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| <title>Using Annotations with declare statements</title><link rel="stylesheet" href="aspectj-docs.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.44"><link rel="home" href="index.html" title="The AspectJTM 5 Development Kit Developer's Notebook"><link rel="up" href="annotations.html" title="Chapter 2. Annotations"><link rel="previous" href="annotations-pointcuts-and-advice.html" title="Join Point Matching based on Annotations"><link rel="next" href="annotations-declare.html" title="Declare Annotation"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Using Annotations with declare statements</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="annotations-pointcuts-and-advice.html">Prev</a> </td><th width="60%" align="center">Chapter 2. Annotations</th><td width="20%" align="right"> <a accesskey="n" href="annotations-declare.html">Next</a></td></tr></table><hr></div><div class="sect1"><a name="annotations-decp"></a><div class="titlepage"><div><h2 class="title" style="clear: both"><a name="annotations-decp"></a>Using Annotations with declare statements</h2></div></div><div class="sect2"><a name="declare-error-and-declare-warning"></a><div class="titlepage"><div><h3 class="title"><a name="declare-error-and-declare-warning"></a>Declare error and declare warning</h3></div></div><p> | |
| Since pointcut expressions in AspectJ 5 support join point matching based | |
| on annotations, this facility can be exploited when writing | |
| <tt>declare warning</tt> and <tt>declare error</tt> | |
| statements. For example: | |
| </p><pre class="programlisting"> | |
| declare warning : withincode(@PerformanceCritical * *(..)) && | |
| call(@ExpensiveOperation * *(..)) | |
| : "Expensive operation called from within performance critical section"; | |
| </pre><pre class="programlisting"> | |
| declare error : call(* org.xyz.model.*.*(..)) && | |
| !@within(Trusted) | |
| : "Untrusted code should not call the model classes directly"; | |
| </pre></div><div class="sect2"><a name="declare-parents"></a><div class="titlepage"><div><h3 class="title"><a name="declare-parents"></a>declare parents</h3></div></div><p> | |
| The general form of a <tt>declare parents</tt> statement is: | |
| </p><pre class="programlisting"> | |
| declare parents : TypePattern extends Type; | |
| declare parents : TypePattern implements TypeList; | |
| </pre><p> | |
| Since AspectJ 5 supports annotations as part of a type pattern | |
| specification, it is now possible to match types based on the presence | |
| of annotations <span class="emphasis"><i>with either class-file or runtime retention</i></span>. | |
| For example: | |
| </p><div class="variablelist"><dl><dt><a name="d0e1520"></a><span class="term">declare parents : (@Secured *) implements SecuredObject;</span></dt><dd><p><a name="d0e1523"></a> | |
| All types with the <tt>@Secured</tt> annotation | |
| implement the <tt>SecuredObject</tt> inteface. | |
| </p></dd><dt><a name="d0e1532"></a><span class="term">declare parents : (@Secured BankAccount+) implements SecuredObject;</span></dt><dd><p><a name="d0e1535"></a> | |
| The subset of types drawn from the <tt>BankAccount</tt> type and any subtype of | |
| <tt>BankAccount</tt>, where the | |
| <tt>@Secured</tt> annotation is present, implement the | |
| <tt>SecuredObject</tt> interface. | |
| </p></dd></dl></div><p>An annotation type may not be used as the target of a declare parents | |
| statement. If an annotation type is named explicitly as the target of a | |
| declare parents statement, a compilation error will result. If an annotation | |
| type is matched by a non-explicit type pattern used in a declare parents | |
| statement it will be ignored (and an XLint warning issued).</p></div><div class="sect2"><a name="declare-precedence"></a><div class="titlepage"><div><h3 class="title"><a name="declare-precedence"></a>declare precedence</h3></div></div><p> | |
| The general form of a declare precedence statement is: | |
| </p><pre class="programlisting"> | |
| declare precedence : TypePatList; | |
| </pre><p> | |
| AspectJ 5 allows the type patterns in the list to include annotation information | |
| as part of the pattern specification. For example: | |
| </p><div class="variablelist"><dl><dt><a name="d0e1562"></a><span class="term">declare precedence : (@Security *),*;</span></dt><dd><p><a name="d0e1565"></a> | |
| All aspects with the <tt>@Security</tt> annotation | |
| take precedence over any other aspects in the system. (Or, more | |
| informally, all security-related aspects take precedence). | |
| </p></dd></dl></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="annotations-pointcuts-and-advice.html">Prev</a> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right"> <a accesskey="n" href="annotations-declare.html">Next</a></td></tr><tr><td width="40%" align="left">Join Point Matching based on Annotations </td><td width="20%" align="center"><a accesskey="u" href="annotations.html">Up</a></td><td width="40%" align="right"> Declare Annotation</td></tr></table></div></body></html> |