Java tutorial
/* ******************************************************************* * Copyright (c) 1999-2001 Xerox Corporation, * 2002 Palo Alto Research Center, Incorporated (PARC). * All rights reserved. * This program and the accompanying materials are made available * under the terms of the Eclipse Public License v1.0 * which accompanies this distribution and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * Xerox/PARC initial implementation * ******************************************************************/ package org.aspectj.bridge; import java.io.PrintStream; import java.io.PrintWriter; import java.util.ArrayList; /** * Signal that a process was aborted before completion. This may contain a structured IMessage which indicates why the process was * aborted (e.g., the underlying exception). For processes using try/catch to complete a method abruptly but complete the process * normally (e.g., a test failure causes the test to abort but the reporting and testing continues normally), use the static methods * to borrow and return a "porter" to avoid the expense of constructing a stack trace each time. A porter stack trace is invalid, * and it should only be used to convey a message. E.g., to print the stack of the AbortException and any contained message: * * <pre> * catch (AbortException ae) { * IMessage m = ae.getMessage(); * if (!ae.isPorter()) ae.printStackTrace(System.err); * Throwable thrown = ae.getThrown(); * if (null != thrown) thrown.printStackTrace(System.err); * } * </pre> * * @author PARC * @author Andy Clement */ public class AbortException extends RuntimeException { // XXX move porters out, handle proxy better private static final long serialVersionUID = -7211791639898586417L; private boolean isSilent = false; /** used when message text is null */ public static final String NO_MESSAGE_TEXT = "AbortException (no message)"; private static final ArrayList<AbortException> porters = new ArrayList<AbortException>(); /** * Get a porter exception from the pool. Porter exceptions do <b>not</b> have valid stack traces. They are used only to avoid * generating stack traces when using throw/catch to abruptly complete but continue. */ public static AbortException borrowPorter(IMessage message) { AbortException result; synchronized (porters) { if (porters.size() > 0) { result = porters.get(0); } else { result = new AbortException(); result.setIsSilent(false); } } result.setIMessage(message); result.isPorter = true; return result; } /** * Return (or add) a porter exception to the pool. */ public static void returnPorter(AbortException porter) { synchronized (porters) { if (porters.contains(porter)) { throw new IllegalStateException("already have " + porter); } else { porters.add(porter); } } } /** @return NO_MESSAGE_TEXT or message.getMessage() if not null */ private static String extractMessage(IMessage message) { if (null == message) { return NO_MESSAGE_TEXT; } else { String m = message.getMessage(); if (null == m) { return NO_MESSAGE_TEXT; } else { return m; } } } /** structured message abort */ protected IMessage message; /** true if this is a porter exception - only used to hold message */ protected boolean isPorter; /** abort with default String message */ public AbortException() { this("ABORT"); isSilent = true; } /** abort with message */ public AbortException(String s) { super(null != s ? s : NO_MESSAGE_TEXT); this.message = null; } /** abort with structured message */ public AbortException(IMessage message) { super(extractMessage(message)); this.message = message; } /** @return IMessage structured message, if set */ public IMessage getIMessage() { return message; } /** * The stack trace of a porter is invalid; it is only used to carry a message (which may itself have a wrapped exception). * * @return true if this exception is only to carry exception */ public boolean isPorter() { return isPorter; } /** @return Throwable at bottom of IMessage chain, if any */ public Throwable getThrown() { Throwable result = null; IMessage m = getIMessage(); if (null != m) { result = m.getThrown(); if (result instanceof AbortException) { return ((AbortException) result).getThrown(); } } return result; } private void setIMessage(IMessage message) { this.message = message; } // ----------- proxy attempts /** * Get message for this AbortException, either associated explicitly as message or implicitly as IMessage message or its thrown * message. * * @see java.lang.Throwable#getMessage() */ public String getMessage() { String message = super.getMessage(); if ((null == message) || (NO_MESSAGE_TEXT == message)) { IMessage m = getIMessage(); if (null != m) { message = m.getMessage(); if (null == message) { Throwable thrown = m.getThrown(); if (null != thrown) { message = thrown.getMessage(); } } } if (null == message) { message = NO_MESSAGE_TEXT; // better than nothing } } return message; } /** * @see java.lang.Throwable#printStackTrace() */ public void printStackTrace() { printStackTrace(System.out); } /** * Print the stack trace of any enclosed thrown or this otherwise. * * @see java.lang.Throwable#printStackTrace(PrintStream) */ public void printStackTrace(PrintStream s) { IMessage m = getIMessage(); Throwable thrown = (null == m ? null : m.getThrown()); if (!isPorter() || (null == thrown)) { s.println("Message: " + m); super.printStackTrace(s); } else { thrown.printStackTrace(s); } } /** * Print the stack trace of any enclosed thrown or this otherwise. * * @see java.lang.Throwable#printStackTrace(PrintWriter) */ public void printStackTrace(PrintWriter s) { IMessage m = getIMessage(); Throwable thrown = (null == m ? null : m.getThrown()); if (null == thrown) { // Always print if (isPorter()) { s.println("(Warning porter AbortException without thrown)"); } s.println("Message: " + m); super.printStackTrace(s); } else { thrown.printStackTrace(s); } } public boolean isSilent() { return isSilent; } public void setIsSilent(boolean isSilent) { this.isSilent = isSilent; } }