exceptionutils.java

一个Java持久层类库

		for ( int i = 0, isize = CAUSE_METHOD_NAMES.length; i < isize; i++ ) {
			try {
				Method method = cls.getMethod( CAUSE_METHOD_NAMES[i], null );
				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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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/>
	 * <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;
	}

}