自定义类加载器以及打破双亲委派模型解析

import java.io.FileInputStream;
 
public class MyClassLoader extends ClassLoader {
 
    private String classPath;
 
    public MyClassLoader(String classPath) {
        this.classPath = classPath;
    }
 
    private byte[] loadByte(String name) throws Exception {
        name = name.replaceAll("\\.", "/");
        FileInputStream fis = new FileInputStream(classPath + "/" + name + ".class");
        int len = fis.available();
        byte[] data = new byte[len];
        fis.read(data);
        fis.close();
        return data;
    }
 
    @Override
    protected Class<?> findClass(String name) {
        byte[] data = new byte[0];
        try {
            data = loadByte(name);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return defineClass(name, data, 0, data.length);
    }
}

public class MyClassLoaderTest {
 
    public static void main(String[] args) throws Exception {
        MyClassLoader classLoader = new MyClassLoader("D:/test");
        Class clazz = classLoader.loadClass("com.hys.test.User");
        System.out.println(clazz.getClassLoader().getClass().getName());
    }
}

@Override
protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
    synchronized (getClassLoadingLock(name)) {
        Class<?> c = findLoadedClass(name);
        if (c == null) {
            c = findClass(name);
        }
        if (resolve) {
            resolveClass(c);
        }
        return c;
    }
}