exceptionutils.java

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                if ( method != null && Throwable.class.isAssignableFrom( method.getReturnType() ) ) {
                    return true;
                }
            } 
            catch (NoSuchMethodException ignored) {} 
            catch (SecurityException ignored) {}
        }

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

        return false;
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Counts the number of <code>Throwable</code> objects in the
     * exception chain.</p>
     * 
     * <p>A throwable without cause will return <code>1</code>.
     * A throwable with one cause will return <code>2</code> and so on.
     * A <code>null</code> throwable will return <code>0</code>.</p>
     * 
     * @param throwable  the throwable to inspect, may be null
     * @return the count of throwables, zero if null input
     */
    public static int getThrowableCount(Throwable throwable) {
        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>
     * 
     * <p>A throwable without cause will return an array containing
     * one element - the input throwable.
     * A throwable with one cause will return an array containing
     * two elements. - the input throwable and the cause throwable.
     * A <code>null</code> throwable will return an array size zero.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @return the array of throwables, never null
     */
    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>Returns the (zero based) index of the first <code>Throwable</code>
     * that matches the specified type in the exception chain.</p>
     * 
     * <p>A <code>null</code> throwable returns <code>-1</code>.
     * A <code>null</code> type returns <code>-1</code>.
     * No match in the chain returns <code>-1</code>.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param type  the type to search for
     * @return the index into the throwable chain, -1 if no match or null input
     */
    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 from
     * a specified index.</p>
     * 
     * <p>A <code>null</code> throwable returns <code>-1</code>.
     * A <code>null</code> type returns <code>-1</code>.
     * No match in the chain returns <code>-1</code>.
     * A negative start index is treated as zero.
     * A start index greater than the number of throwables returns <code>-1</code>.</p>
     *
     * @param throwable  the throwable to inspect, may be null
     * @param type  the type to search for
     * @param fromIndex  the (zero based) index of the starting position,
     *  negative treated as zero, larger than chain size returns -1
     * @return the index into the throwable chain, -1 if no match or null input
     */
    public static int indexOfThrowable(Throwable throwable, Class type, int fromIndex) {
        if (throwable == null) {
            return -1;
        }
        if (fromIndex < 0) {
            fromIndex = 0;
        }
        Throwable[] throwables = ExceptionUtils.getThrowables(throwable);
        if (fromIndex >= throwables.length) {
            return -1;
        }
        for (int i = fromIndex; i < throwables.length; i++) {
            if ( throwables[i].getClass().equals(type) ) {
                return i;
            }
        }
        return -1;
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Prints a compact stack trace for the root cause of a throwable
     * to <code>System.err</code>.</p>
     * 
     * <p>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>
     *
     * <p>The method is equivalent to <code>printStackTrace</code> for throwables
     * that don't have nested causes.</p>
     * 
     * @param throwable  the throwable to output
     * @since 2.0
     */
    public static void printRootCauseStackTrace(Throwable throwable) {
        printRootCauseStackTrace(throwable, System.err);
    }

    /**
     * <p>Prints a compact stack trace for the root cause of a throwable.</p>
     *
     * <p>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>
     *
     * <p>The method is equivalent to <code>printStackTrace</code> for throwables
     * that don't have nested causes.</p>
     * 
     * @param throwable  the throwable to output, may be null
     * @param stream  the stream to output to, may not be null
     * @throws IllegalArgumentException if the stream is <code>null</code>
     * @since 2.0
     */
    public static void printRootCauseStackTrace(Throwable throwable, PrintStream stream) {
        if (throwable == null) {
            return;
        }
        if (stream == null) {
            throw new IllegalArgumentException("The PrintStream must not be null");
        }
        String trace[] = getRootCauseStackTrace(throwable);
        for (int i = 0; i < trace.length; i++) {
            stream.println(trace[i]);
        }
        stream.flush();
    }

    /**
     * <p>Prints a compact stack trace for the root cause of a throwable.</p>
     *
     * <p>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>
     *
     * <p>The method is equivalent to <code>printStackTrace</code> for throwables
     * that don't have nested causes.</p>
     * 
     * @param throwable  the throwable to output, may be null
     * @param writer  the writer to output to, may not be null
     * @throws IllegalArgumentException if the writer is <code>null</code>
     * @since 2.0
     */
    public static void printRootCauseStackTrace(Throwable throwable, PrintWriter writer) {
        if (throwable == null) {
            return;
        }
        if (writer == null) {
            throw new IllegalArgumentException("The PrintWriter must not be null");
        }
        String trace[] = getRootCauseStackTrace(throwable);
        for (int i = 0; i < trace.length; i++) {
            writer.println(trace[i]);
        }
        writer.flush();
    }
    
    //-----------------------------------------------------------------------
    /**
     * <p>Creates a compact stack trace for the root cause of the supplied
     * <code>Throwable</code>.</p>
     * 
     * @param throwable  the throwable to examine, may be null
     * @return an array of stack trace frames, never null
     * @since 2.0
     */
    public static String[] getRootCauseStackTrace(Throwable throwable) {
        if (throwable == null) {
            return ArrayHelper.EMPTY_STRING_ARRAY;
        }
        Throwable throwables[] = getThrowables(throwable);
        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] );
    }

    /**
     * <p>Removes common frames from the cause trace given the two stack traces.</p>
     * 
     * @param causeFrames  stack trace of a cause throwable
     * @param wrapperFrames  stack trace of a wrapper throwable
     * @throws IllegalArgumentException if either argument is null
     * @since 2.0
     */
    public static void removeCommonFrames(List causeFrames, List wrapperFrames) {
        if (causeFrames == null || wrapperFrames == null) {
            throw new IllegalArgumentException("The List must not be null");
        }
        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--;
        }
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Gets the stack trace from a Throwable as a String.</p>
     *
     * @param throwable  the <code>Throwable</code> to be examined
     * @return the stack trace as generated by the exception's
     *  <code>printStackTrace(PrintWriter)</code> method
     */
    public static String getStackTrace(Throwable throwable) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw, true);
        throwable.printStackTrace(pw);
        return sw.getBuffer().toString();
    }

    /**
     * <p>A way to get the entire nested stack-trace of an throwable.</p>
     *
     * @param throwable  the <code>Throwable</code> to be examined
     * @return the nested stack trace, with the root cause first
     * @since 2.0
     */
    public static String getFullStackTrace(Throwable throwable) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw, true);
        Throwable[] ts = getThrowables(throwable);
        for (int i = 0; i < ts.length; i++) {
            ts[i].printStackTrace(pw);
            if ( isNestedThrowable( ts[i] ) ) {
                break;
            }
        }
        return sw.getBuffer().toString();
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Captures the stack trace associated with the specified
     * <code>Throwable</code> object, decomposing it into a list of
     * stack frames.</p>
     *
     * @param throwable  the <code>Throwable</code> to exaamine, may be null
     * @return an array of strings describing each stack frame, never null
     */
    public static String[] getStackFrames(Throwable throwable) {
        if (throwable == null) {
            return ArrayHelper.EMPTY_STRING_ARRAY;
        }
        return getStackFrames( getStackTrace(throwable) );
    }
    
    /**
     * <p>Functionality shared between the
     * <code>getStackFrames(Throwable)</code> methods of this and the
     * {@link org.apache.commons.lang.exception.NestableDelegate}
     * classes.</p>
     */
    static String[] getStackFrames(String stackTrace) {
        String linebreak = 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[ list.size() ] );
    }

    /**
     * <p>Produces a <code>List</code> of stack frames - the message
     * is not included.</p>
     *
     * <p>This works in most cases - it will only fail if the exception
     * message contains a line that starts with:
     * <code>&quot;&nbsp;&nbsp;&nbsp;at&quot;.</code></p>
     * 
     * @param t is any throwable
     * @return List of stack frames
     */
    static List getStackFrameList(Throwable t) {
        String stackTrace = getStackTrace(t);
        String linebreak = 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;
    }
    
}