Function OutputEventHandler

Core/ClientSMLSWIG/Java/JavaCallbackByHand.h:707–805

This is the C++ handler which will be called by clientSML when the event fires. Then from here we need to call back to Java to pass back the message.

// This is the C++ handler which will be called by clientSML when the event fires.
// Then from here we need to call back to Java to pass back the message.
static void OutputEventHandler(void* pUserData, sml::Agent* pAgent, char const* pAttributeName, sml::WMElement* pWmeAdded)
{
    // The user data is the class we declared above, where we store the Java data to use in the callback.
    JavaCallbackData* pJavaData = (JavaCallbackData*)pUserData ;
    
    // Now try to call back to Java
    JNIEnv* jenv = pJavaData->GetEnv() ;
    
    // We start from the Java object whose method we wish to call.
    jobject jobj = pJavaData->m_HandlerObject ;
    jclass cls = jenv->GetObjectClass(jobj) ;
    
    if (cls == 0)
    {
        printf("Failed to get Java class\n") ;
        return ;
    }
    
    // Look up the Java method we want to call.
    // The method name is passed in by the user (and needs to match exactly, including case).
    // The method should be owned by the m_HandlerObject that the user also passed in.
    // Any slip here and you get a NoSuchMethod exception and my Java VM shuts down.
    // Method sig here is:
    // Object userData, String agentName, String attributeName, WMElement* wmeAdded
    jmethodID mid = jenv->GetMethodID(cls, pJavaData->m_HandlerMethod.c_str(), "(Ljava/lang/Object;Ljava/lang/String;Ljava/lang/String;Lsml/WMElement;)V") ;
    
    if (mid == 0)
    {
        printf("Failed to get Java method\n") ;
        return ;
    }
    
    // Convert our C++ strings to Java strings
    jstring agentName = pAgent != NULL ? jenv->NewStringUTF(pAgent->GetAgentName()) : 0 ;
    jstring attributeName = pAttributeName != NULL ? jenv->NewStringUTF(pAttributeName) : 0 ;
    
    // Wrap our C++ WMElement object with a SWIG sml/WMElement Java object so we can
    // pass it back to Java.
    // OK, time to roll up our JNI sleeves and get dirty.  We need to create a new Java object.
    // Step one is getting the constructor for that class: <init> as the method name and void (V)
    char const* kClassName = "sml/WMElement" ;
    jclass jsmlClass = jenv->FindClass(kClassName) ;
    
    if (!jsmlClass)
    {
        // Cleaning up the local references just in case
        jenv->DeleteLocalRef(agentName);
        jenv->DeleteLocalRef(attributeName);
        return ;
    }
    
    // We want to grab the SWIG constructor which in Java is:
    //  protected WMElement(long cPtr, boolean cMemoryOwn) {
    //    swigCMemOwn = cMemoryOwn;
    //    swigCPtr = cPtr;
    //  }
    // J == long, Z == boolean so looking for constructor (long, boolean)
    jmethodID cons = jenv->GetMethodID(jsmlClass, "<init>", "(JZ)V") ;