/*

  * 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 java.lang.reflect.Constructor;

 import org.apache.commons.workflow.Context;

 import org.apache.commons.workflow.Descriptor;

 import org.apache.commons.workflow.StepException;

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

 /**

  * <p>Create a new object of the specified class, using the constructor that

  * accepts the arguments specified by the associated <code>Descriptor</code>

  * objects.  The <strong>first</strong> descriptor must identify the

  * <code>java.lang.Class</code> object to be used to construct the new

  * object.</p>

  *

  * <p><strong>FIXME</strong> - Constructors that take primitive arguments are

  * not recognized and matched up to the wrapper classes.</p>

  *

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

  * @author Craig R. McClanahan

  */

 public class ConstructStep extends DescriptorStep {

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

     /**

      * Construct a default instance of this Step.

      */

     public ConstructStep() {

         super();

     }

     /**

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

      *

      * @param id Step identifier

      */

     public ConstructStep(String id) {

         super();

         setId(id);

     }

     /**

      * Construct an instance of this Step with the specified identifier

      * and associated Descriptor.

      *

      * @param id Step identifier

      * @param descriptor Initial descriptor

      */

     public ConstructStep(String id, Descriptor descriptor) {

         super();

         setId(id);

         addDescriptor(descriptor);

     }

     // --------------------------------------------------------- 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 {

         // Identify the Class object to be used for object construction

         Descriptor descriptors[] = findDescriptors();

         if (descriptors.length < 1)

             throw new StepException

                 ("No descriptor for Class to construct", this);

         Class clazz = null;

         try {

             clazz = (Class) descriptors[0].get(context);

             if (clazz == null)

                 throw new StepException

                     ("No Class selected by first descriptor", this);

         } catch (ClassCastException e) {

             throw new StepException

                 ("First descriptor does not select a Class", this);

         }

         // Assemble arrays of the argument types and values

         Class[] types = new Class[descriptors.length - 1];

         Object[] values = new Object[descriptors.length - 1];

         for (int i = 1; i < descriptors.length; i++) {

             values[i-1] = descriptors[i].get(context);

             types[i-1] = descriptors[i].getType();

             if (types[i-1] == null) {

                 if (values[i-1] == null)

                     types[i-1] = Object.class;

                 else

                     types[i-1] = values[i-1].getClass();

             }

         }

         // Find a constructor that accepts this set of types

         Constructor constructor = null;

         try {

             constructor = clazz.getConstructor(types);

         } catch (NoSuchMethodException e) {

             throw new StepException

                 ("Cannot find constructor for " +

                  signature(clazz.getName(), types), this);

         }

         // Invoke the constructor to create a new object

         Object object = null;

         try {

             object = constructor.newInstance(values);

         } catch (Throwable t) {

             throw new StepException

                 ("Exception from constructor " +

                  signature(clazz.getName(), types), t, this);

         }

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

         context.push(object);

     }

     /**

      * Render a string representation of this Step.

      */

     public String toString() {

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

         if (getId() != null) {

             sb.append(" id=\"");

             sb.append(getId());

             sb.append("\"");

         }

         sb.append(">");

         Descriptor descriptors[] = findDescriptors();

         for (int i = 0; i < descriptors.length; i++)

             sb.append(descriptors[i].toString());

         sb.append("</core:construct>");

         return (sb.toString());

     }

     // ------------------------------------------------------ Protected Methods

     /**

      * Return a method signature useful in debugging and exception messages.

      *

      * @param name Method name

      * @param types Parameter types

      */

     protected String signature(String name, Class types[]) {

         StringBuffer sb = new StringBuffer(name);

         sb.append('(');

         for (int i = 0; i < types.length; i++) {

             if (i > 0)

                 sb.append(',');

             sb.append(types[i].getName());

         }

         sb.append(')');

         return (sb.toString());

     }

 }