How to get list of classes from a package (original) (raw)
Ulf Zibis Ulf.Zibis at gmx.de
Mon Feb 16 21:30:31 UTC 2009
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Am 16.02.2009 21:35, Rémi Forax schrieb:
Tom Hawtin a écrit :
David M. Lloyd wrote:
On 02/16/2009 10:22 AM, Ulf Zibis wrote:
can anybody tell me, how I could get al list or enumeration of the classes, which belong to a package. I can't see any appropriate method in java.lang.Package :-( This isn't really possible at run time, since one doesn't know whether a class exists until one tries to load it. The classloader might not even know. Also, a package can span classloaders, adding more complexity to the problem. IIRC, you will get a different Package for each class loader, for a given package name. Certainly classes with the same package name will not have Java access to default/protected members/classes/interface/constructors from different class loaders. But yes, a list of classes is not necessarily complete. Also, IIRC, Proxy dynamically inserts classes into packages as well. Tom Hawtin Ulf, if you can create an agent, you can get all loaded classes: http://download.java.net/jdk7/docs/api/java/lang/instrument/Instrumentation.html#getAllLoadedClasses() But if you want thoses classes to find some that implement an interface, java.util.ServiceLoader is your friend: http://download.java.net/jdk7/docs/api/java/util/ServiceLoader.html cheers, Rémi
Hi David, Tom and Rémi,
very much thanks for your hints. They were really valuable. :-) I just finished to code a tricky solution:
package sun.nio.cs;
import java.io.; import java.net.; import java.nio.charset.; import java.util.; import java.util.jar.*;
/** *
@author Ulf Zibis <Ulf.Zibis at CoSoCo.de> */ public class LegacyCharsets {
private static StandardCharsets standChars = new StandardCharsets(); // Maps lowered canonical names to legacy class names static final Map<String,String> legacyClassNameMap;
static { legacyClassNameMap = new HashMap(256); collectLegacyClassNames("StandardCharsets.class"); collectLegacyClassNames("ext/DelegatableDecoder.class"); }
@SuppressWarnings("static-access") private static void collectLegacyClassNames(String searchAnchor) { String[] paths =
LegacyCharsets.class.getResource(searchAnchor).getPath().split("!"); paths[1] = paths[1].substring(paths[1].indexOf('/')+1, paths[1].lastIndexOf('/')); try { Enumeration en = new JarFile(new File(new URI(paths[0]))).entries(); while (en.hasMoreElements()) { String name = en.nextElement().getName(); int extPos; if (name.indexOf('$') < 0 && name.startsWith(paths[1]) && (extPos = name.indexOf(".class")) > 0) { Class c = Class.forName(name.substring(0, extPos).replace('/', '.'), true, LegacyCharsets.class.getClassLoader()); if (Charset.class.isAssignableFrom(c)) try {
legacyClassNameMap.put(standChars.toLower(((Charset)c.newInstance()).name()),
c.getName().substring("sun.nio.cs.".length())); } catch (IllegalAccessException iae) { } catch (InstantiationException ie) {} } } } catch (Exception ex) { System.err.println(ex); } }
@SuppressWarnings("static-access")
static Charset legacyCharset(String canonicalName) {
return standChars.newCharsetForClassName(legacyClassNameMap.get(standChars.toLower(canonicalName))); } }
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