ozoneclassloader.java

用Java写的面相对象的数据库管理系统

// You can redistribute this software and/or modify it under the terms of
// the Ozone Core License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-2000 by SMB GmbH. All rights reserved.
//
// $Id: OzoneClassLoader.java,v 1.3 2000/10/28 16:55:17 daniela Exp $

package org.ozoneDB.core;

import java.io.*;
import org.ozoneDB.*;
import org.ozoneDB.DxLib.*;


/**
 * Ozone specific class loader. This compiles/runs with JDK 1.2 only. To make
 * it run with JDK 1.1 see CLassManager.classForName() method.
 * 
 * 
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.3 $Date: 2000/10/28 16:55:17 $
 */
class OzoneClassLoader extends ClassLoader {
    
    protected DxMap classTable;
    
    
    public OzoneClassLoader() {
        super();
        flushCache();
    }
    
    
    protected void flushCache() {
        classTable = new DxHashMap( 100 );
    } 
    
    
    protected Class findClass( String name ) throws ClassNotFoundException {
        if (name.startsWith( "java" )) {
            throw new ClassNotFoundException( "I'm not here to load system classes." );
        } 
        
        StringBuffer resourceName = new StringBuffer( name );
        for (int i = 0; i < resourceName.length(); i++) {
            if (resourceName.charAt( i ) == '.') {
                resourceName.setCharAt( i, '/' );
            } 
        } 
        resourceName.append( ".class" );
        
        InputStream classIn = getSystemClassLoader().getSystemResourceAsStream( resourceName.toString() );
        if (classIn == null) {
            throw new ClassNotFoundException( "Unable to locate resource." );
        } 
        
        try {
            byte[] classBytes = new byte[classIn.available()];
            classIn.read( classBytes );
            classIn.close();
            Class cl = defineClass( name, classBytes, 0, classBytes.length, null );
            return cl;
        } catch (Exception e) {
            e.printStackTrace();
            throw new ClassNotFoundException( e.toString() );
        } 
    } 
    
    
    public Class loadClass( String name ) throws ClassNotFoundException {
        return loadClass( name, false );
    } 
    
    
    protected Class loadClass( String name, boolean resolve ) throws ClassNotFoundException {
        if (name.startsWith( "java" )) {
            return getSystemClassLoader().loadClass( name );
        } else {
            Class cl = (Class)classTable.elementForKey( name );
            if (cl == null) {
                cl = primitiveType( name );
                if (cl == null) {
                    // this really loads the requested class in this ClassLoader but cause
                    // compatibility problems with already loaded classes
                    //cl = findClass (name);
                    //if (resolve)
                    //    resolveClass (cl);
                    
                    // this works around the compatibility problems but causes the reloadClasses()
                    // method to not work
                    cl = getSystemClassLoader().loadClass( name );
                } 
                classTable.addForKey( cl, name );
            } 
            return cl;
        } 
    } 
    
    
    /**
     * Load primitive types with default class loader.
     */
    protected static Class primitiveType( String name ) {
        if (name.equals( "int" )) {
            return Integer.TYPE;
        } else if (name.equals( "char" )) {
            return Character.TYPE;
        } else if (name.equals( "byte" )) {
            return Byte.TYPE;
        } else if (name.equals( "double" )) {
            return Byte.TYPE;
        } else if (name.equals( "float" )) {
            return Byte.TYPE;
        } else if (name.equals( "long" )) {
            return Long.TYPE;
        } else if (name.equals( "short" )) {
            return Short.TYPE;
        } else if (name.equals( "boolean" )) {
            return Boolean.TYPE;
        } else {
            return null;
        } 
    } 
    
}