1

我有一个文件写如下：

package JNI;

public class Natives {

    public static final int PAGE_READONLY = 0x02;
    public static final int PAGE_READWRITE = 0x04;
    public static final int PAGE_WRITECOPY = 0x08;
    public static final int FILE_MAP_COPY = 0x0001;
    public static final int FILE_MAP_WRITE = 0x0002;
    public static final int FILE_MAP_READ = 0x0004;

    public static native long createFileMapping(long hFile, int lpAttributes, int dwMaximumSizeHigh, int dwMaximumSizeLow, String lpName);

    public static native long openFileMapping(int dwDesiredAccess, boolean bInheritHandle, String lpName);

    public static native long mapViewOfFile(long hFileMap, int dwDesiredAccess, int dwFileOffsetHigh, int dwFileOffsetLow, int dwNumberOfBytesToMap);

    public static native long unmapViewOfFile(long hFileMap);

    public static native long closeHandle(long hFile);
}

然后我使用 javah 生成 jni 文件：

extern "C" JNIEXPORT jlong JNICALL Java_JNI_Natives_createFileMapping(JNIEnv *env, jclass, jlong hFile, jint lpProtect, jint dwMaximumSizeHigh, jint dwMaximumSizeLow, jstring lpName)
{
    HANDLE hFileMap = nullptr;
    LPCSTR Name = env->GetStringUTFChars(lpName, nullptr);

    if ((hFileMap = CreateFileMapping(hFile == -1 ? INVALID_HANDLE_VALUE : reinterpret_cast<HANDLE>(hFile), nullptr, lpProtect, dwMaximumSizeHigh, dwMaximumSizeLow, Name)) != nullptr)
    {
        if (errno ==  ERROR_ALREADY_EXISTS)
        {
            CloseHandle(hFileMap);
        }
    }

    env->ReleaseStringUTFChars(lpName, Name);
    return reinterpret_cast<jlong>(hFileMap);
}

extern "C" JNIEXPORT jlong JNICALL Java_JNI_Natives_openFileMapping(JNIEnv *env, jclass, jint dwDesiredAccess, jboolean bInheritHandle, jstring lpName)
{
    LPCSTR Name = env->GetStringUTFChars(lpName, nullptr);
    HANDLE hFileMap = OpenFileMapping(dwDesiredAccess, static_cast<bool>(bInheritHandle), Name);
    env->ReleaseStringUTFChars(lpName, Name);
    return reinterpret_cast<jlong>(hFileMap);
}

extern "C" JNIEXPORT jlong JNICALL Java_JNI_Natives_mapViewOfFile(JNIEnv *, jclass, jlong hFileMap, jint dwDesiredAccess, jint dwFileOffsetHigh, jint dwFileOffsetLow, jint dwNumberOfBytesToMap)
{
    void* pData = MapViewOfFile(reinterpret_cast<HANDLE>(hFileMap), dwDesiredAccess, dwFileOffsetHigh, dwFileOffsetLow, dwNumberOfBytesToMap);
    return reinterpret_cast<jlong>(pData);
}

extern "C" JNIEXPORT jlong JNICALL Java_JNI_Natives_unmapViewOfFile(JNIEnv *, jclass, jlong hFileMap)
{
    return reinterpret_cast<jboolean>(static_cast<uint8_t>(UnmapViewOfFile(reinterpret_cast<void*>(hFileMap))));
}

extern "C" JNIEXPORT jlong JNICALL Java_JNI_Natives_closeHandle(JNIEnv *, jclass, jlong hFile)
{
    return reinterpret_cast<jboolean>(static_cast<uint8_t>(CloseHandle(reinterpret_cast<HANDLE>(hFile))));
}

但是一旦 DLL 加载，我就会调用这样的函数：

长句柄 = Natives.createFileMapping(-1, Natives.FILE_MAP_READ | Natives.FILE_MAP_WRITE, 500, 0, "NativeDLL"); 调试（句柄）；

它打印：

跑：

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x0000000061288f69, pid=4692, tid=844
#
# JRE version: 7.0_21-b11
# Java VM: Java HotSpot(TM) 64-Bit Server VM (23.21-b01 mixed mode windows-amd64 compressed oops)
# Problematic frame:
# V  [jvm.dll+0x38f69]
#
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
#
# An error report file with more information is saved as:
# C:\Users\Brandon\Documents\NetBeansProjects\Smart\hs_err_pid4692.log
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.sun.com/bugreport/crash.jsp
#
Java Result: 1

任何想法我做错了什么？

4

2 回答 2

1

可能是权限问题。

您可以考虑使用Java Native Access/JNA，它比您单独实现的原生平台 API 的实现更加可靠和可靠（当然取决于经验）。它被 Netbeans IDE 等使用。

具体参见包含这些方法的com.sun.jna.platform.win32 Kernel32 接口。

于 2013-05-10T15:24:20.453 回答
1

我建议您使用 Unicode 支持编码和构建您的 JNI DLL，并用于GetStringChars创建 UTF-16 字符串以传递给CreateFileMapping. 没有任何版本CreateFileMapping采用GetStringUTFChars. 如果您必须使用 ANSI 版本，则在调用CreateFileMapping.

IMO，GetStringUTFChars应该命名为GetStringUTF8Chars.

不要忘记GetStringChars配对ReleaseStringChars。

于 2013-05-10T15:55:00.163 回答