Drop in replacement for the standard class loader of the JVM. You can use it - * in conjunction with the JavaWrapper to dynamically modify/create classes - * as they're requested.
- * - *This class loader recognizes special requests in a distinct - * format, i.e., when the name of the requested class contains with - * "$$BCEL$$" it calls the createClass() method with that name - * (everything bevor the $$BCEL$$ is considered to be the package - * name. You can subclass the class loader and override that - * method. "Normal" classes class can be modified by overriding the - * modifyClass() method which is called just before defineClass().
- * - *There may be a number of packages where you have to use the default - * class loader (which may also be faster). You can define the set of packages - * where to use the system class loader in the constructor. The default value contains - * "java.", "sun.", "javax."
- * - * @author M. Dahm - * @see JavaWrapper - * @see ClassPath - */ -public class ClassLoader extends java.lang.ClassLoader { - private Hashtable classes = new Hashtable(); // Hashtable is synchronized thus thread-safe - private String[] ignored_packages = { - "java.", "javax.", "sun." - }; - private Repository repository = SyntheticRepository.getInstance(); - private java.lang.ClassLoader deferTo = ClassLoader.getSystemClassLoader(); - - public ClassLoader() { - } - - public ClassLoader(java.lang.ClassLoader deferTo) { - this.deferTo = deferTo; - this.repository = new ClassLoaderRepository(deferTo); - } - - /** @param ignored_packages classes contained in these packages will be loaded - * with the system class loader - */ - public ClassLoader(String[] ignored_packages) { - addIgnoredPkgs(ignored_packages); - } - - public ClassLoader(java.lang.ClassLoader deferTo, String [] ignored_packages) { - this.deferTo = deferTo; - this.repository = new ClassLoaderRepository(deferTo); - - addIgnoredPkgs(ignored_packages); - } - - private void addIgnoredPkgs(String[] ignored_packages) { - String[] new_p = new String[ignored_packages.length + this.ignored_packages.length]; - - System.arraycopy(this.ignored_packages, 0, new_p, 0, this.ignored_packages.length); - System.arraycopy(ignored_packages, 0, new_p, this.ignored_packages.length, - ignored_packages.length); - - this.ignored_packages = new_p; - } - - protected Class loadClass(String class_name, boolean resolve) - throws ClassNotFoundException - { - Class cl = null; - - /* First try: lookup hash table. - */ - if((cl=(Class)classes.get(class_name)) == null) { - /* Second try: Load system class using system class loader. You better - * don't mess around with them. - */ - for(int i=0; i < ignored_packages.length; i++) { - if(class_name.startsWith(ignored_packages[i])) { - cl = deferTo.loadClass(class_name); - break; - } - } - - if(cl == null) { - JavaClass clazz = null; - - /* Third try: Special request? - */ - if(class_name.indexOf("$$BCEL$$") >= 0) - clazz = createClass(class_name); - else { // Fourth try: Load classes via repository - if ((clazz = repository.loadClass(class_name)) != null) { - clazz = modifyClass(clazz); - } - else - throw new ClassNotFoundException(class_name); - } - - if(clazz != null) { - byte[] bytes = clazz.getBytes(); - cl = defineClass(class_name, bytes, 0, bytes.length); - } else // Fourth try: Use default class loader - cl = Class.forName(class_name); - } - - if(resolve) - resolveClass(cl); - } - - classes.put(class_name, cl); - - return cl; - } - - /** Override this method if you want to alter a class before it gets actually - * loaded. Does nothing by default. - */ - protected JavaClass modifyClass(JavaClass clazz) { - return clazz; - } - - /** - * Override this method to create you own classes on the fly. The - * name contains the special token $$BCEL$$. Everything before that - * token is consddered to be a package name. You can encode you own - * arguments into the subsequent string. You must regard however not - * to use any "illegal" characters, i.e., characters that may not - * appear in a Java class name too