Java Jni Test

Java JNI Test

1. HelloWorld

가.  Java

        Test.java

public class Test {                  public Test(){                          }         static{                 System.loadLibrary("JniTest");         }         public native static void getTest();                  public static void main(String[] args){                         Test test = new Test();                         test.getTest();         } }

        

나. C++

        Test.cpp

#include <jni.h> #include "Test.h" #include <iostream> /*  * Class:     Test  * Method:    getTest  * Signature: ()V  */ JNIEXPORT void JNICALL Java_Test_getTest  (JNIEnv *, jclass jobj){           std::cout<<"Hello"<<std::endl; }

다.  순서

1) javah -jni Test (Test.h 헤더 파일 생성)

2) g++ -c -fPIC -I$JAVA_HOME/include -I$JAVA_HOME/include/linux Test.cpp (Object 생성)

3) g++ -shared -o libJniTest.so Test.o (Dll/SO 파일 생성)

4) java -Djava.library.path=. Test (실행)

2. C++ String 값 받아오기

가.  Java

        com.jni.test,JniTest.java

package com.jni.test;   public class JniTest {                  static{                 System.loadLibrary("JniStringTest");         }         public JniTest(){                 String msg= getMessage();                 System.out.println(msg);         }         public native static String getMessage();                  public static void main(String[] args){                 new JniTest();         } }

        

나. C++

        Test.cpp

#include <jni.h> #include <stdlib.h> #include "com_jni_test_JniTest.h" /* Class:     com_jni_test_JniTest  * Method:    getMessage  * Signature: ()Ljava/lang/String;  */ JNIEXPORT jstring JNICALL Java_com_jni_test_JniTest_getMessage(JNIEnv * env, jclass jobj){         jstring msg;         msg = env->NewStringUTF("hhhh");         return msg; }

다.  순서

1) javah -jni com.jni.test.JniTest

2) g++ -c -fPIC -I$JAVA_HOME/include -I$JAVA_HOME/include/linux com_jni_test_JniTest.cpp

3) g++ -shared -o libJniStringTest.so com_jni_test_JniTest.o

4) java -Djava.library.path=. com.jni.test.JniTest (실행)

3. C++ String 값 넘기기

가.  Java

        com.jni.test,JniReturnTest.java

package com.jni.test;   public class JniReturnTest {           static{                 System.loadLibrary("jniReturnTest");         }         public static native String getMassageDiff(String msg);         public static void main(String[] args){                 String msg = JniReturnTest.getMassageDiff("donghun");                 System.out.println(msg);         } }

        

나. C++

        com_jni_test_jniReturnTest.cpp

#include <jni.h> #include <stdlib.h> #include "com_jni_test_JniReturnTest.h" JNIEXPORT jstring JNICALL Java_com_jni_test_JniReturnTest_getMassageDiff (JNIEnv * env, jclass jobj,jstring jstr1) {         char temp[256] = {0};         jstring msg;         char* param=(char*)env->GetStringUTFChars(jstr1,0);         sprintf(temp,"%s hun",param);         msg = env->NewStringUTF(temp);         free(param);         return msg; }

다.  순서

1) javah -jni com.jni.test.JniTest

2) g++ -c -fPIC -I$JAVA_HOME/include -I$JAVA_HOME/include/linux com_jni_test_JniTest.cpp

3) g++ -shared -o libJniReturnTest.so com_jni_test_jniReturnTest.cpp.o

4) java -Djava.library.path=. com.jni.test.JniReturnTest (실행)