从 Java 调用 Windows 内核函数的最简单方法是什么？

发布于 2024-07-23 15:29:04 字数 637 浏览 5 评论 0 原文

在寻找如何做到这一点时，我发现了一些关于不同选项的模糊讨论，例如 JNI 与 JNA，但具体示例并不多。

上下文：如果 Java 的 File.renameTo() 无法完成其工作（无论出于何种原因；这有点问题），我想直接使用这个本机 Windows 函数，该函数在 kernel32.dll 中定义（来自这个答案）：

BOOL WINAPI MoveFile(
  __in  LPCTSTR lpExistingFileName,
  __in  LPCTSTR lpNewFileName
);

那么，无论使用什么方法，您将如何从 Java 代码中调用该函数？我正在寻找最简单的方法，使用最少量的非Java 代码或额外步骤（例如在编译或部署中）。

原文

While searching for how to do this, I found some vague discussion about different options, like JNI vs JNA, but not much in the way of concrete examples.

Context: if Java's File.renameTo() cannot do it's job (for whatever reason; it is a little problematic), I'd like to fall back to directly using this native Windows function, which is defined in kernel32.dll (from this answer):

BOOL WINAPI MoveFile(
  __in  LPCTSTR lpExistingFileName,
  __in  LPCTSTR lpNewFileName
);

So, using whatever approach, how exactly would you call that function from within Java code? I'm looking for the simplest way, with the minimum amount of non-Java code or extra steps (e.g. in compilation or deployment).

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独自←快乐 2024-07-30 15:29:04

如果您使用 JNA，请考虑直接调用 MoveFileW - 无需提供配置信息即可在 Unicode 和 ANSI 调用之间进行选择。

import java.io.*;
import com.sun.jna.*;

public class Ren {

  static interface Kernel32 extends Library {
    public static Kernel32 INSTANCE = (Kernel32) Native
        .loadLibrary("Kernel32", Kernel32.class);

    public static int FORMAT_MESSAGE_FROM_SYSTEM = 4096;
    public static int FORMAT_MESSAGE_IGNORE_INSERTS = 512;

    public boolean MoveFileW(WString lpExistingFileName,
        WString lpNewFileName);

    public int GetLastError();

    public int FormatMessageW(int dwFlags,
        Pointer lpSource, int dwMessageId,
        int dwLanguageId, char[] lpBuffer, int nSize,
        Pointer Arguments);
  }

  public static String getLastError() {
    int dwMessageId = Kernel32.INSTANCE.GetLastError();
    char[] lpBuffer = new char[1024];
    int lenW = Kernel32.INSTANCE.FormatMessageW(
        Kernel32.FORMAT_MESSAGE_FROM_SYSTEM
            | Kernel32.FORMAT_MESSAGE_IGNORE_INSERTS, null,
        dwMessageId, 0, lpBuffer, lpBuffer.length, null);
    return new String(lpBuffer, 0, lenW);
  }

  public static void main(String[] args) throws IOException {
    String from = ".\\from.txt";
    String to = ".\\to.txt";
    new FileOutputStream(from).close();
    if (!Kernel32.INSTANCE.MoveFileW(new WString(from),
        new WString(to))) {
      throw new IOException(getLastError());
    }
  }
}

编辑：我在检查代码后编辑了我的答案 - 我在签名中使用 char[] 是错误的 - 最好使用 WString。

If you go with JNA, consider invoking MoveFileW directly - it saves having to provide configuration info to choose between Unicode and ANSI calls.

import java.io.*;
import com.sun.jna.*;

public class Ren {

  static interface Kernel32 extends Library {
    public static Kernel32 INSTANCE = (Kernel32) Native
        .loadLibrary("Kernel32", Kernel32.class);

    public static int FORMAT_MESSAGE_FROM_SYSTEM = 4096;
    public static int FORMAT_MESSAGE_IGNORE_INSERTS = 512;

    public boolean MoveFileW(WString lpExistingFileName,
        WString lpNewFileName);

    public int GetLastError();

    public int FormatMessageW(int dwFlags,
        Pointer lpSource, int dwMessageId,
        int dwLanguageId, char[] lpBuffer, int nSize,
        Pointer Arguments);
  }

  public static String getLastError() {
    int dwMessageId = Kernel32.INSTANCE.GetLastError();
    char[] lpBuffer = new char[1024];
    int lenW = Kernel32.INSTANCE.FormatMessageW(
        Kernel32.FORMAT_MESSAGE_FROM_SYSTEM
            | Kernel32.FORMAT_MESSAGE_IGNORE_INSERTS, null,
        dwMessageId, 0, lpBuffer, lpBuffer.length, null);
    return new String(lpBuffer, 0, lenW);
  }

  public static void main(String[] args) throws IOException {
    String from = ".\\from.txt";
    String to = ".\\to.txt";
    new FileOutputStream(from).close();
    if (!Kernel32.INSTANCE.MoveFileW(new WString(from),
        new WString(to))) {
      throw new IOException(getLastError());
    }
  }
}

EDIT: I've edited my answer after checking the code - I was mistaken about using char[] in the signature - it is better to use WString.

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