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| <title>thisJoinPoint</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 Programming Guide"><link rel="up" href="language.html" title="Chapter 2. The AspectJ Language"><link rel="previous" href="language-interType.html" title="Inter-type declarations"><link rel="next" href="examples.html" title="Chapter 3. Examples"></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">thisJoinPoint</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="language-interType.html">Prev</a> </td><th width="60%" align="center">Chapter 2. The AspectJ Language</th><td width="20%" align="right"> <a accesskey="n" href="examples.html">Next</a></td></tr></table><hr></div><div class="sect1"><a name="language-thisJoinPoint"></a><div class="titlepage"><div><h2 class="title" style="clear: both"><a name="language-thisJoinPoint"></a>thisJoinPoint</h2></div></div><p> |
| AspectJ provides a special reference variable, |
| <tt>thisJoinPoint</tt>, that contains reflective |
| information about the current join point for the advice to use. The |
| <tt>thisJoinPoint</tt> variable can only be used in the |
| context of advice, just like <tt>this</tt> can only be used |
| in the context of non-static methods and variable initializers. In |
| advice, <tt>thisJoinPoint</tt> is an object of type <a href="../api/org/aspectj/lang/JoinPoint.html" target="_top"><tt>org.aspectj.lang.JoinPoint</tt></a>. |
| </p><p> |
| One way to use it is simply to print it out. Like all Java objects, |
| <tt>thisJoinPoint</tt> has a <tt>toString()</tt> |
| method that makes quick-and-dirty tracing easy: |
| </p><pre class="programlisting"> |
| aspect TraceNonStaticMethods { |
| before(Point p): target(p) && call(* *(..)) { |
| System.out.println("Entering " + thisJoinPoint + " in " + p); |
| } |
| } |
| </pre><p> |
| The type of <tt>thisJoinPoint</tt> includes a rich |
| reflective class hierarchy of signatures, and can be used to access |
| both static and dynamic information about join points such as the |
| arguments of the join point: |
| |
| <pre class="programlisting"> |
| thisJoinPoint.getArgs() |
| </pre> |
| |
| In addition, it holds an object consisting of all the static |
| information about the join point such as corresponding line number |
| and static signature: |
| |
| <pre class="programlisting"> |
| thisJoinPoint.getStaticPart() |
| </pre> |
| |
| If you only need the static information about the join point, you may |
| access the static part of the join point directly with the special |
| variable <tt>thisJoinPointStaticPart</tt>. Using |
| <tt>thisJoinPointStaticPart</tt> will avoid the run-time |
| creation of the join point object that may be necessary when using |
| <tt>thisJoinPoint</tt> directly. |
| </p><p>It is always the case that |
| </p><pre class="programlisting"> |
| thisJoinPointStaticPart == thisJoinPoint.getStaticPart() |
| |
| thisJoinPoint.getKind() == thisJoinPointStaticPart.getKind() |
| thisJoinPoint.getSignature() == thisJoinPointStaticPart.getSignature() |
| thisJoinPoint.getSourceLocation() == thisJoinPointStaticPart.getSourceLocation() |
| </pre><p> |
| One more reflective variable is available: |
| <tt>thisEnclosingJoinPointStaticPart</tt>. This, like |
| <tt>thisJoinPointStaticPart</tt>, only holds the static |
| part of a join point, but it is not the current but the enclosing |
| join point. So, for example, it is possible to print out the calling |
| source location (if available) with |
| </p><pre class="programlisting"> |
| before() : execution (* *(..)) { |
| System.err.println(thisEnclosingJoinPointStaticPart.getSourceLocation()) |
| } |
| </pre></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="language-interType.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="examples.html">Next</a></td></tr><tr><td width="40%" align="left">Inter-type declarations </td><td width="20%" align="center"><a accesskey="u" href="language.html">Up</a></td><td width="40%" align="right"> Chapter 3. Examples</td></tr></table></div></body></html> |
