How to get list of classes from a package (original) (raw)

Ulf Zibis Ulf.Zibis at gmx.de
Mon Feb 16 22:35:37 UTC 2009

Martin,

thanks for your additional hints.

I'm aware, that my solution is not suitable for general cases, but it solves my needs perfectly. For my enhancement of charsets I need to compare my new coders against the legacy coders from rt.jar + charsets.jar from JDK 6 for testing equality.

-Ulf

Am 16.02.2009 23:08, Martin Buchholz schrieb:

Ulf,

This kind of solution is likely to be brittle. For example, you appear to assume that the code you are looking for is in a jar file. But it might not be; in jdk "developer mode", they are likely to be in a "classes" directory. Martin On Mon, Feb 16, 2009 at 13:30, Ulf Zibis <Ulf.Zibis at gmx.de> wrote:

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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