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Added SneakyThrows which finishes the documentation for the features pages.
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@@ -80,6 +80,9 @@
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<antcall target="-integrateSnippet">
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<param name="transformationName" value="Synchronized" />
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</antcall>
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<antcall target="-integrateSnippet">
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<param name="transformationName" value="SneakyThrows" />
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</antcall>
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<mkdir dir="dist" />
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<tar destfile="dist/website.tar">
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<tarfileset dir="build/website" />
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@@ -0,0 +1,19 @@
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import lombok.Lombok;
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public class SneakyThrowsExample implements Runnable {
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public String utf8ToString(byte[] bytes) {
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try {
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return new String(bytes, "UTF-8");
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} catch (UnsupportedEncodingException e) {
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throw Lombok.sneakyThrow(e);
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}
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}
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public void run() {
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try {
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throw new Throwable();
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} catch (Throwable t) {
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throw Lombok.sneakyThrow(t);
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}
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}
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}
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@@ -0,0 +1,13 @@
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import lombok.SneakyThrows;
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public class SneakyThrowsExample implements Runnable {
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@SneakyThrows(UnsupportedEncodingException.class)
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public String utf8ToString(byte[] bytes) {
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return new String(bytes, "UTF-8");
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}
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@SneakyThrows
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public void run() {
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throw new Throwable();
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}
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}
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@@ -0,0 +1,78 @@
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<!DOCTYPE html>
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<html><head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<link rel="stylesheet" type="text/css" href="../logi/reset.css" />
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<link rel="stylesheet" type="text/css" href="features.css" />
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<link rel="shortcut icon" href="../favicon.ico" type="image/x-icon" />
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<meta name="description" content="Spice up your java" />
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<title>@SneakyThrows</title>
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<!--[if lt IE 7]><script type="text/javascript" src="logi/iepngfix_tilebg.js"></script><![endif]-->
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</head><body><div id="pepper">
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<div class="minimumHeight"></div>
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<div class="meat">
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<div class="header"><a href="../index.html">Project Lombok</a></div>
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<h1>@SneakyThrows</h1>
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<div class="byline">To boldly throw checked exceptions where no one has thrown them before!</div>
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<div class="overview">
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<h3>Overview</h3>
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<p>
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<code>@SneakyThrows</code> can be used to sneakily throw checked exceptions without actually declaring this in your method's <code>throws</code>
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clause. This somewhat contentious ability should be used carefully, of course. The code generated by lombok will not ignore, wrap, replace,
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or otherwise modify the thrown checked exception; it simply fakes out the compiler. On the JVM (class file) level, all exceptions, checked or not,
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can be thrown regardless of the <code>throws</code> clause of your methods, which is why this works.
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</p><p>
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<em><strong>CAREFUL: </strong><em>Unlike other lombok transformations, you need to put <strong>lombok.jar</strong> on your classpath when
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you run your program.
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</p><p>
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Common use cases for when you want to opt out of the checked exception mechanism center around 2 situations:<br /><li>
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<ul>A needlessly strict interface, such as <code>Runnable</code> - whatever exception propagates out of your <code>run()</code> method,
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checked or not, it will be passed to the <code>Thread</code>'s unhandled exception handler. Catching a checked exception and wrapping it
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in some sort of <code>RuntimeException</code> is only obscuring the real cause of the issue.</ul>
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<ul>An 'impossible' exception. For example, <code>new String(someByteArray, "UTF-8");</code> declares that it can throw an
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<code>UnsupportedEncodingException</code> but according to the JVM specification, UTF-8 <em>must</em> always be available. An
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<code>UnsupportedEncodingException</code> here is about as likely as a <code>ClassNotFoundError</code> when you use a String object,
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and you don't catch those either!</ul>
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</p><p>
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Be aware that it is <em>impossible</em> to catch sneakily thrown checked types directly, as javac will not let you write a catch block
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for an exception type that no method call in the try body declares as thrown. This problem is not relevant in either of the use cases listed
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above, so let this serve as a warning that you should not use the <code>@SneakyThrows</code> mechanism without some deliberation!
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</p><p>
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You can pass any number of exceptions to the <code>@SneakyThrows</code> annotation. If you pass no exceptions, you may throw any
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exception sneakily.
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</div>
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<div class="snippets">
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<div class="pre">
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<h3>With Lombok</h3>
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<div class="snippet">@HTML_PRE@</div>
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</div>
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<div class="sep"></div>
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<div class="post">
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<h3>Vanilla Java</h3>
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<div class="snippet">@HTML_POST@</div>
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</div>
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</div>
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<div style="clear: left;"></div>
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<div class="overview">
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<h3>Small print</h3><div class="smallprint">
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<p>
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Because <code>@SneakyThrows</code> is an implementation detail and not part of your method signature, it is an error if you try to
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declare a checked exception as sneakily thrown when you don't call any methods that throw this exception. (Doing so is perfectly legal
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for <code>throws</code> statements to accomodate subclasses). Similarly, <code>@SneakyThrows</code> does not inherit.
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</p><p>
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For the nay-sayers in the crowd: Out of the box, Eclipse will offer a 'quick-fix' for uncaught exceptions that wraps the offending
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statement in a try/catch block with just <code>e.printStackTrace()</code> in the catch block. This is so spectacularly non-productive
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compared to just sneakily throwing the exception onwards, that Roel and Reinier feel more than justified in claiming that the
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checked exception system is far from perfect, and thus an opt-out mechanism is warranted.
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</p><p>
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Currently usage of <code>@SneakyThrows</code> requires you to have <code>lombok.jar</code> in the classpath at runtime. However, in the future
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we will attempt to eliminate this requirement - when we figure out how we can do that. If anyone has a good idea on how to make that happen, let us know!
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</p>
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</div>
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</div>
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<div class="footer">
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<a href="index.html">Back to features</a> | <a href="Synchronized.html">Previous feature (@Synchronized)</a> | <span class="disabled">Next feature</span><br />
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<span class="copyright">Copyright © 2009 Reinier Zwitserloot and Roel Spilker, licensed under the <a href="http://www.opensource.org/licenses/mit-license.php">MIT licence</a>.</span>
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</div>
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<div style="clear: both;"></div>
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</div>
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</div></body></html>
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