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Merge branch 'jder-java-doc-fix'

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* jder-java-doc-fix:
  Improvements to Java Memory Management docs
  Avoid possible GC issues in Java example code
This commit is contained in:
William S Fulton 2017-09-19 20:36:19 +01:00
commit bde40302bf
1 changed files with 26 additions and 14 deletions
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Doc/Manual/Java.html
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@ -8165,40 +8165,52 @@ public class Container {
// Ensure that the GC doesn't collect any Element set from Java
// as the underlying C++ class stores a shallow copy
private Element elementReference;
private long getCPtrAndAddReference(Element element) {
elementReference = element;
return Element.getCPtr(element);
}
public void setElement(Element e) {
exampleJNI.Container_setElement(swigCPtr, this, getCPtrAndAddReference(e), e);
exampleJNI.Container_setElement(swigCPtr, this, Element.getCPtr(e), e);
elementReference = e;
}
}
</pre>
</div>
<p>
The following typemaps will generate the desired code.
The 'javain' typemap matches the input parameter type for the <tt>setElement</tt> method.
The 'javacode' typemap simply adds in the specified code into the Java proxy class.
The following typemaps can be used to generate this code:
</p>
<div class="code">
<pre>
%typemap(javain) Element *e "getCPtrAndAddReference($javainput)"
%typemap(javacode) Container %{
// Ensure that the GC doesn't collect any element set from Java
// as the underlying C++ class stores a shallow copy
private Element elementReference;
private long getCPtrAndAddReference(Element element) {
elementReference = element;
return Element.getCPtr(element);
}
%}
%typemap(javain,
post=" elementReference = $javainput;"
) Element *e "Element.getCPtr($javainput)"
</pre>
</div>
<p>
The 'javacode' typemap simply adds in the specified code into the Java proxy class.
The 'javain' typemap matches the input parameter type and name for the <tt>setElement</tt> method and
the 'post' typemap attribute allows adding code after the JNI call.
The 'post' code is generated into a finally block after the JNI call so the resulting code isn't quite
as mentioned earlier, <tt>setElement</tt> is actually:
</p>
<div class="code">
<pre>
public void setElement(Element e) {
try {
exampleJNI.Container_setElement(swigCPtr, this, Element.getCPtr(e), e);
} finally {
elementReference = e;
}
}
</pre>
</div>
<H3><a name="Java_date_marshalling">25.10.13 Date marshalling using the javain typemap and associated attributes</a></H3>