clojure_interop.clj

#!/usr/bin/env -S jank -I/usr/lib/jvm/java-21-openjdk-amd64/include -I/usr/lib/jvm/java-21-openjdk-amd64/include/linux -L/usr/lib/jvm/java-21-openjdk-amd64/lib/server -ljvm run

(ns clojure-interop)

(cpp/raw "
#include <jni.h>

JavaVM *vm;
JNIEnv *env;

std::string jvm_clojure_eval(const std::string code) {
  if (vm == nullptr) {
    JavaVMOption options[1];
    options[0].optionString = \"-Djava.class.path=clojure-1.12.1.jar:spec.alpha-0.5.238.jar:core.specs.alpha-0.4.74.jar\";

    JavaVMInitArgs vm_args;
    vm_args.version = JNI_VERSION_21;
    vm_args.options = options;
    vm_args.nOptions = 1;
    vm_args.ignoreUnrecognized = JNI_FALSE;

    JNI_CreateJavaVM(&vm, (void **)&env, &vm_args);
  }

  jclass clojure_clazz = env->FindClass(\"clojure/java/api/Clojure\");

  jstring jstr_core = env->NewStringUTF(\"clojure.core\");
  jstring jstr_eval = env->NewStringUTF(\"eval\");
  jstring jstr_read_string = env->NewStringUTF(\"read-string\");

  jmethodID var_method = env->GetStaticMethodID(clojure_clazz, \"var\", \"(Ljava/lang/Object;Ljava/lang/Object;)Lclojure/lang/IFn;\");
  jobject eval_var = env->CallStaticObjectMethod(clojure_clazz, var_method, jstr_core, jstr_eval);
  jobject read_var = env->CallStaticObjectMethod(clojure_clazz, var_method, jstr_core, jstr_read_string);

  jclass ifn_clazz = env->FindClass(\"clojure/lang/IFn\");
  jmethodID ifn_invoke_method = env->GetMethodID(ifn_clazz, \"invoke\", \"(Ljava/lang/Object;)Ljava/lang/Object;\");

  jstring code_jstr = env->NewStringUTF(code.c_str());
  jobject invoke_read_string_result = env->CallObjectMethod(read_var, ifn_invoke_method, code_jstr);
  jobject invoke_eval_result = env->CallObjectMethod(eval_var, ifn_invoke_method, invoke_read_string_result);

  jstring jstr_pr_str = env->NewStringUTF(\"pr-str\");
  jobject ifn_pr_str_method = env->CallStaticObjectMethod(clojure_clazz, var_method, jstr_core, jstr_pr_str);
  jobject invoke_pr_str_result = env->CallObjectMethod(ifn_pr_str_method, ifn_invoke_method, invoke_eval_result);

  return std::string(env->GetStringUTFChars((jstring)invoke_pr_str_result, NULL));
}
")

(defmacro jvm-eval [& body]
  `(->>
    (pr-str (quote (do ~@body)))
    (cpp/jvm_clojure_eval )
    (read-string)))

(println "Hello from jank" (clojure-version))

(println "----")

(->>
 (jvm-eval
  '("A list" "returned from" "JVM Clojure"))
 (pr-str))

(jvm-eval
 (println "Hello from Clojure" (clojure-version))
 (println "Running on java" (System/getProperty "java.version"))
 (println "The date is" (java.util.Date/new))

 (import [javax.swing JFrame JButton])
 (let [frame  (JFrame. "Hello")
       button (JButton. "Swing in jank?")]
   (.add frame button)
   (.pack frame)
   (.setVisible frame true))

 (Thread/sleep Long/MAX_VALUE))