diff options
Diffstat (limited to 'docs/adk15ProgGuideDB/covariance.xml')
| -rw-r--r-- | docs/adk15ProgGuideDB/covariance.xml | 94 |
1 files changed, 31 insertions, 63 deletions
diff --git a/docs/adk15ProgGuideDB/covariance.xml b/docs/adk15ProgGuideDB/covariance.xml index 4e1e2f8de..b6b0d7e70 100644 --- a/docs/adk15ProgGuideDB/covariance.xml +++ b/docs/adk15ProgGuideDB/covariance.xml @@ -6,7 +6,7 @@ <title>Covariance in Java 5</title> <para> - Java 5 (and hence AspectJ 1.5) allows you to narrow the return type + Java 5 (and hence AspectJ 5) allows you to narrow the return type in an overriding method. For example: </para> @@ -42,16 +42,30 @@ b.whoAreYou(); ]]></programlisting> - <para>Then the call and execution join points for <literal>whoAreYou</literal> - are matched as follows:</para> + <para>The signatures for the call join point <literal>a.whoAreYou()</literal> are + simply:</para> + + <programlisting><![CDATA[ + A A.whoAreYou() + ]]></programlisting> + + <para>The signatures for the call join point <literal>b.whoAreYou()</literal> are: + </para> + + <programlisting><![CDATA[ + A A.whoAreYou() + B B.whoAreYou() + ]]></programlisting> + + <para>Following the join point matching rules given in <xref linkend="jpsigs"/>,</para> <variablelist> <varlistentry> <term>call(* whoAreYou())</term> <listitem> - <para>Matches both calls, (since it places no constraint on the - return type of the join point signature). + <para>Matches both calls, (since each call join point has at least + one matching signature). </para> </listitem> </varlistentry> @@ -59,8 +73,8 @@ <varlistentry> <term>call(* A.whoAreYou())</term> <listitem> - <para>Matches both calls, (since the original declaring type - of <literal>whoAreYou</literal> is <literal>A</literal>). + <para>Matches both calls, (since each call join point has at least + one matching signature). </para> </listitem> </varlistentry> @@ -68,9 +82,8 @@ <varlistentry> <term>call(A whoAreYou())</term> <listitem> - <para>Matches both calls, (since the signature of - <literal>whoAreYou</literal>) in the original declaring type - has a return type of <literal>A</literal>). + <para>Matches both calls, (since each call join point has at least + one matching signature). </para> </listitem> </varlistentry> @@ -78,9 +91,8 @@ <varlistentry> <term>call(A B.whoAreYou())</term> <listitem> - <para>Does not match anything - the signature of <literal>whoAreYou</literal> - as overriden in <literal>B</literal> has a return type of - <literal>B</literal>, not <literal>A</literal>. A lint warning is + <para>Does not match anything - neither of the call join points + has a signature matched by this pattern. A lint warning is given for the call <literal>a.whoAreYou()</literal> ("does not match because declaring type is A, if match required use target(B)"). </para> @@ -91,9 +103,8 @@ <term>call(A+ B.whoAreYou())</term> <listitem> <para>Matches the call to <literal>b.whoAreYou()</literal> since - the return type <literal>B</literal> in the method signature - is matched by the type pattern <literal>A+</literal>. A lint warning is - given for the call <literal>a.whoAreYou()</literal> ("does not match + the signature pattern matches the signature <literal>B B.whoAreYou()</literal>. + A lint warning is given for the call <literal>a.whoAreYou()</literal> ("does not match because declaring type is A, if match required use target(B)"). </para> </listitem> @@ -102,8 +113,8 @@ <varlistentry> <term>call(B A.whoAreYou())</term> <listitem> - <para>Does not match anything - there is no method declared in - <literal>A</literal> with a return type of <literal>B</literal>. + <para>Does not match anything since neither join point has a + signature matched by this pattern. </para> </listitem> </varlistentry> @@ -129,52 +140,9 @@ <para>The rule for signature matching at call and execution join points is unchanged from AspectJ 1.2: a call or execution pointcut matches if the signature pattern matches at least one of the signatures of the - join point, and if the most-specific matched signature is also matched + join point, and if the modifiers of the method or constructor are matched by any modifier pattern or annotation pattern that may be present.</para> - <para>For a call or execution join point, the signatures of a join point - for the call or execution of a method <literal>Rtype T.m(params)</literal> - are determined as follows:</para> - <itemizedlist> - <listitem> - If <literal>m(params)</literal> is defined in <literal>T</literal>, - then the signature of <literal>m(params)</literal> in <literal>T</literal> is - a signature of the join point: <literal>Rtype T.m(params)</literal>. - If <literal>T</literal> does not - provide its own definition of <literal>m</literal>, then the signature - <literal>Rtype' T.m(params)</literal> - is a signature of the join point, where <literal>Rtype'</literal> is the return type of - the definition of <literal>m</literal> inherited by <literal>T</literal>. - </listitem> - <listitem> - For each super-type <literal>S</literal> of <literal>T</literal> that is a valid receiver - for a call to <literal>m</literal>, then the signature of <literal>m(params)</literal> in - <literal>S</literal> is a signature - of the join point: <literal>Rtype S.m(params)</literal>. - If <literal>S</literal> does not provide its - own definition of <literal>m</literal>, then the signature - <literal>Rtype' S.m(params)</literal> is a - signature of the join point, where <literal>Rtype'</literal> is the return type of the - definition of <literal>m</literal> inherited by <literal>S</literal>. - </listitem> - </itemizedlist> - - <para>A call to <literal>b.whoAreYou()</literal> has the join point signatures - </para> - - <itemizedlist> - <listitem>B B.whoAreYou()</listitem> - <listitem>A A.whoAreYou()</listitem> - </itemizedlist> - - <para>Following the rule given, it is easy to see why for example - <literal>call(B A.whoAreYou())</literal> does not match anything as - this pattern matches neither of the signatures at the join point. In - contrast, the pointcut expression <literal>call(A+ B.whoAreYou())</literal> - does match the call to <literal>b.whoAreYou()</literal> because it matches - the second of the signatures at the join point.</para> - </sect1> - - + </sect1> </chapter> |