UPDATE 1: Indeed, the URL format differences cause the error. Here is a unit test (cut and obfuscated by hand; hope I didn't miss anything) showing the problem:
@Test
public void wheresWaldo2() throws ClassNotFoundException, IllegalAccessException, InstantiationException, IOException, NoSuchMethodException {
// Find Waldo from file:/someLocation/waldo.jar. Prove that works.
URL waldosJar = new File("/someLocation/waldo.jar").toURI().toURL();
assertNotNull(waldosJar);
assertEquals("file", waldosJar.getProtocol());
String waldosPath = waldosJar.getPath();
assertNotNull(waldosPath);
assertTrue(waldosPath.endsWith("/waldo.jar"));
ClassLoader cl = new URLClassLoader(new URL[] { waldosJar }, this.getClass().getClassLoader());
Class<?> waldosClass = cl.loadClass("com.foobar.Waldo");
assertNotNull(waldosClass);
assertEquals("com.foobar.Waldo", waldosClass.getName());
assertSame(cl, waldosClass.getClassLoader());
Class<?> jimbosClass = cl.loadClass("com.foobar.Jimbo"); // Note: works
assertNotNull(jimbosClass);
// Find Waldo from jar:file:/someLocation/waldo.jar!/. Prove that works.
// This URL, when passed to a URLClassLoader, should result in the same
// functionality as the first one. But it doesn't.
waldosJar = new URL("jar:" + waldosJar.toExternalForm() + "!/");
assertEquals("jar", waldosJar.getProtocol());
assertEquals("file:" + waldosPath + "!/", waldosJar.getPath());
cl = new URLClassLoader(new URL[] { waldosJar }, this.getClass().getClassLoader());
waldosClass = cl.loadClass("com.foobar.Waldo");
assertNotNull(waldosClass);
assertEquals("com.foobar.Waldo", waldosClass.getName());
assertSame(cl, waldosClass.getClassLoader());
jimbosClass = cl.loadClass("com.foobar.Jimbo"); // XXX FAILS
}
UPDATE 0: The problem may have to do with the supposed, but not actual, equivalence between two URLs referring to a jar file. For example, the following two URLs are supposed to refer to the same file:
file:/myjar.jarjar:file:/myjar.jar!/
When I pass a URL built from the first format to my machinery, I think things are working. When I pass a URL built from the second format, I get the results described below. I am testing more to confirm all this beyond a doubt.
ORIGINAL QUESTION
(I am aware of this question.)
I have a jar file, waldo.jar, that contains a META-INF/MANIFEST.MF that looks like this:
Manifest-Version: 1.0
Class-Path: jimbo.jar
It also has a class at the following location within it:
com/foobar/Waldo.class
The class' source code is essentially:
package com.foobar;
public class Waldo {
public Jimbo getJimbo() {
return null;
}
}
Next, in the same directory, I have a jar file, jimbo.jar, that contains a class at the following location within it:
com/foobar/Jimbo.class
That class' source code is essentially:
package com.foobar;
public class Jimbo {
}
Now I construct a URLClassLoader with a URL to waldo.jar. To review: jimbo.jar contains Jimbo and is "next to" waldo.jar, and is listed in waldo.jar's META-INF/MANIFEST-MF's Class-Path header appropriately. waldo.jar contains Waldo, that has a code reference to Jimbo. With me so far?
I can load com.foobar.Waldo just fine. But if I do something with Waldo that involves com.foobar.Jimbo, like, for example, calling Waldo.class.getDeclaredMethod("getJimbo"), I get a NoClassDefFoundError. Here is a sample stack:
java.lang.NoClassDefFoundError: com/foobar/Jimbo
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
at java.lang.Class.getDeclaredMethod(Class.java:2128)
at com.foobar.TestClassLoadingProblems.wheresWaldo(TestClassLoadingProblems.java:115)
Caused by:
java.lang.ClassNotFoundException: com.foobar.Jimbo
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at com.foobar.MyClassLoader.findClass(...) // calls super.findClass()
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
This suggests to me that URLClassLoader is not consulting the Class-Path header properly in all cases (I'm aware of how it works in general).
Can anyone shed light on what is happening here?
