code: /*
   * 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.commons.lang.exception;
  
  import java.io.PrintStream;
  import java.io.PrintWriter;
  import java.io.Serializable;
  import java.io.StringWriter;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  
  /**
   * <p>A shared implementation of the nestable exception functionality.</p>
   * <p>
   * The code is shared between 
   * {@link org.apache.commons.lang.exception.NestableError NestableError},
   * {@link org.apache.commons.lang.exception.NestableException NestableException} and
   * {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
   * </p>
   * 
   * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
   * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
   * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
   * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
   * @author Sean C. Sullivan
   * @author Stephen Colebourne
   * @since 1.0
   * @version $Id: NestableDelegate.java 437554 2006-08-28 06:21:41Z bayard $
   */
  public class NestableDelegate implements Serializable {
  
      /**
       * Required for serialization support.
       * 
       * @see java.io.Serializable
       */
      private static final long serialVersionUID = 1L;
  
      /**
       * Constructor error message.
       */
      private transient static final String MUST_BE_THROWABLE =
          "The Nestable implementation passed to the NestableDelegate(Nestable) "
              + "constructor must extend java.lang.Throwable";
  
      /**
       * Holds the reference to the exception or error that we're
       * wrapping (which must be a {@link
       * org.apache.commons.lang.exception.Nestable} implementation).
       */
      private Throwable nestable = null;
      
      /**
       * Whether to print the stack trace top-down.
       * This public flag may be set by calling code, typically in initialisation.
       * This exists for backwards compatability, setting it to false will return
       * the library to v1.0 behaviour (but will affect all users of the library
       * in the classloader).
       * @since 2.0
       */
      public static boolean topDown = true;
      
      /**
       * Whether to trim the repeated stack trace.
       * This public flag may be set by calling code, typically in initialisation.
       * This exists for backwards compatability, setting it to false will return
       * the library to v1.0 behaviour (but will affect all users of the library
       * in the classloader).
       * @since 2.0
       */
      public static boolean trimStackFrames = true;
      
      /**
       * Whether to match subclasses via indexOf.
       * This public flag may be set by calling code, typically in initialisation.
       * This exists for backwards compatability, setting it to false will return
       * the library to v2.0 behaviour (but will affect all users of the library
       * in the classloader).
       * @since 2.1
       */
      public static boolean matchSubclasses = true;
  
      /**
       * Constructs a new <code>NestableDelegate</code> instance to manage the
       * specified <code>Nestable</code>.
       *
       * @param nestable the Nestable implementation (<i>must</i> extend
       * {@link java.lang.Throwable})
       * @since 2.0
       */
      public NestableDelegate(Nestable nestable) {
          if (nestable instanceof Throwable) {
              this.nestable = (Throwable) nestable;
          } else {
              throw new IllegalArgumentException(MUST_BE_THROWABLE);
          }
      }
  
      /**
       * Returns the error message of the <code>Throwable</code> in the chain of <code>Throwable</code>s at the
       * specified index, numbered from 0.
       * 
       * @param index
       *            the index of the <code>Throwable</code> in the chain of <code>Throwable</code>s
       * @return the error message, or null if the <code>Throwable</code> at the specified index in the chain does not
       *         contain a message
       * @throws IndexOutOfBoundsException
       *             if the <code>index</code> argument is negative or not less than the count of <code>Throwable</code>s
       *             in the chain
       * @since 2.0
       */
      public String getMessage(int index) {
          Throwable t = this.getThrowable(index);
          if (Nestable.class.isInstance(t)) {
              return ((Nestable) t).getMessage(0);
          }
          return t.getMessage();
      }
  
      /**
       * Returns the full message contained by the <code>Nestable</code> and any nested <code>Throwable</code>s.
       * 
       * @param baseMsg
       *            the base message to use when creating the full message. Should be generally be called via
       *            <code>nestableHelper.getMessage(super.getMessage())</code>, where <code>super</code> is an
       *            instance of {@link java.lang.Throwable}.
       * @return The concatenated message for this and all nested <code>Throwable</code>s
       * @since 2.0
       */
      public String getMessage(String baseMsg) {
          Throwable nestedCause = ExceptionUtils.getCause(this.nestable);
          String causeMsg = nestedCause == null ? null : nestedCause.getMessage();
          if (nestedCause == null || causeMsg == null) {
              return baseMsg; // may be null, which is a valid result
          }
          if (baseMsg == null) {
              return causeMsg;
          }
          return baseMsg + ": " + causeMsg;
      }
  
      /**
       * Returns the error message of this and any nested <code>Throwable</code>s in an array of Strings, one element
       * for each message. Any <code>Throwable</code> not containing a message is represented in the array by a null.
       * This has the effect of cause the length of the returned array to be equal to the result of the
       * {@link #getThrowableCount()} operation.
       * 
       * @return the error messages
       * @since 2.0
       */
      public String[] getMessages() {
          Throwable[] throwables = this.getThrowables();
          String[] msgs = new String[throwables.length];
          for (int i = 0; i < throwables.length; i++) {
              msgs[i] =
                  (Nestable.class.isInstance(throwables[i])
                      ? ((Nestable) throwables[i]).getMessage(0)
                      : throwables[i].getMessage());
          }
          return msgs;
      }
  
      /**
       * Returns the <code>Throwable</code> in the chain of
       * <code>Throwable</code>s at the specified index, numbered from 0.
       *
       * @param index the index, numbered from 0, of the <code>Throwable</code> in
       * the chain of <code>Throwable</code>s
       * @return the <code>Throwable</code>
       * @throws IndexOutOfBoundsException if the <code>index</code> argument is
       * negative or not less than the count of <code>Throwable</code>s in the
       * chain
       * @since 2.0
       */
      public Throwable getThrowable(int index) {
          if (index == 0) {
              return this.nestable;
          }
          Throwable[] throwables = this.getThrowables();
          return throwables[index];
      }
  
      /**
       * Returns the number of <code>Throwable</code>s contained in the
       * <code>Nestable</code> contained by this delegate.
       *
       * @return the throwable count
       * @since 2.0
       */
      public int getThrowableCount() {
          return ExceptionUtils.getThrowableCount(this.nestable);
      }
  
      /**
       * Returns this delegate's <code>Nestable</code> and any nested
       * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
       * element for each <code>Throwable</code>.
       *
       * @return the <code>Throwable</code>s
       * @since 2.0
       */
      public Throwable[] getThrowables() {
          return ExceptionUtils.getThrowables(this.nestable);
      }
  
      /**
       * Returns the index, numbered from 0, of the first <code>Throwable</code>
       * that matches the specified type, or a subclass, in the chain of <code>Throwable</code>s
       * with an index greater than or equal to the specified index.
       * The method returns -1 if the specified type is not found in the chain.
       * <p>
       * NOTE: From v2.1, we have clarified the <code>Nestable</code> interface
       * such that this method matches subclasses.
       * If you want to NOT match subclasses, please use
       * {@link ExceptionUtils#indexOfThrowable(Throwable, Class, int)}
       * (which is avaiable in all versions of lang).
       * An alternative is to use the public static flag {@link #matchSubclasses}
       * on <code>NestableDelegate</code>, however this is not recommended.
       *
       * @param type  the type to find, subclasses match, null returns -1
       * @param fromIndex the index, numbered from 0, of the starting position in
       * the chain to be searched
       * @return index of the first occurrence of the type in the chain, or -1 if
       * the type is not found
       * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
       * is negative or not less than the count of <code>Throwable</code>s in the
       * chain
       * @since 2.0
       */
      public int indexOfThrowable(Class type, int fromIndex) {
          if (type == null) {
              return -1;
          }
          if (fromIndex < 0) {
              throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
          }
          Throwable[] throwables = ExceptionUtils.getThrowables(this.nestable);
          if (fromIndex >= throwables.length) {
              throw new IndexOutOfBoundsException("The start index was out of bounds: "
                  + fromIndex + " >= " + throwables.length);
          }
          if (matchSubclasses) {
              for (int i = fromIndex; i < throwables.length; i++) {
                  if (type.isAssignableFrom(throwables[i].getClass())) {
                      return i;
                  }
              }
          } else {
              for (int i = fromIndex; i < throwables.length; i++) {
                  if (type.equals(throwables[i].getClass())) {
                      return i;
                  }
              }
          }
          return -1;
      }
  
      /**
       * Prints the stack trace of this exception the the standar error
       * stream.
       */
      public void printStackTrace() {
          printStackTrace(System.err);
      }
  
      /**
       * Prints the stack trace of this exception to the specified
       * stream.
       *
       * @param out <code>PrintStream</code> to use for output.
       * @see #printStackTrace(PrintWriter)
       */
      public void printStackTrace(PrintStream out) {
          synchronized (out) {
              PrintWriter pw = new PrintWriter(out, false);
              printStackTrace(pw);
              // Flush the PrintWriter before it's GC'ed.
              pw.flush();
          }
      }
  
      /**
       * Prints the stack trace of this exception to the specified
       * writer. If the Throwable class has a <code>getCause</code>
       * method (i.e. running on jre1.4 or higher), this method just 
       * uses Throwable's printStackTrace() method. Otherwise, generates
       * the stack-trace, by taking into account the 'topDown' and 
       * 'trimStackFrames' parameters. The topDown and trimStackFrames 
       * are set to 'true' by default (produces jre1.4-like stack trace).
       *
       * @param out <code>PrintWriter</code> to use for output.
       */
      public void printStackTrace(PrintWriter out) {
          Throwable throwable = this.nestable;
          // if running on jre1.4 or higher, use default printStackTrace
          if (ExceptionUtils.isThrowableNested()) {
              if (throwable instanceof Nestable) {
                  ((Nestable)throwable).printPartialStackTrace(out);
              } else {
                  throwable.printStackTrace(out);
              }
              return;
          }
  
          // generating the nested stack trace
          List stacks = new ArrayList();
          while (throwable != null) {
              String[] st = getStackFrames(throwable);
              stacks.add(st);
              throwable = ExceptionUtils.getCause(throwable);
          }
  
          // If NOT topDown, reverse the stack
          String separatorLine = "Caused by: ";
          if (!topDown) {
              separatorLine = "Rethrown as: ";
              Collections.reverse(stacks);
          }
  
          // Remove the repeated lines in the stack
          if (trimStackFrames) {
            trimStackFrames(stacks);
          }
  
          synchronized (out) {
              for (Iterator iter=stacks.iterator(); iter.hasNext();) {
                  String[] st = (String[]) iter.next();
                  for (int i=0, len=st.length; i < len; i++) {
                      out.println(st[i]);
                  }
                  if (iter.hasNext()) {
                      out.print(separatorLine);
                  }
              }
          }
      }
  
      /**
       * Captures the stack trace associated with the specified
       * <code>Throwable</code> object, decomposing it into a list of
       * stack frames.
       *
       * @param t The <code>Throwable</code>.
       * @return  An array of strings describing each stack frame.
       * @since 2.0
       */
      protected String[] getStackFrames(Throwable t) {
          StringWriter sw = new StringWriter();
          PrintWriter pw = new PrintWriter(sw, true);
  
          // Avoid infinite loop between decompose() and printStackTrace().
          if (t instanceof Nestable) {
              ((Nestable) t).printPartialStackTrace(pw);
          } else {
              t.printStackTrace(pw);
          }
          return ExceptionUtils.getStackFrames(sw.getBuffer().toString());
      }
      
      /**
       * Trims the stack frames. The first set is left untouched. The rest
       * of the frames are truncated from the bottom by comparing with
       * one just on top.
       *
       * @param stacks The list containing String[] elements
       * @since 2.0
       */
      protected void trimStackFrames(List stacks) {
           for (int size=stacks.size(), i=size-1; i > 0; i--) {
               String[] curr = (String[]) stacks.get(i);
               String[] next = (String[]) stacks.get(i-1); 
               
               List currList = new ArrayList(Arrays.asList(curr));
               List nextList = new ArrayList(Arrays.asList(next));
               ExceptionUtils.removeCommonFrames(currList, nextList);
  
               int trimmed = curr.length - currList.size();
               if (trimmed > 0) {
                   currList.add("\t... "+trimmed+" more");
                   stacks.set(
                       i, 
                       currList.toArray(new String[currList.size()])
                   );
               }
           }
       }
  }
  