Custom class loader returns NoSuchMethodException in listFilesAndDirs() method call

[kavin.gasc]

I am trying to invoke the method listFilesAndDirs() of org.apache.commons.io.FileUtils using my own custom class loader. But it returns NoSuchMethodException.
Code used for method invoke.

MyLoader c=new MyLoader();
Class cls=c.loadClass("org.apache.commons.io.FileUtils");
//to display the available methods
Method m[] = cls.getDeclaredMethods();
for (int i = 0; i < m.length; i++)
  System.out.println(m[i].toString());
 
// to get a listFilesAndDirs method
Method me=cls.getMethod("listFilesAndDirs",new Class[] { File.class, IOFileFilter.class,
            IOFileFilter.class });

Code used for class loader

public class MyLoader extends ClassLoader {
private  String classPath;
public MyLoader()
{
 
}
private String jarFile = "D:/Project/lib/commons-io-2.4.jar";;          //Path to the jar file  
private Hashtable classes = new Hashtable(); //used to cache already defined classes  
 
public Class loadClass(String className) throws ClassNotFoundException {  
 
return findClass(className);  
}  
 
public Class findClass(String className) {  
//System.out.println(className+" is loaded by Custom class Loader");
 
 
byte classByte[];  
Class result = null;  
 
result = (Class) classes.get(className); //checks in cached classes  
if (result != null) {  
    return result;  
}  
 
 
 
try {
    JarFile jar = new JarFile(jarFile);  
    classPath=className.replaceAll("\\.", "/");
    JarEntry entry = jar.getJarEntry(classPath + ".class"); 
    if(entry==null)
    {
         return findSystemClass(className);  
    }
    else
    {
 
    InputStream is = jar.getInputStream(entry);  
    ByteArrayOutputStream byteStream = new ByteArrayOutputStream();  
    int nextValue = is.read();  
    while (-1 != nextValue) {  
        byteStream.write(nextValue);  
        nextValue = is.read();  
    }  
 
    classByte = byteStream.toByteArray(); 
    result = defineClass(className, classByte, 0, classByte.length, null);  
    classes.put(className, result);  
    return result;  
    }
} catch (Exception e) {  
    return null;  
}  
 
 
 } 
 }

call of cls.getDeclaredMethods() will return the method org.apache.commons.io.FileUtils.listFilesAndDirs(j ava.io.File,org.apache.commons.io.filefilter.IOFil eFilter,org.apache.commons.io.filefilter.IOFileFil ter)

but cls.getMethod("listFilesAndDirs",new Class[] { File.class, IOFileFilter.class, IOFileFilter.class }); returns the following error

java.lang.NoSuchMethodException: org.apache.commons.io.FileUtils.listFilesAndDirs(j ava.io.File, org.apache.commons.io.filefilter.IOFileFilter, org.apache.commons.io.filefilter.IOFileFilter) at java.lang.Class.getDeclaredMethod(Class.java:1937) at Sample.main(Sample.java:30)

[copeg]

Interesting problem...my suspicion is that you have two different ClassLoaders which is causing two different class definitions. The problem then becomes when you're custom ClassLoader reads in a class, it's dependencies may be different than that already on the classpath (in this case, IOFileFilter.class). When you try and call a method, the Class parameters your code defines differs from that of the Class you read in. As evidence, try calling getMethod() on a method that doesn't rely on any of the 3rd party classes, for instance sizeof(). or moveFile()

Edit: Running this through Eclipse debugger, sure enough if IOFileFilter.class defined from 'IOFileFilter.class' differs from that defined by getParameterTypes() of the corresponding method. Given the code in Class compares using ==, the getMethod search fails. Try defining the class using your ClassLoader:

Class ioFileFilter = c.loadClass("org.apache.commons.io.filefilter.IOFileFilter");

[GregBrannon]

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