问题描述
#include <stdio.h>
#include <jni.h>
JNIEnv* create_vm() {
JavaVM* jvm;
JNIEnv* env;
JavaVMInitArgs args;
JavaVMOption options[1];
/* There is a new JNI_VERSION_1_4, but it doesn't add anything for the purposes of our example. */
args.version = JNI_VERSION_1_2;
args.nOptions = 1;
options[0].optionString = "-Djava.class.path=/home/test/workspace/pankajs/"
"jikes/JikesRVMia32-linuxproduction/target/tests/stress/prototype/basic/classes";
args.options = options;
args.ignoreUnrecognized = JNI_FALSE;
JNI_CreateJavaVM(&jvm, (void **)&env, &args);
return env;
}
void invoke_class(JNIEnv* env) {
jclass helloWorldClass;
jmethodID mainMethod;
jobjectArray applicationArgs;
jstring applicationArg0;
helloWorldClass = (*env)->FindClass(env, "/test/org/jikesrvm/basic/core/bytecode/TestSwitch");
mainMethod = (*env)->GetStaticMethodID(env, helloWorldClass, "main", "([Ljava/lang/String;)V");
applicationArgs = (*env)->NewObjectArray(env, 1, (*env)->FindClass(env, "java/lang/String"), NULL);
applicationArg0 = (*env)->NewStringUTF(env, "From-C-program");
(*env)->SetObjectArrayElement(env, applicationArgs, 0, applicationArg0);
(*env)->CallStaticVoidMethod(env, helloWorldClass, mainMethod, applicationArgs);
}
int main(int argc, char **argv) {
JNIEnv* env = create_vm();
invoke_class( env );
}
I am trying to learn how JVM is actually invoked from bootstrap C files.
I found this example on internet and I am facing some problems while running it.
I am properly specify the build commands as far as I know as,
g++ -g -I /usr/lib/jvm/java-6-sun-1.6.0.26/include -I /usr/lib/jvm/java-6-sun-1.6.0.26/include/linux CallJVM.c
My intention is to actually run it using jikesrvm but to experiment this I choseto work with JVM.The error I am getting is :
CallJVM.c: In function ‘JNIEnv* create_vm()’:
CallJVM.c:14:4: warning: deprecated conversion from string constant to ‘char*’
CallJVM.c: In function ‘void invoke_class(JNIEnv*)’:
CallJVM.c:28:26: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
CallJVM.c:30:21: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
CallJVM.c:32:26: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
CallJVM.c:32:57: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
CallJVM.c:33:26: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
CallJVM.c:34:8: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
CallJVM.c:36:8: error: base operand of ‘->’ has non-pointer type ‘JNIEnv’
I noticed the different ways of implementing in C and C++ but I think I am writing it correctly.
Edit: On compiling with gcc ,I am getting
undefined reference to `JNI_CreateJavaVM'
and it is what was being prompted in eclipse but I thought my configurations are not apt.When I use ctrl+click
it takes me to referenced jni.h as well but still why it is missing reference ?am specifically mentioning my folders on include path.
You are using the C
variant, but are compiling with g++
, which invokes the C++
compiler (even if your source file has a .c
extension).
Either change the C
variants like
(*env)->FindClass(env, ...)
to the C++
variants, like
env->FindClass(...)
or switch your compiler to gcc
to compile the source as C
code.
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