guacamole/src/main/java/org/apache/guacamole/extension/ExtensionClassLoader.java - guacamole-client - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing,
  * software distributed under the License is distributed on an
  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  * KIND, either express or implied.  See the License for the
  * specific language governing permissions and limitations
  * under the License.
  */

 package org.apache.guacamole.extension;

 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 import org.apache.guacamole.GuacamoleException;
 import org.apache.guacamole.GuacamoleServerException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 /**
  * ClassLoader implementation which prioritizes the classes defined within a
  * given extension .jar file. Unlike the standard URLClassLoader, classes
  * within the parent ClassLoader are only used if they are not defined within
  * the given .jar. If classes are defined in both the parent and the extension
  * .jar, the versions defined within the extension .jar are used.
  */
 public class ExtensionClassLoader extends URLClassLoader {

     /**
      * Logger for this class.
      */
     private static final Logger logger = LoggerFactory.getLogger(ExtensionClassLoader.class);

     /**
      * The prefix that should be given to the temporary directory containing
      * all library .jar files that were bundled with the extension.
      */
     private static final String EXTENSION_TEMP_DIR_PREFIX = "guac-extension-lib-";

     /**
      * The prefix that should be given to any files created for temporary
      * storage of a library .jar file that was bundled with the extension.
      */
     private static final String EXTENSION_TEMP_LIB_PREFIX = "bundled-";

     /**
      * The ClassLoader to use if class resolution through the extension .jar
      * fails.
      */
     private final ClassLoader parent;

     /**
      * Returns the URL that refers to the given file. If the given file refers
      * to a directory, an exception is thrown.
      *
      * @param file
      *     The file to determine the URL of.
      *
      * @return
      *     A URL that refers to the given file.
      *
      * @throws GuacamoleException
      *     If the given file refers to a directory.
      */
     private static URL getFileURL(File file) throws GuacamoleException {

         // Validate extension-related file is indeed a file
         if (!file.isFile())
             throw new GuacamoleServerException("\"" + file + "\" is not a file.");

         try {
             return file.toURI().toURL();
         }
         catch (MalformedURLException e) {
             throw new GuacamoleServerException(e);
         }

     }

     /**
      * Copies all bytes of data from a file within a .jar to a destination
      * file.
      *
      * @param jar
      *     The JarFile containing the file to be copied.
      *
      * @param source
      *     The JarEntry representing the file to be copied within the given
      *     JarFile.
      *
      * @param dest
      *     The destination file that the data should be copied to.
      *
      * @throws IOException
      *     If an error occurs reading from the source .jar or writing to the
      *     destination file.
      */
     private static void copyEntryToFile(JarFile jar, JarEntry source, File dest)
             throws IOException {

         int length;
         byte[] buffer = new byte[8192];

         try (InputStream input = jar.getInputStream(source)) {
             try (OutputStream output = new FileOutputStream(dest)) {

                 while ((length = input.read(buffer)) > 0) {
                     output.write(buffer, 0, length);
                 }

             }
         }

     }

     /**
      * Returns the URLs for the .jar files relevant to the given extension .jar
      * file. Unless the extension bundles additional Java libraries, only the
      * URL of the extension .jar will be returned. If additional Java libraries
      * are bundled within the extension, URLs for those libraries will be
      * included, as well. Temporary directories and/or files will be created as
      * necessary to house bundled libraries. Only .jar files located directly
      * within the root of the main extension .jar are considered.
      *
      * @param extension
      *     The extension .jar file to generate URLs for.
      *
      * @param temporaryFiles
      *     A modifiable List that should be populated with all temporary files
      *     created for the given extension. These files should be deleted on
      *     application shutdown in reverse order.
      *
      * @return
      *     An array of all URLs relevant to the given extension .jar.
      *
      * @throws GuacamoleException
      *     If the given file is not actually a file, the contents of the file
      *     cannot be read, or any necessary temporary files/directories cannot
      *     be created.
      */
     private static URL[] getExtensionURLs(File extension,
             List<File> temporaryFiles) throws GuacamoleException {

         try (JarFile extensionJar = new JarFile(extension)) {

             // Include extension itself within classpath
             List<URL> urls = new ArrayList<>();
             urls.add(getFileURL(extension));

             Path extensionTempLibDir = null;

             // Iterate through all entries (files) within the extension .jar,
             // adding any nested .jar files within the archive root to the
             // classpath
             Enumeration<JarEntry> entries = extensionJar.entries();
             while (entries.hasMoreElements()) {

                 JarEntry entry = entries.nextElement();
                 String name = entry.getName();

                 // Consider only .jar files located in root of archive
                 if (entry.isDirectory() ||! name.endsWith(".jar") || name.indexOf('/') != -1)
                     continue;

                 // Create temporary directory for housing this extension's
                 // bundled .jar files, if not already created
                 try {
                     if (extensionTempLibDir == null) {
                         extensionTempLibDir = Files.createTempDirectory(EXTENSION_TEMP_DIR_PREFIX);
                         temporaryFiles.add(extensionTempLibDir.toFile());
                         extensionTempLibDir.toFile().deleteOnExit();
                     }
                 }
                 catch (IOException e) {
                     throw new GuacamoleServerException("Temporary directory "
                             + "for libraries bundled with extension \""
                             + extension + "\" could not be created.", e);
                 }

                 // Create temporary file to hold the contents of the current
                 // bundled .jar
                 File tempLibrary;
                 try {
                     tempLibrary = Files.createTempFile(extensionTempLibDir, EXTENSION_TEMP_LIB_PREFIX, ".jar").toFile();
                     temporaryFiles.add(tempLibrary);
                     tempLibrary.deleteOnExit();
                 }
                 catch (IOException e) {
                     throw new GuacamoleServerException("Temporary file "
                             + "for library \"" + name + "\" bundled with "
                             + "extension \"" + extension + "\" could not be "
                             + "created.", e);
                 }

                 // Copy contents of bundled .jar to temporary file
                 try {
                     copyEntryToFile(extensionJar, entry, tempLibrary);
                 }
                 catch (IOException e) {
                     throw new GuacamoleServerException("Contents of library "
                             + "\"" + name + "\" bundled with extension \""
                             + extension + "\" could not be copied to a "
                             + "temporary file.", e);
                 }

                 // Add temporary .jar file to classpath
                 urls.add(getFileURL(tempLibrary));

             }

             if (extensionTempLibDir != null)
                 logger.debug("Libraries bundled within extension \"{}\" have been "
                         + "copied to temporary directory \"{}\".", extension, extensionTempLibDir);

             return urls.toArray(new URL[0]);

         }
         catch (IOException e) {
             throw new GuacamoleServerException("Contents of extension \""
                     + extension + "\" cannot be read.", e);
         }

     }

     /**
      * Creates a new ExtensionClassLoader configured to load classes from the
      * given extension .jar. If a necessary class cannot be found within the
      * .jar, the given parent ClassLoader is used. Calling this function
      * multiple times will not affect previously-returned instances of
      * ExtensionClassLoader.
      *
      * @param extension
      *     The extension .jar file from which classes should be loaded.
      *
      * @param temporaryFiles
      *     A modifiable List that should be populated with all temporary files
      *     created for the given extension. These files should be deleted on
      *     application shutdown in reverse order.
      *
      * @param parent
      *     The ClassLoader to use if class resolution through the extension
      *     .jar fails.
      *
      * @throws GuacamoleException
      *     If the given file is not actually a file, or the contents of the
      *     file cannot be read.
      */
     public ExtensionClassLoader(File extension, List<File> temporaryFiles,
             ClassLoader parent) throws GuacamoleException {
         super(getExtensionURLs(extension, temporaryFiles), null);
         this.parent = parent;
     }

     @Override
     protected Class<?> findClass(String string) throws ClassNotFoundException {

         // Search only within the given URLs
         try {
             return super.findClass(string);
         }

         // Search parent classloader ONLY if not found within given URLs
         catch (ClassNotFoundException e) {
             return parent.loadClass(string);
         }

     }

 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing,
	* software distributed under the License is distributed on an
	* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	* KIND, either express or implied. See the License for the
	* specific language governing permissions and limitations
	* under the License.
	*/

	package org.apache.guacamole.extension;

	import java.io.File;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.net.MalformedURLException;
	import java.net.URL;
	import java.net.URLClassLoader;
	import java.nio.file.Files;
	import java.nio.file.Path;
	import java.util.ArrayList;
	import java.util.Enumeration;
	import java.util.List;
	import java.util.jar.JarEntry;
	import java.util.jar.JarFile;
	import org.apache.guacamole.GuacamoleException;
	import org.apache.guacamole.GuacamoleServerException;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;

	/**
	* ClassLoader implementation which prioritizes the classes defined within a
	* given extension .jar file. Unlike the standard URLClassLoader, classes
	* within the parent ClassLoader are only used if they are not defined within
	* the given .jar. If classes are defined in both the parent and the extension
	* .jar, the versions defined within the extension .jar are used.
	*/
	public class ExtensionClassLoader extends URLClassLoader {

	/**
	* Logger for this class.
	*/
	private static final Logger logger = LoggerFactory.getLogger(ExtensionClassLoader.class);

	/**
	* The prefix that should be given to the temporary directory containing
	* all library .jar files that were bundled with the extension.
	*/
	private static final String EXTENSION_TEMP_DIR_PREFIX = "guac-extension-lib-";

	/**
	* The prefix that should be given to any files created for temporary
	* storage of a library .jar file that was bundled with the extension.
	*/
	private static final String EXTENSION_TEMP_LIB_PREFIX = "bundled-";

	/**
	* The ClassLoader to use if class resolution through the extension .jar
	* fails.
	*/
	private final ClassLoader parent;

	/**
	* Returns the URL that refers to the given file. If the given file refers
	* to a directory, an exception is thrown.
	*
	* @param file
	* The file to determine the URL of.
	*
	* @return
	* A URL that refers to the given file.
	*
	* @throws GuacamoleException
	* If the given file refers to a directory.
	*/
	private static URL getFileURL(File file) throws GuacamoleException {

	// Validate extension-related file is indeed a file
	if (!file.isFile())
	throw new GuacamoleServerException("\"" + file + "\" is not a file.");

	try {
	return file.toURI().toURL();
	}
	catch (MalformedURLException e) {
	throw new GuacamoleServerException(e);
	}

	}

	/**
	* Copies all bytes of data from a file within a .jar to a destination
	* file.
	*
	* @param jar
	* The JarFile containing the file to be copied.
	*
	* @param source
	* The JarEntry representing the file to be copied within the given
	* JarFile.
	*
	* @param dest
	* The destination file that the data should be copied to.
	*
	* @throws IOException
	* If an error occurs reading from the source .jar or writing to the
	* destination file.
	*/
	private static void copyEntryToFile(JarFile jar, JarEntry source, File dest)
	throws IOException {

	int length;
	byte[] buffer = new byte[8192];

	try (InputStream input = jar.getInputStream(source)) {
	try (OutputStream output = new FileOutputStream(dest)) {

	while ((length = input.read(buffer)) > 0) {
	output.write(buffer, 0, length);
	}

	}
	}

	}

	/**
	* Returns the URLs for the .jar files relevant to the given extension .jar
	* file. Unless the extension bundles additional Java libraries, only the
	* URL of the extension .jar will be returned. If additional Java libraries
	* are bundled within the extension, URLs for those libraries will be
	* included, as well. Temporary directories and/or files will be created as
	* necessary to house bundled libraries. Only .jar files located directly
	* within the root of the main extension .jar are considered.
	*
	* @param extension
	* The extension .jar file to generate URLs for.
	*
	* @param temporaryFiles
	* A modifiable List that should be populated with all temporary files
	* created for the given extension. These files should be deleted on
	* application shutdown in reverse order.
	*
	* @return
	* An array of all URLs relevant to the given extension .jar.
	*
	* @throws GuacamoleException
	* If the given file is not actually a file, the contents of the file
	* cannot be read, or any necessary temporary files/directories cannot
	* be created.
	*/
	private static URL[] getExtensionURLs(File extension,
	List<File> temporaryFiles) throws GuacamoleException {

	try (JarFile extensionJar = new JarFile(extension)) {

	// Include extension itself within classpath
	List<URL> urls = new ArrayList<>();
	urls.add(getFileURL(extension));

	Path extensionTempLibDir = null;

	// Iterate through all entries (files) within the extension .jar,
	// adding any nested .jar files within the archive root to the
	// classpath
	Enumeration<JarEntry> entries = extensionJar.entries();
	while (entries.hasMoreElements()) {

	JarEntry entry = entries.nextElement();
	String name = entry.getName();

	// Consider only .jar files located in root of archive
	if (entry.isDirectory() \|\|! name.endsWith(".jar") \|\| name.indexOf('/') != -1)
	continue;

	// Create temporary directory for housing this extension's
	// bundled .jar files, if not already created
	try {
	if (extensionTempLibDir == null) {
	extensionTempLibDir = Files.createTempDirectory(EXTENSION_TEMP_DIR_PREFIX);
	temporaryFiles.add(extensionTempLibDir.toFile());
	extensionTempLibDir.toFile().deleteOnExit();
	}
	}
	catch (IOException e) {
	throw new GuacamoleServerException("Temporary directory "
	+ "for libraries bundled with extension \""
	+ extension + "\" could not be created.", e);
	}

	// Create temporary file to hold the contents of the current
	// bundled .jar
	File tempLibrary;
	try {
	tempLibrary = Files.createTempFile(extensionTempLibDir, EXTENSION_TEMP_LIB_PREFIX, ".jar").toFile();
	temporaryFiles.add(tempLibrary);
	tempLibrary.deleteOnExit();
	}
	catch (IOException e) {
	throw new GuacamoleServerException("Temporary file "
	+ "for library \"" + name + "\" bundled with "
	+ "extension \"" + extension + "\" could not be "
	+ "created.", e);
	}

	// Copy contents of bundled .jar to temporary file
	try {
	copyEntryToFile(extensionJar, entry, tempLibrary);
	}
	catch (IOException e) {
	throw new GuacamoleServerException("Contents of library "
	+ "\"" + name + "\" bundled with extension \""
	+ extension + "\" could not be copied to a "
	+ "temporary file.", e);
	}

	// Add temporary .jar file to classpath
	urls.add(getFileURL(tempLibrary));

	}

	if (extensionTempLibDir != null)
	logger.debug("Libraries bundled within extension \"{}\" have been "
	+ "copied to temporary directory \"{}\".", extension, extensionTempLibDir);

	return urls.toArray(new URL[0]);

	}
	catch (IOException e) {
	throw new GuacamoleServerException("Contents of extension \""
	+ extension + "\" cannot be read.", e);
	}

	}

	/**
	* Creates a new ExtensionClassLoader configured to load classes from the
	* given extension .jar. If a necessary class cannot be found within the
	* .jar, the given parent ClassLoader is used. Calling this function
	* multiple times will not affect previously-returned instances of
	* ExtensionClassLoader.
	*
	* @param extension
	* The extension .jar file from which classes should be loaded.
	*
	* @param temporaryFiles
	* A modifiable List that should be populated with all temporary files
	* created for the given extension. These files should be deleted on
	* application shutdown in reverse order.
	*
	* @param parent
	* The ClassLoader to use if class resolution through the extension
	* .jar fails.
	*
	* @throws GuacamoleException
	* If the given file is not actually a file, or the contents of the
	* file cannot be read.
	*/
	public ExtensionClassLoader(File extension, List<File> temporaryFiles,
	ClassLoader parent) throws GuacamoleException {
	super(getExtensionURLs(extension, temporaryFiles), null);
	this.parent = parent;
	}

	@Override
	protected Class<?> findClass(String string) throws ClassNotFoundException {

	// Search only within the given URLs
	try {
	return super.findClass(string);
	}

	// Search parent classloader ONLY if not found within given URLs
	catch (ClassNotFoundException e) {
	return parent.loadClass(string);
	}

	}

	}