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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html><head><title>Java Image I/O API Guide: 3 - Writing Image I/O Applications</title></head><body bgcolor="#ffffff"> <table summary="layout" width="100%"><tr><td><!-- Bug in Communicator w/font: NavBar text disappears for Times 14pt pref. --><!-- font size="-1" --> <a href="imageio_guideTOC.fm.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/imageio_guideTOC.fm.html">CONTENTS</a> | <a href="apps.fm7.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/apps.fm7.html">PREV</a> | <a href="extending.fm1.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/extending.fm1.html">NEXT</a> <!-- | <a href="copyright.fm.html">INDEX</a> --><!-- /font --></td><td align=right><i>Java<sup><font size="-1">TM</font></sup></font> Image I/O API Guide</i></td></tr></table><br> <p><hr size="8" width="35%" align="left" noshade><h2><a name="997341"><i>3.8 </i> Handling Errors using <code>IIOException</code></a></h2><blockquote><a name="997068"><!-- --></a>In the examples above, the possibility of fatal errors was not considered. Errors may result from a number of sources, including true I/O errors (e.g., file not found, file unreadable, file on corrupt media), security violations (e.g., no permission to read files from an applet), file format problems (file contents corrupted, file using a variant of the format that is not supported by the plug-in), or even bugs in the API implementation or in the plug-in.<p><a name="997069"><!-- --></a>The Image I/O API makes use of its own subclass of the standard <code>IOException</code> class, called <code>IIOException</code>. <code>IIOException</code>s are used to signal all errors encountered during the parsing of a source file (e.g., an incorrect checksum or an invalid value for a particular byte within the file), including true I/O errors that result in an <code>IOException</code> being thrown within the reader.<p><a name="998535"><!-- --></a>An <code>IIOException</code> contains a (non-localized) message describing the reason for the exception, as well as a reference to another <code>Exception</code> that was the cause of the <code>IIOException</code>, if one exists.<p><a name="997071"><!-- --></a>Thus, application code that attempts to provide graceful handling of errors will look something like:<p></blockquote><blockquote><pre>File f = new File("c:\images\myimage.gif");ImageInputStream iis = null;try { iis = ImageIO.createImageInputStream(f);} catch (IIOException iioe1) { System.out.println("Unable to create an input stream!"); return;}reader.setInput(stream);try { reader.read(0, param);} catch (IIOException iioe2) { System.out.println("An error occurred during reading: " + iioe2.getMessage()); Throwable t = iioe2.getCause(); if ((t != null) && (t instanceof IOException)) { System.out.println("Caused by IOException: " + t.getMessage()); }}</pre></blockquote><blockquote><a name="997090"><!-- --></a><p></blockquote><br><hr><!-- Bug in Communicator w/font: NavBar text disappears for Times 14pt pref. --><!-- font size="-1" --> <a href="imageio_guideTOC.fm.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/imageio_guideTOC.fm.html">CONTENTS</a> | <a href="apps.fm7.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/apps.fm7.html">PREV</a> | <a href="extending.fm1.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/extending.fm1.html">NEXT</a> <!-- | <a href="copyright.fm.html">INDEX</a> --><!-- /font --><hr><font size="-1"><i><A HREF="copyright.fm.html" tppabs="http://java.sun.com/j2se/1.4.2/docs/guide/imageio/spec/copyright.fm.html">Copyright</a> © 2001 Sun Microsystems, Inc. All Rights Reserved.</i></font><!-- This HTML file was created with Quadralay WebWorks Publisher 3.5.0 --><!-- by Suzette Pelouch --><!-- Last updated: Fri Apr 27 11:22:59 2001 --> </body><script language="JavaScript" src="s_code_remote.js" tppabs="http://java.sun.com/js/omi/jsc/s_code_remote.js"></script></html>⌨️ 快捷键说明
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