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<h2>Exceptions Rules ("<i>rulesets/exceptions.xml</i>")<a name="Exceptions_Rules_rulesetsexceptions.xml"></a></h2><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<div class="section">
<h3><a name="CatchArrayIndexOutOfBoundsException">CatchArrayIndexOutOfBoundsException</a> Rule<a name="CatchArrayIndexOutOfBoundsException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Checks for catching a <tt>ArrayIndexOutOfBoundsException</tt>. Catching <tt>ArrayIndexOutOfBoundsException</tt> should be avoided in the first place by checking the array size before accessing an array element. Catching the exception may mask underlying errors.</p></div>
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<h3><a name="CatchError">CatchError</a> Rule<a name="CatchError_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for catching a <tt>Error</tt>. In most cases that is much too broad, and is also dangerous because it can catch exceptions such as <tt>ThreadDeath</tt> and <tt>OutOfMemoryError</tt>.</p></div>
<div class="section">
<h3><a name="CatchException">CatchException</a> Rule<a name="CatchException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for catching a <tt>Exception</tt>. In most cases that is too broad or general. It should usually be restricted to framework or infrastructure code, rather than application code.</p></div>
<div class="section">
<h3><a name="CatchIllegalMonitorStateException">CatchIllegalMonitorStateException</a> Rule<a name="CatchIllegalMonitorStateException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>Dubious catching of IllegalMonitorStateException. IllegalMonitorStateException is generally only thrown in case of a design flaw in your code (calling wait or notify on an object you do not hold a lock on).</p></div>
<div class="section">
<h3><a name="CatchIndexOutOfBoundsException">CatchIndexOutOfBoundsException</a> Rule<a name="CatchIndexOutOfBoundsException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Checks for catching a <tt>IndexOutOfBoundsException</tt>. Catching <tt>IndexOutOfBoundsException</tt> should be avoided in the first place by checking for a valid index before accessing an indexed element. Catching the exception may mask underlying errors.</p></div>
<div class="section">
<h3><a name="CatchNullPointerException">CatchNullPointerException</a> Rule<a name="CatchNullPointerException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for catching a <tt>NullPointerException</tt>. Catching <tt>NullPointerException</tt> is never appropriate. It should be avoided in the first place with proper null checking, and it can mask underlying errors.</p></div>
<div class="section">
<h3><a name="CatchRuntimeException">CatchRuntimeException</a> Rule<a name="CatchRuntimeException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for catching a <tt>RuntimeException</tt>. In most cases that is too broad or general. It should usually be restricted to framework or infrastructure code, rather than application code.</p></div>
<div class="section">
<h3><a name="CatchThrowable">CatchThrowable</a> Rule<a name="CatchThrowable_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for catching a <tt>Throwable</tt>. In most cases that is much too broad, and is also dangerous because it can catch exceptions such as <tt>ThreadDeath</tt> and <tt>OutOfMemoryError</tt>.</p></div>
<div class="section">
<h3><a name="ConfusingClassNamedException">ConfusingClassNamedException</a> Rule<a name="ConfusingClassNamedException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>This class is not derived from another exception, but ends with 'Exception'. This will be confusing to users of this class.</p></div>
<div class="section">
<h3><a name="ExceptionExtendsError">ExceptionExtendsError</a> Rule<a name="ExceptionExtendsError_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Errors are system exceptions. Do not extend them.</p>
<p>Examples:</p>
<div>
<pre> class MyError extends Error { } // violation
class MyError extends java.lang.Error { } // violation
class MyException extends Exception { } // OK
</pre></div></div>
<div class="section">
<h3><a name="ExceptionExtendsThrowable">ExceptionExtendsThrowable</a> Rule<a name="ExceptionExtendsThrowable_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.21</i></p>
<p>Checks for classes that extend <tt>Throwable</tt>. Custom exception classes should subclass <tt>Exception</tt> or one of its descendants.</p>
<p>Example of violations:</p>
<div>
<pre> class MyException extends Throwable { } // violation
</pre></div></div>
<div class="section">
<h3><a name="ExceptionNotThrown">ExceptionNotThrown</a> Rule<a name="ExceptionNotThrown_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.18</i></p>
<p>Checks for an exception constructor call without a <tt>throw</tt> as the last statement within a catch block. This rule treats any constructor call for a class named <i>xxx</i><b>Exception</b> as an exception constructor call.</p>
<p>Example of violations:</p>
<div>
<pre> void execute() {
try { } catch(Exception e) { new Exception(e) } // violation
}
try {
doStuff()
} catch(DaoException e) {
log.warning("Ooops", e)
new ServiceException(e) // violation
} catch(Exception e) {
new SystemException(e) // violation
}
try {
doStuff()
} catch(Exception e) { throw new DaoException(e) } // ok
</pre></div></div>
<div class="section">
<h3><a name="MissingNewInThrowStatement">MissingNewInThrowStatement</a> Rule<a name="MissingNewInThrowStatement_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>A common Groovy mistake when throwing exceptions is to forget the new keyword. For instance, <tt>throw RuntimeException()</tt> instead of <tt>throw new RuntimeException()</tt>. If the error path is not unit tested then the production system will throw a Method Missing exception and hide the root cause. This rule finds constructs like <tt>throw RuntimeException()</tt> that look like a new keyword was meant to be used but forgotten.</p>
<p>The following code will all cause violations:</p>
<div>
<pre> throw RuntimeException() // ends in Exceptions, first letter Capitalized
throw RuntimeFailure() // ends in Failure, first letter Capitalized
throw RuntimeFault(foo) // ends in Fault, first letter Capitalized
</pre></div>
<p>The following code will not cause any exceptions:</p>
<div>
<pre> throw new RuntimeException()
throw runtimeFailure() // first letter lowercase, assumed to be method call
</pre></div></div>
<div class="section">
<h3><a name="ReturnNullFromCatchBlock">ReturnNullFromCatchBlock</a> Rule<a name="ReturnNullFromCatchBlock_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>Returning null from a catch block often masks errors and requires the client to handle error codes. In some coding styles this is discouraged. This rule ignores methods with <tt>void</tt> return type.</p></div>
<div class="section">
<h3><a name="SwallowThreadDeath">SwallowThreadDeath</a> Rule<a name="SwallowThreadDeath_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.14</i> Detects code that catches java.lang.ThreadDeath without re-throwing it.</p>
<p>Example of violations:</p>
<div>
<pre> try {
def a = 0
} catch (ThreadDeath td) {
td.printStackTrace()
}
</pre></div></div>
<div class="section">
<h3><a name="ThrowError">ThrowError</a> Rule<a name="ThrowError_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for throwing an instance of <tt>java.lang.Error</tt>. This is not appropriate within normal application code. Throw an instance of a more specific exception subclass instead.</p></div>
<div class="section">
<h3><a name="ThrowException">ThrowException</a> Rule<a name="ThrowException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for throwing an instance of <tt>java.lang.Exception</tt>. Throw an instance of a more specific exception subclass instead.</p></div>
<div class="section">
<h3><a name="ThrowNullPointerException">ThrowNullPointerException</a> Rule<a name="ThrowNullPointerException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for throwing an instance of <tt>java.lang.NullPointerException</tt>. Applications should never throw a <tt>NullPointerException</tt>.</p></div>
<div class="section">
<h3><a name="ThrowRuntimeException">ThrowRuntimeException</a> Rule<a name="ThrowRuntimeException_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for throwing an instance of <tt>java.lang.RuntimeException</tt>. Throw an instance of a more specific exception subclass instead.</p></div>
<div class="section">
<h3><a name="ThrowThrowable">ThrowThrowable</a> Rule<a name="ThrowThrowable_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for throwing an instance of <tt>java.lang.Throwable</tt>. Throw an instance of a more specific exception subclass instead.</p></div></div>
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