antclassloader.java

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    /**
     * Logs a message through the project object if one has been provided.
     *
     * @param message The message to log.
     *                Should not be <code>null</code>.
     *
     * @param priority The logging priority of the message.
     */
    protected void log(String message, int priority) {
        if (project != null) {
            project.log(message, priority);
        }
        //         else {
        //             System.out.println(message);
        //         }
    }

    /**
     * Sets the current thread's context loader to this classloader, storing
     * the current loader value for later resetting.
     */
    public void setThreadContextLoader() {
        if (isContextLoaderSaved) {
            throw new BuildException("Context loader has not been reset");
        }
        if (LoaderUtils.isContextLoaderAvailable()) {
            savedContextLoader = LoaderUtils.getContextClassLoader();
            ClassLoader loader = this;
            if (project != null
                && "only".equals(project.getProperty("build.sysclasspath"))) {
                loader = this.getClass().getClassLoader();
            }
            LoaderUtils.setContextClassLoader(loader);
            isContextLoaderSaved = true;
        }
    }

    /**
     * Resets the current thread's context loader to its original value.
     */
    public void resetThreadContextLoader() {
        if (LoaderUtils.isContextLoaderAvailable()
            && isContextLoaderSaved) {
            LoaderUtils.setContextClassLoader(savedContextLoader);
            savedContextLoader = null;
            isContextLoaderSaved = false;
        }
    }


    /**
     * Adds an element to the classpath to be searched.
     *
     * @param pathElement The path element to add. Must not be
     *                    <code>null</code>.
     *
     * @exception BuildException if the given path element cannot be resolved
     *                           against the project.
     */
    public void addPathElement(String pathElement) throws BuildException {
        File pathComponent
            = project != null ? project.resolveFile(pathElement)
            : new File(pathElement);
        try {
            addPathFile(pathComponent);
        } catch (IOException e) {
            throw new BuildException(e);
        }
    }

    /**
     * Add a path component.
     * This simply adds the file, unlike addPathElement
     * it does not open jar files and load files from
     * their CLASSPATH entry in the manifest file.
     * @param file the jar file or directory to add.
     */
    public void addPathComponent(File file) {
        if (pathComponents.contains(file)) {
            return;
        }
        pathComponents.addElement(file);
    }

    /**
     * Add a file to the path.
     * Reads the manifest, if available, and adds any additional class path jars
     * specified in the manifest.
     *
     * @param pathComponent the file which is to be added to the path for
     *                      this class loader
     *
     * @throws IOException if data needed from the file cannot be read.
     */
    protected void addPathFile(File pathComponent) throws IOException {
        pathComponents.addElement(pathComponent);
        if (pathComponent.isDirectory()) {
            return;
        }

        String absPathPlusTimeAndLength =
            pathComponent.getAbsolutePath() + pathComponent.lastModified() + "-"
            + pathComponent.length();
        String classpath = (String) pathMap.get(absPathPlusTimeAndLength);
        if (classpath == null) {
            ZipFile jarFile = null;
            InputStream manifestStream = null;
            try {
                jarFile = new ZipFile(pathComponent);
                manifestStream
                    = jarFile.getInputStream(new ZipEntry("META-INF/MANIFEST.MF"));

                if (manifestStream == null) {
                    return;
                }
                Reader manifestReader
                    = new InputStreamReader(manifestStream, "UTF-8");
                org.apache.tools.ant.taskdefs.Manifest manifest
                    = new org.apache.tools.ant.taskdefs.Manifest(manifestReader);
                classpath
                    = manifest.getMainSection().getAttributeValue("Class-Path");

            } catch (org.apache.tools.ant.taskdefs.ManifestException e) {
                // ignore
            } finally {
                FileUtils.close(manifestStream);
                if (jarFile != null) {
                    jarFile.close();
                }
            }
            if (classpath == null) {
                classpath = "";
            }
            pathMap.put(absPathPlusTimeAndLength, classpath);
        }

        if (!"".equals(classpath)) {
            URL baseURL = FILE_UTILS.getFileURL(pathComponent);
            StringTokenizer st = new StringTokenizer(classpath);
            while (st.hasMoreTokens()) {
                String classpathElement = st.nextToken();
                URL libraryURL = new URL(baseURL, classpathElement);
                if (!libraryURL.getProtocol().equals("file")) {
                    log("Skipping jar library " + classpathElement
                        + " since only relative URLs are supported by this"
                        + " loader", Project.MSG_VERBOSE);
                    continue;
                }
                String decodedPath = Locator.decodeUri(libraryURL.getFile());
                File libraryFile = new File(decodedPath);
                if (libraryFile.exists() && !isInPath(libraryFile)) {
                    addPathFile(libraryFile);
                }
            }
        }
    }

    /**
     * Returns the classpath this classloader will consult.
     *
     * @return the classpath used for this classloader, with elements
     *         separated by the path separator for the system.
     */
    public String getClasspath() {
        StringBuffer sb = new StringBuffer();
        boolean firstPass = true;
        Enumeration componentEnum = pathComponents.elements();
        while (componentEnum.hasMoreElements()) {
            if (!firstPass) {
                sb.append(System.getProperty("path.separator"));
            } else {
                firstPass = false;
            }
            sb.append(((File) componentEnum.nextElement()).getAbsolutePath());
        }
        return sb.toString();
    }

    /**
     * Sets whether this classloader should run in isolated mode. In
     * isolated mode, classes not found on the given classpath will
     * not be referred to the parent class loader but will cause a
     * ClassNotFoundException.
     *
     * @param isolated Whether or not this classloader should run in
     *                 isolated mode.
     */
    public synchronized void setIsolated(boolean isolated) {
        ignoreBase = isolated;
    }

    /**
     * Forces initialization of a class in a JDK 1.1 compatible, albeit hacky
     * way.
     *
     * @param theClass The class to initialize.
     *                 Must not be <code>null</code>.
     *
     * @deprecated since 1.6.x.
     *             Use Class.forName with initialize=true instead.
     */
    public static void initializeClass(Class theClass) {
        // ***HACK*** We ask the VM to create an instance
        // by voluntarily providing illegal arguments to force
        // the VM to run the class' static initializer, while
        // at the same time not running a valid constructor.

        final Constructor[] cons = theClass.getDeclaredConstructors();
        //At least one constructor is guaranteed to be there, but check anyway.
        if (cons != null) {
            if (cons.length > 0 && cons[0] != null) {
                final String[] strs = new String[NUMBER_OF_STRINGS];
                try {
                    cons[0].newInstance((Object[]) strs);
                    // Expecting an exception to be thrown by this call:
                    // IllegalArgumentException: wrong number of Arguments
                } catch (Exception e) {
                    // Ignore - we are interested only in the side
                    // effect - that of getting the static initializers
                    // invoked.  As we do not want to call a valid
                    // constructor to get this side effect, an
                    // attempt is made to call a hopefully
                    // invalid constructor - come on, nobody
                    // would have a constructor that takes in
                    // 256 String arguments ;-)
                    // (In fact, they can't - according to JVM spec
                    // section 4.10, the number of method parameters is limited
                    // to 255 by the definition of a method descriptor.
                    // Constructors count as methods here.)
                }
            }
        }
    }

    /**
     * Adds a package root to the list of packages which must be loaded on the
     * parent loader.
     *
     * All subpackages are also included.
     *
     * @param packageRoot The root of all packages to be included.
     *                    Should not be <code>null</code>.
     */
    public void addSystemPackageRoot(String packageRoot) {
        systemPackages.addElement(packageRoot
                                  + (packageRoot.endsWith(".") ? "" : "."));
    }

    /**
     * Adds a package root to the list of packages which must be loaded using
     * this loader.
     *
     * All subpackages are also included.
     *
     * @param packageRoot The root of all packages to be included.
     *                    Should not be <code>null</code>.
     */
    public void addLoaderPackageRoot(String packageRoot) {
        loaderPackages.addElement(packageRoot
                                  + (packageRoot.endsWith(".") ? "" : "."));
    }

    /**
     * Loads a class through this class loader even if that class is available
     * on the parent classpath.
     *
     * This ensures that any classes which are loaded by the returned class
     * will use this classloader.
     *
     * @param classname The name of the class to be loaded.
     *                  Must not be <code>null</code>.
     *
     * @return the required Class object
     *
     * @exception ClassNotFoundException if the requested class does not exist
     *                                   on this loader's classpath.
     */
    public Class forceLoadClass(String classname)
        throws ClassNotFoundException {
        log("force loading " + classname, Project.MSG_DEBUG);

        Class theClass = findLoadedClass(classname);

        if (theClass == null) {
            theClass = findClass(classname);
        }

        return theClass;
    }

    /**
     * Loads a class through this class loader but defer to the parent class
     * loader.
     *
     * This ensures that instances of the returned class will be compatible
     * with instances which have already been loaded on the parent
     * loader.
     *
     * @param classname The name of the class to be loaded.
     *                  Must not be <code>null</code>.
     *
     * @return the required Class object
     *
     * @exception ClassNotFoundException if the requested class does not exist
     * on this loader's classpath.
     */
    public Class forceLoadSystemClass(String classname)
        throws ClassNotFoundException {
        log("force system loading " + classname, Project.MSG_DEBUG);

        Class theClass = findLoadedClass(classname);

        if (theClass == null) {
            theClass = findBaseClass(classname);
        }

        return theClass;
    }

    /**
     * Returns a stream to read the requested resource name.
     *
     * @param name 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 on the loader's classpath.
     */
    public InputStream getResourceAsStream(String name) {

        InputStream resourceStream = null;
        if (isParentFirst(name)) {
            resourceStream = loadBaseResource(name);
            if (resourceStream != null) {
                log("ResourceStream for " + name
                    + " loaded from parent loader", Project.MSG_DEBUG);

            } else {
                resourceStream = loadResource(name);
                if (resourceStream != null) {
                    log("ResourceStream for " + name
                        + " loaded from ant loader", Project.MSG_DEBUG);
                }
            }
        } else {
            resourceStream = loadResource(name);
            if (resourceStream != null) {
                log("ResourceStream for " + name
                    + " loaded from ant loader", Project.MSG_DEBUG);

            } else {
                resourceStream = loadBaseResource(name);
                if (resourceStream != null) {
                    log("ResourceStream for " + name
                        + " loaded from parent loader", Project.MSG_DEBUG);
                }
            }
        }

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

        return resourceStream;
    }

    /**
     * Returns a stream to read the requested resource name from this loader.
     *
     * @param name 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 on the loader's classpath.
     */
    private InputStream loadResource(String name) {
        // we need to search the components of the path to see if we can
        // find the class we want.
        InputStream stream = null;

        Enumeration e = pathComponents.elements();
        while (e.hasMoreElements() && stream == null) {
            File pathComponent = (File) e.nextElement();
            stream = getResourceStream(pathComponent, name);
        }
        return stream;
    }