ClassLoader

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/* * @(#)ClassLoader.java 1.189 05/11/17 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.lang; import java.io.InputStream; import java.io.IOException; import java.io.File; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.net.MalformedURLException; import java.net.URL; import java.security.AccessController; import java.security.AccessControlContext; import java.security.CodeSource; import java.security.Policy; import java.security.PrivilegedAction; import java.security.PrivilegedActionException; import java.security.PrivilegedExceptionAction; import java.security.ProtectionDomain; import java.util.Enumeration; import java.util.Hashtable; import java.util.HashMap; import java.util.HashSet; import java.util.Set; import java.util.Stack; import java.util.Map; import java.util.Vector; import sun.jkernel.DownloadManager; import sun.misc.ClassFileTransformer; import sun.misc.CompoundEnumeration; import sun.misc.Resource; import sun.misc.URLClassPath; import sun.misc.VM; import sun.reflect.Reflection; import sun.security.util.SecurityConstants; /** * A class loader is an object that is responsible for loading classes. The * class <tt>ClassLoader</tt> is an abstract class. Given the <a * href="#name">binary name</a> of a class, a class loader should attempt to * locate or generate data that constitutes a definition for the class. A * typical strategy is to transform the name into a file name and then read a * "class file" of that name from a file system. * * Every {@link Class <tt>Class</tt>} object contains a {@link * Class#getClassLoader() reference} to the <tt>ClassLoader</tt> that defined * it. * * <tt>Class</tt> 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 <tt>ClassLoader</tt> 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 <tt>ClassLoader</tt> class uses a delegation model to search for * classes and resources. Each instance of <tt>ClassLoader</tt> has an * associated parent class loader. When requested to find a class or * resource, a <tt>ClassLoader</tt> 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 <tt>ClassLoader</tt> instance. * * 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 * <tt>CLASSPATH</tt> 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) * <tt>defineClass</tt>} converts an array of bytes into an instance of class * <tt>Class</tt>. Instances of this newly defined class can be created using * {@link Class#newInstance <tt>Class.newInstance</tt>}. * * 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 <tt>loadClass</tt>} 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: * * <blockquote><pre> * ClassLoader loader = new NetworkClassLoader(host, port); * Object main = loader.loadClass("Main", true).newInstance(); * . . . * </pre></blockquote> * * The network class loader subclass must define the methods {@link * #findClass <tt>findClass</tt>} and <tt>loadClassData</tt> 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 <tt>defineClass</tt>} to * create a class instance. A sample implementation is: * * <blockquote><pre> * 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 * . . . * } * } * </pre></blockquote> * * <h4> <a name="name">Binary names</a> </h4> * * Any class name provided as a {@link String} parameter to methods in * <tt>ClassLoader</tt> must be a binary name as defined by the <a * href="http://java.sun.com/docs/books/jls/">Java Language Specification</a>. * * Examples of valid class names include: * <blockquote><pre> * "java.lang.String" * "javax.swing.JSpinner$DefaultEditor" * "java.security.KeyStore$Builder$FileBuilder$1" * "java.net.URLClassLoader$3$1" * </pre></blockquote> * * @version 1.189, 11/17/05 * @see #resolveClass(Class) * @since 1.0 */ public abstract class ClassLoader { private static native void registerNatives(); static { registerNatives(); } // 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 boolean initialized = false; // The parent class loader for delegation private ClassLoader parent; // Hashtable that maps packages to certs private Hashtable package2certs = new Hashtable(11); // Shared among all packages with unsigned classes java.security.cert.Certificate[] nocerts; // The classes loaded by this class loader. The only purpose of this table // is to keep the classes from being GC'ed until the loader is GC'ed. private Vector classes = new Vector(); // The initiating protection domains for all classes loaded by this loader private Set domains = new HashSet(); // Invoked by the VM to record every loaded class with this loader. void addClass(Class c) { classes.addElement(c); } // The packages defined in this class loader. Each package name is mapped // to its corresponding Package object. private HashMap packages = new HashMap(); /** * Creates a new class loader using the specified parent class loader for * delegation. * * If there is a security manager, its {@link * SecurityManager#checkCreateClassLoader() * <tt>checkCreateClassLoader</tt>} method is invoked. This may result in * a security exception. * * @param parent * The parent class loader * * @throws SecurityException * If a security manager exists and its * <tt>checkCreateClassLoader</tt> method doesn't allow creation * of a new class loader. * * @since 1.2 */ protected ClassLoader(ClassLoader parent) { SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkCreateClassLoader(); } this.parent = parent; initialized = true; } /** * Creates a new class loader using the <tt>ClassLoader</tt> returned by * the method {@link #getSystemClassLoader() * <tt>getSystemClassLoader()</tt>} as the parent class loader. * * If there is a security manager, its {@link * SecurityManager#checkCreateClassLoader() * <tt>checkCreateClassLoader</tt>} method is invoked. This may result in * a security exception. * * @throws SecurityException * If a security manager exists and its * <tt>checkCreateClassLoader</tt> method doesn't allow creation * of a new class loader. */ protected ClassLoader() { SecurityManager security = System.getSecurityManager(); if (security != null) { security.checkCreateClassLoader(); } this.parent = getSystemClassLoader(); initialized = true; } // -- Class -- /** * Loads the class with the specified <a href="#name" mce_href="#name">binary name</a>. * This method searches for classes in the same manner as the {@link * #loadClass(String, boolean)} method. It is invoked by the Java virtual * machine to resolve class references. Invoking this method is equivalent * to invoking {@link #loadClass(String, boolean) <tt>loadClass(name, * false)</tt>}. * * @param name * The <a href="#name" mce_href="#name">binary name</a> of the class * * @return The resulting <tt>Class</tt> object * * @throws ClassNotFoundException * If the class was not found */ public Class<?> loadClass(String name) throws ClassNotFoundException { return loadClass(name, false); } /** * Loads the class with the specified <a href="#name" mce_href="#name">binary name</a>. The * default implementation of this method searches for classes in the * following order: * * <ol> * * <li> Invoke {@link #findLoadedClass(String)} to check if the class * has already been loaded. </li> * * <li> Invoke the {@link #loadClass(String) <tt>loadClass</tt>} method * on the parent class loader. If the parent is <tt>null</tt> the class * loader built-in to the virtual machine is used, instead. </li> * * <li> Invoke the {@link #findClass(String)} method to find the * class. </li> * * </ol> * * If the class was found using the above steps, and the * <tt>resolve</tt> flag is true, this method will then invoke the {@link * #resolveClass(Class)} method on the resulting <tt>Class</tt> object. * * Subclasses of <tt>ClassLoader</tt> are encouraged to override {@link * #findClass(String)}, rather than this method. * * @param name * The <a href="#name" mce_href="#name">binary name</a> of the class * * @param resolve * If <tt>true</tt> then resolve the class * * @return The resulting <tt>Class</tt> object * * @throws ClassNotFoundException * If the class could not be found */ protected synchronized Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException { // 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 = findBootstrapClass0(name); } } catch (ClassNotFoundException e) { // If still not found, then invoke findClass in order // to find the class. c = findClass(name); } } if (resolve) { resolveClass(c); } return c; } // This method is invoked by the virtual machine to load a class. private synchronized Class loadClassInternal(String name) throws ClassNotFoundException { return loadClass(name); } private 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 PrivilegedAction() { public Object run() { sm.checkPackageAccess(name.substring(0, i)); return null; } }, new AccessControlContext(new ProtectionDomain[] {pd})); } } domains.add(pd); } /** * Finds the class with the specified <a href="#name" mce_href="#name">binary name</a>. * This method should be overridden by class loader implementations that * follow the delegation model for loading classes, and will be invoked by * the {@link #loadClass <tt>loadClass</tt>} method after checking the * parent class loader for the requested class. The default implementation * throws a <tt>ClassNotFoundException</tt>. * * @param name * The <a href="#name" mce_href="#name">binary name</a> of the class * * @return The resulting <tt>Class</tt> object * * @throws ClassNotFoundException * If the class could not be found * * @since 1.2 */ protected Class<?> findClass(String name) throws ClassNotFoundException { throw new ClassNotFoundException(name); } /** * Converts an array of bytes into an instance of class <tt>Class</tt>. * Before the <tt>Class</tt> can be used it must be resolved. This method * is deprecated in favor of the version that takes a <a * href="#name">binary name</a> as its first argument, and is more secure. * * @param b * The bytes that make up the class data. The bytes in positions * <tt>off</tt> through <tt>off+len-1</tt> should have the format * of a valid class file as defined by the <a * href="http://java.sun.com/docs/books/vmspec/">Java Virtual * Machine Specification</a>. * * @param off * The start offset in <tt>b</tt> of the class data * * @param len * The length of the class data * * @return The <tt>Class</tt> object that was created from the specified * class data * * @throws ClassFormatError * If the data did not contain a valid class * * @throws IndexOutOfBoundsException * If either <tt>off</tt> or <tt>len</tt> is negative, or if * <tt>off+len</tt> is greater than <tt>b.length</tt>. * * @see #loadClass(String, boolean) * @see #resolveClass(Class) * * @deprecated Replaced by {@link #defineClass(String, byte[], int, int) * defineClass(String, byte[], int, int)} */ @Deprecated protected final Class<?> defineClass(byte[] b, int off, int len) throws ClassFormatError { return defineClass(null, b, off, len, null); } /** * Converts an array of bytes into an instance of class <tt>Class</tt>. * Before the <tt>Class</tt> can be used it must be resolved. * * This method assigns a default {@link java.security.ProtectionDomain * <tt>ProtectionDomain</tt>} to the newly defined class. The * <tt>ProtectionDomain</tt> is effectively granted the same set of * permissions returned when {@link * java.security.Policy#getPermissions(java.security.CodeSource) * <tt>Policy.getPolicy().getPermissions(new CodeSource(null, null))</tt>} * is invoked. The default domain is created on the first invocation of * {@link #defineClass(String, byte[], int, int) <tt>defineClass</tt>}, * and re-used on subsequent invocations. * * To assign a specific <tt>ProtectionDomain</tt> to the class, use * the {@link #defineClass(String, byte[], int, int, * java.security.ProtectionDomain) <tt>defineClass</tt>} method that takes a * <tt>ProtectionDomain</tt> as one of its arguments. * * @param name * The expected <a href="#name" mce_href="#name">binary name</a> of the class, or * <tt>null</tt> if not known * * @param b * The bytes that make up the class data. The bytes in positions * <tt>off</tt> through <tt>off+len-1</tt> should have the format * of a valid class file as defined by the <a * href="http://java.sun.com/docs/books/vmspec/">Java Virtual * Machine Specification</a>. * * @param off * The start offset in <tt>b</tt> of the class data * * @param len * The length of the class data * * @return The <tt>Class</tt> object that was created from the specified * class data. * * @throws ClassFormatError * If the data did not contain a valid class * * @throws IndexOutOfBoundsException * If either <tt>off</tt> or <tt>len</tt> is negative, or if * <tt>off+len</tt> is greater than <tt>b.length</tt>. * * @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 * <tt>name</tt> begins with "<tt>java.</tt>". * * @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 protectionDomain) { 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 (protectionDomain == null) { protectionDomain = getDefaultDomain(); } if (name != null) checkCerts(name, protectionDomain.getCodeSource()); return protectionDomain; } private String defineClassSourceLocation(ProtectionDomain protectionDomain) { CodeSource cs = protectionDomain.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 protectionDomain, ClassFormatError cfe, String source) throws ClassFormatError { // Class format error - try to transform the bytecode and // define the class again // Object[] transformers = ClassFileTransformer.getTransformers(); Class c = null; for (int i = 0; transformers != null && i < transformers.length; i++) { try { // Transform byte code using transformer byte[] tb = ((ClassFileTransformer) transformers[i]).transform(b, off, len); c = defineClass1(name, tb, 0, tb.length, protectionDomain, 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 protectionDomain) { if (protectionDomain.getCodeSource() != null) { java.security.cert.Certificate certs[] = protectionDomain.getCodeSource().getCertificates(); if (certs != null) setSigners(c, certs); } } /** * Converts an array of bytes into an instance of class <tt>Class</tt>, * with an optional <tt>ProtectionDomain</tt>. If the domain is * <tt>null</tt>, 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 <tt>CodeSource</tt>} within the * <tt>ProtectionDomain</tt> of the class. Any classes added to that * package must contain the same set of certificates or a * <tt>SecurityException</tt> will be thrown. Note that if * <tt>name</tt> is <tt>null</tt>, this check is not performed. * You should always pass in the <a href="#name" mce_href="#name">binary name</a> 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 <tt>name</tt> cannot begin with "<tt>java.</tt>", since * all classes in the "<tt>java.*</tt> packages can only be defined by the * bootstrap class loader. If <tt>name</tt> is not <tt>null</tt>, it * must be equal to the <a href="#name" mce_href="#name">binary name</a> of the class * specified by the byte array "<tt>b</tt>", otherwise a {@link * <tt>NoClassDefFoundError</tt>} will be thrown. * * @param name * The expected <a href="#name" mce_href="#name">binary name</a> of the class, or * <tt>null</tt> if not known * * @param b * The bytes that make up the class data. The bytes in positions * <tt>off</tt> through <tt>off+len-1</tt> should have the format * of a valid class file as defined by the <a * href="http://java.sun.com/docs/books/vmspec/">Java Virtual * Machine Specification</a>. * * @param off * The start offset in <tt>b</tt> of the class data * * @param len * The length of the class data * * @param protectionDomain * The ProtectionDomain of the class * * @return The <tt>Class</tt> object created from the data, * and optional <tt>ProtectionDomain</tt>. * * @throws ClassFormatError * If the data did not contain a valid class * * @throws NoClassDefFoundError * If <tt>name</tt> is not equal to the <a href="#name" mce_href="#name">binary * name</a> of the class specified by <tt>b</tt> * * @throws IndexOutOfBoundsException * If either <tt>off</tt> or <tt>len</tt> is negative, or if * <tt>off+len</tt> is greater than <tt>b.length</tt>. * * @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 <tt>name</tt> begins with * "<tt>java.</tt>". */ 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 <tt>ByteBuffer</tt>} * into an instance of class <tt>Class</tt>, * with an optional <tt>ProtectionDomain</tt>. If the domain is * <tt>null</tt>, 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<tt>.defineClass(</tt>name<tt>,</tt> * bBuffer<tt>,</tt> pd<tt>)</tt> yields exactly the same * result as the statements * * <blockquote><tt> * ... * byte[] temp = new byte[</tt>bBuffer<tt>.{@link java.nio.ByteBuffer#remaining * remaining}()]; * </tt>bBuffer<tt>.{@link java.nio.ByteBuffer#get(byte[]) * get}(temp); * return {@link #defineClass(String, byte[], int, int, ProtectionDomain) * </tt>cl<tt>.defineClass}(</tt>name<tt>, temp, 0, temp.length, </tt>pd<tt>); * </tt></blockquote> * * @param name * The expected <a href="#name" mce_href="#name">binary name</a. of the class, or * <tt>null</tt> if not known * * @param b * The bytes that make up the class data. The bytes from positions * <tt>b.position()</tt> through <tt>b.position() + b.limit() -1 </tt> * should have the format of a valid class file as defined by the <a * href="http://java.sun.com/docs/books/vmspec/">Java Virtual * Machine Specification</a>. * * @param protectionDomain * The ProtectionDomain of the class, or <tt>null</tt>. * * @return The <tt>Class</tt> object created from the data, * and optional <tt>ProtectionDomain</tt>. * * @throws ClassFormatError * If the data did not contain a valid class. * * @throws NoClassDefFoundError * If <tt>name</tt> is not equal to the <a href="#name" mce_href="#name">binary * name</a> of the class specified by <tt>b</tt> * * @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 <tt>name</tt> begins with * "<tt>java.</tt>". * * @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 private 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 synchronized void checkCerts(String name, CodeSource cs) { int i = name.lastIndexOf('.'); String pname = (i == -1) ? "" : name.substring(0, i); java.security.cert.Certificate[] pcerts = (java.security.cert.Certificate[]) package2certs.get(pname); if (pcerts == null) { // first class in this package gets to define which // certificates must be the same for all other classes // in this package if (cs != null) { pcerts = cs.getCertificates(); } if (pcerts == null) { if (nocerts == null) nocerts = new java.security.cert.Certificate[0]; pcerts = nocerts; } package2certs.put(pname, pcerts); } else { java.security.cert.Certificate[] certs = null; if (cs != null) { certs = cs.getCertificates(); } if (!compareCerts(pcerts, certs)) { throw new SecurityException("class /""+ name + "/"'s signer information does not match signer information of other classes in the same package"); } } } /** * check to make sure the certs for the new class (certs) are the same as * the certs for the first class inserted in the package (pcerts) */ private boolean compareCerts(java.security.cert.Certificate[] pcerts, java.security.cert.Certificate[] certs) { // certs can be null, indicating no certs. if ((certs == null) || (certs.length == 0)) { return pcerts.length == 0; } // the length must be the same at this point if (certs.length != pcerts.length) return false; // go through and make sure all the certs in one array // are in the other and vice-versa. boolean match; for (int i = 0; i < certs.length; i++) { match = false; for (int j = 0; j < pcerts.length; j++) { if (certs[i].equals(pcerts[j])) { match = true; break; } } if (!match) return false; } // now do the same for pcerts for (int i = 0; i < pcerts.length; i++) { match = false; for (int j = 0; j < certs.length; j++) { if (pcerts[i].equals(certs[j])) { match = true; break; } } if (!match) return false; } return true; } /** * Links the specified class. This (misleadingly named) method may be * used by a class loader to link a class. If the class <tt>c</tt> has * already been linked, then this method simply returns. Otherwise, the * class is linked as described in the "Execution" chapter of the <a * href="http://java.sun.com/docs/books/jls/">Java Language * Specification</a>. * * * @param c * The class to link * * @throws NullPointerException * If <tt>c</tt> is <tt>null</tt>. * * @see #defineClass(String, byte[], int, int) */ protected final void resolveClass(Class<?> c) { check(); resolveClass0(c); } private native void resolveClass0(Class c); /** * Finds a class with the specified <a href="#name" mce_href="#name">binary name</a>, * loading it if necessary. * * This method loads the class through the system class loader (see * {@link #getSystemClassLoader()}). The <tt>Class</tt> object returned * might have more than one <tt>ClassLoader</tt> associated with it. * Subclasses of <tt>ClassLoader</tt> need not usually invoke this method, * because most class loaders need to override just {@link * #findClass(String)}. * * @param name * The <a href="#name" mce_href="#name">binary name</a> of the class * * @return The <tt>Class</tt> object for the specified <tt>name</tt> * * @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); return findBootstrapClass(name); } return system.loadClass(name); } private Class findBootstrapClass0(String name) throws ClassNotFoundException { check(); if (!checkName(name)) throw new ClassNotFoundException(name); return findBootstrapClass(name); } private native Class findBootstrapClass(String name) throws ClassNotFoundException; // 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 <a href="#name" mce_href="#name">binary name</a> if this * loader has been recorded by the Java virtual machine as an initiating * loader of a class with that <a href="#name" mce_href="#name">binary name</a>. Otherwise * <tt>null</tt> is returned. * * @param name * The <a href="#name" mce_href="#name">binary name</a> of the class * * @return The <tt>Class</tt> object, or <tt>null</tt> 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 <tt>Class</tt> 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 '<tt>/</tt>'-separated path name that * identifies the resource. * * This method will first search the parent class loader for the * resource; if the parent is <tt>null</tt> 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 <tt>URL</tt> object for reading the resource, or * <tt>null</tt> 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 <tt>/</tt>-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 <tt>URL</tt>} 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 Enumeration<URL> getResources(String name) throws IOException { Enumeration[] tmp = new Enumeration[2]; if (parent != null) { tmp[0] = parent.getResources(name); } else { tmp[0] = getBootstrapResources(name); } tmp[1] = findResources(name); return new CompoundEnumeration(tmp); } /** * Finds the resource with the given name. Class loader implementations * should override this method to specify where to find resources. * * @param name * The resource name * * @return A <tt>URL</tt> object for reading the resource, or * <tt>null</tt> if the resource could not be found * * @since 1.2 */ protected URL findResource(String name) { return null; } /** * Returns an enumeration of {@link java.net.URL <tt>URL</tt>} objects * representing all the resources with the given name. Class loader * implementations should override this method to specify where to load * resources from. * * @param name * The resource name * * @return An enumeration of {@link java.net.URL <tt>URL</tt>} objects for * the resources * * @throws IOException * If I/O errors occur * * @since 1.2 */ protected Enumeration<URL> findResources(String name) throws IOException { return new CompoundEnumeration(new Enumeration[0]); } /** * Find 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 A {@link java.net.URL <tt>URL</tt>} object for reading the * resource, or <tt>null</tt> if the resource could not be found * * @since 1.1 */ public static URL getSystemResource(String name) { ClassLoader system = getSystemClassLoader(); if (system == null) { return getBootstrapResource(name); } return system.getResource(name); } /** * Finds all resources of the specified name from the search path used to * load classes. The resources thus found are returned as an * {@link java.util.Enumeration <tt>Enumeration</tt>} of {@link * java.net.URL <tt>URL</tt>} objects. * * The 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 <tt>URL</tt>} * objects * * @throws IOException * If I/O errors occur * @since 1.2 */ public static Enumeration<URL> getSystemResources(String name) throws IOException { ClassLoader system = getSystemClassLoader(); if (system == null) { return getBootstrapResources(name); } return system.getResources(name); } /** * Find resources from the VM's built-in classloader. */ private static URL getBootstrapResource(String name) { try { // If this is a known JRE resource, ensure that its bundle is // downloaded. If it isn't known, we just ignore the download // failure and check to see if we can find the resource anyway // (which is possible if the boot class path has been modified). sun.jkernel.DownloadManager.getBootClassPathEntryForResource(name); } catch (NoClassDefFoundError e) { // This happens while Java itself is being compiled; DownloadManager // isn't accessible when this code is first invoked. It isn't an // issue, as if we can't find DownloadManager, we can safely assume // that additional code is not available for download. } URLClassPath ucp = getBootstrapClassPath(); Resource res = ucp.getResource(name); return res != null ? res.getURL() : null; } /** * Find resources from the VM's built-in classloader. */ private static Enumeration getBootstrapResources(String name) throws IOException { final Enumeration e = getBootstrapClassPath().getResources(name); return new Enumeration () { public Object nextElement() { return ((Resource)e.nextElement()).getURL(); } public boolean hasMoreElements() { return e.hasMoreElements(); } }; } // Returns the URLClassPath that is used for finding system resources. static URLClassPath getBootstrapClassPath() { return sun.misc.Launcher.getBootstrapClassPath(); } /** * Returns an input stream for reading the specified resource. * * The 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 <tt>null</tt> * 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 <tt>null</tt> * 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 <tt>null</tt> to represent the bootstrap class loader. This method * will return <tt>null</tt> 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 <tt>null</tt> and is not an ancestor of this class loader, then this * method invokes the security manager's {@link * SecurityManager#checkPermission(java.security.Permission) * <tt>checkPermission</tt>} method with a {@link * RuntimePermission#RuntimePermission(String) * <tt>RuntimePermission("getClassLoader")</tt>} permission to verify * access to the parent class loader is permitted. If not, a * <tt>SecurityException</tt> will be thrown. * * @return The parent <tt>ClassLoader</tt> * * @throws SecurityException * If a security manager exists and its <tt>checkPermission</tt> * method doesn't allow access to this class loader's parent class * loader. * * @since 1.2 */ public final ClassLoader getParent() { if (parent == null) return null; SecurityManager sm = System.getSecurityManager(); if (sm != null) { ClassLoader ccl = getCallerClassLoader(); if (ccl != null && !isAncestor(ccl)) { sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); } } return parent; } /** * Returns the system class loader for delegation. This is the default * delegation parent for new <tt>ClassLoader</tt> 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 <tt>Thread</tt>. * * The default system class loader is an implementation-dependent * instance of this class. * * If the system property "<tt>java.system.class.loader</tt>" 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 <tt>ClassLoader</tt> 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 <tt>null</tt> 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) * <tt>checkPermission</tt>} method with a {@link * RuntimePermission#RuntimePermission(String) * <tt>RuntimePermission("getClassLoader")</tt>} permission to verify * access to the system class loader. If not, a * <tt>SecurityException</tt> will be thrown. * * @return The system <tt>ClassLoader</tt> for delegation, or * <tt>null</tt> if none * * @throws SecurityException * If a security manager exists and its <tt>checkPermission</tt> * 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 "<tt>java.system.class.loader</tt>" * property. * * @throws Error * If the system property "<tt>java.system.class.loader</tt>" * 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 */ public static ClassLoader getSystemClassLoader() { initSystemClassLoader(); if (scl == null) { return null; } SecurityManager sm = System.getSecurityManager(); if (sm != null) { ClassLoader ccl = getCallerClassLoader(); if (ccl != null && ccl != scl && !scl.isAncestor(ccl)) { sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION); } } 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 { PrivilegedExceptionAction a; a = new SystemClassLoaderAction(scl); scl = (ClassLoader) AccessController.doPrivileged(a); } 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; } // Returns the invoker's class loader, or null if none. // NOTE: This must always be invoked when there is exactly one intervening // frame from the core libraries on the stack between this method's // invocation and the desired invoker. static ClassLoader getCallerClassLoader() { // NOTE use of more generic Reflection.getCallerClass() Class caller = Reflection.getCallerClass(3); // 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(); } // The class loader for the system private static ClassLoader scl; // Set to true once the system class loader has been set private static boolean sclSet; // -- Package -- /** * Defines a package by name in this <tt>ClassLoader</tt>. 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 <tt>null</tt>, then this package is sealed with * respect to the given code source {@link java.net.URL * <tt>URL</tt>} object. Otherwise, the package is not sealed. * * @return The newly defined <tt>Package</tt> 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 <tt>Package</tt> that has been defined by this class loader * or any of its ancestors. * * @param name * The package name * * @return The <tt>Package</tt> corresponding to the given name, or * <tt>null</tt> if not found * * @since 1.2 */ protected Package getPackage(String name) { synchronized (packages) { Package pkg = (Package)packages.get(name); if (pkg == null) { if (parent != null) { pkg = parent.getPackage(name); } else { pkg = Package.getSystemPackage(name); } if (pkg != null) { packages.put(name, pkg); } } return pkg; } } /** * Returns all of the <tt>Packages</tt> defined by this class loader and * its ancestors. * * @return The array of <tt>Package</tt> objects defined by this * <tt>ClassLoader</tt> * * @since 1.2 */ protected Package[] getPackages() { Map map; synchronized (packages) { map = (Map)packages.clone(); } Package[] pkgs; if (parent != null) { pkgs = parent.getPackages(); } else { pkgs = Package.getSystemPackages(); } if (pkgs != null) { for (int i = 0; i < pkgs.length; i++) { String pkgName = pkgs[i].getName(); if (map.get(pkgName) == null) { map.put(pkgName, pkgs[i]); } } } return (Package[])map.values().toArray(new Package[map.size()]); } // -- Native library access -- /** * Returns the absolute path name of a native library. The VM invokes this * method to locate the native libraries that belong to classes loaded with * this class loader. If this method returns <tt>null</tt>, the VM * searches the library along the path specified as the * "<tt>java.library.path</tt>" property. * * @param libname * The library name * * @return The absolute path of the native library * * @see System#loadLibrary(String) * @see System#mapLibraryName(String) * * @since 1.2 */ protected String findLibrary(String libname) { return null; } /** * The inner class NativeLibrary denotes a loaded native library instance. * Every classloader contains a vector of loaded native libraries in the * private field <tt>nativeLibraries</tt>. The native libraries loaded * into the system are entered into the <tt>systemNativeLibraries</tt> * vector. * * Every native library requires a particular version of JNI. This is * denoted by the private <tt>jniVersion</tt> 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. * * @version 1.189 11/17/05 * @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. private 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 ((NativeLibrary) (ClassLoader.nativeLibraryContext.peek())).fromClass; } } // The "default" domain. Set as the default ProtectionDomain on newly // created classes. private ProtectionDomain defaultDomain = null; // Returns (and initializes) the default domain. private synchronized ProtectionDomain getDefaultDomain() { if (defaultDomain == null) { CodeSource cs = new CodeSource(null, (java.security.cert.Certificate[]) null); defaultDomain = new ProtectionDomain(cs, null, this, null); } return defaultDomain; } // All native library names we've loaded. private static Vector loadedLibraryNames = new Vector(); // Native libraries belonging to system classes. private static Vector systemNativeLibraries = new Vector(); // Native libraries associated with the class loader. private Vector nativeLibraries = new Vector(); // native libraries being loaded/unloaded. private static Stack nativeLibraryContext = new Stack(); // The paths searched for libraries static private String usr_paths[]; static private String sys_paths[]; private static String[] initializePath(String propname) { String ldpath = System.getProperty(propname, ""); String ps = File.pathSeparator; int ldlen = ldpath.length(); int i, j, n; // Count the separators in the path i = ldpath.indexOf(ps); n = 0; while (i >= 0) { n++; i = ldpath.indexOf(ps, i + 1); } // allocate the array of paths - n :'s = n + 1 path elements String[] paths = new String[n + 1]; // Fill the array with paths from the ldpath n = i = 0; j = ldpath.indexOf(ps); while (j >= 0) { if (j - i > 0) { paths[n++] = ldpath.substring(i, j); } else if (j - i == 0) { paths[n++] = "."; } i = j + 1; j = ldpath.indexOf(ps, i); } paths[n] = ldpath.substring(i, ldlen); return paths; } // Invoked in the java.lang.Runtime class to implement load and loadLibrary. static void loadLibrary(Class fromClass, String name, boolean isAbsolute) { try { if (!DownloadManager.isJREComplete() && !DownloadManager.isCurrentThreadDownloading()) { DownloadManager.downloadFile("bin/" + System.mapLibraryName(name)); // it doesn't matter if the downloadFile call returns false -- // it probably just means that this is a user library, as // opposed to a JRE library } } catch (IOException e) { throw new UnsatisfiedLinkError("Error downloading library " + name + ": " + e); } catch (NoClassDefFoundError e) { // This happens while Java itself is being compiled; DownloadManager // isn't accessible when this code is first invoked. It isn't an // issue, as if we can't find DownloadManager, we can safely assume // that additional code is not available for download. } ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader(); if (sys_paths == null) { usr_paths = initializePath("java.library.path"); sys_paths = initializePath("sun.boot.library.path"); } if (isAbsolute) { if (loadLibrary0(fromClass, new File(name))) { return; } throw new UnsatisfiedLinkError("Can't load library: " + name); } if (loader != null) { String libfilename = loader.findLibrary(name); if (libfilename != null) { File libfile = new File(libfilename); if (!libfile.isAbsolute()) { throw new UnsatisfiedLinkError( "ClassLoader.findLibrary failed to return an absolute path: " + libfilename); } if (loadLibrary0(fromClass, libfile)) { return; } throw new UnsatisfiedLinkError("Can't load " + libfilename); } } for (int i = 0 ; i < sys_paths.length ; i++) { File libfile = new File(sys_paths[i], System.mapLibraryName(name)); if (loadLibrary0(fromClass, libfile)) { return; 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