Java JNA库详解与本地系统交互实战记录(推荐)

// 示例：获取当前操作系统平台信息
import com.sun.jna.platform;
public class platforminfo {
    public static void main(string[] args) {
        if (platform.iswindows()) {
            system.out.println("当前平台是 windows");
        } else if (platform.islinux()) {
            system.out.println("当前平台是 linux");
        } else if (platform.ismac()) {
            system.out.println("当前平台是 macos");
        }
    }
}

// 示例：定义一个本地库接口
import com.sun.jna.library;
import com.sun.jna.native;
public interface clibrary extends library {
    clibrary instance = (clibrary) native.loadlibrary("c", clibrary.class);
    int system(string command);
}

// 使用示例
public class clibrarytest {
    public static void main(string[] args) {
        clibrary.instance.system("echo hello from c");
    }
}

// 设置jna加载库的路径
system.setproperty("jna.library.path", "/opt/native/libs");
// 显式加载一个本地库
com.sun.jna.nativelibrary.addsearchpath("mylib", "/usr/local/lib");
// 获取本地库实例
com.sun.jna.nativelibrary.getinstance("mylib");

<dependency>
    <groupid>net.java.dev.jna</groupid>
    <artifactid>jna</artifactid>
    <version>5.13.0</version>
</dependency>

dependencies {
    implementation 'net.java.dev.jna:jna:5.13.0'
}

java -djna.library.path=/path/to/native/libs -jar myapp.jar

// windows平台调用c库示例
clibrary.instance = (clibrary) native.loadlibrary("msvcrt", clibrary.class);

# linux下设置库路径
export ld_library_path=/opt/mylibs:$ld_library_path
# macos下设置库路径
export dyld_library_path=/opt/mylibs:$dyld_library_path

graph td
    a[java程序] --> b[调用native.loadlibrary]
    b --> c{平台判断}
    c -->|windows| d[加载dll]
    c -->|linux| e[加载so]
    c -->|macos| f[加载dylib]
    d --> g[调用本地函数]
    e --> g
    f --> g

import com.sun.jna.library;
import com.sun.jna.native;
public interface clibrary extends library {
    clibrary instance = native.load("c", clibrary.class);
    void printf(string format, object... args);
}

import com.sun.jna.win32.stdcalllibrary;
public interface user32 extends stdcalllibrary {
    user32 instance = (user32) native.load("user32", user32.class);
    boolean messageboxw(int hwnd, string text, string caption, int type);
}

import com.sun.jna.win32.stdcalllibrary;
import com.sun.jna.native;
public class messageboxexample {
    public interface user32 extends stdcalllibrary {
        user32 instance = (user32) native.load("user32", user32.class);
        boolean messageboxw(int hwnd, string text, string caption, int type);
    }
    public static void main(string[] args) {
        user32.instance.messageboxw(0, "hello from jna!", "jna demo", 0);
    }
}

public interface user32 extends stdcalllibrary {
    user32 instance = (user32) native.load("user32", user32.class);
    pointer findwindoww(string lpclassname, string lpwindowname);
}
public class findwindowexample {
    public static void main(string[] args) {
        pointer hwnd = user32.instance.findwindoww(null, "notepad");
        if (hwnd != null) {
            system.out.println("notepad window found.");
        } else {
            system.out.println("notepad window not found.");
        }
    }
}

pointer hwnd = user32.instance.findwindoww(null, "calculator");
if (hwnd != null) {
    // 可以传入 hwnd 到其他函数如 showwindow, sendmessage 等
    system.out.println("calculator hwnd: " + hwnd);
}

typedef struct _rect {
    long left;
    long top;
    long right;
    long bottom;
} rect, *prect;

import com.sun.jna.structure;
import java.util.list;
public class rect extends structure {
    public int left;
    public int top;
    public int right;
    public int bottom;
    @override
    protected list<string> getfieldorder() {
        return list.of("left", "top", "right", "bottom");
    }
}

pointer hwnd = user32.instance.findwindoww(null, "notepad");
rect rect = new rect();
user32.instance.getwindowrect(hwnd, rect);
system.out.println("window rect: " + rect.left + "," + rect.top + " - " + rect.right + "," + rect.bottom);

import com.sun.jna.memory;
import com.sun.jna.pointer;
public class memoryexample {
    public static void main(string[] args) {
        memory mem = new memory(4);
        mem.setint(0, 0x12345678);
        system.out.printf("memory value: 0x%x\n", mem.getint(0));
    }
}

import com.sun.jna.callback;
import com.sun.jna.library;
import com.sun.jna.native;
public interface clibrary extends library {
    clibrary instance = native.load("c", clibrary.class);
    interface intcallback extends callback {
        void invoke(int value);
    }
    void registercallback(intcallback cb);
}

void registercallback(void (*cb)(int));

clibrary.instance.registercallback(() -> system.out.println("callback called!"));

string libpath = "c:/libs/nativelib.dll";
nativelibrary lib = nativelibrary.getinstance(libpath);
function function = lib.getfunction("nativefunction");
function.invokeint(new object[]{123});

try {
    nativelibrary lib = nativelibrary.getinstance("mylib");
} catch (unsatisfiedlinkerror e) {
    system.err.println("failed to load library: " + e.getmessage());
}

graph td
    a[尝试加载本地库] --> b{是否成功加载?}
    b -->|是| c[调用库函数]
    b -->|否| d[捕获unsatisfiedlinkerror异常]
    d --> e[输出错误日志]
    d --> f[尝试备用路径或策略]

import com.sun.jna.native;
import com.sun.jna.win32.stdcalllibrary;
public interface user32 extends stdcalllibrary {
    user32 instance = native.load("user32", user32.class);
    int messageboxw(int hwnd, string text, string caption, int type);
}

import com.sun.jna.native;
import com.sun.jna.pointer;
import com.sun.jna.win32.stdcalllibrary;
public interface advapi32 extends stdcalllibrary {
    advapi32 instance = native.load("advapi32", advapi32.class);
    int regopenkeyexw(pointer hkey, string subkey, int options, int samdesired, pointer[] phkresult);
}

import com.sun.jna.library;
import com.sun.jna.native;
public interface clibrary extends library {
    clibrary instance = native.load("c", clibrary.class);
    int getpid();
}

system.out.println("current pid: " + clibrary.instance.getpid());

current pid: 12345

// hello.c
#include <stdio.h>
void say_hello() {
    printf("hello from c\n");
}

gcc -shared -o libhello.so -fpic hello.c

import com.sun.jna.library;
import com.sun.jna.native;
public interface hellolib extends library {
    hellolib instance = native.load("/path/to/libhello.so", hellolib.class);
    void say_hello();
}

import com.sun.jna.library;
import com.sun.jna.native;
public interface clibrary extends library {
    clibrary instance = native.load("c", clibrary.class);
    int getpid();
}

system.out.println("current pid: " + clibrary.instance.getpid());

// myobjcclass.m
#import <foundation/foundation.h>
void sayhellofromobjc() {
    nslog(@"hello from objective-c");
}

clang -dynamiclib -o libobjcbridge.dylib myobjcclass.m -framework foundation

import com.sun.jna.library;
import com.sun.jna.native;
public interface objcbridge extends library {
    objcbridge instance = native.load("/path/to/libobjcbridge.dylib", objcbridge.class);
    void sayhellofromobjc();
}

public interface systeminfo {
    int getprocessid();
}
// windows实现
class windowssysteminfo implements systeminfo {
    @override
    public int getprocessid() {
        return kernel32.instance.getcurrentprocessid();
    }
}
// linux/macos实现
class unixsysteminfo implements systeminfo {
    @override
    public int getprocessid() {
        return clibrary.instance.getpid();
    }
}

systeminfo sysinfo = system.getproperty("os.name").tolowercase().contains("win") 
                     ? new windowssysteminfo() 
                     : new unixsysteminfo();
system.out.println("pid: " + sysinfo.getprocessid());

string os = system.getproperty("os.name").tolowercase();
if (os.contains("win")) {
    // 加载windows dll
} else if (os.contains("mac")) {
    // 加载.dylib
} else {
    // 加载.so
}

import java.util.logging.logger;
public class nativelogger {
    private static final logger logger = logger.getlogger("jnanative");
    public static void logerror(string message, throwable e) {
        logger.severe(message + ": " + e.getmessage());
    }
}

try {
    int pid = sysinfo.getprocessid();
} catch (unsatisfiedlinkerror e) {
    nativelogger.logerror("native library not found", e);
} catch (exception e) {
    nativelogger.logerror("unexpected error", e);
}

graph td
    a[开始] --> b{操作系统判断}
    b -->|windows| c[加载windows库]
    b -->|linux| d[加载linux库]
    b -->|macos| e[加载macos库]
    c --> f[调用win32 api]
    d --> g[调用libc系统调用]
    e --> h[调用foundation或c接口]
    f & g & h --> i[统一接口返回结果]
    i --> j[统一日志与异常处理]
    j --> k[结束]

public interface clibrary extends library {
    clibrary instance = native.load("c", clibrary.class);
    int system(string command);  // 调用 libc 的 system 函数
}
// 调用方式
clibrary.instance.system("ls -l");

public class rect extends structure {
    public int left, top, right, bottom;
    @override
    protected list<string> getfieldorder() {
        return arrays.aslist("left", "top", "right", "bottom");
    }
}

executorservice executor = executors.newfixedthreadpool(4);
future<?> future = executor.submit(() -> {
    clibrary.instance.somenativefunction();
});

public class nativelibraryloader {
    private static final clibrary c_lib_instance = native.load("c", clibrary.class);
    public static clibrary getclibrary() {
        return c_lib_instance;
    }
}

rect rect = new rect();
for (int i = 0; i < 1000; i++) {
    getwindowrect(hwnd, rect); // 复用 rect 实例
}

int size = 1024 * 1024;
bytebuffer buffer = bytebuffer.allocatedirect(size);
// 将 buffer 传递给本地函数
somenativefunction(buffer, size);

public interface user32 extends library {
    user32 instance = native.load("user32", user32.class);
    hwnd findwindow(string lpclassname, string lpwindowname);
    boolean postmessage(hwnd hwnd, int msg, wparam wparam, lparam lparam);
}

filedescriptor fd = openserialport("/dev/ttys0");
write(fd, "hello".getbytes(), 5);

public interface sysinfo extends library {
    sysinfo instance = native.load("sysinfo", sysinfo.class);
    long gettotalmemory();  // 返回系统总内存大小
    long getfreememory();   // 返回可用内存大小
}