/*

  * 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.myfaces.shared.util;

 import java.lang.reflect.Method;

 import java.util.ArrayList;

 import java.util.List;

 /**

  * Various helpers to deal with exception

  */

 public final class ExceptionUtils

 {

     private ExceptionUtils()

     {

     }

     /**

      * <p>

      * returns a list of all throwables (including the one you passed in) wrapped by the given throwable.

      * In contrast to a simple call to <code>getClause()</code> on each throwable it will also check if 

      * the throwable class contain a method <code>getRootCause()</code> (e.g. ServletException or JspException)

      * and call it instead.

      * </p>

      * <p>

      * The first list element will your passed in exception, the last list element is the cause. 

      * </p>

      */

     public static List getExceptions(Throwable cause)

     {

         List exceptions = new ArrayList(10);

         exceptions.add(cause);

         do

         {

             Throwable nextCause;

             try

             {

                 Method rootCause = cause.getClass().getMethod("getRootCause", new Class[]{});

                 nextCause = (Throwable) rootCause.invoke(cause, new Object[]{});

             }

             catch(Exception e)

             {

                 nextCause = cause.getCause();

             }

             if (cause == nextCause)

             {

                 break;

             }

             if (nextCause != null)

             {

                 exceptions.add(nextCause);

             }

             cause = nextCause;

         }

         while (cause != null);

         return exceptions;

     }

     /**

      * Find a throwable message starting with the last element.<br />

      * Returns the first throwable message where <code>throwable.getMessage() != null</code> 

      */

     public static String getExceptionMessage(List throwables)

     {

         if (throwables == null)

         {

             return null;

         }

         for (int i = throwables.size()-1; i>0; i--)

         {

             Throwable t = (Throwable) throwables.get(i);

             if (t.getMessage() != null)

             {

                 return t.getMessage();

             }

         }

         return null;

     }

 }