2、Java调用C语言（JNative法）
这个方法也是挺麻烦的……
一、下载JNative.jar，把它放在你jdk下的\jre\lib\ext目录下
二、在 F:\MinGW\JNative 新建 Test.java：
public class Test {
public static void main(String[] args) throws NativeException, IllegalAccessException {
// 例1
JNative n1 = new JNative("test.dll", "add");
n1.setRetVal(Type.INT);
n1.setParameter(0, 11); //C语言add函数的第一个参数是11
n1.setParameter(1, 9); //C语言add函数的第二个参数是9
n1.invoke(); //执行
int re1 = Integer.parseInt(n1.getRetVal()); //获取返回结果
System.out.println("例1：addresult = "+re1);
// 例2
JNative n2= new JNative("test.dll", "addArray");
int len=3;
//定义一个int指针p1，一个int占4个字节，(4 * len)可以理解成有len个int。若是double则(8 * len)，以此类推
Pointer p1 = new Pointer(MemoryBlockFactory.createMemoryBlock(4 * len));
Pointer p2 = new Pointer(MemoryBlockFactory.createMemoryBlock(4 * len));
Pointer p3 = new Pointer(MemoryBlockFactory.createMemoryBlock(4 * len));
p1.setIntAt(0, 11);p1.setIntAt(4, 18);p1.setIntAt(8, 21);
p2.setIntAt(0, 44);p2.setIntAt(4, 56);p2.setIntAt(8, 100);
n2.setRetVal(Type.VOID);
n2.setParameter(0, p1);
n2.setParameter(1, p2);
n2.setParameter(2, p3);
n2.setParameter(3, len);
n2.invoke();
for (int i = 0; i < len; i++) {
System.out.println("例2：addArray"+(i+1)+" = "+p3.getAsInt(i*4));
}
p1.dispose();
p2.dispose();
p3.dispose();
// 例3
JNative n3 = new JNative("test.dll", "stringFun");
n3.setRetVal(Type.STRING);
String inputString = "kun";
String outputString = "";
Pointer p4 = Pointer.createPointerFromString(inputString);
Pointer p5 = Pointer.createPointerFromString(outputString);
n3.setParameter(0, p4);
n3.setParameter(1, p5);
n3.invoke();
System.out.println("例3：outputString = "+n3.getRetVal()); p4.dispose(); p5.dispose();
}
}
三、再新建一个 test.c：
#include <stdio.h>
#include <malloc.h>
int add(int a, int b) {
return (a + b);
}
void addArray(int *a,int *b,int *c,int len) {
int i;
for(i=0;i<len;i++) {
c[i]=a[i]+b[i];
}
}
char* stringFun(char *str1,char *str2) {
printf("例3：intputString = %s\n",str1);
str2 = (char*)malloc(sizeof(char)*17);
str2 = "HG-U133_Plus_2.0";
return str2;
}
四、生成dll：
方法一：如果安装了MinGW
f: cd MinGW/JNative
gcc -Wall -shared test.c -o test.dll
javac Test.java
java Test
这时目录下新生成了JNativeCpp.dll、test.dll、Test.class
方法二：如果安装了Rtools（注意：我是Win7系统）
f: cd MinGW/JNative
R CMD SHLIB test.c
javac Test.java
java Test
这时目录下新生成了JNativeCpp.dll、test.dll、test.o、Test.class
结果：
