processclassloader.java

workflow first jbpm

/*
 * JBoss, Home of Professional Open Source
 * Copyright 2005, JBoss Inc., and individual contributors as indicated
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jbpm.instantiation;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;

import org.jbpm.JbpmException;
import org.jbpm.file.def.FileDefinition;
import org.jbpm.graph.def.ProcessDefinition;

public class ProcessClassLoader extends ClassLoader {
  
  private ProcessDefinition processDefinition = null;

  public ProcessClassLoader( ClassLoader parent, ProcessDefinition processDefinition ) {
    super(parent);
    this.processDefinition = processDefinition;
  }

  public URL findResource(String name) {
    URL url = null;
    FileDefinition fileDefinition = processDefinition.getFileDefinition();
    if (fileDefinition!=null) {
      // if the name of the resources starts with a / 
      if (name.startsWith("/")) {
        // then we start searching from the root of the process archive

        // we know that the leading slashes are removed in the names of the 
        // file definitions, therefor we skip the leading slashes
        while (name.startsWith("/")) {
          name = name.substring(1);
        }
      } else {
        // otherwise, (if the resource is relative), we look in the classes
        // directory in the process archive
        name = "classes/"+name;
      }

      byte[] bytes = null;
      if (fileDefinition.hasFile(name)) {
        bytes = fileDefinition.getBytes(name);
      }
      if (bytes!=null) {
        try {
          url = new URL(null, "processresource://"+processDefinition.getName()+"/classes/"+name, new BytesUrlStreamHandler(bytes));
        } catch (MalformedURLException e) {
          throw new JbpmException("couldn't create url", e);
        }
      }
    }
    return url;
  }
  
  public static class BytesUrlStreamHandler extends URLStreamHandler {
    byte[] bytes;
    public BytesUrlStreamHandler(byte[] bytes) {
      this.bytes = bytes;
    }
    protected URLConnection openConnection(URL u) throws IOException {
      return new BytesUrlConnection(bytes, u);
    }
  }

  public static class BytesUrlConnection extends URLConnection {
    byte[] bytes = null;
    public BytesUrlConnection(byte[] bytes, URL u) {
      super(u);
      this.bytes = bytes;
    }
    public void connect() throws IOException {
    }
    public InputStream getInputStream() throws IOException {
      return new ByteArrayInputStream(bytes);
    }
  }

  public Class findClass(String name) throws ClassNotFoundException {
    Class clazz = null;

    FileDefinition fileDefinition = processDefinition.getFileDefinition();
    if (fileDefinition!=null) {
      String fileName = "classes/" + name.replace( '.', '/' ) + ".class";
      byte[] classBytes;
      try {
        classBytes = fileDefinition.getBytes(fileName);
        clazz = defineClass(name, classBytes, 0, classBytes.length);
      } catch (JbpmException e) {
        clazz = null;
      }
    }

    if (clazz==null) {
      throw new ClassNotFoundException("class '"+name+"' could not be found by the process classloader");
    }

    return clazz;
  }
}