antclassloader.java

java ant的源码！非常值得看的源码

        }
    }

    /**
     * Get the manifest from the given jar, if it is indeed a jar and it has a
     * manifest
     *
     * @param container the File from which a manifest is required.
     *
     * @return the jar's manifest or null is the container is not a jar or it
     *         has no manifest.
     *
     * @exception IOException if the manifest cannot be read.
     */
    private Manifest getJarManifest(File container) throws IOException {
        if (container.isDirectory()) {
            return null;
        }
        JarFile jarFile = null;
        try {
            jarFile = new JarFile(container);
            return jarFile.getManifest();
        } finally {
            if (jarFile != null) {
                jarFile.close();
            }
        }
    }

    /**
     * Define the package information when the class comes from a
     * jar with a manifest
     *
     * @param container the jar file containing the manifest
     * @param packageName the name of the package being defined.
     * @param manifest the jar's manifest
     */
    protected void definePackage(File container, String packageName,
                                 Manifest manifest) {
        String sectionName = packageName.replace('.', '/') + "/";

        String specificationTitle = null;
        String specificationVendor = null;
        String specificationVersion = null;
        String implementationTitle = null;
        String implementationVendor = null;
        String implementationVersion = null;
        String sealedString = null;
        URL sealBase = null;

        Attributes sectionAttributes = manifest.getAttributes(sectionName);
        if (sectionAttributes != null) {
            specificationTitle
                = sectionAttributes.getValue(Name.SPECIFICATION_TITLE);
            specificationVendor
                = sectionAttributes.getValue(Name.SPECIFICATION_VENDOR);
            specificationVersion
                = sectionAttributes.getValue(Name.SPECIFICATION_VERSION);
            implementationTitle
                = sectionAttributes.getValue(Name.IMPLEMENTATION_TITLE);
            implementationVendor
                = sectionAttributes.getValue(Name.IMPLEMENTATION_VENDOR);
            implementationVersion
                = sectionAttributes.getValue(Name.IMPLEMENTATION_VERSION);
            sealedString
                = sectionAttributes.getValue(Name.SEALED);
        }

        Attributes mainAttributes = manifest.getMainAttributes();
        if (mainAttributes != null) {
            if (specificationTitle == null) {
                specificationTitle
                    = mainAttributes.getValue(Name.SPECIFICATION_TITLE);
            }
            if (specificationVendor == null) {
                specificationVendor
                    = mainAttributes.getValue(Name.SPECIFICATION_VENDOR);
            }
            if (specificationVersion == null) {
                specificationVersion
                    = mainAttributes.getValue(Name.SPECIFICATION_VERSION);
            }
            if (implementationTitle == null) {
                implementationTitle
                    = mainAttributes.getValue(Name.IMPLEMENTATION_TITLE);
            }
            if (implementationVendor == null) {
                implementationVendor
                    = mainAttributes.getValue(Name.IMPLEMENTATION_VENDOR);
            }
            if (implementationVersion == null) {
                implementationVersion
                    = mainAttributes.getValue(Name.IMPLEMENTATION_VERSION);
            }
            if (sealedString == null) {
                sealedString
                    = mainAttributes.getValue(Name.SEALED);
            }
        }

        if (sealedString != null && sealedString.equalsIgnoreCase("true")) {
            try {
                sealBase = new URL(FileUtils.getFileUtils().toURI(container.getAbsolutePath()));
            } catch (MalformedURLException e) {
                // ignore
            }
        }

        definePackage(packageName, specificationTitle, specificationVersion,
                      specificationVendor, implementationTitle,
                      implementationVersion, implementationVendor, sealBase);
    }


    /**
     * Reads a class definition from a stream.
     *
     * @param stream The stream from which the class is to be read.
     *               Must not be <code>null</code>.
     * @param classname The name of the class in the stream.
     *                  Must not be <code>null</code>.
     * @param container the file or directory containing the class.
     *
     * @return the Class object read from the stream.
     *
     * @exception IOException if there is a problem reading the class from the
     * stream.
     * @exception SecurityException if there is a security problem while
     * reading the class from the stream.
     */
    private Class getClassFromStream(InputStream stream, String classname,
                                     File container)
        throws IOException, SecurityException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        int bytesRead = -1;
        byte[] buffer = new byte[BUFFER_SIZE];

        while ((bytesRead = stream.read(buffer, 0, BUFFER_SIZE)) != -1) {
            baos.write(buffer, 0, bytesRead);
        }

        byte[] classData = baos.toByteArray();
        return defineClassFromData(container, classData, classname);
    }

    /**
     * Searches for and load a class on the classpath of this class loader.
     *
     * @param name 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 findClass(String name) throws ClassNotFoundException {
        log("Finding class " + name, Project.MSG_DEBUG);

        return findClassInComponents(name);
    }

    /**
     * Indicate if the given file is in this loader's path
     *
     * @param component the file which is to be checked
     *
     * @return true if the file is in the class path
     */
    protected boolean isInPath(File component) {
        for (Enumeration e = pathComponents.elements(); e.hasMoreElements();) {
            File pathComponent = (File) e.nextElement();
            if (pathComponent.equals(component)) {
                return true;
            }
        }
        return false;
    }


    /**
     * Finds a class on the given classpath.
     *
     * @param name 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.
     */
    private Class findClassInComponents(String name)
        throws ClassNotFoundException {
        // we need to search the components of the path to see if
        // we can find the class we want.
        InputStream stream = null;
        String classFilename = getClassFilename(name);
        try {
            Enumeration e = pathComponents.elements();
            while (e.hasMoreElements()) {
                File pathComponent = (File) e.nextElement();
                try {
                    stream = getResourceStream(pathComponent, classFilename);
                    if (stream != null) {
                        log("Loaded from " + pathComponent + " "
                            + classFilename, Project.MSG_DEBUG);
                        return getClassFromStream(stream, name, pathComponent);
                    }
                } catch (SecurityException se) {
                    throw se;
                } catch (IOException ioe) {
                    // ioe.printStackTrace();
                    log("Exception reading component " + pathComponent
                        + " (reason: " + ioe.getMessage() + ")",
                        Project.MSG_VERBOSE);
                }
            }

            throw new ClassNotFoundException(name);
        } finally {
            try {
                if (stream != null) {
                    stream.close();
                }
            } catch (IOException e) {
                //ignore
            }
        }
    }

    /**
     * Finds a system class (which should be loaded from the same classloader
     * as the Ant core).
     *
     * For JDK 1.1 compatibility, this uses the findSystemClass method if
     * no parent classloader has been specified.
     *
     * @param name 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.
     */
    private Class findBaseClass(String name) throws ClassNotFoundException {
        if (parent == null) {
            return findSystemClass(name);
        } else {
            return parent.loadClass(name);
        }
    }

    /**
     * Cleans up any resources held by this classloader. Any open archive
     * files are closed.
     */
    public synchronized void cleanup() {
        for (Enumeration e = zipFiles.elements(); e.hasMoreElements();) {
            ZipFile zipFile = (ZipFile) e.nextElement();
            try {
                zipFile.close();
            } catch (IOException ioe) {
                // ignore
            }
        }
        zipFiles = new Hashtable();
        if (project != null) {
            project.removeBuildListener(this);
        }
        project = null;
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the buildStarted event
     */
    public void buildStarted(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * Cleans up any resources held by this classloader at the end
     * of a build.
     *
     * @param event the buildFinished event
     */
    public void buildFinished(BuildEvent event) {
        cleanup();
    }

    /**
     * Cleans up any resources held by this classloader at the end of
     * a subbuild if it has been created for the subbuild's project
     * instance.
     *
     * @param event the buildFinished event
     *
     * @since Ant 1.6.2
     */
    public void subBuildFinished(BuildEvent event) {
        if (event.getProject() == project) {
            cleanup();
        }
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the buildStarted event
     *
     * @since Ant 1.6.2
     */
    public void subBuildStarted(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the targetStarted event
     */
    public void targetStarted(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the targetFinished event
     */
    public void targetFinished(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the taskStarted event
     */
    public void taskStarted(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the taskFinished event
     */
    public void taskFinished(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * Empty implementation to satisfy the BuildListener interface.
     *
     * @param event the messageLogged event
     */
    public void messageLogged(BuildEvent event) {
        // Not significant for the class loader.
    }

    /**
     * add any libraries that come with different java versions
     * here
     */
    public void addJavaLibraries() {
        Vector packages = JavaEnvUtils.getJrePackages();
        Enumeration e = packages.elements();
        while (e.hasMoreElements()) {
            String packageName = (String) e.nextElement();
            addSystemPackageRoot(packageName);
        }
    }

    /**
     * Returns a <code>String</code> representing this loader.
     * @return the path that this classloader has.
     */
    public String toString() {
        return "AntClassLoader[" + getClasspath() + "]";
    }

}