox <gi...@apache.org> on 2022/06/22 13:22:23 UTC
[GitHub] [felix-atomos] sten-navie opened a new issue, #60: ClassCastException when starting org.eclipse.equinox.metatype as a "Standard Bundle"
sten-navie opened a new issue, #60:
URL: https://github.com/apache/felix-atomos/issues/60
During my experiments with Atomos I encountered the following issue.
Having the following modules in a bootlayer:
```
org.eclipse.osgi-3.17.200.jar
org.apache.felix.atomos-1.0.0.jar
org.apache.felix.gogo.command-1.1.0.jar
org.apache.felix.gogo.runtime-1.1.2.jar
osgi.core-8.0.0-AtomosEquinox.jar
org.osgi.service.metatype-1.4.1.jar
org.osgi.service.cm-1.6.1.jar
```
First I start the above modules by placing them into a folder named atomos-test and running:
`java --add-modules=ALL-MODULE-PATH -p atomos-test -m org.apache.felix.atomos`
If I now try to install and start equinox.metatype as a "Standard Bundle" via the gogo-shell, I get a ClassCastException:
```
g! felix:install file:////PATH_TO_MY_FILES/org.eclipse.equinox.metatype-1.6.100.jar
Bundle ID: 42
g! start 42
java.lang.ClassCastException: class com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl cannot be cast to class javax.xml.parsers.SAXParserFactory (com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl is in module java.xml of loader 'bootstrap'; javax.xml.parsers.SAXParserFactory is in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @162a66a1)
```
- Tested with java 11 and 17.
- If I place the equinox.metatype jar into the atomos-test folder and run it from the boot-layer, everything works.
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[GitHub] [felix-atomos] tjwatson closed issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
tjwatson closed issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
URL: https://github.com/apache/felix-atomos/issues/60
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[GitHub] [felix-atomos] laeubi commented on issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
laeubi commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1164191408
Do you use any startup options? Can you make sure that `osgi.compatibility.bootdelegation=false` is used?
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[GitHub] [felix-atomos] sten-navie commented on issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
sten-navie commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1169949229
I can confirm that applying PR #61 fixes this problem for me. Many thanks!
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[GitHub] [felix-atomos] sten-navie commented on issue #60: ClassCastException when starting org.eclipse.equinox.metatype as a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
sten-navie commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1163248236
> > javax.xml.parsers.SAXParserFactory is in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @162a66a1)
>
> This indicates to me that you may have another "normal" bundle that is exporting `javax.xml.parsers` package also?
This was my first thought, so I created a simple setup with just the jars listed above. There are no other "normal" bundles than the metatype one. Running `which 42 javax.xml.parsers.SAXParserFactory`(where 42 is the bundle id of the meta-type bundle gives me:
```
Loaded from: java.xml_11.0.14 [14]
```
Interestingly enough if I run `which 0 javax.xml.parsers.SAXParserFactory`, even though the the system bundle does not list a export for javax.xml.parsers, I get the response:
```
Loaded from: boot class loader
```
My understanding of class loader delegation in equinox is very limited, but when running my "real" app in the debugger I observed the following:
- It seems that meta-type bundle SAXParserFactory.class is in the "un-named" module and a has a EquinoxClassLoader. (Checked by putting a breakpoint where the metatype bundle activator starts tracking SaxParserFactories).
- The factory returned by equinox in org.eclipse.osgi.internal.framework.XMLParsingServiceFactory uses a SAXParserFactory.class from the "javax.xml" module and null class loader. (Checked by breaking in XMLParsingServiceFactory.createService and stepping into SaxParserFactory.newInstance which specifies the class).
best regards,
Sten
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[GitHub] [felix-atomos] tjwatson commented on issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
tjwatson commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1164763512
This is happening because `java.lang.Module.getClassLoader()` is returning null even though the javadoc says nothing about returning null. It appears to return null for modules in the boot layer. I guess that makes sense, but it means we need to handle the case for delegating to the boot layer modules for non java.* packages.
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[GitHub] [felix-atomos] tjwatson commented on issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
tjwatson commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1170004149
I went ahead and merged and opened an issue to add a testcase.
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[GitHub] [felix-atomos] tjwatson commented on issue #60: ClassCastException when starting org.eclipse.equinox.metatype as a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
tjwatson commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1163112489
> javax.xml.parsers.SAXParserFactory is in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @162a66a1)
This indicates to me that you may have another "normal" bundle that is exporting `javax.xml.parsers` package also?
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[GitHub] [felix-atomos] sten-navie commented on issue #60: ClassCastException when starting org.eclipse.equinox.metatype as a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
sten-navie commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1164154832
This does not seem to be related the equinox metatype implementation. I was able to repeat the same problem, by writing a simple Activator that just tracks javax.xml.parsers.SAXParserFactory. When receiving the reference I print out some info about the received class vs the wanted class and then try to cast the result, which again results in a ClassCastException:
```
g! lb
START LEVEL 1
ID|State |Level|Name
0|Active | 0|OSGi System Bundle (3.17.200.v20220215-2237)|3.17.200.v20220215-2237
1|Active | 1|java.base (11.0.14)|11.0.14
2|Active | 1|java.compiler (11.0.14)|11.0.14
3|Active | 1|java.datatransfer (11.0.14)|11.0.14
4|Active | 1|java.desktop (11.0.14)|11.0.14
5|Active | 1|java.logging (11.0.14)|11.0.14
6|Active | 1|java.management (11.0.14)|11.0.14
7|Active | 1|java.management.rmi (11.0.14)|11.0.14
8|Active | 1|java.naming (11.0.14)|11.0.14
9|Active | 1|java.prefs (11.0.14)|11.0.14
10|Active | 1|java.rmi (11.0.14)|11.0.14
11|Active | 1|java.security.jgss (11.0.14)|11.0.14
12|Active | 1|java.security.sasl (11.0.14)|11.0.14
13|Active | 1|java.smartcardio (11.0.14)|11.0.14
14|Active | 1|java.xml (11.0.14)|11.0.14
15|Active | 1|java.xml.crypto (11.0.14)|11.0.14
16|Active | 1|jdk.charsets (11.0.14)|11.0.14
17|Active | 1|jdk.compiler (11.0.14)|11.0.14
18|Active | 1|jdk.crypto.cryptoki (11.0.14)|11.0.14
19|Active | 1|jdk.crypto.ec (11.0.14)|11.0.14
20|Active | 1|jdk.internal.opt (11.0.14)|11.0.14
21|Active | 1|jdk.jartool (11.0.14)|11.0.14
22|Active | 1|jdk.javadoc (11.0.14)|11.0.14
23|Active | 1|jdk.jdeps (11.0.14)|11.0.14
24|Active | 1|jdk.jfr (11.0.14)|11.0.14
25|Active | 1|jdk.jlink (11.0.14)|11.0.14
26|Active | 1|jdk.localedata (11.0.14)|11.0.14
27|Active | 1|jdk.management (11.0.14)|11.0.14
28|Active | 1|jdk.management.jfr (11.0.14)|11.0.14
29|Active | 1|jdk.naming.dns (11.0.14)|11.0.14
30|Active | 1|jdk.naming.rmi (11.0.14)|11.0.14
31|Active | 1|jdk.security.auth (11.0.14)|11.0.14
32|Active | 1|jdk.security.jgss (11.0.14)|11.0.14
33|Active | 1|jdk.unsupported.desktop (11.0.14)|11.0.14
34|Active | 1|jdk.zipfs (11.0.14)|11.0.14
35|Active | 1|atomos (1.0.0)|1.0.0
36|Active | 1|Apache Felix Gogo Command (1.1.0)|1.1.0
37|Active | 1|Apache Felix Gogo Runtime (1.1.2)|1.1.2
38|Active | 1|Apache Felix Gogo Shell (1.1.2)|1.1.2
39|Active | 1|osgi.core (0.0.0)|0.0.0
g! felix:install file:///<REDACTED-PATH>/tmp/atomos-test/atomos-saxparser-test-1.0.0-SNAPSHOT.jar
Bundle ID: 40
g! felix:start 40
Starting SAX Test
Start tracking.
Wanted class : javax.xml.parsers.SAXParserFactory Module = unnamed module @554f5786, Loader = org.eclipse.osgi.internal.loader.EquinoxClassLoader@2097740[java.xml:11.0.14(id=14)]
Received impl class : com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl Module = module java.xml, Loader = null
Super class : javax.xml.parsers.SAXParserFactory Module = module java.xml, Loader = null
Super class : java.lang.Object Module = module java.base, Loader = null
Trying to cast
java.lang.ClassCastException: Cannot cast com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl to javax.xml.parsers.SAXParserFactory
```
The relevant code (full code here https://gist.github.com/sten-navie/278b2efa077d170fb530083c0648b2dd):
```
System.out.println("Starting SAX Test");
Class<SAXParserFactory> wantedClass = SAXParserFactory.class;
// use raw types, so that we do not immediately trigger a class-cast exception via an implicit cast
serviceTracker = new ServiceTracker(bundleContext, wantedClass, new ServiceTrackerCustomizer() {
@Override
public Object addingService(ServiceReference serviceReference) {
Object s = bundleContext.getService(serviceReference);
if (s == null) {
System.out.println("Got null ref!!!");
return null;
}
Class<?> implcl = s.getClass();
printClass("Wanted class", wantedClass);
printClass("Received impl class", implcl);
Class<?> supercl = implcl.getSuperclass();
while (supercl != null) {
printClass("Super class", supercl);
supercl = supercl.getSuperclass();
}
// try to cast
System.out.println("Trying to cast");
SAXParserFactory f = wantedClass.cast(s);
System.out.println("Cast successful. Done!");
return f;
}
```
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[GitHub] [felix-atomos] sten-navie commented on issue #60: ClassCastException when retrieving a SaxParserFactory service ref created by Equinox from a "Standard Bundle"
Posted by GitBox <gi...@apache.org>.
sten-navie commented on issue #60:
URL: https://github.com/apache/felix-atomos/issues/60#issuecomment-1164287132
> Do you use any startup options? Can you make sure that `osgi.compatibility.bootdelegation=false` is used?
For my simple test I do not set any startup options. So it is whatever options Atomos.main sets.
I tried to add `osgi.compatibility.bootdelegation=false` but it does not change the result.
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