java调用c++函数的简单笔记

java使用jni调用c++动态库函数.

步骤：

１．编写java测试代码如下：

 1 public class CallNativeDemo {
 2     native void func();
 3 
 4     native double add(double a, double b);
 5 
 6     public static void main(String[] args) {
 7         System.loadLibrary("Main");
 8         CallNativeDemo callNativeDemo = new CallNativeDemo();
 9         callNativeDemo.func();
10         System.out.println(callNativeDemo.add(1,2));
11     }
12 }

2. 使用javac　对代码进行编译：

javac CallNativeDemo.java

3.使用javah　生成CallNativeDemo.h头文件.

javah -cp . CallNativeDemo

生成的代码如下：

 1 /* DO NOT EDIT THIS FILE - it is machine generated */
 2 #include <jni.h>
 3 /* Header for class CallNativeDemo */
 4 
 5 #ifndef _Included_CallNativeDemo
 6 #define _Included_CallNativeDemo
 7 #ifdef __cplusplus
 8 extern "C" {
 9 #endif
10 /*
11  * Class:     CallNativeDemo
12  * Method:    func
13  * Signature: ()V
14  */
15 JNIEXPORT void JNICALL Java_CallNativeDemo_func
16   (JNIEnv *, jobject);
17 
18 /*
19  * Class:     CallNativeDemo
20  * Method:    add
21  * Signature: (DD)D
22  */
23 JNIEXPORT jdouble JNICALL Java_CallNativeDemo_add
24   (JNIEnv *, jobject, jdouble, jdouble);
25 
26 #ifdef __cplusplus
27 }
28 #endif
29 #endif

View Code

1 #include <jni.h> 2 #include <stdio.h> 3 /* 4 * Class: CallNativeDemo 5 * Method: func 6 * Signature: ()V 7 */ 8 extern "C"{ 9 JNIEXPORT void JNICALL Java_CallNativeDemo_func 10 (JNIEnv *env, jobject job){ 11 printf("hello world! by java and C++ "); 12 } 13 14 /* 15 * Class: CallNativeDemo 16 * Method: add 17 * Signature: (II)V 18 */ 19 JNIEXPORT jdouble JNICALL Java_CallNativeDemo_add 20 (JNIEnv *env, jobject job, jdouble a, jdouble b){ 21 22 return a+b; 23 } 24 }

1 #makefile 2 3 .SUFFIXES: .o.cpp 4 .PHONY: clean 5 .PHONY: start 6 7 8 JDKLIB =/home/gongxijun/java/jdk1.7.0_40/include 9 CC =g++ 10 SRC =Main.cpp 11 OBJS =$(SRC:.cpp =.o) 12 OS = libMain.so 13 14 .PHONY: start 15 start: $(OBJS) 16 $(CC) -shared -fpic -I $(JDKLIB) -I $(JDKLIB)/linux -o $(OS) $(OBJS) 17 .o.cpp:$(SRC) 18 $(CC) -g -Wall $@ -c $< 19 .PHONY: clean 20 clean: 21 rm -f $(OBJS)

java调用c++函数的简单笔记

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