jstring, String, char* 变换函数【转】

最新推荐文章于 2025-03-22 01:53:56 发布

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本文介绍如何在Java和C++中互相转换字符串。通过JNI接口实现Java字符串(jstring)到C++字符串(char*)及std::string的转换，同时也展示了从C++字符串到Java字符串(jstring)的转换方法。

#include <malloc.h>
#include <string.h>
#include <stdlib.h>
#include <vcclr.h>

using namespace System;
using namespace System::Text;

// jstring To String
String^ jstringToStr(JNIEnv* env, jstring jstr)
{
    char* str = jstringTostring(env, jstr);
    String^ value = gcnew String(str);
    free(str);
    return value;
}

// jstring To char*
char* jstringTostring(JNIEnv* env, jstring jstr)
{
    char* rtn = NULL;
    jclass clsstring = env->FindClass("java/lang/String");
    jstring strencode = env->NewStringUTF("utf-8");
    jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");
    jbyteArray barr = (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);
    jsize alen = env->GetArrayLength(barr);
    jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);
    if (alen > 0)
    {
        rtn = (char*)malloc(alen + 1);
        memcpy(rtn, ba, alen);
        rtn[alen] = 0;
    }
    env->ReleaseByteArrayElements(barr, ba, 0);
    return rtn;
}

// String To jstring
jstring strTojstring(JNIEnv* env, String^ rtn)
{
    pin_ptr<const wchar_t> wch = PtrToStringChars(rtn);
    size_t convertedChars = 0;
    size_t sizeInBytes = ((rtn->Length + 1) * 2);
    char *ch = (char *)malloc(sizeInBytes);
    errno_t err = wcstombs_s(&convertedChars,
        ch, sizeInBytes,
        wch, sizeInBytes);
    jstring js = stringTojstring(env, ch);
    free(ch);
    return js;
}

// char* To jstring
jstring stringTojstring(JNIEnv* env, const char* pat)
{
    jclass strClass = env->FindClass("Ljava/lang/String;");
    jmethodID ctorID = env->GetMethodID(strClass, "<init>", "([BLjava/lang/String;)V");
    jbyteArray bytes = env->NewByteArray(strlen(pat));
    env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);
    jstring encoding = env->NewStringUTF("utf-8");
    return (jstring)env->NewObject(strClass, ctorID, bytes, encoding);
}

 
std::string jstring2str(JNIEnv* env, jstring jstr)
{   

    char*   rtn   =   NULL;   

    jclass   clsstring   =   env->FindClass("java/lang/String");   

    jstring   strencode   =   env->NewStringUTF("GB2312");   

    jmethodID   mid   =   env->GetMethodID(clsstring,   "getBytes",   "(Ljava/lang/String;)[B");   

    jbyteArray   barr=   (jbyteArray)env->CallObjectMethod(jstr,mid,strencode);   

    jsize   alen   =   env->GetArrayLength(barr);   

    jbyte*   ba   =   env->GetByteArrayElements(barr,JNI_FALSE);   

    if(alen   >   0)   

    {   

        rtn   =   (char*)malloc(alen+1);         

        memcpy(rtn,ba,alen);   

        rtn[alen]=0;   

    }   

    env->ReleaseByteArrayElements(barr,ba,0);   

    std::string stemp(rtn);

    free(rtn);

    return   stemp;   
}