FileDocCategorySizeDatePackage
ClassLoader.javaAPI DocJava SE 5 API70824Fri Aug 26 14:57:02 BST 2005java.lang

ClassLoader

public abstract class ClassLoader extends Object
A class loader is an object that is responsible for loading classes. The class ClassLoader is an abstract class. Given the binary name 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 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.

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:

ClassLoader loader = new NetworkClassLoader(host, port);
Object main = loader.loadClass("Main", true).newInstance();
 . . .

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:

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

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:

"java.lang.String"
"javax.swing.JSpinner$DefaultEditor"
"java.security.KeyStore$Builder$FileBuilder$1"
"java.net.URLClassLoader$3$1"
version
1.186, 08/02/04
see
#resolveClass(Class)
since
1.0

Fields Summary
private boolean
initialized
private ClassLoader
parent
private Hashtable
package2certs
Certificate[]
nocerts
private Vector
classes
private Set
domains
private HashMap
packages
private static sun.misc.URLClassPath
bootstrapClassPath
private static ClassLoader
scl
private static boolean
sclSet
private ProtectionDomain
defaultDomain
private static Vector
loadedLibraryNames
private static Vector
systemNativeLibraries
private Vector
nativeLibraries
private static Stack
nativeLibraryContext
private static String[]
usr_paths
private static String[]
sys_paths
private boolean
defaultAssertionStatus
private Map
packageAssertionStatus
Map
classAssertionStatus
Constructors Summary
protected ClassLoader(ClassLoader parent)
Creates a new class loader using the specified parent class loader for delegation.

If there is a security manager, its {@link SecurityManager#checkCreateClassLoader() checkCreateClassLoader} 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 checkCreateClassLoader method doesn't allow creation of a new class loader.
since
1.2


                                                                                                               
       
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	this.parent = parent;
	initialized = true;
    
protected ClassLoader()
Creates a new class loader using the ClassLoader returned by the method {@link #getSystemClassLoader() getSystemClassLoader()} as the parent class loader.

If there is a security manager, its {@link SecurityManager#checkCreateClassLoader() checkCreateClassLoader} method is invoked. This may result in a security exception.

throws
SecurityException If a security manager exists and its checkCreateClassLoader method doesn't allow creation of a new class loader.

	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	    security.checkCreateClassLoader();
	}
	this.parent = getSystemClassLoader();
	initialized = true;
    
Methods Summary
voidaddClass(java.lang.Class c)


    // Invoked by the VM to record every loaded class with this loader.
       
        classes.addElement(c);
    
private voidcheck()

	if (!initialized) {
	    throw new SecurityException("ClassLoader object not initialized");
	}
    
private synchronized voidcheckCerts(java.lang.String name, java.security.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");
	    }
	}
    
private booleancheckName(java.lang.String name)

	if ((name == null) || (name.length() == 0))
   	    return true;
	if ((name.indexOf('/") != -1)
	    || (!VM.allowArraySyntax() && (name.charAt(0) == '[")))
   	    return false;
 	return true;
    
private voidcheckPackageAccess(java.lang.Class cls, java.security.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);
    
public synchronized voidclearAssertionStatus()
Sets the default assertion status for this class loader to false and discards any package defaults or class assertion status settings associated with the class loader. This method is provided so that class loaders can be made to ignore any command line or persistent assertion status settings and "start with a clean slate."

since
1.4

        /*
         * Whether or not "Java assertion maps" are initialized, set
         * them to empty maps, effectively ignoring any present settings.
         */
        classAssertionStatus = new HashMap();
        packageAssertionStatus = new HashMap();

        defaultAssertionStatus = false;
    
private booleancompareCerts(java.security.cert.Certificate[] pcerts, java.security.cert.Certificate[] certs)
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)

	// 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;
    
protected final java.lang.ClassdefineClass(byte[] b, int off, int len)
Converts an array of bytes into an instance of class Class. Before the Class can be used it must be resolved. This method is deprecated in favor of the version that takes a binary name as its first argument, and is more secure.

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.
see
#loadClass(String, boolean)
see
#resolveClass(Class)
deprecated
Replaced by {@link #defineClass(String, byte[], int, int) defineClass(String, byte[], int, int)}

	return defineClass(null, b, off, len, null);
    
protected final java.lang.ClassdefineClass(java.lang.String name, byte[] b, int off, int len)
Converts an array of bytes into an instance of class Class. Before the Class can be used it must be resolved.

This 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

	return defineClass(name, b, off, len, null);
    
protected final java.lang.ClassdefineClass(java.lang.String name, byte[] b, int off, int len, java.security.ProtectionDomain protectionDomain)
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.".

	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;
    
protected final java.lang.ClassdefineClass(java.lang.String name, java.nio.ByteBuffer b, java.security.ProtectionDomain protectionDomain)
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

...
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);

param
name The expected binary namenull 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

	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 java.lang.ClassdefineClass0(java.lang.String name, byte[] b, int off, int len, java.security.ProtectionDomain pd)

private native java.lang.ClassdefineClass1(java.lang.String name, byte[] b, int off, int len, java.security.ProtectionDomain pd, java.lang.String source)

private native java.lang.ClassdefineClass2(java.lang.String name, java.nio.ByteBuffer b, int off, int len, java.security.ProtectionDomain pd, java.lang.String source)

private java.lang.StringdefineClassSourceLocation(java.security.ProtectionDomain protectionDomain)

	CodeSource cs = protectionDomain.getCodeSource();
	String source = null;
	if (cs != null && cs.getLocation() != null) {
	    source = cs.getLocation().toString();
	}
	return source;
    
protected java.lang.PackagedefinePackage(java.lang.String name, java.lang.String specTitle, java.lang.String specVersion, java.lang.String specVendor, java.lang.String implTitle, java.lang.String implVersion, java.lang.String implVendor, java.net.URL sealBase)
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

	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;
	}
    
private java.lang.ClassdefineTransformedClass(java.lang.String name, byte[] b, int off, int len, java.security.ProtectionDomain protectionDomain, java.lang.ClassFormatError cfe, java.lang.String source)

        // 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;
    
synchronized booleandesiredAssertionStatus(java.lang.String className)
Returns the assertion status that would be assigned to the specified class if it were to be initialized at the time this method is invoked. If the named class has had its assertion status set, the most recent setting will be returned; otherwise, if any package default assertion status pertains to this class, the most recent setting for the most specific pertinent package default assertion status is returned; otherwise, this class loader's default assertion status is returned.

param
className The fully qualified class name of the class whose desired assertion status is being queried.
return
The desired assertion status of the specified class.
see
#setClassAssertionStatus(String, boolean)
see
#setPackageAssertionStatus(String, boolean)
see
#setDefaultAssertionStatus(boolean)
since
1.4

        Boolean result;

        // assert classAssertionStatus   != null;
        // assert packageAssertionStatus != null;

        // Check for a class entry
        result = (Boolean)classAssertionStatus.get(className);
        if (result != null)
            return result.booleanValue();

        // Check for most specific package entry
        int dotIndex = className.lastIndexOf(".");
        if (dotIndex < 0) { // default package
            result = (Boolean)packageAssertionStatus.get(null);
            if (result != null)
                return result.booleanValue();
        }
        while(dotIndex > 0) {
            className = className.substring(0, dotIndex);
            result = (Boolean)packageAssertionStatus.get(className);
            if (result != null)
                return result.booleanValue();
            dotIndex = className.lastIndexOf(".", dotIndex-1);
        }

        // Return the classloader default
        return defaultAssertionStatus;
    
private native java.lang.ClassfindBootstrapClass(java.lang.String name)

private java.lang.ClassfindBootstrapClass0(java.lang.String name)

	check();
	if (!checkName(name))
	    throw new ClassNotFoundException(name);
	return findBootstrapClass(name);
    
protected java.lang.ClassfindClass(java.lang.String name)
Finds the class with the specified binary name. 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 loadClass} method after checking the parent class loader for the requested class. The default implementation throws a ClassNotFoundException.

param
name The binary name of the class
return
The resulting Class object
throws
ClassNotFoundException If the class could not be found
since
1.2

	throw new ClassNotFoundException(name);
    
protected java.lang.StringfindLibrary(java.lang.String libname)
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 null, the VM searches the library along the path specified as the "java.library.path" 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

        return null;
    
protected final java.lang.ClassfindLoadedClass(java.lang.String name)
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

	check();
	if (!checkName(name))
	    return null;
	return findLoadedClass0(name);
    
private final native java.lang.ClassfindLoadedClass0(java.lang.String name)

static longfindNative(java.lang.ClassLoader loader, java.lang.String name)

        Vector libs =
	    loader != null ? loader.nativeLibraries : systemNativeLibraries;
	synchronized (libs) {
	    int size = libs.size();
	    for (int i = 0; i < size; i++) {
	        NativeLibrary lib = (NativeLibrary)libs.elementAt(i);
		long entry = lib.find(name);
		if (entry != 0)
		    return entry;
	    }
	}
	return 0;
    
protected java.net.URLfindResource(java.lang.String name)
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 URL object for reading the resource, or null if the resource could not be found
since
1.2

	return null;
    
protected java.util.EnumerationfindResources(java.lang.String name)
Returns an enumeration of {@link java.net.URL URL} 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 URL} objects for the resources
throws
IOException If I/O errors occur
since
1.2

	return new CompoundEnumeration(new Enumeration[0]);
    
protected final java.lang.ClassfindSystemClass(java.lang.String name)
Finds a class with the specified binary name, loading it if necessary.

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()

	check();
	ClassLoader system = getSystemClassLoader();
	if (system == null) {
	    if (!checkName(name))
		throw new ClassNotFoundException(name);
	    return findBootstrapClass(name);
	}
	return system.loadClass(name);
    
static sun.misc.URLClassPathgetBootstrapClassPath()

	if (bootstrapClassPath == null) {
	    bootstrapClassPath = sun.misc.Launcher.getBootstrapClassPath();
	}
	return bootstrapClassPath;
    
private static java.net.URLgetBootstrapResource(java.lang.String name)
Find resources from the VM's built-in classloader.

	URLClassPath ucp = getBootstrapClassPath();
	Resource res = ucp.getResource(name);
	return res != null ? res.getURL() : null;
    
private static java.util.EnumerationgetBootstrapResources(java.lang.String name)
Find resources from the VM's built-in classloader.

	final Enumeration e = getBootstrapClassPath().getResources(name);
	return new Enumeration () {
	    public Object nextElement() {
		return ((Resource)e.nextElement()).getURL();
	    }
	    public boolean hasMoreElements() {
		return e.hasMoreElements();
	    }
	};
    
static java.lang.ClassLoadergetCallerClassLoader()

        // 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();
    
private synchronized java.security.ProtectionDomaingetDefaultDomain()


    // Returns (and initializes) the default domain.
        
	if (defaultDomain == null) {
	    CodeSource cs =
		new CodeSource(null, (java.security.cert.Certificate[]) null);
	    defaultDomain = new ProtectionDomain(cs, null, this, null);
	}
	return defaultDomain;
    
protected java.lang.PackagegetPackage(java.lang.String name)
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

	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;
	}
    
protected java.lang.Package[]getPackages()
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

	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()]);
    
public final java.lang.ClassLoadergetParent()
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

	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;
    
public java.net.URLgetResource(java.lang.String name)
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

	URL url;
	if (parent != null) {
	    url = parent.getResource(name);
	} else {
	    url = getBootstrapResource(name);
	}
	if (url == null) {
	    url = findResource(name);
	}
	return url;
    
public java.io.InputStreamgetResourceAsStream(java.lang.String name)
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 null if the resource could not be found
since
1.1

	URL url = getResource(name);
	try {
	    return url != null ? url.openStream() : null;
	} catch (IOException e) {
	    return null;
	}
    
public java.util.EnumerationgetResources(java.lang.String name)
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

	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);
    
public static java.lang.ClassLoadergetSystemClassLoader()
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

	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;
    
public static java.net.URLgetSystemResource(java.lang.String name)
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 URL} object for reading the resource, or null if the resource could not be found
since
1.1

	ClassLoader system = getSystemClassLoader();
	if (system == null) {
	    return getBootstrapResource(name);
	}
	return system.getResource(name);
    
public static java.io.InputStreamgetSystemResourceAsStream(java.lang.String name)
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

        URL url = getSystemResource(name);
        try {
            return url != null ? url.openStream() : null;
        } catch (IOException e) {
            return null;
        }
    
public static java.util.EnumerationgetSystemResources(java.lang.String 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 Enumeration} of {@link java.net.URL URL} 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 URL} objects
throws
IOException If I/O errors occur
since
1.2

	ClassLoader system = getSystemClassLoader();
	if (system == null) {
	    return getBootstrapResources(name);
	}
	return system.getResources(name);
    
private static synchronized voidinitSystemClassLoader()

	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;
	}
    
private voidinitializeJavaAssertionMaps()

        // assert Thread.holdsLock(this);

        classAssertionStatus = new HashMap();
        packageAssertionStatus = new HashMap();
        AssertionStatusDirectives directives = retrieveDirectives();

        for(int i = 0; i < directives.classes.length; i++)
            classAssertionStatus.put(directives.classes[i],
                              Boolean.valueOf(directives.classEnabled[i]));

        for(int i = 0; i < directives.packages.length; i++)
            packageAssertionStatus.put(directives.packages[i],
                              Boolean.valueOf(directives.packageEnabled[i]));

        defaultAssertionStatus = directives.deflt;
    
private static java.lang.String[]initializePath(java.lang.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;
    
booleanisAncestor(java.lang.ClassLoader cl)

	ClassLoader acl = this;
	do {
	    acl = acl.parent;
	    if (cl == acl) {
		return true;
	    }
	} while (acl != null);
	return false;
    
public java.lang.ClassloadClass(java.lang.String name)
Loads the class with the specified binary name. 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) loadClass(name, false)}.

param
name The binary name of the class
return
The resulting Class object
throws
ClassNotFoundException If the class was not found

	return loadClass(name, false);
    
protected synchronized java.lang.ClassloadClass(java.lang.String name, boolean resolve)
Loads the class with the specified binary name. The default implementation of this method searches for classes in the following order:

  1. Invoke {@link #findLoadedClass(String)} to check if the class has already been loaded.

  2. 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.

  3. 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.

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

	// 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;
    
private synchronized java.lang.ClassloadClassInternal(java.lang.String name)

	return loadClass(name);
    
static voidloadLibrary(java.lang.Class fromClass, java.lang.String name, boolean isAbsolute)

        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;
	    }
	}
	if (loader != null) {
	    for (int i = 0 ; i < usr_paths.length ; i++) {
	        File libfile = new File(usr_paths[i],
					System.mapLibraryName(name));
		if (loadLibrary0(fromClass, libfile)) {
		    return;
		}
	    }
	}
	// Oops, it failed
        throw new UnsatisfiedLinkError("no " + name + " in java.library.path");
    
private static booleanloadLibrary0(java.lang.Class fromClass, java.io.File file)

	Boolean exists = (Boolean)
	    AccessController.doPrivileged(new PrivilegedAction() {
		public Object run() {
		    return new Boolean(file.exists());
		}
	    });
	if (!exists.booleanValue()) {
	    return false;
	}
        String name;
	try {
	    name = file.getCanonicalPath();
	} catch (IOException e) {
	    return false;
	}
        ClassLoader loader =
	    (fromClass == null) ? null : fromClass.getClassLoader();
        Vector libs =
	    loader != null ? loader.nativeLibraries : systemNativeLibraries;
	synchronized (libs) {
	    int size = libs.size();
	    for (int i = 0; i < size; i++) {
	        NativeLibrary lib = (NativeLibrary)libs.elementAt(i);
		if (name.equals(lib.name)) {
		    return true;
		}
	    }

	    synchronized (loadedLibraryNames) {
	        if (loadedLibraryNames.contains(name)) {
		    throw new UnsatisfiedLinkError
		        ("Native Library " +
			 name +
			 " already loaded in another classloader");
		}
		/* If the library is being loaded (must be by the same thread,
		 * because Runtime.load and Runtime.loadLibrary are
		 * synchronous). The reason is can occur is that the JNI_OnLoad
		 * function can cause another loadLibrary invocation.
		 *
		 * Thus we can use a static stack to hold the list of libraries
		 * we are loading.
		 *
		 * If there is a pending load operation for the library, we
		 * immediately return success; otherwise, we raise
		 * UnsatisfiedLinkError.
		 */
		int n = nativeLibraryContext.size();
		for (int i = 0; i < n; i++) {
		    NativeLibrary lib = (NativeLibrary)
		        nativeLibraryContext.elementAt(i);
		    if (name.equals(lib.name)) {
		        if (loader == lib.fromClass.getClassLoader()) {
			    return true;
			} else {
			    throw new UnsatisfiedLinkError
			        ("Native Library " +
				 name +
				 " is being loaded in another classloader");
			}
		    }
		}
		NativeLibrary lib = new NativeLibrary(fromClass, name);
		nativeLibraryContext.push(lib);
		try {
		    lib.load(name);
		} finally {
		    nativeLibraryContext.pop();
		}
		if (lib.handle != 0) {
		    loadedLibraryNames.addElement(name);
		    libs.addElement(lib);
		    return true;
		}
		return false;
	    }
	}
    
private voidpostDefineClass(java.lang.Class c, java.security.ProtectionDomain protectionDomain)

	if (protectionDomain.getCodeSource() != null) {
	    java.security.cert.Certificate certs[] =
		protectionDomain.getCodeSource().getCertificates();
	    if (certs != null)
		setSigners(c, certs);
	}
    
private java.security.ProtectionDomainpreDefineClass(java.lang.String name, java.security.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 static native voidregisterNatives()

protected final voidresolveClass(java.lang.Class c)
Links the specified class. This (misleadingly named) method may be used by a class loader to link a class. If the class c has already been linked, then this method simply returns. Otherwise, the class is linked as described in the "Execution" chapter of the Java Language Specification.

param
c The class to link
throws
NullPointerException If c is null.
see
#defineClass(String, byte[], int, int)

	check();
	resolveClass0(c);
    
private native voidresolveClass0(java.lang.Class c)

private static native java.lang.AssertionStatusDirectivesretrieveDirectives()

public synchronized voidsetClassAssertionStatus(java.lang.String className, boolean enabled)
Sets the desired assertion status for the named top-level class in this class loader and any nested classes contained therein. This setting takes precedence over the class loader's default assertion status, and over any applicable per-package default. This method has no effect if the named class has already been initialized. (Once a class is initialized, its assertion status cannot change.)

If the named class is not a top-level class, this invocation will have no effect on the actual assertion status of any class, and its return value is undefined.

param
className The fully qualified class name of the top-level class whose assertion status is to be set.
param
enabled true if the named class is to have assertions enabled when (and if) it is initialized, false if the class is to have assertions disabled.
since
1.4

        if (classAssertionStatus == null)
            initializeJavaAssertionMaps();

        classAssertionStatus.put(className, Boolean.valueOf(enabled));
    
public synchronized voidsetDefaultAssertionStatus(boolean enabled)
Sets the default assertion status for this class loader. This setting determines whether classes loaded by this class loader and initialized in the future will have assertions enabled or disabled by default. This setting may be overridden on a per-package or per-class basis by invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link #setClassAssertionStatus(String, boolean)}.

param
enabled true if classes loaded by this class loader will henceforth have assertions enabled by default, false if they will have assertions disabled by default.
since
1.4


                                                                                                                      
         
        if (classAssertionStatus == null)
            initializeJavaAssertionMaps();

        defaultAssertionStatus = enabled;
    
public synchronized voidsetPackageAssertionStatus(java.lang.String packageName, boolean enabled)
Sets the package default assertion status for the named package. The package default assertion status determines the assertion status for classes initialized in the future that belong to the named package or any of its "subpackages".

A subpackage of a package named p is any package whose name begins with "p.". For example, javax.swing.text is a subpackage of javax.swing, and both java.util and java.lang.reflect are subpackages of java.

In the event that multiple package defaults apply to a given class, the package default pertaining to the most specific package takes precedence over the others. For example, if javax.lang and javax.lang.reflect both have package defaults associated with them, the latter package default applies to classes in javax.lang.reflect.

Package defaults take precedence over the class loader's default assertion status, and may be overridden on a per-class basis by invoking {@link #setClassAssertionStatus(String, boolean)}.

param
packageName The name of the package whose package default assertion status is to be set. A null value indicates the unnamed package that is "current" (Java Language Specification, section 7.4.2).
param
enabled true if classes loaded by this classloader and belonging to the named package or any of its subpackages will have assertions enabled by default, false if they will have assertions disabled by default.
since
1.4

        if (packageAssertionStatus == null)
            initializeJavaAssertionMaps();

        packageAssertionStatus.put(packageName, Boolean.valueOf(enabled));
    
protected final voidsetSigners(java.lang.Class c, java.lang.Object[] signers)
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

        check();
	c.setSigners(signers);