fileclassloader.java

精通tomcat书籍原代码,希望大家共同学习

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class FileClassLoader extends ClassLoader {
	//定义要查找类的位置
    public static final String drive = "d:/ch09/testClassLoader";
    public static final String fileType = ".class";

	//重载查找类函数
    public Class findClass(String name) {
        byte[] data = loadClassData(name);
        return defineClass(name, data, 0, data.length);
    }
	
	//从预定义位置加载类数据
    public byte[] loadClassData(String name) {
        FileInputStream fis = null;
        byte[] data = null;
        try {
            fis = new FileInputStream(new File(drive + name + fileType));
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            int ch = 0;
            while ((ch = fis.read()) != -1) {
                baos.write(ch);
            }
            data = baos.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return data;
    }
	
    public static void main(String[] args) throws Exception {		
        FileClassLoader loader = new FileClassLoader();
		//加载类
        Class objClass = loader.loadClass("HelloWorld", true);
		//创建类的实例
        Object obj = objClass.newInstance();
        System.out.println(objClass.getName());
        System.out.println(objClass.getClassLoader());
		//调用类的函数
        System.out.println(((HelloWorld)obj).getInfor());
    }
}