Java Native Access

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title: "Java Native Access" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["java-platform"] description: "Java library" topic_path: "general/java-platform" source: "https://en.wikipedia.org/wiki/Java_Native_Access" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Java library ::

::data[format=table title="Infobox software"]

FieldValue
nameJava Native Access
released
latest release version5.17.0
latest release date{{cite web
urlhttps://github.com/java-native-access/jna/releases/tag/5.17.0
titleRelease 5.17.0
websiteGitHub
date2025-03-16}}
operating systemWindows, macOS, Android, AIX, FreeBSD, Linux, OpenBSD, Solaris, Windows Mobile
platformJava 1.4 or later (for JNA 3.5.2 or earlier), Java 1.6 for JNA 4.0.0 and later
size1.83 MB (archived)
programming languageC and Java
genreSoftware Library
licenseLGPL version 2.1 or later and (from version 4.0 onward) the Apache Software License, version 2.0
website
authorTodd Fast, Timothy Wall, Liang Chen
::

| name = Java Native Access | logo = | screenshot = | caption = | developer = | released =

012 -- | latest release version = 5.17.0 | latest release date = {{cite web | url=https://github.com/java-native-access/jna/releases/tag/5.17.0 | title=Release 5.17.0 | website=GitHub | date=2025-03-16}} | latest preview version = | latest preview date = | operating system = Windows, macOS, Android, AIX, FreeBSD, Linux, OpenBSD, Solaris, Windows Mobile | platform = Java 1.4 or later (for JNA 3.5.2 or earlier), Java 1.6 for JNA 4.0.0 and later | size = 1.83 MB (archived) | programming language = C and Java | genre = Software Library | license = LGPL version 2.1 or later and (from version 4.0 onward) the Apache Software License, version 2.0 | website = | author = Todd Fast, Timothy Wall, Liang Chen

Java Native Access (JNA) is a community-developed library that provides Java programs easy access to native shared libraries without using the Java Native Interface (JNI). JNA's design aims to provide native access in a natural way with a minimum of effort. Unlike JNI, no boilerplate or generated glue code is required.

Since Java 22, the Foreign Function and Memory API was provided as a standard modern alternative.

Architecture

The JNA library uses a small native library called foreign function interface library (libffi) to dynamically invoke native code. The JNA library uses native functions allowing code to load a library by name and retrieve a pointer to a function within that library, and uses libffi library to invoke it, all without static bindings, header files, or any compile phase. The developer uses a Java interface to describe functions and structures in the target native library. This makes it quite easy to take advantage of native platform features without incurring the high development overhead of configuring and building JNI code.

JNA is built and tested on macOS, Microsoft Windows, FreeBSD / OpenBSD, Solaris, Linux, AIX, Windows Mobile, and Android. It is also possible to tweak and recompile the native build configurations to make it work on most other platforms that run Java.

Mapping types

The following table shows an overview of types mapping between Java and native code and supported by the JNA library.

::data[format=table]

Native TypeSizeJava TypeCommon Windows Types
8-bit integer
16-bit integer
16/32-bit character
32-bit integer
boolean value
32/64-bit integer
long long64-bit integer
32-bit FP
64-bit FP
C string
::

Note: The meaning of changes between and according to some preprocessor definitions. follows.

Memory byte alignment for data structures

Native libraries have no standardized memory byte alignment flavor. JNA defaults to an OS platform specific setting, that can be overridden by a library specific custom alignment. If the alignment details are not given in the documentation of the native library, the correct alignment must be determined by trial and error during implementation of the Java wrapper.

Example

The following program loads the local C standard library implementation and uses it to call the ** function.

Note: The following code is portable and works the same on Windows and POSIX (Linux / Unix / macOS) platforms.

::code[lang=java] package org.wikipedia.examples;

import com.sun.jna.Library; import com.sun.jna.Native; import com.sun.jna.Platform;

// Simple example of native library declaration and usage. public class HelloWorld { public interface CLibrary extends Library { CLibrary INSTANCE = (CLibrary) Native.loadLibrary( (Platform.isWindows() ? "msvcrt" : "c"), CLibrary.class); void printf(String format, Object... args); }

public static void main(String[] args) {
    CLibrary.INSTANCE.printf("Hello, World\n");
    for (int i = 0; i < args.length; i++) {
        CLibrary.INSTANCE.printf("Argument %d: %s\n", i, args[i]);
    }
}

} ::

The following program loads the C POSIX library and uses it to call the standard ** function.

Note: The following code is portable and works the same on POSIX standards platforms.

::code[lang=java] package org.wikipedia.examples;

import com.sun.jna.Library; import com.sun.jna.Native;

// Simple example of native C POSIX library declaration and usage. public class Example { public interface Posix extends Library { public int chmod(String filename, int mode); public int chown(String filename, int user, int group); public int rename(String oldpath, String newpath); public int kill(int pid, int signal); public int link(String oldpath, String newpath); public int mkdir(String path, int mode); public int rmdir(String path); }

public static void main(String[] args) {
    // It is possible to load msvcrt for its partial POSIX support on Windows...
    Posix posix = (Posix) Native.loadLibrary("c", Posix.class);
    // but it will still fail on Windows due to /tmp being missing.
    posix.mkdir("/tmp/newdir", 0777);
    posix.rename("/tmp/newdir","/tmp/renamedir");
}

} ::

The program below loads the **** and uses it to call the ** and ** functions.

Note: The following code works only on Windows platforms. ::code[lang=java] package org.wikipedia.examples;

import com.sun.jna.Library; import com.sun.jna.Native;

// Simple example of Windows native library declaration and usage. public class Example { public interface Kernel32 extends Library { // FREQUENCY is expressed in hertz and ranges from 37 to 32767 // DURATION is expressed in milliseconds public boolean Beep(int FREQUENCY, int DURATION); public void Sleep(int DURATION); }

public static void main(String[] args) {
    Kernel32 lib = (Kernel32) Native.loadLibrary("kernel32", Kernel32.class);
    lib.Beep(698, 500);
    lib.Sleep(500);
    lib.Beep(698, 500);
}

} ::

References

References

  1. "Default Type Mappings". jna.dev.java.net.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::

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