core/src/main/java/org/apache/hop/core/plugins/HopURLClassLoader.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hop.core.plugins;

import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.security.ProtectionDomain;

public class HopURLClassLoader extends URLClassLoader {

  private String name;

  public HopURLClassLoader(URL[] url, ClassLoader classLoader) {
    super(url, classLoader);
  }

  public HopURLClassLoader(URL[] url, ClassLoader classLoader, String name) {
    this(url, classLoader);
    this.name = name;
  }

  @Override
  protected void addURL(URL url) {
    super.addURL(url);
  }

  @Override
  public String toString() {
    return super.toString() + " : " + name;
  }

  public void setName(String name) {
    this.name = name;
  }

  @Override
  public String getName() {
    return name;
  }

  protected Class<?> loadClassFromThisLoader(String arg0, boolean arg1)
      throws ClassNotFoundException {
    Class<?> clz;
    if ((clz = findLoadedClass(arg0)) != null) {
      if (arg1) {
        resolveClass(clz);
      }
      return clz;
    }

    if ((clz = findClass(arg0)) != null) {
      if (arg1) {
        resolveClass(clz);
      }
      return clz;
    }
    return clz;
  }

  protected Class<?> loadClassFromParent(String name, boolean resolve)
      throws ClassNotFoundException {
    Class<?> clz;
    if ((clz = getParent().loadClass(name)) != null) {
      if (resolve) {
        resolveClass(clz);
      }
      return clz;
    }
    throw new ClassNotFoundException("Could not find :" + name);
  }

  @Override
  protected synchronized Class<?> loadClass(String name, boolean resolve)
      throws ClassNotFoundException {
    try {
      return loadClassFromThisLoader(name, resolve);
    } catch (ClassNotFoundException | NoClassDefFoundError | SecurityException exception) {
      try {
        return loadClassFromParent(name, resolve);
      } catch (Exception parentException) {
        throw new ClassNotFoundException(
            "Unable to load class '" + name + "' in this classloader or in the parent", exception);
      }
    }
  }

  /*
   * Cglib doe's not creates custom class loader (to access package methods and classes ) it uses reflection to invoke
   * "defineClass", but you can call protected method in subclass without problems:
   */
  public Class<?> loadClass(String name, ProtectionDomain protectionDomain) {
    Class<?> loaded = findLoadedClass(name);
    if (loaded == null) {
      // Get the jar, load the bytes from the jar file, construct class from scratch as in snippet
      // below...

      String newName = name.replace('.', '/');
      InputStream is = getResourceAsStream(newName);
      byte[] driverBytes = toBytes(is);

      loaded = super.defineClass(name, driverBytes, 0, driverBytes.length, protectionDomain);
    }
    return loaded;
  }

  private byte[] toBytes(InputStream is) {
    byte[] retval = new byte[0];
    try {
      int a = is.available();
      while (a > 0) {
        byte[] buffer = new byte[a];
        is.read(buffer);

        byte[] newretval = new byte[retval.length + a];

        for (int i = 0; i < retval.length; i++) {
          newretval[i] = retval[i]; // old part
        }
        for (int i = 0; i < a; i++) {
          newretval[retval.length + i] = buffer[i]; // new part
        }

        retval = newretval;

        a = is.available(); // see what's left
      }
      return retval;
    } catch (Exception e) {
      // TODO: Throw error here!!
      return null;
    }
  }

  @Override
  public URL getResource(String name) {
    URL url = findResource(name);
    if (url == null && getParent() != null) {
      url = getParent().getResource(name);
    }
    return url;
  }
}