JNI小结

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#define _Included_LittleLov_SimpleDLL
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: LittleLov_SimpleDLL
* Method: messageRecv
* Signature: ()Ljava/lang/String;
* (7)编写测试JAVA类文件，详见本文 SampleLov.java 注：文件在LittleLov的上级目录
* (8)切换到命令窗口，跳到LittleLov的父目录，然后键入：javac SampleLov
* (9)执行JNI的测试，切换到命令窗口，键入：java SampleLov 即可以看到输出结果
* (3)通过javah命令把.class二进制文件生成C|C++的.H头文件，具体还是在此目录下，键入命令：javah SimpleDLL
* (4)打开JAVAH命令生成的C头文件：LittleLov_SimpleDLL.h，然后把 #include <jni.h> 改为 #include "jni.h"
}
JNIEXPORT jstring JNICALL Java_LittleLov_SimpleDLL_messageRecv(JNIEnv *env, jclass jclazz)
{
char *cp;
char s[] = "广州市天河区";
cp = s;
jclass jTmp = (env)->FindClass("Ljava/lang/String;");
jint len = (*env)->GetArrayLength(env,bytes);
result = (char *)malloc(len + 1);
(*env)->GetByteArrayRegion(env,bytes,0,len,(jbyte *)result); //return type(void)
}
// LittleLov_SimpleDLL.h
/* DO NOT EDIT THIS FILE - it is machine generated */
#include "jni.h"
/* Header for class LittleLov_SimpleDLL */
#ifndef _Included_LittleLov_SimpleDLL
{
System.out.println("调试现在开始...");
String sRet = SimpleDLL.messageRecv();
System.out.println("返回结果是：" + sRet);
}
}
// LittelLov.cpp : Defines the entry point for the console application.
(*env)->GetStringUTFRegion(env, prompt, 0, len, outbuf);
printf("%s", outbuf);
scanf("%s", inbuf);
return (*env)->NewStringUTF(env, inbuf);
}
Arrays are represented by the jarray reference type and its "subtypes" such as
*/
JNIEXPORT jstring JNICALL Java_LittleLov_SimpleDLL_messageRecv
(JNIEnv *, jclass);
#ifdef __cplusplus
}
#endif
#endif
--------------------------------------------------------------------------------------------------------------------
Java_IntArray_sumArray(JNIEnv *env, jobject obj, jintArray arr)
{
int i, sum = 0;
for (i = 0; i < 10; i++)
{
sum += arr[i];
}
}
You must instead use the proper JNI functions to access primitive array elements,
* (5)编写本地业务，详见本文 LittleLov.cpp
* (6)生成DLL连接库，具体步骤为：
* (a)打开Visual C++，选择“文件” - “新建” - “工程” - “Win32Dynamic-Link Library”
* (b)在工程名称那里键入“Sample”，确定进入下一步
* (f)右单击”Source Files“，然后选择”添加文件到目录“，把LittleLov.cpp导进来
* (g)右单击”Source Header“，然后选择”添加文件到目录“，把jni.h、jni_md.h、LittleLov_SimpleDLL.h导进来
* (h)选择菜单项”组建“，然后，点击”组建生成Sample.dll“，完成连接库的创建过程
//
#include "stdafx.h"
#include "string.h"
#include "LittleLov_SimpleDLL.h"
int main(int argc, char* argv[])
{
printf("Hello World!\n");
return 0;
as shown in the following corrected example:
JNIEXPORT jint JNICALL
Java_IntArray_sumArray(JNIEnv *env, jobject obj, jintArray arr)
{
jint buf[10];
jint i, sum = 0;
}
public native static String messageRecv();
}
// LittleLov.cpp
// SampleLov.java
import LittleLov.SimpleDLL;
public class SampleLov
{
public static void main(String[] arg)
// 获取java String类方法String(byte[],String)的构造器,用于将本地
// byte[]数组转换为一个新String
jmethodID methodID = (env)->GetMethodID(jTmp, "<init>", "([BLjava/lang/String;)V");
// 设置String, 保存语言类型,用于byte数组转换至String时的参数
jstring encoding = (env)->NewStringUTF("GB2312");
// 将byte数组转换为java String,并输出
return (jstring)(env)->NewObject(jTmp, ctorID, bytes, encoding);
JNI小结
/**
* created on 2008-09-03
*
* Note: <p>
* JAVA调用JNI有特定的顺序和步骤，下面就此问题简单做个总结：
* (1)编写JAVA类文件，详见本文 SimpleDLL.java 注：文件建在LittleLov目录下
* (2)编译 SimpleDLL.java 文件，从命令行转到LittleLov目录下，然后键入命令：javac SimpleDLL.java
* (c)选择”一个空的DLL工程“，点击进入下一步，确认完成
* (d)在视图窗口中，选择”文件视图，即FileView“可以看到Sample files
* (e)展开该文件视图，然后可以看到Source Files、Header Files、Resource Files
{ ห้องสมุดไป่ตู้
/* assume the prompt string and user input has
*less than 128 characters
*/
char outbuf[128], inbuf[128];
int len = (*env)->GetStringLength(env, prompt);
jintArray. Just as jstring is not a C string type, neither is jarray a C array
type. You cannot implement the Java_IntArray_sumArray native method by