Java tutorial
package com.free.exception; /* ==================================================================== * 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 acknowledgement: * "This product includes software developed by the * Apache Software Foundation (http://www.apache.org/)." * Alternately, this acknowledgement may appear in the software itself, * if and wherever such third-party acknowledgements 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 apache@apache.org. * * 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/>. */ 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 * @version $Id: NestableDelegate.java,v 1.2 2004/11/21 00:11:27 pgmjsd Exp $ * @since 1.0 */ class NestableDelegate implements Serializable { private static final long serialVersionUID = 6383440074174865493L; /** * Constructor error message. */ private 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. * * @since 2.0 */ private static boolean topDown = true; /** * Whether to trim the repeated stack trace. This public flag may be set by * calling code, typically in initialisation. * * @since 2.0 */ private static boolean trimStackFrames = 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, numbererd 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); } else { 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) { StringBuilder msg = new StringBuilder(); if (baseMsg != null) { msg.append(baseMsg); } Throwable nestedCause = ExceptionHelper.getCause(this.nestable); if (nestedCause != null) { String causeMsg = nestedCause.getMessage(); if (causeMsg != null) { if (baseMsg != null) { msg.append(": "); } msg.append(causeMsg); } } return (msg.length() > 0 ? msg.toString() : null); } /** * 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, numbererd 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 ExceptionHelper.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 ExceptionHelper.getThrowables(this.nestable); } /** * Returns the index, numbered from 0, of the first <code>Throwable</code> * that matches the specified type in the chain of <code>Throwable</code>s * held in this delegate's <code>Nestable</code> with an index greater than or * equal to the specified index, or -1 if the type is not found. * * @param type * <code>Class</code> to be found * @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 (fromIndex < 0) { throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex); } Throwable[] throwables = ExceptionHelper.getThrowables(this.nestable); if (fromIndex >= throwables.length) { throw new IndexOutOfBoundsException( "The start index was out of bounds: " + fromIndex + " >= " + throwables.length); } for (int i = fromIndex; i < throwables.length; i++) { if (throwables[i].getClass().equals(type)) { 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 (ExceptionHelper.isThrowableNested()) { if (throwable instanceof Nestable) { ((Nestable) throwable).printPartialStackTrace(out); } else { throwable.printStackTrace(out); } return; } // generating the nested stack trace List<String[]> stacks = new ArrayList<String[]>(); while (throwable != null) { String[] st = getStackFrames(throwable); stacks.add(st); throwable = ExceptionHelper.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<String[]> 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 ExceptionHelper.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<String[]> 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<String> currList = new ArrayList<String>(Arrays.asList(curr)); List<String> nextList = new ArrayList<String>(Arrays.asList(next)); ExceptionHelper.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()])); } } } }