将字节数组加载到内存类加载器中

  • Z时代
  • 2024-01-10
  • 分类：问答

我想知道如何将字节数组加载到 URLClassLoader中？字节数组是jar文件的解密字节（如下所示）！

大多数内存类加载器都使用ClassLoader而不是URLClassLoader！我需要它使用URLClassLoader。

    byte[] fileB = Util.crypt.getFileBytes(inputFile);
    byte[] dec;
    dec = Util.crypt.decrypt(fileB, "16LENGTHLONGKEYX".getBytes());
    //Load bytes into memory and load a class here?

谢谢！

回答：

我将在这里发布我过去做过的实现：

// main
String className = "tests.compiler.DynamicCompilationHelloWorldEtc";
//...
ClassLoader classLoader = Thread.currentThread().getContextClassLoader(); 
File classesDir = new File(tempDir);
CustomClassLoader ccl = new CustomClassLoader(classLoader, classesDir);         
if (ccl != null) {
    Class clazz = ccl.loadClass(className);
///...
}

我的自定义ClassLoader：

package tests.classloader;
import java.io.File;
import java.io.FileInputStream;
import java.nio.ByteBuffer;
public class CustomClassLoader extends ClassLoader {
    private File classesDir;
    public CustomClassLoader(ClassLoader parent, File classesDir) {
       super(parent);
       this.classesDir = classesDir;
    }
    public Class findClass(String name) {
       byte[] data = loadDataFromAny(name);
       return defineClass(name, data, 0, data.length);
    }
    private byte[] loadDataFromAny(String name) {
        name = name.replace('.', '/');
        name = name + ".class";
        byte[] ret = null;
        try {
            File f = new File(classesDir.getAbsolutePath(), name);
            FileInputStream fis = new FileInputStream(f);
            ByteBuffer bb = ByteBuffer.allocate(4*1024); 
            byte[] buf = new byte[1024];
            int readedBytes = -1;
            while ((readedBytes = fis.read(buf)) != -1) {
                bb.put(buf, 0, readedBytes);
            }
            ret = bb.array();           
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        return ret;
    }
}

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