I\'m writing a plugin for a program written in C++.
Plugins are placed in a specific dir and get called by the main application. I would like to write most of the pl
JNI should be pretty straightforward for this.
I would approach it this way:
You can test your uber-jar from step 2 via a simple standalone java test harness that creates the main clojure class and invokes the appropriate methods; this will let you know that you have a good java/clojure jar in case you run into any issues in the jni invocation in step 3.
As you check the jni references pay particular attention to the slight/subtle calling differences between the c and c++ jni linkages.
Good luck.
I know this question is old but maybe somebody find this useful.
#include <jni.h> /* where everything is defined */
#include <cstring>
int main() {
JavaVM *jvm; /* denotes a Java VM */
JNIEnv *env; /* pointer to native method interface */
JavaVMInitArgs vm_args; /* JDK/JRE 6 VM initialization arguments */
JavaVMOption* options = new JavaVMOption[1];
options[0].optionString = "-Djava.class.path=/home/raoof/.m2/repository/org/clojure/spec.alpha/0.1.143/spec.alpha-0.1.143.jar:/home/raoof/.m2/repository/org/clojure/clojure/1.9.0/clojure-1.9.0.jar";
vm_args.version = JNI_VERSION_1_6;
vm_args.nOptions = 1;
vm_args.options = options;
vm_args.ignoreUnrecognized = false;
/* load and initialize a Java VM, return a JNI interface
* pointer in env */
JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);
delete options;
jclass Clojure = env->FindClass("clojure/java/api/Clojure");
jmethodID var = env->GetStaticMethodID(Clojure, "var", "(Ljava/lang/Object;Ljava/lang/Object;)Lclojure/lang/IFn;");
jobject load_string = env->CallStaticObjectMethod(Clojure, var, env->NewStringUTF("clojure.core"), env->NewStringUTF("load-string"));
jmethodID load_string_invoke = env->GetMethodID(env->GetObjectClass(load_string), "invoke", "(Ljava/lang/Object;)Ljava/lang/Object;");
env->CallObjectMethod(load_string, load_string_invoke, env->NewStringUTF("(prn (+ 1 2 3 4 5))"));
jvm->DestroyJavaVM();
}
and then
g++ -I/usr/lib/jvm/java-8-openjdk-amd64/include -I/usr/lib/jvm/java-8-openjdk-amd64/include/linux/ -L/usr/lib/jvm/java-8-openjdk-amd64/jre/lib/amd64/server -ljvm clojurejvm.cpp
LD_LIBRARY_PATH=/usr/lib/jvm/java-8-openjdk-amd64/jre/lib/amd64/server ./a.out