/*

  * Copyright 1999-2001,2004 The Apache Software Foundation.

  * 

  * Licensed 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.commons.workflow.core;

 import org.apache.commons.workflow.Context;

 import org.apache.commons.workflow.StepException;

 import org.apache.commons.workflow.base.BaseStep;

 /**

  * <p>Load a class with the specified name from the specified class loader,

  * and push the corresponding <code>java.lang.Class</code> object onto the

  * evaluation stack.

  *

  * <p>Supported Attributes:</p>

  * <ul>

  * <li><strong>name</strong> - The fully qualified name of the Java class

  *     to be loaded.  If not specified, the top of the evaluation stack

  *     is popped, converted to a String (if necessary), and used as the

  *     name of the class to be loaded.</li>

  * <li><strong>thread</strong> - Should the class be loaded from the current

  *     Thread's context class loader?  (Default is to load from the same

  *     class loader that loaded this class).</li>

  * </ul>

  *

  * @version $Revision: 155475 $ $Date: 2005-02-26 13:31:11 +0000 (Sat, 26 Feb 2005) $

  * @author Craig R. McClanahan

  */

 public class LoadStep extends BaseStep {

     // ----------------------------------------------------------= Constructors

     /**

      * Construct a default instance of this Step.

      */

     public LoadStep() {

         super();

     }

     /**

      * Construct an instance of this Step with the specified identifier.

      *

      * @param id Step identifier

      */

     public LoadStep(String id) {

         super();

         setId(id);

     }

     /**

      * Construct a fully configured instance of this Step.

      *

      * @param id Step identifier

      * @param name Class name

      */

     public LoadStep(String id, String name) {

         super();

         setId(id);

         setName(name);

     }

     /**

      * Construct a fully configured instance of this Step.

      *

      * @param id Step identifier

      * @param name Class name

      * @param thread Load from thread context class loader?

      */

     public LoadStep(String id, String name, boolean thread) {

         super();

         setId(id);

         setName(name);

         setThread(thread);

     }

     // ------------------------------------------------------------- Properties

     /**

      * The class name to be loaded.

      */

     protected String name = null;

     public String getName() {

         return (this.name);

     }

     public void setName(String name) {

         this.name = name;

     }

     /**

      * Load from the thread context class loader?

      */

     protected boolean thread = false;

     public boolean getThread() {

         return (this.thread);

     }

     public void setThread(boolean thread) {

         this.thread = thread;

     }

     // --------------------------------------------------------- Public Methods

     /**

      * Perform the executable actions related to this Step, in the context of

      * the specified Context.

      *

      * @param context The Context that is tracking our execution state

      *

      * @exception StepException if a processing error has occurred

      */

     public void execute(Context context) throws StepException {

         // Acquire the class loader we will be using

         ClassLoader classLoader = null;

         if (thread)

             classLoader = Thread.currentThread().getContextClassLoader();

         else

             classLoader = this.getClass().getClassLoader();

         if (classLoader == null)

             throw new StepException

                 ("No thread context class loader is available");

         // Calculate the name of the class to be loaded

         String className = getName();

         if (className == null)

             className = context.pop().toString();

         // Load the specified class

         Class clazz = null;

         try {

             clazz = classLoader.loadClass(className);

         } catch (Throwable t) {

             throw new StepException

                 ("Exception from loadClass()", t, this);

         }

         // Push the new Class onto the evaluation stack and return

         context.push(clazz);

     }

     /**

      * Render a string representation of this Step.

      */

     public String toString() {

         StringBuffer sb = new StringBuffer("<core:load");

         if (getId() != null) {

             sb.append(" id=\"");

             sb.append(getId());

             sb.append("\"");

         }

         if (getName() != null) {

             sb.append(" name=\"");

             sb.append(getName());

             sb.append("\"");

         }

         sb.append(" thread=\"");

         sb.append(getThread());

         sb.append("\"/>");

         return (sb.toString());

     }

 }