Classpath Resources

Classpath.java

package net.danieldietrich;

import java.io.File;
import java.net.URI;
import java.net.URL;
import java.util.Collections;
import java.util.regex.Pattern;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

/**
 * Based on the Java classpath specification
 *
 * http://docs.oracle.com/javase/1.5.0/docs/tooldocs/solaris/classpath.html
 * http://docs.oracle.com/javase/1.5.0/docs/tooldocs/windows/classpath.html
 *
 * the classpath is scanned for resources, which match a given regex pattern.
 *
 * Results are passed to a Visitor.
 *
 * @author Daniel Dietrich
 */
public class Classpath {

    private final Pattern pattern;

    public Classpath(final Pattern pattern) {
        this.pattern = pattern;
    }

    public void getResources(final Visitor visitor) throws Exception {
        final String classpath = System.getProperty("java.class.path", ".");
        final String[] classpathElements = classpath.split(File.pathSeparator);
        for (final String element : classpathElements) {
            getResources(element, visitor);
        }
    }

    private void getResources(final String element, final Visitor visitor) throws Exception {
        final File file = new File(element);
        if (file.isDirectory()) {
            getResourcesFromDirectory("", file, visitor);
        } else if (isJarOrZip(file)) {
            getResourcesFromJarFile(file, visitor);
        } else {
            // TODO: LOGGER.info("Ignoring classpath element {}. It is no directory and not a jar/zip file.", element);
        }
    }

    private void getResourcesFromJarFile(final File file, final Visitor visitor) throws Exception {
		final ZipFile zipFile = new ZipFile(file);
		for(final ZipEntry zipEntry : Collections.list(zipFile.entries())) {
			if(!zipEntry.isDirectory()) {
				final String resource = zipEntry.getName();
				final boolean accept = pattern.matcher(resource).matches();
				if(accept) {
					final String path = file.getCanonicalPath().replaceAll("\\\\", "/");
					final String escaped = "jar:file:" + escape(path) + "!/" + escape(resource);
					final URL url = new URI(escaped).toURL();
					visitor.visit(resource, url);
				}
			}
		}
		zipFile.close();
	}

	private void getResourcesFromDirectory(final String path, final File directory,
			final Visitor visitor) throws Exception {
		final File[] fileList = directory.listFiles();
		for(final File file : fileList) {
			if(file.isDirectory()) {
				getResourcesFromDirectory(path + file.getName() + "/", file, visitor);
			} else {
				final String fileName = file.getCanonicalPath();
				final boolean accept = pattern.matcher(fileName).matches();
				if(accept) {
					final URL url = file.toURI().toURL();
					visitor.visit(path + file.getName(), url);
				}
			}
		}
	}

    private boolean isJarOrZip(final File file) {
        // TODO(nice2have): ensure that file content is zip
        final String name = file.getName().toLowerCase();
        return name.endsWith(".jar") || name.endsWith(".zip");
    }

    private String escape(final String s) {
        // TODO(nice2have): escape all characters accordingly to RFC 2396
        return s.replaceAll(" ", "%20");
    }

    public static interface Visitor {
        void visit(String resource, URL url) throws Exception;
    }
}

Main.java

package net.danieldietrich;

import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Pattern;

/**
 * Search the classpath for resources which match a specific pattern.
 *
 * Arguments:
 *   -Dpattern=<search pattern> (optional, default: .*)
 *   -Dregex=[true|false] (optional, default: false)
 *
 * Example:
 *   -Dpattern=*\xml\*.xsd
 * is the same as
 *   -Dpattern=.*\\xml\\.*\.xsd -Dregex=true
 *
 * @author Daniel Dietrich
 */
public class Main {

    public void run(final Pattern pattern) throws Exception {
        new Classpath(pattern).getResources(
                new Classpath.Visitor() {
                    private Map<String, URL> visited = new HashMap<String, URL>();

                    @Override
                    public void visit(final String resource, final URL url) throws Exception {
                        if (!visited.containsKey(resource)) {
                            visited.put(resource, url);
                            /*DELME*/System.out.println("found " + resource + " (" + url + ")");
                            // TODO: LOGGER.info("found {} ({})", resource, url);
                            // TODO: copy resource to a specific place via url.openStream()
                        } else {
                            /*DELME*/System.out.println("skipping " + resource + " (" + url + " overwritten by " + visited.get(resource) + ")");
                            // TODO: LOGGER.info("skipping {} ({} overwritten by {})", resource, url, visited.get(resource));
                        }
                    }
                }
        );
    }

    public static void main(final String[] args) throws Exception {
        new Main().run(getPattern());
    }

    private static Pattern getPattern() {
        final String arg = System.getProperty("pattern");
        if (arg == null) {
            return Pattern.compile(".*");
        } else {
            final boolean isRegex = Boolean.getBoolean("regex");
            final String pattern = isRegex ? arg : arg
                    // escape escape-character
                    .replaceAll("\\\\", "\\\\\\\\")
                    // escape wildcard-character
                    .replaceAll("\\.", "\\\\.")
                    // substitute asterisk '*' with wildcard-character '.*'
                    .replaceAll("\\*", ".*");
            return Pattern.compile(pattern);
        }
    }
}