antclassloader.java

java ant的源码！非常值得看的源码

     * @return a stream to the named resource, or <code>null</code> if
     *         the resource cannot be found.
     */
    private InputStream loadBaseResource(String name) {
        if (parent == null) {
            return getSystemResourceAsStream(name);
        } else {
            return parent.getResourceAsStream(name);
        }
    }

    /**
     * Returns an inputstream to a given resource in the given file which may
     * either be a directory or a zip file.
     *
     * @param file the file (directory or jar) in which to search for the
     *             resource. Must not be <code>null</code>.
     * @param resourceName The name of the resource for which a stream is
     *                     required. Must not be <code>null</code>.
     *
     * @return a stream to the required resource or <code>null</code> if
     *         the resource cannot be found in the given file.
     */
    private InputStream getResourceStream(File file, String resourceName) {
        try {
            if (!file.exists()) {
                return null;
            }

            if (file.isDirectory()) {
                File resource = new File(file, resourceName);

                if (resource.exists()) {
                    return new FileInputStream(resource);
                }
            } else {
                // is the zip file in the cache
                ZipFile zipFile = (ZipFile) zipFiles.get(file);
                if (zipFile == null) {
                    zipFile = new ZipFile(file);
                    zipFiles.put(file, zipFile);
                }
                ZipEntry entry = zipFile.getEntry(resourceName);
                if (entry != null) {
                    return zipFile.getInputStream(entry);
                }
            }
        } catch (Exception e) {
            log("Ignoring Exception " + e.getClass().getName()
                + ": " + e.getMessage() + " reading resource " + resourceName
                + " from " + file, Project.MSG_VERBOSE);
        }

        return null;
    }

    /**
     * Tests whether or not the parent classloader should be checked for
     * a resource before this one. If the resource matches both the
     * "use parent classloader first" and the "use this classloader first"
     * lists, the latter takes priority.
     *
     * @param resourceName The name of the resource to check.
     *                     Must not be <code>null</code>.
     *
     * @return whether or not the parent classloader should be checked for a
     *         resource before this one is.
     */
    private boolean isParentFirst(String resourceName) {
        // default to the global setting and then see
        // if this class belongs to a package which has been
        // designated to use a specific loader first
        // (this one or the parent one)

        // XXX - shouldn't this always return false in isolated mode?

        boolean useParentFirst = parentFirst;

        for (Enumeration e = systemPackages.elements(); e.hasMoreElements();) {
            String packageName = (String) e.nextElement();
            if (resourceName.startsWith(packageName)) {
                useParentFirst = true;
                break;
            }
        }

        for (Enumeration e = loaderPackages.elements(); e.hasMoreElements();) {
            String packageName = (String) e.nextElement();
            if (resourceName.startsWith(packageName)) {
                useParentFirst = false;
                break;
            }
        }

        return useParentFirst;
    }

    /**
     * Used for isolated resource seaching.
     * @return the root classloader of AntClassLoader.
     */
    private ClassLoader getRootLoader() {
        ClassLoader ret = getClass().getClassLoader();
        while (ret != null && ret.getParent() != null) {
            ret = ret.getParent();
        }
        return ret;
    }

    /**
     * Finds the resource with the given name. A resource is
     * some data (images, audio, text, etc) that can be accessed by class
     * code in a way that is independent of the location of the code.
     *
     * @param name The name of the resource for which a stream is required.
     *             Must not be <code>null</code>.
     *
     * @return a URL for reading the resource, or <code>null</code> if the
     *         resource could not be found or the caller doesn't have
     *         adequate privileges to get the resource.
     */
    public URL getResource(String name) {
        // we need to search the components of the path to see if
        // we can find the class we want.
        URL url = null;
        if (isParentFirst(name)) {
            url = (parent == null) ? super.getResource(name)
                : parent.getResource(name);
        }

        if (url != null) {
            log("Resource " + name + " loaded from parent loader",
                Project.MSG_DEBUG);

        } else {
            // try and load from this loader if the parent either didn't find
            // it or wasn't consulted.
            Enumeration e = pathComponents.elements();
            while (e.hasMoreElements() && url == null) {
                File pathComponent = (File) e.nextElement();
                url = getResourceURL(pathComponent, name);
                if (url != null) {
                    log("Resource " + name
                        + " loaded from ant loader",
                        Project.MSG_DEBUG);
                }
            }
        }

        if (url == null && !isParentFirst(name)) {
            // this loader was first but it didn't find it - try the parent
            if (ignoreBase) {
                url = (getRootLoader() == null) ? null
                    : getRootLoader().getResource(name);
            } else {
                url = (parent == null) ? super.getResource(name)
                    : parent.getResource(name);
            }
            if (url != null) {
                log("Resource " + name + " loaded from parent loader",
                    Project.MSG_DEBUG);
            }
        }

        if (url == null) {
            log("Couldn't load Resource " + name, Project.MSG_DEBUG);
        }

        return url;
    }

    /**
     * Returns an enumeration of URLs representing all the resources with the
     * given name by searching the class loader's classpath.
     *
     * @param name The resource name to search for.
     *             Must not be <code>null</code>.
     * @return an enumeration of URLs for the resources
     * @exception IOException if I/O errors occurs (can't happen)
     */
    protected Enumeration/*<URL>*/ findResources(String name) throws IOException {
        Enumeration/*<URL>*/ mine = new ResourceEnumeration(name);
        Enumeration/*<URL>*/ base;
        if (parent != null && parent != getParent()) {
            // Delegate to the parent:
            base = parent.getResources(name);
            // Note: could cause overlaps in case ClassLoader.this.parent has matches.
        } else {
            // ClassLoader.this.parent is already delegated to from
            // ClassLoader.getResources, no need:
            base = new CollectionUtils.EmptyEnumeration();
        }
        if (isParentFirst(name)) {
            // Normal case.
            return CollectionUtils.append(base, mine);
        } else if (ignoreBase) {
            return getRootLoader() == null
                ? mine
                : CollectionUtils.append(
                    mine, getRootLoader().getResources(name));
        } else {
            // Inverted.
            return CollectionUtils.append(mine, base);
        }
    }

    /**
     * Returns the URL of a given resource in the given file which may
     * either be a directory or a zip file.
     *
     * @param file The file (directory or jar) in which to search for
     *             the resource. Must not be <code>null</code>.
     * @param resourceName The name of the resource for which a stream
     *                     is required. Must not be <code>null</code>.
     *
     * @return a stream to the required resource or <code>null</code> if the
     *         resource cannot be found in the given file object.
     */
    protected URL getResourceURL(File file, String resourceName) {
        try {
            if (!file.exists()) {
                return null;
            }

            if (file.isDirectory()) {
                File resource = new File(file, resourceName);

                if (resource.exists()) {
                    try {
                        return FILE_UTILS.getFileURL(resource);
                    } catch (MalformedURLException ex) {
                        return null;
                    }
                }
            } else {
                ZipFile zipFile = (ZipFile) zipFiles.get(file);
                if (zipFile == null) {
                    zipFile = new ZipFile(file);
                    zipFiles.put(file, zipFile);
                }

                ZipEntry entry = zipFile.getEntry(resourceName);
                if (entry != null) {
                    try {
                        return new URL("jar:" + FILE_UTILS.getFileURL(file)
                                       + "!/" + entry);
                    } catch (MalformedURLException ex) {
                        return null;
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * Loads a class with this class loader.
     *
     * This class attempts to load the class in an order determined by whether
     * or not the class matches the system/loader package lists, with the
     * loader package list taking priority. If the classloader is in isolated
     * mode, failure to load the class in this loader will result in a
     * ClassNotFoundException.
     *
     * @param classname The name of the class to be loaded.
     *                  Must not be <code>null</code>.
     * @param resolve <code>true</code> if all classes upon which this class
     *                depends are to be loaded.
     *
     * @return the required Class object
     *
     * @exception ClassNotFoundException if the requested class does not exist
     * on the system classpath (when not in isolated mode) or this loader's
     * classpath.
     */
    protected synchronized Class loadClass(String classname, boolean resolve)
        throws ClassNotFoundException {
        // 'sync' is needed - otherwise 2 threads can load the same class
        // twice, resulting in LinkageError: duplicated class definition.
        // findLoadedClass avoids that, but without sync it won't work.

        Class theClass = findLoadedClass(classname);
        if (theClass != null) {
            return theClass;
        }

        if (isParentFirst(classname)) {
            try {
                theClass = findBaseClass(classname);
                log("Class " + classname + " loaded from parent loader "
                    + "(parentFirst)", Project.MSG_DEBUG);
            } catch (ClassNotFoundException cnfe) {
                theClass = findClass(classname);
                log("Class " + classname + " loaded from ant loader "
                    + "(parentFirst)", Project.MSG_DEBUG);
            }
        } else {
            try {
                theClass = findClass(classname);
                log("Class " + classname + " loaded from ant loader",
                    Project.MSG_DEBUG);
            } catch (ClassNotFoundException cnfe) {
                if (ignoreBase) {
                    throw cnfe;
                }
                theClass = findBaseClass(classname);
                log("Class " + classname + " loaded from parent loader",
                    Project.MSG_DEBUG);
            }
        }

        if (resolve) {
            resolveClass(theClass);
        }

        return theClass;
    }

    /**
     * Converts the class dot notation to a filesystem equivalent for
     * searching purposes.
     *
     * @param classname The class name in dot format (eg java.lang.Integer).
     *                  Must not be <code>null</code>.
     *
     * @return the classname in filesystem format (eg java/lang/Integer.class)
     */
    private String getClassFilename(String classname) {
        return classname.replace('.', '/') + ".class";
    }

    /**
     * Define a class given its bytes
     *
     * @param container the container from which the class data has been read
     *                  may be a directory or a jar/zip file.
     *
     * @param classData the bytecode data for the class
     * @param classname the name of the class
     *
     * @return the Class instance created from the given data
     *
     * @throws IOException if the class data cannot be read.
     */
    protected Class defineClassFromData(File container, byte[] classData,
                                        String classname) throws IOException {
        definePackage(container, classname);
        // XXX should instead make a new ProtectionDomain with a CodeSource
        // corresponding to container.toURI().toURL() and the same
        // PermissionCollection as Project.class.protectionDomain had
        return defineClass(classname, classData, 0, classData.length,
                           Project.class.getProtectionDomain());
    }

    /**
     * Define the package information associated with a class.
     *
     * @param container the file containing the class definition.
     * @param className the class name of for which the package information
     *        is to be determined.
     *
     * @exception IOException if the package information cannot be read from the
     *            container.
     */
    protected void definePackage(File container, String className)
        throws IOException {
        int classIndex = className.lastIndexOf('.');
        if (classIndex == -1) {
            return;
        }

        String packageName = className.substring(0, classIndex);
        if (getPackage(packageName) != null) {
            // already defined
            return;
        }

        // define the package now
        Manifest manifest = getJarManifest(container);

        if (manifest == null) {
            definePackage(packageName, null, null, null, null, null,
                          null, null);
        } else {
            definePackage(container, packageName, manifest);