ClassLoaderDemo0public class ClassLoaderDemo0 extends ClassLoader | Simple Demonstration of a ClassLoader
WILL NOT COMPILE OUT OF THE BOX -- WILL ONLY WORK AS PART OF
THE CLASSLOADER EXERCISE. See ClassLoader1 for a working version. |
| Fields Summary |
|---|
| protected Hashtable | cacheThe Hashtable to keep track of classes, to avoid re-loading them | | byte[] | dataINSERT HERE THE RESULT OF DUMPING DEMO.CLASS | | int | dataLength |
| Methods Summary |
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| private byte[] | genClassData(java.lang.String name)"load", that is, generate, the data for the class
if (dataLength != data.length) // EXPECT COMPILE ERROR in javasrc
throw new IllegalArgumentException(
"data corrupt, " + dataLength + "!=" + data.length);
byte[] bd = new byte[data.length];
for (int i=0; i<bd.length; i++)
bd[i] = (byte)data[i];
return bd;
| | public synchronized java.lang.Class | loadClass(java.lang.String name, boolean resolve)
Class c = (Class)cache.get(name);
if (c == null) {
// System.out.println("loadClass: About to genClassData " + name);
byte mydata[] = genClassData(name);
// System.out.println("loadClass: About to defineClass " + name);
c = defineClass(name, mydata, 0, mydata.length);
System.out.println("loadClass: storing " + name + " in cache.");
cache.put(name, c);
} else
System.out.println("loadClass: found " + name + " in cache.");
if (resolve) {
System.out.println("loadClass: About to resolveClass " + name);
resolveClass(c);
}
return c;
| | public static void | main(java.lang.String[] argv)
System.out.println("ClassLoaderDemo starting");
ClassLoaderDemo0 loader = new ClassLoaderDemo0();
Class c = null;
Object demo;
try {
/* Load the "Demo" class from memory */
System.out.println("About to load class Demo");
c = loader.loadClass("Demo", true);
System.out.println("About to instantiate class Demo");
demo = c.newInstance();
System.out.println("Got Demo class loaded: " + demo);
/* Now try to call a method */
Method mi = c.getMethod("test", null);
mi.invoke(demo, null);
} catch (InvocationTargetException e) {
// The invoked method threw an exception. We get it
// wrapped up inside another exception, hence the
// extra call here:
e.getTargetException().printStackTrace();
System.out.println("Could not run test method");
} catch (Exception e) {
e.printStackTrace();
System.out.println("Could not run test method");
}
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