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git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@5290 626c5289-ae23-0410-ae9c-e8d60b6d4f22
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William S Fulton 2003-11-10 22:34:35 +00:00
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SWIG/Doc/Manual/Java.html
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@ -67,7 +67,6 @@
<li><a href="#n42">Director classes</a>
<li><a href="#n43">Overhead and code bloat</a>
<li><a href="#n44">Simple directors example</a>
<li><a href="#n45">Director method recursion</a>
</ul>
<li><a href="#n46">Common customization features</a>
<ul>
@ -131,8 +130,10 @@ The Java extension to SWIG makes it very easy to plumb in existing C/C++ code fo
It is different to using the 'javah' tool as SWIG will wrap existing C/C++ code, whereas javah takes 'native' Java function declarations and creates C/C++ function prototypes.
SWIG wraps C/C++ code using Java proxy classes and is very useful if you want to have access to large amounts of C/C++ code from Java.
If only one or two JNI functions are needed then using SWIG may be overkill.
An important point to note is that SWIG enables a Java program to easily call into C/C++ code and not visa-versa.
If you primarily want calls from C/C++ into Java then currently SWIG isn't particularly useful as the appropriate JNI code will have to be written by hand.
SWIG enables a Java program to easily call into C/C++ code from Java.
Historically, SWIG was not able to generate any code to call into Java code from C++.
However, SWIG now supports full cross language polymorphism and code is generated to call up from C++ to Java when wrapping C++ virtual methods.
<p>
Java is one of the few non-scripting language modules in SWIG.
@ -2289,7 +2290,6 @@ Although directors make it natural to mix native C++ objects with Java objects (
one should be aware of the obvious fact that method calls to Java objects from C++ will be much slower than calls to C++ objects.
Additionally, compared to classes that do not use directors, the call routing in the director methods adds a small overhead.
This situation can be optimized by selectively enabling director methods (using the %feature directive) for only those methods that are likely to be extended in Java.
The <a href="#java_director_recursive">Director method recursion</a> section details how to reduce some overhead involved in recursion checking code which is generated by default.
<a name="java_directors_example"></a>
@ -2353,44 +2353,6 @@ directorDerived::upcall_method() invoked.
</pre>
</blockquote>
<a name="java_director_recursive"></a>
<a name="n45"></a><H3>15.5.5 Director method recursion</H3>
<p>
The Java module's director code attempts to prevent recursion from the C++ proxy class's code to Java and back through the C++ proxy class.
The most common reason for this loop is a typo in the Java derived class, e.g., <i>pucall_method</i> instead of <i>upcall_method</i> in the following Java code:
<blockquote>
<pre>
public class directorDerived extends DirectorBase {
public directorDerived() {
}
public void pucall_method() {
System.out.println("directorDerived::upcall_method() invoked.");
}
}
</pre>
</blockquote>
Another common typo is a mismatch between the arguments specified in the C++ method declaration and the Java subclass's method declaration.
A <code>SWIG_JavaDirectorRicochet</code> exception is raised in Java when this particular problem is detected at runtime.
</p>
<p>
This feature can be turned off in the SWIG interface file for the entire class,
<blockquote>
<pre>
%feature("director:recursive") DirectorBase
</pre>
</blockquote>
or selectively for individual methods:
<blockquote>
<pre>
%feature("director:recursive") DirectorBase::upcall_method()
</pre>
</blockquote>
<a name="common_customization"></a>
<a name="n46"></a><H2>15.6 Common customization features</H2>
@ -4345,18 +4307,18 @@ Ambulance ambulance = (Ambulance)example.vehicle_factory(0);
ambulance.sound_siren();
</pre></blockquote>
the following typemaps will achieve this.
the following typemaps targeted at the <tt>vehicle_factory</tt> function will achieve this.
Note that in this case, the Java class is constructed using JNI code rather than passing a pointer across the JNI boundary in a Java long for construction in Java code.
<blockquote><pre>
%typemap(jni) Vehicle * "jobject"
%typemap(jtype) Vehicle * "Vehicle"
%typemap(jstype) Vehicle * "Vehicle"
%typemap(javaout) Vehicle * {
%typemap(jni) Vehicle *vehicle_factory "jobject"
%typemap(jtype) Vehicle *vehicle_factory "Vehicle"
%typemap(jstype) Vehicle *vehicle_factory "Vehicle"
%typemap(javaout) Vehicle *vehicle_factory {
return $jnicall;
}
%typemap(out) Vehicle * {
%typemap(out) Vehicle *vehicle_factory {
Ambulance *ambulance = dynamic_cast&lt;Ambulance *&gt;($1);
FireEngine *fireengine = dynamic_cast&lt;FireEngine *&gt;($1);
if (ambulance) {