CVS: plexus-container-new/src/java/org/apache/plexus/util ExceptionUtils.java,NONE,1.1

Update of /cvsroot/plexus/plexus-container-new/src/java/org/apache/plexus/util
In directory eng.werken.com:/tmp/cvs-serv19138

Added Files:
	ExceptionUtils.java 
Log Message:
o Borrowed exception utils.


--- NEW FILE: ExceptionUtils.java ---
/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.plexus.util;

import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.StringTokenizer;

/**
 * <p><code>ExceptionUtils</code> provides utilities for manipulating
 * <code>Throwable</code> objects.</p>
 *
 * @author <a href="mailto:[email protected]">Daniel Rall</a>
 * @author Dmitri Plotnikov
 * @author Stephen Colebourne
 * @since 1.0
 * @version $Id: ExceptionUtils.java,v 1.1 2003/05/01 20:01:04 jvanzyl Exp $
 */
public class ExceptionUtils
{
    /**
     * Used when printing stack frames to denote the start of a
     * wrapped exception.  Package private for accessibility by test
     * suite.
     */
    static final String WRAPPED_MARKER = " [wrapped] ";

    /**
     * The names of methods commonly used to access a wrapped
     * exception.
     */
    protected static String[] CAUSE_METHOD_NAMES = {
        "getCause",
        "getNextException",
        "getTargetException",
        "getException",
        "getSourceException",
        "getRootCause",
        "getCausedByException",
        "getNested"
    };

    /**
     * Constructs a new <code>ExceptionUtils</code>. Protected to
     * discourage instantiation.
     */
    protected ExceptionUtils()
    {
    }

    /**
     * <p>Adds to the list of method names used in the search for <code>Throwable</code>
     * objects.</p>
     *
     * @param methodName  the methodName to add to the list, null and empty strings are ignored
     */
    public static void addCauseMethodName( String methodName )
    {
        if ( methodName != null && methodName.length() > 0 )
        {
            List list = new ArrayList( Arrays.asList( CAUSE_METHOD_NAMES ) );
            list.add( methodName );
            CAUSE_METHOD_NAMES = (String[]) list.toArray( new String[list.size()] );
        }
    }

    /**
     * <p>Introspects the specified <code>Throwable</code> to obtain the cause.</p>
     *
     * <p>The method searches for methods with specific names that return a
     * <code>Throwable</code> object. This will pick up most wrapping exceptions,
     * including those from JDK 1.4, and
     * The method names can be added to using {@link #addCauseMethodName(String)}.
     * The default list searched for are:</p>
     * <ul>
     * <li><code>getCause()</code>
     * <li><code>getNextException()</code>
     * <li><code>getTargetException()</code>
     * <li><code>getException()</code>
     * <li><code>getSourceException()</code>
     * <li><code>getRootCause()</code>
     * <li><code>getCausedByException()</code>
     * <li><code>getNested()</code>
     * </ul>
     *
     * <p>In the absence of any such method, the object is inspected for a
     * <code>detail</code> field assignable to a <code>Throwable</code>.</p>
     *
     * <p>If none of the above is found, returns <code>null</code>.</p>
     *
     * @param throwable The exception to introspect for a cause.
     * @return The cause of the <code>Throwable</code>.
     * @throws NullPointerException if the throwable is null
     */
    public static Throwable getCause( Throwable throwable )
    {
        return getCause( throwable, CAUSE_METHOD_NAMES );
    }

    /**
     * <p>Introspects the specified <code>Throwable</code> to obtain the cause
     * using a supplied array of method names.</p>
     *
     * @param throwable The exception to introspect for a cause.
     * @return The cause of the <code>Throwable</code>.
     * @throws NullPointerException if the method names array is null or contains null
     * @throws NullPointerException if the throwable is null
     */
    public static Throwable getCause( Throwable throwable, String[] methodNames )
    {
        Throwable cause = getCauseUsingWellKnownTypes( throwable );
        if ( cause == null )
        {
            for ( int i = 0; i < methodNames.length; i++ )
            {
                cause = getCauseUsingMethodName( throwable, methodNames[i] );
                if ( cause != null )
                {
                    break;
                }
            }

            if ( cause == null )
            {
                cause = getCauseUsingFieldName( throwable, "detail" );
            }
        }
        return cause;
    }

    /**
     * <p>Walks through the exception chain to the last element -- the
     * "root" of the tree -- using {@link #getCause(Throwable)}, and
     * returns that exception.</p>
     *
     * @param throwable  the throwable to get the root cause for
     * @return The root cause of the <code>Throwable</code>.
     */
    public static Throwable getRootCause( Throwable throwable )
    {
        Throwable cause = getCause( throwable );
        if ( cause != null )
        {
            throwable = cause;
            while ( ( throwable = getCause( throwable ) ) != null )
            {
                cause = throwable;
            }
        }
        return cause;
    }

    /**
     * <p>Uses <code>instanceof</code> checks to examine the exception,
     * looking for well known types which could contain chained or
     * wrapped exceptions.</p>
     *
     * @param throwable  the exception to examine
     * @return The wrapped exception, or <code>null</code> if not
     * found.
     */
    private static Throwable getCauseUsingWellKnownTypes( Throwable throwable )
    {
        if ( throwable instanceof SQLException )
        {
            return ( (SQLException) throwable ).getNextException();
        }
        else if ( throwable instanceof InvocationTargetException )
        {
            return ( (InvocationTargetException) throwable ).getTargetException();
        }
        else
        {
            return null;
        }
    }

    /**
     * <p>Find a throwable by method name.</p>
     *
     * @param throwable  the exception to examine
     * @param methodName  the name of the method to find and invoke
     * @return The wrapped exception, or <code>null</code> if not
     * found.
     */
    private static Throwable getCauseUsingMethodName( Throwable throwable, String methodName )
    {
        Method method = null;
        try
        {
            method = throwable.getClass().getMethod( methodName, null );
        }
        catch ( NoSuchMethodException ignored )
        {
        }
        catch ( SecurityException ignored )
        {
        }

        if ( method != null && Throwable.class.isAssignableFrom( method.getReturnType() ) )
        {
            try
            {
                return (Throwable) method.invoke( throwable, new Object[0] );
            }
            catch ( IllegalAccessException ignored )
            {
            }
            catch ( IllegalArgumentException ignored )
            {
            }
            catch ( InvocationTargetException ignored )
            {
            }
        }
        return null;
    }

    /**
     * <p>Find a throwable by field name.</p>
     *
     * @param throwable  the exception to examine
     * @param fieldName  the name of the attribute to examine
     * @return The wrapped exception, or <code>null</code> if not
     * found.
     */
    private static Throwable getCauseUsingFieldName( Throwable throwable, String fieldName )
    {
        Field field = null;
        try
        {
            field = throwable.getClass().getField( fieldName );
        }
        catch ( NoSuchFieldException ignored )
        {
        }
        catch ( SecurityException ignored )
        {
        }

        if ( field != null && Throwable.class.isAssignableFrom( field.getType() ) )
        {
            try
            {
                return (Throwable) field.get( throwable );
            }
            catch ( IllegalAccessException ignored )
            {
            }
            catch ( IllegalArgumentException ignored )
            {
            }
        }
        return null;
    }

    /**
     * <p>Returns the number of <code>Throwable</code> objects in the
     * exception chain.</p>
     *
     * @param throwable  the exception to inspect
     * @return The throwable count.
     */
    public static int getThrowableCount( Throwable throwable )
    {
        // Count the number of throwables
        int count = 0;
        while ( throwable != null )
        {
            count++;
            throwable = ExceptionUtils.getCause( throwable );
        }
        return count;
    }

    /**
     * <p>Returns the list of <code>Throwable</code> objects in the
     * exception chain.</p>
     *
     * @param throwable  the exception to inspect
     * @return The list of <code>Throwable</code> objects.
     */
    public static Throwable[] getThrowables( Throwable throwable )
    {
        List list = new ArrayList();
        while ( throwable != null )
        {
            list.add( throwable );
            throwable = ExceptionUtils.getCause( throwable );
        }
        return (Throwable[]) list.toArray( new Throwable[list.size()] );
    }

    /**
     * <p>Delegates to {@link #indexOfThrowable(Throwable, Class, int)},
     * starting the search at the beginning of the exception chain.</p>
     *
     * @see #indexOfThrowable(Throwable, Class, int)
     */
    public static int indexOfThrowable( Throwable throwable, Class type )
    {
        return indexOfThrowable( throwable, type, 0 );
    }

    /**
     * <p>Returns the (zero based) index, of the first
     * <code>Throwable</code> that matches the specified type in the
     * exception chain of <code>Throwable</code> objects with an index
     * greater than or equal to the specified index, or
     * <code>-1</code> if the type is not found.</p>
     *
     * @param throwable  the exception to inspect
     * @param type  <code>Class</code> to look for
     * @param fromIndex  the (zero based) index of the starting
     *  position in the chain to be searched
     * @return the first occurrence of the type in the chain, or
     *  <code>-1</code> 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.
     */
    public static int indexOfThrowable( Throwable throwable, Class type, int fromIndex )
    {
        if ( fromIndex < 0 )
        {
            throw new IndexOutOfBoundsException( "Throwable index out of range: " + fromIndex );
        }
        Throwable[] throwables = ExceptionUtils.getThrowables( throwable );
        if ( fromIndex >= throwables.length )
        {
            throw new IndexOutOfBoundsException( "Throwable index out of range: " + fromIndex );
        }
        for ( int i = fromIndex; i < throwables.length; i++ )
        {
            if ( throwables[i].getClass().equals( type ) )
            {
                return i;
            }
        }
        return -1;
    }

    /**
     * Prints a compact stack trace for the root cause of a throwable.
     * The compact stack trace starts with the root cause and prints
     * stack frames up to the place where it was caught and wrapped.
     * Then it prints the wrapped exception and continues with stack frames
     * until the wrapper exception is caught and wrapped again, etc.
     * <p>
     * The method is equivalent to t.printStackTrace() for throwables
     * that don't have nested causes.
     */
    public static void printRootCauseStackTrace( Throwable t, PrintStream stream )
    {
        String trace[] = getRootCauseStackTrace( t );
        for ( int i = 0; i < trace.length; i++ )
        {
            stream.println( trace[i] );
        }
        stream.flush();
    }

    /**
     * Equivalent to printRootCauseStackTrace(t, System.err)
     */
    public static void printRootCauseStackTrace( Throwable t )
    {
        printRootCauseStackTrace( t, System.err );
    }

    /**
     * Same as printRootCauseStackTrace(t, stream), except it takes
     * a PrintWriter as an argument.
     */
    public static void printRootCauseStackTrace( Throwable t, PrintWriter writer )
    {
        String trace[] = getRootCauseStackTrace( t );
        for ( int i = 0; i < trace.length; i++ )
        {
            writer.println( trace[i] );
        }
        writer.flush();
    }

    /**
     * Creates a compact stack trace for the root cause of the supplied
     * throwable.
     *
     * See <code>printRootCauseStackTrace(Throwable t, PrintStream s)</code>
     */
    public static String[] getRootCauseStackTrace( Throwable t )
    {
        Throwable throwables[] = getThrowables( t );
        int count = throwables.length;
        ArrayList frames = new ArrayList();
        List nextTrace = getStackFrameList( throwables[count - 1] );
        for ( int i = count; --i >= 0; )
        {
            List trace = nextTrace;
            if ( i != 0 )
            {
                nextTrace = getStackFrameList( throwables[i - 1] );
                removeCommonFrames( trace, nextTrace );
            }
            if ( i == count - 1 )
            {
                frames.add( throwables[i].toString() );
            }
            else
            {
                frames.add( WRAPPED_MARKER + throwables[i].toString() );
            }
            for ( int j = 0; j < trace.size(); j++ )
            {
                frames.add( trace.get( j ) );
            }
        }
        return (String[]) frames.toArray( new String[0] );
    }

    /**
     * Given two stack traces, removes common frames from the cause trace.
     *
     * @param causeFrames   stack trace of a cause throwable
     * @param wrapperFrames stack trace of a wrapper throwable
     */
    private static void removeCommonFrames( List causeFrames, List wrapperFrames )
    {
        int causeFrameIndex = causeFrames.size() - 1;
        int wrapperFrameIndex = wrapperFrames.size() - 1;
        while ( causeFrameIndex >= 0 && wrapperFrameIndex >= 0 )
        {
            // Remove the frame from the cause trace if it is the same
            // as in the wrapper trace
            String causeFrame = (String) causeFrames.get( causeFrameIndex );
            String wrapperFrame = (String) wrapperFrames.get( wrapperFrameIndex );
            if ( causeFrame.equals( wrapperFrame ) )
            {
                causeFrames.remove( causeFrameIndex );
            }
            causeFrameIndex--;
            wrapperFrameIndex--;
        }
    }

    /**
     * A convenient way of extracting the stack trace from an
     * exception.
     *
     * @param t The <code>Throwable</code>.
     * @return The stack trace as generated by the exception's
     * <code>printStackTrace(PrintWriter)</code> method.
     */
    public static String getStackTrace( Throwable t )
    {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter( sw, true );
        t.printStackTrace( pw );
        return sw.getBuffer().toString();
    }

    /**
     * A way to get the entire nested stack-trace of an throwable.
     *
     * @param t The <code>Throwable</code>.
     * @return The nested stack trace, with the root cause first.
     */
    public static String getFullStackTrace( Throwable t )
    {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter( sw, true );
        Throwable[] ts = getThrowables( t );
        for ( int i = 0; i < ts.length; i++ )
        {
            ts[i].printStackTrace( pw );
            if ( isNestedThrowable( ts[i] ) )
            {
                break;
            }
        }
        return sw.getBuffer().toString();
    }

    /**
     * Whether an Throwable is considered nested or not.
     *
     * @param throwable The <code>Throwable</code>.
     * @return boolean true/false
     */
    public static boolean isNestedThrowable( Throwable throwable )
    {
        if ( throwable == null )
        {
            return false;
        }

        if ( throwable instanceof SQLException )
        {
            return true;
        }
        else if ( throwable instanceof InvocationTargetException )
        {
            return true;
        }

        int sz = CAUSE_METHOD_NAMES.length;
        for ( int i = 0; i < sz; i++ )
        {
            try
            {
                Method method = throwable.getClass().getMethod( CAUSE_METHOD_NAMES[i], null );
                if ( method != null )
                {
                    return true;
                }
            }
            catch ( NoSuchMethodException ignored )
            {
            }
            catch ( SecurityException ignored )
            {
            }
        }

        try
        {
            Field field = throwable.getClass().getField( "detail" );
            if ( field != null )
            {
                return true;
            }
        }
        catch ( NoSuchFieldException ignored )
        {
        }
        catch ( SecurityException ignored )
        {
        }

        return false;
    }

    /**
     * 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.
     */
    public static String[] getStackFrames( Throwable t )
    {
        return getStackFrames( getStackTrace( t ) );
    }

    /**
     * Functionality shared between the
     * <code>getStackFrames(Throwable)</code> methods of this and the
     * classes.
     */
    static String[] getStackFrames( String stackTrace )
    {
        String linebreak = System.getProperty( "line.separator" );
        StringTokenizer frames = new StringTokenizer( stackTrace, linebreak );
        List list = new LinkedList();
        while ( frames.hasMoreTokens() )
        {
            list.add( frames.nextToken() );
        }
        return (String[]) list.toArray( new String[]{
        } );
    }

    /**
     * Produces a List of stack frames - the message is not included.
     * This works in most cases - it will only fail if the exception message
     * contains a line that starts with:  "   at".
     *
     * @param t is any throwable
     * @return List of stack frames
     */
    static List getStackFrameList( Throwable t )
    {
        String stackTrace = getStackTrace( t );
        String linebreak = System.getProperty( "line.separator" );
        StringTokenizer frames = new StringTokenizer( stackTrace, linebreak );
        List list = new LinkedList();
        boolean traceStarted = false;
        while ( frames.hasMoreTokens() )
        {
            String token = frames.nextToken();
            // Determine if the line starts with <whitespace>at
            int at = token.indexOf( "at" );
            if ( at != -1 && token.substring( 0, at ).trim().length() == 0 )
            {
                traceStarted = true;
                list.add( token );
            }
            else if ( traceStarted )
            {
                break;
            }
        }
        return list;
    }
}