ClassLoader

ClassLoader

java.lang

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Java 1.0

This class is the abstract superclass of objects that know how to load Java classes into a Java VM. Given a ClassLoader object, you can dynamically load a class by calling the public loadClass( ) method, specifying the full name of the desired class. You can obtain a resource associated with a class by calling getresource( ) , geTResources( ) , and getresourceAsStream( ) . Many applications do not need to use ClassLoader directly; these applications use the Class.forName( ) and Class.getResource( ) methods to dynamically load classes and resources using the ClassLoader object that loaded the application itself.

In order to load classes over the network or from any source other than the class path , you must use a custom ClassLoader object that knows how to obtain data from that source. A java.net.URLClassLoader is suitable for this purpose for almost all applications. Only rarely should an application need to define a ClassLoader subclass of its own. When this is necessary, the subclass should typically extend java.security.SecureClassLoader and override the findClass( ) method. This method must find the bytes that comprise the named class, then pass them to the defineClass( ) method and return the resulting Class object. In Java 1.2 and later, the findClass( ) method must also define the Package object associated with the class, if it has not already been defined. It can use getPackage( ) and definePackage( ) for this purpose. Custom subclasses of ClassLoader should also override findResource( ) and findResources( ) to enable the public geTResource( ) and getresources( ) methods.

In Java 1.4 and later you can specify whether the classes loaded through a ClassLoader should have assertions ( assert statements) enabled. setDefaultAssertionStatus( ) enables or disables assertions for all loaded classes. setPackageAssertionStatus( ) and setClassAssertionStatus( ) allow you to override the default assertion status for a named package or a named class. Finally, clearAssertionStatus( ) sets the default status to false and discards the assertions status for any named packages and classes.

 public abstract class  ClassLoader  {  // Protected Constructors  protected  ClassLoader  ( );  1.2  protected  ClassLoader  (ClassLoader  parent  );  // Public Class Methods   1.2  public static ClassLoader  getSystemClassLoader  ( );  1.1  public static java.net.URL  getSystemResource  (String  name  );  1.1  public static java.io.InputStream  getSystemResourceAsStream  (String  name  );  1.2  public static java.util.Enumeration<java.net.URL>  getSystemResources  (String  name  )  throws java.io.IOException;  // Public Instance Methods   1.4  public void  clearAssertionStatus  ( );  synchronized   1.2  public final ClassLoader  getParent  ( );  1.1  public java.net.URL  getResource  (String  name  );  1.1  public java.io.InputStream  getResourceAsStream  (String  name  );  1.2  public java.util.Enumeration<java.net.URL>  getResources  (String  name  ) throws  java.io.IOException;  1.1  public Class<?>  loadClass  (String  name  ) throws ClassNotFoundException;  1.4  public void  setClassAssertionStatus  (String  className  , boolean  enabled  );  synchronized   1.4  public void  setDefaultAssertionStatus  (boolean  enabled  );  synchronized   1.4  public void  setPackageAssertionStatus  (String  packageName  , boolean  enabled  );  synchronized   // Protected Instance Methods   5.0  protected final Class<?>  defineClass  (String  name  , java.nio.ByteBuffer  b  ,  java.security.ProtectionDomain protectionDomain)  throws ClassFormatError;  1.1  protected final Class<?>  defineClass  (String  name  , byte[ ]  b  , int  off  , int  len  )  throws ClassFormatError;  1.2  protected final Class<?>  defineClass  (String  name  , byte[ ]  b  , int  off  , int  len  ,  java.security.ProtectionDomain  protectionDomain  )  throws ClassFormatError;  1.2  protected Package  definePackage  (String  name  , String  specTitle  , String  specVersion  ,  String  specVendor  , String  implTitle  , String  implVersion  , String  implVendor  , java.net.URL  sealBase  )  throws IllegalArgumentException;  1.2  protected Class<?>  findClass  (String  name  ) throws ClassNotFoundException;  1.2  protected String  findLibrary  (String  libname  );  constant   1.1  protected final Class<?>  findLoadedClass  (String  name  );  1.2  protected java.net.URL  findResource  (String  name  );  constant   1.2  protected java.util.Enumeration<java.net.URL>  findResources  (String  name  ) throws  java.io.IOException;        protected final Class<?>  findSystemClass  (String  name  ) throws ClassNotFoundException;  1.2  protected Package  getPackage  (String  name  );  1.2  protected Package[ ]  getPackages  ( );        protected Class<?>  loadClass  (String  name  , boolean  resolve  )  throws ClassNotFoundException;  synchronized  protected final void  resolveClass  (Class<?>  c  );  1.1  protected final void  setSigners  (Class<?>  c  , Object[ ]  signers  );  // Deprecated Protected Methods   #  protected final Class<?>  defineClass  (byte[ ]  b  , int  off  , int  len  ) throws ClassFormatError;   } 

Subclasses

java.security.SecureClassLoader

Passed To

Class.forName( ) , THRead.setContextClassLoader( ) , java.lang.instrument.ClassFileTransformer.transform( ) , java.lang.instrument.Instrumentation.getInitiatedClasses( ) , java.lang.reflect.Proxy.{getProxyClass( ) , newProxyInstance( )} , java.net.URLClassLoader.{newInstance( ) , URLClassLoader( )} , java.security.ProtectionDomain.ProtectionDomain( ) , java.security.SecureClassLoader.SecureClassLoader( ) , java.util.ResourceBundle.getBundle( )

Returned By

Class.getClassLoader( ) , SecurityManager.currentClassLoader( ) , Thread.getContextClassLoader( ) , java.security.ProtectionDomain.getClassLoader( )