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POHow to best execute a set of methods even if an exception happens
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  1. POHow to best execute a set of methods even if an exception happens
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    copied!<p>In a current Java project we have code similar to the following example:</p> <pre><code>try { doSomeThing(anObject); } catch (SameException e) { // Do nothing or log, but don't abort current method. } try { doOtherThing(anObject); } catch (SameException e) { // Do nothing or log, but don't abort current method. } // ... some more calls to different method ... try { finallyDoYetSomethingCompletelyDifferent(anObject); } catch (SameException e) { // Do nothing or log, but don't abort current method. } </code></pre> <p>As you can see, several different method are called with the exact same object and for every call the same exception is caught and handled the same (or in a very similar) way. The exception is not re-thrown, but may only be logged and then discarded.</p> <p>The only reason why there is a <code>try-catch</code> around every single method, is to always execute all of the methods, no matter if a previously executed method failed.</p> <p>I don't like the above code at all. It takes up a lot of space, is very repetitive (especially the logging done in the <code>catch</code>-block; not presented here) and just looks bad.</p> <p>I can think of some other ways to write this code, but don't like them very much, either. The following options came to my mind:</p> <p><strong>Loop-switch sequence / for-case paradigm</strong></p> <p>(See <a href="http://en.wikipedia.org/wiki/Loop-switch_sequence" rel="nofollow noreferrer">Wikipedia</a> or <a href="http://thedailywtf.com/Articles/Switched_on_Loops.aspx" rel="nofollow noreferrer">The Daily WTF</a>)</p> <pre><code>for (int i = 0; i &lt;= 9; i++) { try { switch (i) { case 0: doSomeThing(anObject); break; case 1: doOtherSomeThing(anObject); break; // ...More cases... case 9: doYetSomethingCompletelyDifferent(anObject); break; } } catch (SameException e) { // Do nothing or log, but don't abort current method. } } </code></pre> <p>This is obviously bad code, very error-prone and looks amateurish.</p> <p><strong>Reflection</strong></p> <p>Use reflection to get <code>Method</code> objects for the methods to call and store them in a list in the order they are supposed to be executed. Then iterate over this list and call the method using <code>anObject</code> as only parameter. The exception is handled inside of the loop.</p> <p>I don't like this approach, as bugs (for example typos in the method names) only pop up during runtime and the Reflection API is somewhat chatty.</p> <p><strong>Functor</strong></p> <p>Create a Functor class like this:</p> <pre><code>private class Functor { void doStuff(MyObject object) throws SameException; } </code></pre> <p>Then create a list of <code>Functor</code> objects that call the methods. Like this:</p> <pre><code>List&lt;Functor&gt; functors = new ArrayList&lt;Functor&gt;(); functors.add(new Functor() { @Override public void execute(MyObject anObject) { doSomeThing(anObject); } }); functors.add(new Functor() { @Override public void execute(MyObject anObject) { doOtherSomeThing(anObject); } }); </code></pre> <p>Later, iterate this list and call <code>execute()</code> on every <code>Functor</code> object. I can summarize my feeling about this approach with two words: Code bloat.</p> <hr> <p>As I don't really like all four approaches, I would like to discuss this problem here. What do you feel is the best approach? How did you solve similar problems in the past? Is there maybe a much simpler solution I missed completely?</p>
 

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