From 94d4a298ad560f8674d746dea2d51e26e0a97f2a Mon Sep 17 00:00:00 2001
From: Miguel de Icaza Every {@link Class Class} object contains a {@link
- * Class#getClassLoader() reference} to the ClassLoader that defined
- * it.
- *
- * Class objects for array classes are not created by class
- * loaders, but are created automatically as required by the Java runtime.
- * The class loader for an array class, as returned by {@link
- * Class#getClassLoader()} is the same as the class loader for its element
- * type; if the element type is a primitive type, then the array class has no
- * class loader.
- *
- * Applications implement subclasses of ClassLoader in order to
- * extend the manner in which the Java virtual machine dynamically loads
- * classes.
- *
- * Class loaders may typically be used by security managers to indicate
- * security domains.
- *
- * The ClassLoader class uses a delegation model to search for
- * classes and resources. Each instance of ClassLoader has an
- * associated parent class loader. When requested to find a class or
- * resource, a ClassLoader instance will delegate the search for the
- * class or resource to its parent class loader before attempting to find the
- * class or resource itself. The virtual machine's built-in class loader,
- * called the "bootstrap class loader", does not itself have a parent but may
- * serve as the parent of a ClassLoader instance.
- *
- * Class loaders that support concurrent loading of classes are known as
- * parallel capable class loaders and are required to register
- * themselves at their class initialization time by invoking the
- * {@link
- * #registerAsParallelCapable ClassLoader.registerAsParallelCapable}
- * method. Note that the ClassLoader class is registered as parallel
- * capable by default. However, its subclasses still need to register themselves
- * if they are parallel capable. Normally, the Java virtual machine loads classes from the local file
- * system in a platform-dependent manner. For example, on UNIX systems, the
- * virtual machine loads classes from the directory defined by the
- * CLASSPATH environment variable.
- *
- * However, some classes may not originate from a file; they may originate
- * from other sources, such as the network, or they could be constructed by an
- * application. The method {@link #defineClass(String, byte[], int, int)
- * defineClass} converts an array of bytes into an instance of class
- * Class. Instances of this newly defined class can be created using
- * {@link Class#newInstance Class.newInstance}.
- *
- * The methods and constructors of objects created by a class loader may
- * reference other classes. To determine the class(es) referred to, the Java
- * virtual machine invokes the {@link #loadClass loadClass} method of
- * the class loader that originally created the class.
- *
- * For example, an application could create a network class loader to
- * download class files from a server. Sample code might look like:
- *
- * The network class loader subclass must define the methods {@link
- * #findClass findClass} and loadClassData to load a class
- * from the network. Once it has downloaded the bytes that make up the class,
- * it should use the method {@link #defineClass defineClass} to
- * create a class instance. A sample implementation is:
- *
- * Any class name provided as a {@link String} parameter to methods in
- * ClassLoader must be a binary name as defined by
- * The Java™ Language Specification.
- *
- * Examples of valid class names include:
- * If there is a security manager, its {@link
- * SecurityManager#checkCreateClassLoader()
- * checkCreateClassLoader} method is invoked. This may result in
- * a security exception. If there is a security manager, its {@link
- * SecurityManager#checkCreateClassLoader()
- * checkCreateClassLoader} method is invoked. This may result in
- * a security exception.
- * In environments in which the delegation model is not strictly
- * hierarchical, class loaders need to be parallel capable, otherwise class
- * loading can lead to deadlocks because the loader lock is held for the
- * duration of the class loading process (see {@link #loadClass
- * loadClass} methods).
- *
- *
- *
- *
- * ClassLoader loader = new NetworkClassLoader(host, port);
- * Object main = loader.loadClass("Main", true).newInstance();
- * . . .
- *
- *
- *
- * class NetworkClassLoader extends ClassLoader {
- * String host;
- * int port;
- *
- * public Class findClass(String name) {
- * byte[] b = loadClassData(name);
- * return defineClass(name, b, 0, b.length);
- * }
- *
- * private byte[] loadClassData(String name) {
- * // load the class data from the connection
- * . . .
- * }
- * }
- *
Binary names
- *
- *
- *
- * @see #resolveClass(Class)
- * @since 1.0
- */
-public abstract class ClassLoader {
-
- // If initialization succeed this is set to true and security checks will
- // succeed. Otherwise the object is not initialized and the object is
- // useless.
- private final boolean initialized;
-
- // The parent class loader for delegation
- // Note: VM hardcoded the offset of this field, thus all new fields
- // must be added *after* it.
- private final ClassLoader parent;
-
- /**
- * Encapsulates the set of parallel capable loader types.
- */
- private static class ParallelLoaders {
- private ParallelLoaders() {}
-
- // the set of parallel capable loader types
- private static final Set
- * "java.lang.String"
- * "javax.swing.JSpinner$DefaultEditor"
- * "java.security.KeyStore$Builder$FileBuilder$1"
- * "java.net.URLClassLoader$3$1"
- *
Invoke {@link #findLoadedClass(String)} to check if the class - * has already been loaded.
Invoke the {@link #loadClass(String) loadClass} method - * on the parent class loader. If the parent is null the class - * loader built-in to the virtual machine is used, instead.
Invoke the {@link #findClass(String)} method to find the - * class.
If the class was found using the above steps, and the - * resolve flag is true, this method will then invoke the {@link - * #resolveClass(Class)} method on the resulting Class object. - * - *
Subclasses of ClassLoader are encouraged to override {@link - * #findClass(String)}, rather than this method.
- * - *Unless overridden, this method synchronizes on the result of - * {@link #getClassLoadingLock getClassLoadingLock} method - * during the entire class loading process. - * - * @param name - * The binary name of the class - * - * @param resolve - * If true then resolve the class - * - * @return The resulting Class object - * - * @throws ClassNotFoundException - * If the class could not be found - */ - protected Class> loadClass(String name, boolean resolve) - throws ClassNotFoundException - { - synchronized (getClassLoadingLock(name)) { - // First, check if the class has already been loaded - Class c = findLoadedClass(name); - if (c == null) { - try { - if (parent != null) { - c = parent.loadClass(name, false); - } else { - c = findBootstrapClassOrNull(name); - } - } catch (ClassNotFoundException e) { - // ClassNotFoundException thrown if class not found - // from the non-null parent class loader - } - - if (c == null) { - // If still not found, then invoke findClass in order - // to find the class. - c = findClass(name); - } - } - if (resolve) { - resolveClass(c); - } - return c; - } - } - - /** - * Returns the lock object for class loading operations. - * For backward compatibility, the default implementation of this method - * behaves as follows. If this ClassLoader object is registered as - * parallel capable, the method returns a dedicated object associated - * with the specified class name. Otherwise, the method returns this - * ClassLoader object.
- * - * @param className - * The name of the to-be-loaded class - * - * @return the lock for class loading operations - * - * @throws NullPointerException - * If registered as parallel capable and className is null - * - * @see #loadClass(String, boolean) - * - * @since 1.7 - */ - protected Object getClassLoadingLock(String className) { - Object lock = this; - if (parallelLockMap != null) { - Object newLock = new Object(); - lock = parallelLockMap.putIfAbsent(className, newLock); - if (lock == null) { - lock = newLock; - } - } - return lock; - } - - // This method is invoked by the virtual machine to load a class. - final Class loadClassInternal(String name) - throws ClassNotFoundException - { - // For backward compatibility, explicitly lock on 'this' when - // the current class loader is not parallel capable. - if (parallelLockMap == null) { - synchronized (this) { - return loadClass(name); - } - } else { - return loadClass(name); - } - } - - // Invoked by the VM after loading class with this loader. - final void checkPackageAccess(Class cls, ProtectionDomain pd) { - final SecurityManager sm = System.getSecurityManager(); - if (sm != null) { - final String name = cls.getName(); - final int i = name.lastIndexOf('.'); - if (i != -1) { - AccessController.doPrivileged(new PrivilegedActionThis method assigns a default {@link java.security.ProtectionDomain - * ProtectionDomain} to the newly defined class. The - * ProtectionDomain is effectively granted the same set of - * permissions returned when {@link - * java.security.Policy#getPermissions(java.security.CodeSource) - * Policy.getPolicy().getPermissions(new CodeSource(null, null))} - * is invoked. The default domain is created on the first invocation of - * {@link #defineClass(String, byte[], int, int) defineClass}, - * and re-used on subsequent invocations. - * - *
To assign a specific ProtectionDomain to the class, use - * the {@link #defineClass(String, byte[], int, int, - * java.security.ProtectionDomain) defineClass} method that takes a - * ProtectionDomain as one of its arguments.
- * - * @param name - * The expected binary name of the class, or - * null if not known - * - * @param b - * The bytes that make up the class data. The bytes in positions - * off through off+len-1 should have the format - * of a valid class file as defined by - * The Java™ Virtual Machine Specification. - * - * @param off - * The start offset in b of the class data - * - * @param len - * The length of the class data - * - * @return The Class object that was created from the specified - * class data. - * - * @throws ClassFormatError - * If the data did not contain a valid class - * - * @throws IndexOutOfBoundsException - * If either off or len is negative, or if - * off+len is greater than b.length. - * - * @throws SecurityException - * If an attempt is made to add this class to a package that - * contains classes that were signed by a different set of - * certificates than this class (which is unsigned), or if - * name begins with "java.". - * - * @see #loadClass(String, boolean) - * @see #resolveClass(Class) - * @see java.security.CodeSource - * @see java.security.SecureClassLoader - * - * @since 1.1 - */ - protected final Class> defineClass(String name, byte[] b, int off, int len) - throws ClassFormatError - { - return defineClass(name, b, off, len, null); - } - - /* Determine protection domain, and check that: - - not define java.* class, - - signer of this class matches signers for the rest of the classes in - package. - */ - private ProtectionDomain preDefineClass(String name, - ProtectionDomain pd) - { - if (!checkName(name)) - throw new NoClassDefFoundError("IllegalName: " + name); - - if ((name != null) && name.startsWith("java.")) { - throw new SecurityException - ("Prohibited package name: " + - name.substring(0, name.lastIndexOf('.'))); - } - if (pd == null) { - pd = defaultDomain; - } - - if (name != null) checkCerts(name, pd.getCodeSource()); - - return pd; - } - - private String defineClassSourceLocation(ProtectionDomain pd) - { - CodeSource cs = pd.getCodeSource(); - String source = null; - if (cs != null && cs.getLocation() != null) { - source = cs.getLocation().toString(); - } - return source; - } - - private Class defineTransformedClass(String name, byte[] b, int off, int len, - ProtectionDomain pd, - ClassFormatError cfe, String source) - throws ClassFormatError - { - // Class format error - try to transform the bytecode and - // define the class again - // - ClassFileTransformer[] transformers = - ClassFileTransformer.getTransformers(); - Class c = null; - - if (transformers != null) { - for (ClassFileTransformer transformer : transformers) { - try { - // Transform byte code using transformer - byte[] tb = transformer.transform(b, off, len); - c = defineClass1(name, tb, 0, tb.length, - pd, source); - break; - } catch (ClassFormatError cfe2) { - // If ClassFormatError occurs, try next transformer - } - } - } - - // Rethrow original ClassFormatError if unable to transform - // bytecode to well-formed - // - if (c == null) - throw cfe; - - return c; - } - - private void postDefineClass(Class c, ProtectionDomain pd) - { - if (pd.getCodeSource() != null) { - Certificate certs[] = pd.getCodeSource().getCertificates(); - if (certs != null) - setSigners(c, certs); - } - } - - /** - * Converts an array of bytes into an instance of class Class, - * with an optional ProtectionDomain. If the domain is - * null, then a default domain will be assigned to the class as - * specified in the documentation for {@link #defineClass(String, byte[], - * int, int)}. Before the class can be used it must be resolved. - * - *The first class defined in a package determines the exact set of - * certificates that all subsequent classes defined in that package must - * contain. The set of certificates for a class is obtained from the - * {@link java.security.CodeSource CodeSource} within the - * ProtectionDomain of the class. Any classes added to that - * package must contain the same set of certificates or a - * SecurityException will be thrown. Note that if - * name is null, this check is not performed. - * You should always pass in the binary name of the - * class you are defining as well as the bytes. This ensures that the - * class you are defining is indeed the class you think it is. - * - *
The specified name cannot begin with "java.", since - * all classes in the "java.* packages can only be defined by the - * bootstrap class loader. If name is not null, it - * must be equal to the binary name of the class - * specified by the byte array "b", otherwise a {@link - * NoClassDefFoundError} will be thrown.
- * - * @param name - * The expected binary name of the class, or - * null if not known - * - * @param b - * The bytes that make up the class data. The bytes in positions - * off through off+len-1 should have the format - * of a valid class file as defined by - * The Java™ Virtual Machine Specification. - * - * @param off - * The start offset in b of the class data - * - * @param len - * The length of the class data - * - * @param protectionDomain - * The ProtectionDomain of the class - * - * @return The Class object created from the data, - * and optional ProtectionDomain. - * - * @throws ClassFormatError - * If the data did not contain a valid class - * - * @throws NoClassDefFoundError - * If name is not equal to the binary - * name of the class specified by b - * - * @throws IndexOutOfBoundsException - * If either off or len is negative, or if - * off+len is greater than b.length. - * - * @throws SecurityException - * If an attempt is made to add this class to a package that - * contains classes that were signed by a different set of - * certificates than this class, or if name begins with - * "java.". - */ - protected final Class> defineClass(String name, byte[] b, int off, int len, - ProtectionDomain protectionDomain) - throws ClassFormatError - { - check(); - protectionDomain = preDefineClass(name, protectionDomain); - - Class c = null; - String source = defineClassSourceLocation(protectionDomain); - - try { - c = defineClass1(name, b, off, len, protectionDomain, source); - } catch (ClassFormatError cfe) { - c = defineTransformedClass(name, b, off, len, protectionDomain, cfe, - source); - } - - postDefineClass(c, protectionDomain); - return c; - } - - /** - * Converts a {@link java.nio.ByteBuffer ByteBuffer} - * into an instance of class Class, - * with an optional ProtectionDomain. If the domain is - * null, then a default domain will be assigned to the class as - * specified in the documentation for {@link #defineClass(String, byte[], - * int, int)}. Before the class can be used it must be resolved. - * - *The rules about the first class defined in a package determining the - * set of certificates for the package, and the restrictions on class names - * are identical to those specified in the documentation for {@link - * #defineClass(String, byte[], int, int, ProtectionDomain)}. - * - *
An invocation of this method of the form - * cl.defineClass(name, - * bBuffer, pd) yields exactly the same - * result as the statements - * - *
- * ...- * - * @param name - * The expected binary name. of the class, or - * null if not known - * - * @param b - * The bytes that make up the class data. The bytes from positions - * b.position() through b.position() + b.limit() -1 - * should have the format of a valid class file as defined by - * The Java™ Virtual Machine Specification. - * - * @param protectionDomain - * The ProtectionDomain of the class, or null. - * - * @return The Class object created from the data, - * and optional ProtectionDomain. - * - * @throws ClassFormatError - * If the data did not contain a valid class. - * - * @throws NoClassDefFoundError - * If name is not equal to the binary - * name of the class specified by b - * - * @throws SecurityException - * If an attempt is made to add this class to a package that - * contains classes that were signed by a different set of - * certificates than this class, or if name begins with - * "java.". - * - * @see #defineClass(String, byte[], int, int, ProtectionDomain) - * - * @since 1.5 - */ - protected final Class> defineClass(String name, java.nio.ByteBuffer b, - ProtectionDomain protectionDomain) - throws ClassFormatError - { - check(); - - int len = b.remaining(); - - // Use byte[] if not a direct ByteBufer: - if (!b.isDirect()) { - if (b.hasArray()) { - return defineClass(name, b.array(), - b.position() + b.arrayOffset(), len, - protectionDomain); - } else { - // no array, or read-only array - byte[] tb = new byte[len]; - b.get(tb); // get bytes out of byte buffer. - return defineClass(name, tb, 0, len, protectionDomain); - } - } - - protectionDomain = preDefineClass(name, protectionDomain); - - Class c = null; - String source = defineClassSourceLocation(protectionDomain); - - try { - c = defineClass2(name, b, b.position(), len, protectionDomain, - source); - } catch (ClassFormatError cfe) { - byte[] tb = new byte[len]; - b.get(tb); // get bytes out of byte buffer. - c = defineTransformedClass(name, tb, 0, len, protectionDomain, cfe, - source); - } - - postDefineClass(c, protectionDomain); - return c; - } - - private native Class defineClass0(String name, byte[] b, int off, int len, - ProtectionDomain pd); - - private native Class defineClass1(String name, byte[] b, int off, int len, - ProtectionDomain pd, String source); - - private native Class defineClass2(String name, java.nio.ByteBuffer b, - int off, int len, ProtectionDomain pd, - String source); - - // true if the name is null or has the potential to be a valid binary name - static boolean checkName(String name) { - if ((name == null) || (name.length() == 0)) - return true; - if ((name.indexOf('/') != -1) - || (!VM.allowArraySyntax() && (name.charAt(0) == '['))) - return false; - return true; - } - - private void checkCerts(String name, CodeSource cs) { - int i = name.lastIndexOf('.'); - String pname = (i == -1) ? "" : name.substring(0, i); - - Certificate[] certs = null; - if (cs != null) { - certs = cs.getCertificates(); - } - Certificate[] pcerts = null; - if (parallelLockMap == null) { - synchronized (this) { - pcerts = package2certs.get(pname); - if (pcerts == null) { - package2certs.put(pname, (certs == null? nocerts:certs)); - } - } - } else { - pcerts = ((ConcurrentHashMap
- * byte[] temp = new byte[bBuffer.{@link - * java.nio.ByteBuffer#remaining remaining}()];
- * bBuffer.{@link java.nio.ByteBuffer#get(byte[]) - * get}(temp);
- * return {@link #defineClass(String, byte[], int, int, ProtectionDomain) - * cl.defineClass}(name, temp, 0, - * temp.length, pd);
- *
This method loads the class through the system class loader (see - * {@link #getSystemClassLoader()}). The Class object returned - * might have more than one ClassLoader associated with it. - * Subclasses of ClassLoader need not usually invoke this method, - * because most class loaders need to override just {@link - * #findClass(String)}.
- * - * @param name - * The binary name of the class - * - * @return The Class object for the specified name - * - * @throws ClassNotFoundException - * If the class could not be found - * - * @see #ClassLoader(ClassLoader) - * @see #getParent() - */ - protected final Class> findSystemClass(String name) - throws ClassNotFoundException - { - check(); - ClassLoader system = getSystemClassLoader(); - if (system == null) { - if (!checkName(name)) - throw new ClassNotFoundException(name); - Class cls = findBootstrapClass(name); - if (cls == null) { - throw new ClassNotFoundException(name); - } - return cls; - } - return system.loadClass(name); - } - - /** - * Returns a class loaded by the bootstrap class loader; - * or return null if not found. - */ - private Class findBootstrapClassOrNull(String name) - { - check(); - if (!checkName(name)) return null; - - return findBootstrapClass(name); - } - - // return null if not found - private native Class findBootstrapClass(String name); - - // Check to make sure the class loader has been initialized. - private void check() { - if (!initialized) { - throw new SecurityException("ClassLoader object not initialized"); - } - } - - /** - * Returns the class with the given binary name if this - * loader has been recorded by the Java virtual machine as an initiating - * loader of a class with that binary name. Otherwise - * null is returned. - * - * @param name - * The binary name of the class - * - * @return The Class object, or null if the class has - * not been loaded - * - * @since 1.1 - */ - protected final Class> findLoadedClass(String name) { - check(); - if (!checkName(name)) - return null; - return findLoadedClass0(name); - } - - private native final Class findLoadedClass0(String name); - - /** - * Sets the signers of a class. This should be invoked after defining a - * class. - * - * @param c - * The Class object - * - * @param signers - * The signers for the class - * - * @since 1.1 - */ - protected final void setSigners(Class> c, Object[] signers) { - check(); - c.setSigners(signers); - } - - - // -- Resource -- - - /** - * 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. - * - *The name of a resource is a '/'-separated path name that - * identifies the resource. - * - *
This method will first search the parent class loader for the - * resource; if the parent is null the path of the class loader - * built-in to the virtual machine is searched. That failing, this method - * will invoke {@link #findResource(String)} to find the resource.
- * - * @param name - * The resource name - * - * @return A URL object for reading the resource, or - * null if the resource could not be found or the invoker - * doesn't have adequate privileges to get the resource. - * - * @since 1.1 - */ - public URL getResource(String name) { - URL url; - if (parent != null) { - url = parent.getResource(name); - } else { - url = getBootstrapResource(name); - } - if (url == null) { - url = findResource(name); - } - return url; - } - - /** - * Finds all the resources 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. - * - *The name of a resource is a /-separated path name that - * identifies the resource. - * - *
The search order is described in the documentation for {@link - * #getResource(String)}.
- * - * @param name - * The resource name - * - * @return An enumeration of {@link java.net.URL URL} objects for - * the resource. If no resources could be found, the enumeration - * will be empty. Resources that the class loader doesn't have - * access to will not be in the enumeration. - * - * @throws IOException - * If I/O errors occur - * - * @see #findResources(String) - * - * @since 1.2 - */ - public EnumerationThe search order is described in the documentation for {@link - * #getSystemResource(String)}.
- * - * @param name - * The resource name - * - * @return An enumeration of resource {@link java.net.URL URL} - * objects - * - * @throws IOException - * If I/O errors occur - - * @since 1.2 - */ - public static EnumerationThe search order is described in the documentation for {@link - * #getResource(String)}.
- * - * @param name - * The resource name - * - * @return An input stream for reading the resource, or null - * if the resource could not be found - * - * @since 1.1 - */ - public InputStream getResourceAsStream(String name) { - URL url = getResource(name); - try { - return url != null ? url.openStream() : null; - } catch (IOException e) { - return null; - } - } - - /** - * Open for reading, a resource of the specified name from the search path - * used to load classes. This method locates the resource through the - * system class loader (see {@link #getSystemClassLoader()}). - * - * @param name - * The resource name - * - * @return An input stream for reading the resource, or null - * if the resource could not be found - * - * @since 1.1 - */ - public static InputStream getSystemResourceAsStream(String name) { - URL url = getSystemResource(name); - try { - return url != null ? url.openStream() : null; - } catch (IOException e) { - return null; - } - } - - - // -- Hierarchy -- - - /** - * Returns the parent class loader for delegation. Some implementations may - * use null to represent the bootstrap class loader. This method - * will return null in such implementations if this class loader's - * parent is the bootstrap class loader. - * - *If a security manager is present, and the invoker's class loader is - * not null and is not an ancestor of this class loader, then this - * method invokes the security manager's {@link - * SecurityManager#checkPermission(java.security.Permission) - * checkPermission} method with a {@link - * RuntimePermission#RuntimePermission(String) - * RuntimePermission("getClassLoader")} permission to verify - * access to the parent class loader is permitted. If not, a - * SecurityException will be thrown.
- * - * @return The parent ClassLoader - * - * @throws SecurityException - * If a security manager exists and its checkPermission - * method doesn't allow access to this class loader's parent class - * loader. - * - * @since 1.2 - */ - @CallerSensitive - public final ClassLoader getParent() { - if (parent == null) - return null; - SecurityManager sm = System.getSecurityManager(); - if (sm != null) { - checkClassLoaderPermission(parent, Reflection.getCallerClass()); - } - return parent; - } - - /** - * Returns the system class loader for delegation. This is the default - * delegation parent for new ClassLoader instances, and is - * typically the class loader used to start the application. - * - *This method is first invoked early in the runtime's startup - * sequence, at which point it creates the system class loader and sets it - * as the context class loader of the invoking Thread. - * - *
The default system class loader is an implementation-dependent - * instance of this class. - * - *
If the system property "java.system.class.loader" is defined - * when this method is first invoked then the value of that property is - * taken to be the name of a class that will be returned as the system - * class loader. The class is loaded using the default system class loader - * and must define a public constructor that takes a single parameter of - * type ClassLoader which is used as the delegation parent. An - * instance is then created using this constructor with the default system - * class loader as the parameter. The resulting class loader is defined - * to be the system class loader. - * - *
If a security manager is present, and the invoker's class loader is - * not null and the invoker's class loader is not the same as or - * an ancestor of the system class loader, then this method invokes the - * security manager's {@link - * SecurityManager#checkPermission(java.security.Permission) - * checkPermission} method with a {@link - * RuntimePermission#RuntimePermission(String) - * RuntimePermission("getClassLoader")} permission to verify - * access to the system class loader. If not, a - * SecurityException will be thrown.
- * - * @return The system ClassLoader for delegation, or - * null if none - * - * @throws SecurityException - * If a security manager exists and its checkPermission - * method doesn't allow access to the system class loader. - * - * @throws IllegalStateException - * If invoked recursively during the construction of the class - * loader specified by the "java.system.class.loader" - * property. - * - * @throws Error - * If the system property "java.system.class.loader" - * is defined but the named class could not be loaded, the - * provider class does not define the required constructor, or an - * exception is thrown by that constructor when it is invoked. The - * underlying cause of the error can be retrieved via the - * {@link Throwable#getCause()} method. - * - * @revised 1.4 - */ - @CallerSensitive - public static ClassLoader getSystemClassLoader() { - initSystemClassLoader(); - if (scl == null) { - return null; - } - SecurityManager sm = System.getSecurityManager(); - if (sm != null) { - checkClassLoaderPermission(scl, Reflection.getCallerClass()); - } - return scl; - } - - private static synchronized void initSystemClassLoader() { - if (!sclSet) { - if (scl != null) - throw new IllegalStateException("recursive invocation"); - sun.misc.Launcher l = sun.misc.Launcher.getLauncher(); - if (l != null) { - Throwable oops = null; - scl = l.getClassLoader(); - try { - scl = AccessController.doPrivileged( - new SystemClassLoaderAction(scl)); - } catch (PrivilegedActionException pae) { - oops = pae.getCause(); - if (oops instanceof InvocationTargetException) { - oops = oops.getCause(); - } - } - if (oops != null) { - if (oops instanceof Error) { - throw (Error) oops; - } else { - // wrap the exception - throw new Error(oops); - } - } - } - sclSet = true; - } - } - - // Returns true if the specified class loader can be found in this class - // loader's delegation chain. - boolean isAncestor(ClassLoader cl) { - ClassLoader acl = this; - do { - acl = acl.parent; - if (cl == acl) { - return true; - } - } while (acl != null); - return false; - } - - // Tests if class loader access requires "getClassLoader" permission - // check. A class loader 'from' can access class loader 'to' if - // class loader 'from' is same as class loader 'to' or an ancestor - // of 'to'. The class loader in a system domain can access - // any class loader. - private static boolean needsClassLoaderPermissionCheck(ClassLoader from, - ClassLoader to) - { - if (from == to) - return false; - - if (from == null) - return false; - - return !to.isAncestor(from); - } - - // Returns the class's class loader, or null if none. - static ClassLoader getClassLoader(Class> caller) { - // This can be null if the VM is requesting it - if (caller == null) { - return null; - } - // Circumvent security check since this is package-private - return caller.getClassLoader0(); - } - - static void checkClassLoaderPermission(ClassLoader cl, Class> caller) { - SecurityManager sm = System.getSecurityManager(); - if (sm != null) { - // caller can be null if the VM is requesting it - ClassLoader ccl = getClassLoader(caller); - if (needsClassLoaderPermissionCheck(ccl, cl)) { - sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); - } - } - } - - // The class loader for the system - // @GuardedBy("ClassLoader.class") - private static ClassLoader scl; - - // Set to true once the system class loader has been set - // @GuardedBy("ClassLoader.class") - private static boolean sclSet; - - - // -- Package -- - - /** - * Defines a package by name in this ClassLoader. This allows - * class loaders to define the packages for their classes. Packages must - * be created before the class is defined, and package names must be - * unique within a class loader and cannot be redefined or changed once - * created. - * - * @param name - * The package name - * - * @param specTitle - * The specification title - * - * @param specVersion - * The specification version - * - * @param specVendor - * The specification vendor - * - * @param implTitle - * The implementation title - * - * @param implVersion - * The implementation version - * - * @param implVendor - * The implementation vendor - * - * @param sealBase - * If not null, then this package is sealed with - * respect to the given code source {@link java.net.URL - * URL} object. Otherwise, the package is not sealed. - * - * @return The newly defined Package object - * - * @throws IllegalArgumentException - * If package name duplicates an existing package either in this - * class loader or one of its ancestors - * - * @since 1.2 - */ - protected Package definePackage(String name, String specTitle, - String specVersion, String specVendor, - String implTitle, String implVersion, - String implVendor, URL sealBase) - throws IllegalArgumentException - { - synchronized (packages) { - Package pkg = getPackage(name); - if (pkg != null) { - throw new IllegalArgumentException(name); - } - pkg = new Package(name, specTitle, specVersion, specVendor, - implTitle, implVersion, implVendor, - sealBase, this); - packages.put(name, pkg); - return pkg; - } - } - - /** - * Returns a Package that has been defined by this class loader - * or any of its ancestors. - * - * @param name - * The package name - * - * @return The Package corresponding to the given name, or - * null if not found - * - * @since 1.2 - */ - protected Package getPackage(String name) { - Package pkg; - synchronized (packages) { - pkg = packages.get(name); - } - if (pkg == null) { - if (parent != null) { - pkg = parent.getPackage(name); - } else { - pkg = Package.getSystemPackage(name); - } - if (pkg != null) { - synchronized (packages) { - Package pkg2 = packages.get(name); - if (pkg2 == null) { - packages.put(name, pkg); - } else { - pkg = pkg2; - } - } - } - } - return pkg; - } - - /** - * Returns all of the Packages defined by this class loader and - * its ancestors. - * - * @return The array of Package objects defined by this - * ClassLoader - * - * @since 1.2 - */ - protected Package[] getPackages() { - MapEvery native library requires a particular version of JNI. This is - * denoted by the private jniVersion field. This field is set by - * the VM when it loads the library, and used by the VM to pass the correct - * version of JNI to the native methods.
- * - * @see ClassLoader - * @since 1.2 - */ - static class NativeLibrary { - // opaque handle to native library, used in native code. - long handle; - // the version of JNI environment the native library requires. - private int jniVersion; - // the class from which the library is loaded, also indicates - // the loader this native library belongs. - Class fromClass; - // the canonicalized name of the native library. - String name; - - native void load(String name); - native long find(String name); - native void unload(); - - public NativeLibrary(Class fromClass, String name) { - this.name = name; - this.fromClass = fromClass; - } - - protected void finalize() { - synchronized (loadedLibraryNames) { - if (fromClass.getClassLoader() != null && handle != 0) { - /* remove the native library name */ - int size = loadedLibraryNames.size(); - for (int i = 0; i < size; i++) { - if (name.equals(loadedLibraryNames.elementAt(i))) { - loadedLibraryNames.removeElementAt(i); - break; - } - } - /* unload the library. */ - ClassLoader.nativeLibraryContext.push(this); - try { - unload(); - } finally { - ClassLoader.nativeLibraryContext.pop(); - } - } - } - } - // Invoked in the VM to determine the context class in - // JNI_Load/JNI_Unload - static Class getFromClass() { - return ClassLoader.nativeLibraryContext.peek().fromClass; - } - } - - // All native library names we've loaded. - private static Vector