java 如何将 jstring 转换为 wchar_t *
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How do I convert jstring to wchar_t *
提问by gergonzalez
Let's say that on the C++ side my function takes a variable of type jstringnamed myString. I can convert it to an ANSI string as follows:
假设在 C++ 方面，我的函数采用jstring名为myString. 我可以将其转换为 ANSI 字符串，如下所示：
const char* ansiString = env->GetStringUTFChars(myString, 0);
is there a way of getting
有没有办法得到
const wchar_t* unicodeString =...
const wchar_t* unicodeString =...
回答by gergonzalez
If this helps someone... I've used this function for an Android project:
如果这对某人有帮助...我已将此功能用于 Android 项目：
std::wstring Java_To_WStr(JNIEnv *env, jstring string)
{
std::wstring value;
const jchar *raw = env->GetStringChars(string, 0);
jsize len = env->GetStringLength(string);
const jchar *temp = raw;
while (len > 0)
{
value += *(temp++);
len--;
}
env->ReleaseStringChars(string, raw);
return value;
}
An improved solution could be (Thanks for the feedback):
改进的解决方案可能是（感谢您的反馈）：
std::wstring Java_To_WStr(JNIEnv *env, jstring string)
{
std::wstring value;
const jchar *raw = env->GetStringChars(string, 0);
jsize len = env->GetStringLength(string);
value.assign(raw, raw + len);
env->ReleaseStringChars(string, raw);
return value;
}
回答by Andreas Rieder
And who frees wsz? I would recommend STL!
谁释放了 wsz？我会推荐STL！
std::wstring JavaToWSZ(JNIEnv* env, jstring string)
{
std::wstring value;
if (string == NULL) {
return value; // empty string
}
const jchar* raw = env->GetStringChars(string, NULL);
if (raw != NULL) {
jsize len = env->GetStringLength(string);
value.assign(raw, len);
env->ReleaseStringChars(string, raw);
}
return value;
}
回答by Chris Jester-Young
A portable and robust solution is to use iconv, with the understanding that you have to know what encoding your system wchar_tuses (UTF-16 on Windows, UTF-32 on many Unix systems, for example).
一个可移植且健壮的解决方案是使用iconv，并了解您必须知道您的系统wchar_t使用什么编码（例如，Windows 上的 UTF-16，许多 Unix 系统上的 UTF-32）。
If you want to minimise your dependency on third-party code, you can also hand-roll your own UTF-8 converter. This is easy if converting to UTF-32, somewhat harder with UTF-16 because you have to handle surrogate pairs too. :-P Also, you must be careful to reject non-shortestforms, or it can open up security bugs in some cases.
如果您想尽量减少对第三方代码的依赖，您还可以手动滚动您自己的 UTF-8 转换器。如果转换为 UTF-32，这很容易，而使用 UTF-16 则有点困难，因为您也必须处理代理对。:-P 此外，您必须小心拒绝非最短形式，否则在某些情况下可能会打开安全漏洞。
回答by Adam Mitz
JNI has a GetStringChars() function as well. The return type is const jchar*, jchar is 16-bit on win32 so in a way that would be compatible with wchar_t. Not sure if it's real UTF-16 or something else...
JNI 也有一个 GetStringChars() 函数。返回类型是 const jchar*，jchar 在 win32 上是 16 位的，所以在某种程度上与 wchar_t 兼容。不确定它是真正的 UTF-16 还是其他东西......
回答by Benj
I know this was asked a year ago, but I don't like the other answers so I'm going to answer anyway. Here's how we do it in our source:
我知道这是一年前问的，但我不喜欢其他答案，所以我还是要回答。以下是我们在源代码中的做法：
wchar_t * JavaToWSZ(JNIEnv* env, jstring string)
{
if (string == NULL)
return NULL;
int len = env->GetStringLength(string);
const jchar* raw = env->GetStringChars(string, NULL);
if (raw == NULL)
return NULL;
wchar_t* wsz = new wchar_t[len+1];
memcpy(wsz, raw, len*2);
wsz[len] = 0;
env->ReleaseStringChars(string, raw);
return wsz;
}
EDIT: This solution works well on platforms where wchar_t is 2 bytes, some platforms have a 4 byte wchar_t in which case this solution will not work.
编辑：此解决方案在 wchar_t 为 2 字节的平台上运行良好，某些平台具有 4 字节 wchar_t 在这种情况下此解决方案将不起作用。
回答by Benj
Just use env->GetStringChars(myString, 0); Java pass Unicode by it's nature
只需使用 env->GetStringChars(myString, 0); Java 本质上通过 Unicode
回答by 1800 INFORMATION
回答by Vladimir Ivanov
Rather simple. But do not forget to free the memory by ReleaseStringChars
相当简单。但是不要忘记通过 ReleaseStringChars 释放内存
JNIEXPORT jboolean JNICALL Java_TestClass_test(JNIEnv * env, jobject, jstring string)
{
const wchar_t * utf16 = (wchar_t *)env->GetStringChars(string, NULL);
...
env->ReleaseStringChars(string, utf16);
}
回答by shizhen wang
I try to jstring->char->wchar_t
我尝试 jstring->char->wchar_t
char* js2c(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;
}
jstring c2js(JNIEnv* env, const 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);
free(buffer);
}
return rtn;
}
jstring w2js(JNIEnv *env, wchar_t *src)
{
size_t len = wcslen(src) + 1;
size_t converted = 0;
char *dest;
dest = (char*)malloc(len * sizeof(char));
wcstombs_s(&converted, dest, len, src, _TRUNCATE);
jstring dst = c2js(env, dest);
return dst;
}
wchar_t *js2w(JNIEnv *env, jstring src) {
char *dest = js2c(env, src);
size_t len = strlen(dest) + 1;
size_t converted = 0;
wchar_t *dst;
dst = (wchar_t*)malloc(len * sizeof(wchar_t));
mbstowcs_s(&converted, dst, len, dest, _TRUNCATE);
return dst;
}
回答by Eng.Fouad
Here is how I converted jstringto LPWSTR.
这是我如何转换jstring为LPWSTR.
const char* nativeString = env->GetStringUTFChars(javaString, 0);
size_t size = strlen(nativeString) + 1;
LPWSTR lpwstr = new wchar_t[size];
size_t outSize;
mbstowcs_s(&outSize, lpwstr, size, nativeString, size - 1);
