Java example source code file (AppletClassLoader.java)
The AppletClassLoader.java Java example source code
/*
* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.applet;
import java.lang.NullPointerException;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.SocketPermission;
import java.net.URLConnection;
import java.net.MalformedURLException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.io.File;
import java.io.FilePermission;
import java.io.IOException;
import java.io.BufferedInputStream;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.NoSuchElementException;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.PrivilegedAction;
import java.security.PrivilegedExceptionAction;
import java.security.PrivilegedActionException;
import java.security.CodeSource;
import java.security.Permission;
import java.security.PermissionCollection;
import sun.awt.AppContext;
import sun.awt.SunToolkit;
import sun.misc.IOUtils;
import sun.net.www.ParseUtil;
import sun.security.util.SecurityConstants;
/**
* This class defines the class loader for loading applet classes and
* resources. It extends URLClassLoader to search the applet code base
* for the class or resource after checking any loaded JAR files.
*/
public class AppletClassLoader extends URLClassLoader {
private URL base; /* applet code base URL */
private CodeSource codesource; /* codesource for the base URL */
private AccessControlContext acc;
private boolean exceptionStatus = false;
private final Object threadGroupSynchronizer = new Object();
private final Object grabReleaseSynchronizer = new Object();
private boolean codebaseLookup = true;
private volatile boolean allowRecursiveDirectoryRead = true;
/*
* Creates a new AppletClassLoader for the specified base URL.
*/
protected AppletClassLoader(URL base) {
super(new URL[0]);
this.base = base;
this.codesource =
new CodeSource(base, (java.security.cert.Certificate[]) null);
acc = AccessController.getContext();
}
public void disableRecursiveDirectoryRead() {
allowRecursiveDirectoryRead = false;
}
/**
* Set the codebase lookup flag.
*/
void setCodebaseLookup(boolean codebaseLookup) {
this.codebaseLookup = codebaseLookup;
}
/*
* Returns the applet code base URL.
*/
URL getBaseURL() {
return base;
}
/*
* Returns the URLs used for loading classes and resources.
*/
public URL[] getURLs() {
URL[] jars = super.getURLs();
URL[] urls = new URL[jars.length + 1];
System.arraycopy(jars, 0, urls, 0, jars.length);
urls[urls.length - 1] = base;
return urls;
}
/*
* Adds the specified JAR file to the search path of loaded JAR files.
* Changed modifier to protected in order to be able to overwrite addJar()
* in PluginClassLoader.java
*/
protected void addJar(String name) throws IOException {
URL url;
try {
url = new URL(base, name);
} catch (MalformedURLException e) {
throw new IllegalArgumentException("name");
}
addURL(url);
// DEBUG
//URL[] urls = getURLs();
//for (int i = 0; i < urls.length; i++) {
// System.out.println("url[" + i + "] = " + urls[i]);
//}
}
/*
* Override loadClass so that class loading errors can be caught in
* order to print better error messages.
*/
public synchronized Class loadClass(String name, boolean resolve)
throws ClassNotFoundException
{
// First check if we have permission to access the package. This
// should go away once we've added support for exported packages.
int i = name.lastIndexOf('.');
if (i != -1) {
SecurityManager sm = System.getSecurityManager();
if (sm != null)
sm.checkPackageAccess(name.substring(0, i));
}
try {
return super.loadClass(name, resolve);
} catch (ClassNotFoundException e) {
//printError(name, e.getException());
throw e;
} catch (RuntimeException e) {
//printError(name, e);
throw e;
} catch (Error e) {
//printError(name, e);
throw e;
}
}
/*
* Finds the applet class with the specified name. First searches
* loaded JAR files then the applet code base for the class.
*/
protected Class findClass(String name) throws ClassNotFoundException {
int index = name.indexOf(";");
String cookie = "";
if(index != -1) {
cookie = name.substring(index, name.length());
name = name.substring(0, index);
}
// check loaded JAR files
try {
return super.findClass(name);
} catch (ClassNotFoundException e) {
}
// Otherwise, try loading the class from the code base URL
// 4668479: Option to turn off codebase lookup in AppletClassLoader
// during resource requests. [stanley.ho]
if (codebaseLookup == false)
throw new ClassNotFoundException(name);
// final String path = name.replace('.', '/').concat(".class").concat(cookie);
String encodedName = ParseUtil.encodePath(name.replace('.', '/'), false);
final String path = (new StringBuffer(encodedName)).append(".class").append(cookie).toString();
try {
byte[] b = (byte[]) AccessController.doPrivileged(
new PrivilegedExceptionAction() {
public Object run() throws IOException {
try {
URL finalURL = new URL(base, path);
// Make sure the codebase won't be modified
if (base.getProtocol().equals(finalURL.getProtocol()) &&
base.getHost().equals(finalURL.getHost()) &&
base.getPort() == finalURL.getPort()) {
return getBytes(finalURL);
}
else {
return null;
}
} catch (Exception e) {
return null;
}
}
}, acc);
if (b != null) {
return defineClass(name, b, 0, b.length, codesource);
} else {
throw new ClassNotFoundException(name);
}
} catch (PrivilegedActionException e) {
throw new ClassNotFoundException(name, e.getException());
}
}
/**
* Returns the permissions for the given codesource object.
* The implementation of this method first calls super.getPermissions,
* to get the permissions
* granted by the super class, and then adds additional permissions
* based on the URL of the codesource.
* <p>
* If the protocol is "file"
* and the path specifies a file, permission is granted to read all files
* and (recursively) all files and subdirectories contained in
* that directory. This is so applets with a codebase of
* file:/blah/some.jar can read in file:/blah/, which is needed to
* be backward compatible. We also add permission to connect back to
* the "localhost".
*
* @param codesource the codesource
* @throws NullPointerException if {@code codesource} is {@code null}.
* @return the permissions granted to the codesource
*/
protected PermissionCollection getPermissions(CodeSource codesource)
{
final PermissionCollection perms = super.getPermissions(codesource);
URL url = codesource.getLocation();
String path = null;
Permission p;
try {
p = url.openConnection().getPermission();
} catch (java.io.IOException ioe) {
p = null;
}
if (p instanceof FilePermission) {
path = p.getName();
} else if ((p == null) && (url.getProtocol().equals("file"))) {
path = url.getFile().replace('/', File.separatorChar);
path = ParseUtil.decode(path);
}
if (path != null) {
final String rawPath = path;
if (!path.endsWith(File.separator)) {
int endIndex = path.lastIndexOf(File.separatorChar);
if (endIndex != -1) {
path = path.substring(0, endIndex + 1) + "-";
perms.add(new FilePermission(path,
SecurityConstants.FILE_READ_ACTION));
}
}
final File f = new File(rawPath);
final boolean isDirectory = f.isDirectory();
// grant codebase recursive read permission
// this should only be granted to non-UNC file URL codebase and
// the codesource path must either be a directory, or a file
// that ends with .jar or .zip
if (allowRecursiveDirectoryRead && (isDirectory ||
rawPath.toLowerCase().endsWith(".jar") ||
rawPath.toLowerCase().endsWith(".zip"))) {
Permission bperm;
try {
bperm = base.openConnection().getPermission();
} catch (java.io.IOException ioe) {
bperm = null;
}
if (bperm instanceof FilePermission) {
String bpath = bperm.getName();
if (bpath.endsWith(File.separator)) {
bpath += "-";
}
perms.add(new FilePermission(bpath,
SecurityConstants.FILE_READ_ACTION));
} else if ((bperm == null) && (base.getProtocol().equals("file"))) {
String bpath = base.getFile().replace('/', File.separatorChar);
bpath = ParseUtil.decode(bpath);
if (bpath.endsWith(File.separator)) {
bpath += "-";
}
perms.add(new FilePermission(bpath, SecurityConstants.FILE_READ_ACTION));
}
}
}
return perms;
}
/*
* Returns the contents of the specified URL as an array of bytes.
*/
private static byte[] getBytes(URL url) throws IOException {
URLConnection uc = url.openConnection();
if (uc instanceof java.net.HttpURLConnection) {
java.net.HttpURLConnection huc = (java.net.HttpURLConnection) uc;
int code = huc.getResponseCode();
if (code >= java.net.HttpURLConnection.HTTP_BAD_REQUEST) {
throw new IOException("open HTTP connection failed.");
}
}
int len = uc.getContentLength();
// Fixed #4507227: Slow performance to load
// class and resources. [stanleyh]
//
// Use buffered input stream [stanleyh]
InputStream in = new BufferedInputStream(uc.getInputStream());
byte[] b;
try {
b = IOUtils.readFully(in, len, true);
} finally {
in.close();
}
return b;
}
// Object for synchronization around getResourceAsStream()
private Object syncResourceAsStream = new Object();
private Object syncResourceAsStreamFromJar = new Object();
// Flag to indicate getResourceAsStream() is in call
private boolean resourceAsStreamInCall = false;
private boolean resourceAsStreamFromJarInCall = false;
/**
* Returns an input stream for reading the specified resource.
*
* The search order is described in the documentation for {@link
* #getResource(String)}.<p>
*
* @param name the resource name
* @return an input stream for reading the resource, or <code>null
* if the resource could not be found
* @since JDK1.1
*/
public InputStream getResourceAsStream(String name)
{
if (name == null) {
throw new NullPointerException("name");
}
try
{
InputStream is = null;
// Fixed #4507227: Slow performance to load
// class and resources. [stanleyh]
//
// The following is used to avoid calling
// AppletClassLoader.findResource() in
// super.getResourceAsStream(). Otherwise,
// unnecessary connection will be made.
//
synchronized(syncResourceAsStream)
{
resourceAsStreamInCall = true;
// Call super class
is = super.getResourceAsStream(name);
resourceAsStreamInCall = false;
}
// 4668479: Option to turn off codebase lookup in AppletClassLoader
// during resource requests. [stanley.ho]
if (codebaseLookup == true && is == null)
{
// If resource cannot be obtained,
// try to download it from codebase
URL url = new URL(base, ParseUtil.encodePath(name, false));
is = url.openStream();
}
return is;
}
catch (Exception e)
{
return null;
}
}
/**
* Returns an input stream for reading the specified resource from the
* the loaded jar files.
*
* The search order is described in the documentation for {@link
* #getResource(String)}.<p>
*
* @param name the resource name
* @return an input stream for reading the resource, or <code>null
* if the resource could not be found
* @since JDK1.1
*/
public InputStream getResourceAsStreamFromJar(String name) {
if (name == null) {
throw new NullPointerException("name");
}
try {
InputStream is = null;
synchronized(syncResourceAsStreamFromJar) {
resourceAsStreamFromJarInCall = true;
// Call super class
is = super.getResourceAsStream(name);
resourceAsStreamFromJarInCall = false;
}
return is;
} catch (Exception e) {
return null;
}
}
/*
* Finds the applet resource with the specified name. First checks
* loaded JAR files then the applet code base for the resource.
*/
public URL findResource(String name) {
// check loaded JAR files
URL url = super.findResource(name);
// 6215746: Disable META-INF/* lookup from codebase in
// applet/plugin classloader. [stanley.ho]
if (name.startsWith("META-INF/"))
return url;
// 4668479: Option to turn off codebase lookup in AppletClassLoader
// during resource requests. [stanley.ho]
if (codebaseLookup == false)
return url;
if (url == null)
{
//#4805170, if it is a call from Applet.getImage()
//we should check for the image only in the archives
boolean insideGetResourceAsStreamFromJar = false;
synchronized(syncResourceAsStreamFromJar) {
insideGetResourceAsStreamFromJar = resourceAsStreamFromJarInCall;
}
if (insideGetResourceAsStreamFromJar) {
return null;
}
// Fixed #4507227: Slow performance to load
// class and resources. [stanleyh]
//
// Check if getResourceAsStream is called.
//
boolean insideGetResourceAsStream = false;
synchronized(syncResourceAsStream)
{
insideGetResourceAsStream = resourceAsStreamInCall;
}
// If getResourceAsStream is called, don't
// trigger the following code. Otherwise,
// unnecessary connection will be made.
//
if (insideGetResourceAsStream == false)
{
// otherwise, try the code base
try {
url = new URL(base, ParseUtil.encodePath(name, false));
// check if resource exists
if(!resourceExists(url))
url = null;
} catch (Exception e) {
// all exceptions, including security exceptions, are caught
url = null;
}
}
}
return url;
}
private boolean resourceExists(URL url) {
// Check if the resource exists.
// It almost works to just try to do an openConnection() but
// HttpURLConnection will return true on HTTP_BAD_REQUEST
// when the requested name ends in ".html", ".htm", and ".txt"
// and we want to be able to handle these
//
// Also, cannot just open a connection for things like FileURLConnection,
// because they succeed when connecting to a nonexistent file.
// So, in those cases we open and close an input stream.
boolean ok = true;
try {
URLConnection conn = url.openConnection();
if (conn instanceof java.net.HttpURLConnection) {
java.net.HttpURLConnection hconn =
(java.net.HttpURLConnection) conn;
// To reduce overhead, using http HEAD method instead of GET method
hconn.setRequestMethod("HEAD");
int code = hconn.getResponseCode();
if (code == java.net.HttpURLConnection.HTTP_OK) {
return true;
}
if (code >= java.net.HttpURLConnection.HTTP_BAD_REQUEST) {
return false;
}
} else {
/**
* Fix for #4182052 - stanleyh
*
* The same connection should be reused to avoid multiple
* HTTP connections
*/
// our best guess for the other cases
InputStream is = conn.getInputStream();
is.close();
}
} catch (Exception ex) {
ok = false;
}
return ok;
}
/*
* Returns an enumeration of all the applet resources with the specified
* name. First checks loaded JAR files then the applet code base for all
* available resources.
*/
public Enumeration findResources(String name) throws IOException {
final Enumeration e = super.findResources(name);
// 6215746: Disable META-INF/* lookup from codebase in
// applet/plugin classloader. [stanley.ho]
if (name.startsWith("META-INF/"))
return e;
// 4668479: Option to turn off codebase lookup in AppletClassLoader
// during resource requests. [stanley.ho]
if (codebaseLookup == false)
return e;
URL u = new URL(base, ParseUtil.encodePath(name, false));
if (!resourceExists(u)) {
u = null;
}
final URL url = u;
return new Enumeration() {
private boolean done;
public Object nextElement() {
if (!done) {
if (e.hasMoreElements()) {
return e.nextElement();
}
done = true;
if (url != null) {
return url;
}
}
throw new NoSuchElementException();
}
public boolean hasMoreElements() {
return !done && (e.hasMoreElements() || url != null);
}
};
}
/*
* Load and resolve the file specified by the applet tag CODE
* attribute. The argument can either be the relative path
* of the class file itself or just the name of the class.
*/
Class loadCode(String name) throws ClassNotFoundException {
// first convert any '/' or native file separator to .
name = name.replace('/', '.');
name = name.replace(File.separatorChar, '.');
// deal with URL rewriting
String cookie = null;
int index = name.indexOf(";");
if(index != -1) {
cookie = name.substring(index, name.length());
name = name.substring(0, index);
}
// save that name for later
String fullName = name;
// then strip off any suffixes
if (name.endsWith(".class") || name.endsWith(".java")) {
name = name.substring(0, name.lastIndexOf('.'));
}
try {
if(cookie != null)
name = (new StringBuffer(name)).append(cookie).toString();
return loadClass(name);
} catch (ClassNotFoundException e) {
}
// then if it didn't end with .java or .class, or in the
// really pathological case of a class named class or java
if(cookie != null)
fullName = (new StringBuffer(fullName)).append(cookie).toString();
return loadClass(fullName);
}
/*
* The threadgroup that the applets loaded by this classloader live
* in. In the sun.* implementation of applets, the security manager's
* (AppletSecurity) getThreadGroup returns the thread group of the
* first applet on the stack, which is the applet's thread group.
*/
private AppletThreadGroup threadGroup;
private AppContext appContext;
public ThreadGroup getThreadGroup() {
synchronized (threadGroupSynchronizer) {
if (threadGroup == null || threadGroup.isDestroyed()) {
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
threadGroup = new AppletThreadGroup(base + "-threadGroup");
// threadGroup.setDaemon(true);
// threadGroup is now destroyed by AppContext.dispose()
// Create the new AppContext from within a Thread belonging
// to the newly created ThreadGroup, and wait for the
// creation to complete before returning from this method.
AppContextCreator creatorThread = new AppContextCreator(threadGroup);
// Since this thread will later be used to launch the
// applet's AWT-event dispatch thread and we want the applet
// code executing the AWT callbacks to use their own class
// loader rather than the system class loader, explicitly
// set the context class loader to the AppletClassLoader.
creatorThread.setContextClassLoader(AppletClassLoader.this);
creatorThread.start();
try {
synchronized(creatorThread.syncObject) {
while (!creatorThread.created) {
creatorThread.syncObject.wait();
}
}
} catch (InterruptedException e) { }
appContext = creatorThread.appContext;
return null;
}
});
}
return threadGroup;
}
}
/*
* Get the AppContext, if any, corresponding to this AppletClassLoader.
*/
public AppContext getAppContext() {
return appContext;
}
int usageCount = 0;
/**
* Grab this AppletClassLoader and its ThreadGroup/AppContext, so they
* won't be destroyed.
*/
public void grab() {
synchronized(grabReleaseSynchronizer) {
usageCount++;
}
getThreadGroup(); // Make sure ThreadGroup/AppContext exist
}
protected void setExceptionStatus()
{
exceptionStatus = true;
}
public boolean getExceptionStatus()
{
return exceptionStatus;
}
/**
* Release this AppletClassLoader and its ThreadGroup/AppContext.
* If nothing else has grabbed this AppletClassLoader, its ThreadGroup
* and AppContext will be destroyed.
*
* Because this method may destroy the AppletClassLoader's ThreadGroup,
* this method should NOT be called from within the AppletClassLoader's
* ThreadGroup.
*
* Changed modifier to protected in order to be able to overwrite this
* function in PluginClassLoader.java
*/
protected void release() {
AppContext tempAppContext = null;
synchronized(grabReleaseSynchronizer) {
if (usageCount > 1) {
--usageCount;
} else {
synchronized(threadGroupSynchronizer) {
tempAppContext = resetAppContext();
}
}
}
// Dispose appContext outside any sync block to
// prevent potential deadlock.
if (tempAppContext != null) {
try {
tempAppContext.dispose(); // nuke the world!
} catch (IllegalThreadStateException e) { }
}
}
/*
* reset classloader's AppContext and ThreadGroup
* This method is for subclass PluginClassLoader to
* reset superclass's AppContext and ThreadGroup but do
* not dispose the AppContext. PluginClassLoader does not
* use UsageCount to decide whether to dispose AppContext
*
* @return previous AppContext
*/
protected AppContext resetAppContext() {
AppContext tempAppContext = null;
synchronized(threadGroupSynchronizer) {
// Store app context in temp variable
tempAppContext = appContext;
usageCount = 0;
appContext = null;
threadGroup = null;
}
return tempAppContext;
}
// Hash map to store applet compatibility info
private HashMap jdk11AppletInfo = new HashMap();
private HashMap jdk12AppletInfo = new HashMap();
/**
* Set applet target level as JDK 1.1.
*
* @param clazz Applet class.
* @param bool true if JDK is targeted for JDK 1.1;
* false otherwise.
*/
void setJDK11Target(Class clazz, boolean bool)
{
jdk11AppletInfo.put(clazz.toString(), Boolean.valueOf(bool));
}
/**
* Set applet target level as JDK 1.2.
*
* @param clazz Applet class.
* @param bool true if JDK is targeted for JDK 1.2;
* false otherwise.
*/
void setJDK12Target(Class clazz, boolean bool)
{
jdk12AppletInfo.put(clazz.toString(), Boolean.valueOf(bool));
}
/**
* Determine if applet is targeted for JDK 1.1.
*
* @param applet Applet class.
* @return TRUE if applet is targeted for JDK 1.1;
* FALSE if applet is not;
* null if applet is unknown.
*/
Boolean isJDK11Target(Class clazz)
{
return (Boolean) jdk11AppletInfo.get(clazz.toString());
}
/**
* Determine if applet is targeted for JDK 1.2.
*
* @param applet Applet class.
* @return TRUE if applet is targeted for JDK 1.2;
* FALSE if applet is not;
* null if applet is unknown.
*/
Boolean isJDK12Target(Class clazz)
{
return (Boolean) jdk12AppletInfo.get(clazz.toString());
}
private static AppletMessageHandler mh =
new AppletMessageHandler("appletclassloader");
/*
* Prints a class loading error message.
*/
private static void printError(String name, Throwable e) {
String s = null;
if (e == null) {
s = mh.getMessage("filenotfound", name);
} else if (e instanceof IOException) {
s = mh.getMessage("fileioexception", name);
} else if (e instanceof ClassFormatError) {
s = mh.getMessage("fileformat", name);
} else if (e instanceof ThreadDeath) {
s = mh.getMessage("filedeath", name);
} else if (e instanceof Error) {
s = mh.getMessage("fileerror", e.toString(), name);
}
if (s != null) {
System.err.println(s);
}
}
}
/*
* The AppContextCreator class is used to create an AppContext from within
* a Thread belonging to the new AppContext's ThreadGroup. To wait for
* this operation to complete before continuing, wait for the notifyAll()
* operation on the syncObject to occur.
*/
class AppContextCreator extends Thread {
Object syncObject = new Object();
AppContext appContext = null;
volatile boolean created = false;
AppContextCreator(ThreadGroup group) {
super(group, "AppContextCreator");
}
public void run() {
appContext = SunToolkit.createNewAppContext();
created = true;
synchronized(syncObject) {
syncObject.notifyAll();
}
} // run()
} // class AppContextCreator
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