Java与C之间通过JNI传递中文字符串
Java与C之间通过JNI传递中文字符串简介
本文提供一个具体的实例,说明Java和C之间通过JNI传递含有中文字符串的参数,解决中文乱码问题（双字节或多字节乱码）。本文给出具体的源代码，对源代码进行了解释，C部分提供了 C和C++两种方式实现的完整代码。并且所有代码均在实验环境下测试通过。本文读者须对Java和C(或C++)有一定的基础知识。
实验环境
Windows XP （或Windows2000）
j2sdk1.4.2/j2re1.4.2
Microsoft VisualC++6.0
安装好j2sdk后需要设置环境变量
CLASSPATH=.;C:\j2sdk1.4.2\bin;C:\j2sdk1.4.2\lib\dt.jar;C:\j2sdk1.4.2\lib\tools.jar;C:\j2sdk1.4.2\lib\htmlconverter.jar（j2sdk安装在c:\j2sdk1.4.2目录下）
源代码及代码说明
Java代码：
/*
* javactransfer.java
* By dpwu
* e-mail：[email]dpwu_js@sina.com.cn[/email]
*/
public class javactransfer
{
public String hypotenuse(String send_buf,String recv_buf,int errno)
{
return hypotenuse0(send_buf,recv_buf,errno);
}
private native String hypotenuse0(String send_buf,String recv_buf,int errno);
static
{
System.loadLibrary("javactransfer");//调用dll
}
public static void main( String[] args )
{
javactransfer obj= new javactransfer();
System.out.println("");
System.out.println("");
System.out.println(" begin!");
System.out.println("");
System.out.println("");
String javasend="发送中文chinese!";
System.out.println(" java send:"+"["+javasend+"]");
String javarecv=obj.hypotenuse("teststr",javasend,1);
//javasend传含有中文字符串给C
//javarecv接受C含有中的文字符串
System.out.println(" java recv:"+"["+javarecv+"]");
System.out.println("");
System.out.println("");
System.out.println(" end!");
}
}
C实现代码为：
/*
* javactransfer.c
* By dpwu
* e-mail：[email]dpwu_js@sina.com.cn[/email]
*/
#include <windows.h>
#include "javactransfer.h"//通过javah –jni javactransfer 生成
#include <stdio.h>
#include "stdlib.h"
#include "string.h"
char* jstringToWindows( JNIEnv *env, jstring jstr );
jstring WindowsTojstring( JNIEnv* env, char* str );
JNIEXPORT jstring JNICALL
Java_javactransfer_hypotenuse0(JNIEnv *env,jobject obj,jstring send_buf,jstring recv_buf,jint errno)
{
char * Buf_Return;
Buf_Return = (char*)malloc(1024);
const char * recvtest = jstringToWindows( env, recv_buf );
/*上句recvtest接收Java传过来的中文字符串正确,如果改为下句,则出现乱码:
const char * recvtest = (*env)->GetStringUTFChars( env,recv_buf,0);
*/
printf( " c recv :[%s]\n" , recvtest);
sprintf(Buf_Return,"接收中文chinese!");
printf( "\n\n\n c send :[%s]\n" , Buf_Return);
recv_buf = WindowsTojstring(env ,Buf_Return);
/*上句recv_buf传windows本地C中含有中文字符串给Java正确;如果改为下句出现乱码:
recv_buf = (*env)->NewStringUTF( env, Buf_Return );
*/
return recv_buf;
}
char* jstringToWindows( JNIEnv *env, jstring jstr )
{
int length = (*env)->GetStringLength(env,jstr );
const jchar* jcstr = (*env)->GetStringChars(env,jstr, 0 );
char* rtn = (char*)malloc( length*2+1 );
int size = 0;
size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr, length, rtn,(length*2+1), NULL, NULL );
if( size <= 0 )
return NULL;
(*env)->ReleaseStringChars(env,jstr, jcstr );
rtn[size] = 0;
return rtn;
}
jstring WindowsTojstring( JNIEnv* env, char* str )
{
jstring rtn = 0;
int slen = strlen(str);
unsigned short* buffer = 0;
if( slen == 0 )
rtn = (*env)->NewStringUTF(env,str );
else
{
int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, NULL, 0 );
buffer = malloc( length*2 + 1 );
if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, (LPWSTR)buffer, length ) >0 )
rtn = (*env)->NewString( env, (jchar*)buffer, length );
}
if( buffer )
free( buffer );
return rtn;
}
若javactransfer.java,javactransfer.c均放在d:\javac目录下
在命令操作符下执行以下几步：
javac javactransfer.java :编译java源代码;
javah –jni javactransfer :生成头文件;
cl -Ic:\j2sdk1.4.2\include -Ic:\j2sdk1.4.2\include\win32 -LD javactransfer.c -Fejavactransfer.dll
通过Microsoft Visual C++将C源代码生成dll文件，供java调用。
执行结果如下：
键入：java javactranfer 可以看到结果
C++实现代码为:
/*
* javactransfer.cpp
* By dpwu
* e-mail：[email]dpwu_js@sina.com.cn[/email]
*/
#include <windows.h>
#include "javactransfer.h"//通过javah –jni javactransfer 生成
#include <stdio.h>
#include "stdlib.h"
#include "string.h"
char* jstringToWindows( JNIEnv *env, jstring jstr );
jstring WindowsTojstring( JNIEnv* env, char* str );
JNIEXPORT jstring JNICALL
Java_javactransfer_hypotenuse0(JNIEnv *env,jobject obj,jstring send_buf,jstring recv_buf,jint _tperrno)
{
char * Buf_Return;
Buf_Return = (char*)malloc(1024);
const char * ctest = jstringToWindows( env, recv_buf );
/*
如果把上句改为下句，C接收Java字符串时将出现乱码：
const char *ctest = (env)->GetStringUTFChars( recv_buf , 0);
*/
printf( " c recv :[%s]\n" , ctest);
sprintf(Buf_Return,"接收中文chinese!");
printf( "\n\n\n c send :[%s]\n" , Buf_Return);
recv_buf = WindowsTojstring(env ,Buf_Return);
/*上句执行正确,如果把上句换成下句,Java在接收C字符串时出现乱码
recv_buf = (env)->NewStringUTF(Buf_Return);
*/
return recv_buf;
}
char* jstringToWindows( JNIEnv *env, jstring jstr )
{
int length = (env)->GetStringLength(jstr );
const jchar* jcstr = (env)->GetStringChars(jstr, 0 );
char* rtn = (char*)malloc( length*2+1 );
int size = 0;
size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr, length, rtn,(length*2+1), NULL, NULL );
if( size <= 0 )
return NULL;
(env)->ReleaseStringChars(jstr, jcstr );
rtn[size] = 0;
return rtn;
}
jstring WindowsTojstring( JNIEnv* env, char* str )
{
jstring rtn = 0;
int slen = strlen(str);
unsigned short * buffer = 0;
if( slen == 0 )
rtn = (env)->NewStringUTF(str );
else
{
int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, NULL, 0 );
buffer = (unsigned short *)malloc( length*2 + 1 );
if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, (LPWSTR)buffer, length ) >0 )
rtn = (env)->NewString( (jchar*)buffer, length );
}
if( buffer )
free( buffer );
return rtn;
}
当为C++实现时,只需要在编译时改为：
cl -Ic:\j2sdk1.4.2\include -Ic:\j2sdk1.4.2\include\win32 -LD javactransfer.cpp -Fejavactransfer.dll
回复 #1 知识型流氓 的帖子
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