JarFileUrlStreamHandler.java

package org.xbib.classloader.jar;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class JarFileUrlStreamHandler extends URLStreamHandler {

    private URL expectedUrl;

    private final JarFile jarFile;

    private final JarEntry jarEntry;

    public static URL createURL(JarFile jarFile, JarEntry jarEntry) throws MalformedURLException {
        return createURL(jarFile, jarEntry, new File(jarFile.getName()).toURI().toURL());
    }

    public static URL createURL(JarFile jarFile, JarEntry jarEntry, URL codeSource) throws MalformedURLException {
        JarFileUrlStreamHandler handler = new JarFileUrlStreamHandler(jarFile, jarEntry);
        URL url = new URL("jar", "", -1, codeSource + "!/" + jarEntry.getName(), handler);
        handler.setExpectedUrl(url);
        return url;
    }

    public JarFileUrlStreamHandler(JarFile jarFile, JarEntry jarEntry) {
        if (jarFile == null) {
            throw new NullPointerException("jarFile is null");
        }
        if (jarEntry == null) {
            throw new NullPointerException("jarEntry is null");
        }

        this.jarFile = jarFile;
        this.jarEntry = jarEntry;
    }

    public void setExpectedUrl(URL expectedUrl) {
        if (expectedUrl == null) {
            throw new NullPointerException("expectedUrl is null");
        }
        this.expectedUrl = expectedUrl;
    }

    public URLConnection openConnection(URL url) throws IOException {
        if (expectedUrl == null) {
            throw new IllegalStateException("expectedUrl was not set");
        }
        // the caller copied the URL reusing a stream handler from a previous call
        if (!expectedUrl.equals(url)) {
            // the new url is supposed to be within our context, so it must have a jar protocol
            if (!"jar".equals(url.getProtocol())) {
                throw new IllegalArgumentException("Unsupported protocol " + url.getProtocol());
            }
            // split the path at "!/" into the file part and entry part
            String path = url.getPath();
            String[] chunks = path.split("!/", 2);
            // if we only got only one chunk, it didn't contain the required "!/" delimiter
            if (chunks.length == 1) {
                throw new MalformedURLException("Url does not contain a '!' character: " + url);
            }
            String file = chunks[0];
            String entryPath = chunks[1];
            // this handler only supports jars on the local file system
            if (!file.startsWith("file:")) {
                // let the system handler deal with this
                return new URL(url.toExternalForm()).openConnection();
            }
            file = file.substring("file:".length());
            // again the new url is supposed to be within our context so it must reference the same jar file
            if (!jarFile.getName().equals(file)) {
                // let the system handler deal with this
                return new URL(url.toExternalForm()).openConnection();
            }
            // get the entry
            JarEntry newEntry = jarFile.getJarEntry(entryPath);
            if (newEntry == null) {
                throw new FileNotFoundException("Entry not found: " + url);
            }
            return new JarFileUrlConnection(url, jarFile, newEntry);
        }
        return new JarFileUrlConnection(url, jarFile, jarEntry);
    }
}