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This article introduces how to embed JAVA in C++. The content is very detailed. Interested friends can use it for reference. I hope it will be helpful to you.

I. parameters for starting a virtual machine

Two basic parameters are required:

The path to the JNI dynamic library is set through java.library.path.

The program jar file is set through java.class.path.

Static string toClassPath (const string& program) {return string ("- Djava.class.path=") + program;}... jvmopt [0] .optionString = (char*) "- Djava.library.path=./lib"; jvmopt [1] .optionString = (char*) classPath.c_str () II. Call the main function

Here I need to pass the width and height parameters to the java program through the main function.

Static jobjectArray prepareProgramArgs (JNIEnv* env, const char* w, const char* h) {jobjectArray ret= (jobjectArray) env- > NewObjectArray (2, env- > FindClass ("java/lang/String"), env- > NewStringUTF (""); env- > SetObjectArrayElement (ret,0, env- > NewStringUTF (w)); env- > SetObjectArrayElement (ret,1, env- > NewStringUTF (h)); return ret;}. JmethodID methodId = env- > GetStaticMethodID (jcls, "main", "([Ljava/lang/String;) V"); if (methodId! = NULL) {jobjectArray args = prepareProgramArgs (env, w, h); env- > CallStaticVoidMethod (jcls, methodId, args); if (env- > ExceptionCheck ()) {env- > ExceptionDescribe (); env- > ExceptionClear ();}} III, complete code # include # include # include using namespace std Static string toClassName (const string& program) {string className; size_t start = program.find_last_of ('/'); size_t end = program.find_last_of ('.'); if (start = = std::string::npos) {start = program.find_last_of ('\'); if (start = = std::string::npos) {start =-1;}} className = program.substr (start+1, end-start-1) Return className;} static string toClassPath (const string& program) {return string ("- Djava.class.path=") + program;} static jobjectArray prepareProgramArgs (JNIEnv* env, const char* w, const char* h) {jobjectArray ret= (jobjectArray) env- > NewObjectArray (2, env- > FindClass ("java/lang/String"), env- > NewStringUTF ("")); env- > SetObjectArrayElement (ret,0, env- > NewStringUTF (w)) Env- > SetObjectArrayElement (ret,1, env- > NewStringUTF (h)); return ret;} int main (int argc, char** argv) {JavaVM* javaVM; JNIEnv* jniEnv; string program; string classPath; string className; const char* w = "320"; const char* h = "480"; JavaVMInitArgs vmArgs; JavaVMOption jvmopt [2]; if (argc)

2) {w = argv [2];} if (argc > 3) {h = argv [3];} program = argv [1]; className = toClassName (program); classPath = toClassPath (program); jvmopt [0] .optionString = (char*) "- Djava.library.path=./lib"; jvmopt [1] .optionString = (char*) classPath.c_str (); vmArgs.options = jvmopt; vmArgs.version = JNI_VERSION_1_8 VmArgs.ignoreUnrecognized = JNI_TRUE; vmArgs.nOptions = sizeof (jvmopt) / sizeof (jvmopt [0]); long flag = JNI_CreateJavaVM (& javaVM, (void**) & jniEnv, & vmArgs); if (flag = = JNI_ERR) {cout FindClass (className.c_str ()); if (jcls = = NULL) {jniEnv- > ExceptionDescribe (); javaVM- > DestroyJavaVM (); return 1 } if (jcls! = NULL) {jmethodID methodId = env- > GetStaticMethodID (jcls, "main", "([Ljava/lang/String;) V"); if (methodId! = NULL) {jobjectArray args = prepareProgramArgs (env, w, h); env- > CallStaticVoidMethod (jcls, methodId, args); if (env- > ExceptionCheck ()) {env- > ExceptionDescribe (); env- > ExceptionClear ();}} else {cout

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