Windows API Generator for Java (Maven / Gradle)

Windows API Generator generates Java code for using the Windows API, also called Java bindings for Windows. The generated code uses Java's Foreign Function and Memory API to make calls to Windows API functions, work with Windows data structures in native memory, and use COM objects. The generator is available as a Maven and a Gradle plugin.

Features

• Generates code for Windows API functions, data structures (struct and union), callback functions, enumerations, constants and COM interfaces
• COM interfaces can be called from Java or implemented in Java
• Generates code for constants of different types: integer, string, GUID, property keys, etc.
• Automatically adds the related data structures, enumerations, etc. to the initially requested scope
• Generated code includes extensive JavaDoc documentation including links to the official Microsoft documentation
• Supports capturing call state, structs of variable length, cbSize etc.
• Generates separate code for Windows x64 and ARM64 where necessary
• Available for both Maven and Gradle
• Plugins run on any platform (not just Windows)
• Based on Windows API metadata curated by Microsoft
• Metadata is built-in; no additional installations are required

Getting Started

• Getting Started with Maven
• Getting Started with Gradle

Example Projects

• Show a Message Box (Java, Maven): messagebox
• Query the Windows Registry (Java, Gradle/Groovy): registry
• Enumerate Windows, demonstrating use of a callback function (Kotlin, Gradle/Kotlin): enum_windows
• Display User Notification, showing use of COM interfaces (Java, Maven): user_notification_java
• Display User Notification, showing use of COM interfaces (Kotlin, Maven): user_notification_kotlin

Prerequisites

• Maven Plugin: Java 21 or higher, Maven 3.8.5 or higher, any platform
• Gradle Plugin: Java 21 or higher, any platform
• Generated code: Java 23 or higher, 64-bit Windows (x64 or ARM64)

Further Documentation

• Maven Plugin
• Gradle Plugin
• Generated Code
• Working with COM Interfaces

Windows API Metadata

As part of the win32metadata GitHub proejct Microsoft maintains metadata for the Windows API (aka Win32 API). The result is available in the Microsoft.Windows.SDK.Win32Metadata NuGet package. The NuGet package mainly contains a .winmd file with the metadata. ECMA-335 defines the format of .winmd files. It is the binary format used by .NET binaries.

This library includes the Windows.Win32.winmd file and uses it as the basis for generating Windows API code.

Windows API Generator vs Jextract

Jextract is another tool for generating Java bindings. This is a comparison of the two tools:

Windows API Generator	Jextract
Generates code for using native libraries	Generates code for using native libraries
Code for Foreign Function and Memory API	Code for Foreign Function and Memory API
Restricted to Windows API	Works with any native library
Processes Windows API metadata curated by Microsoft	Processes C header files
Metadata is built-in	C header files and/or Windows SDK must be installed
Code for functions, structs/unions, callback functions, enumerations, constants, COM interfaces	Code for functions, structs/unions, function pointers, constants
Code for calling COM interfaces and implementing them	No support for COM interfaces
Generates code without Typedefs and names as intended by Microsoft	Generates unnecessary Typedefs and structs with internal names not documented by Microsoft
Determines dependencies and automatically generates all necessary code	Requires multiple iterations to manually specify all dependencies
Constants of different types: integer, string, GUID, property keys, etc.	Integer constants only
Support for capturing call state (GetLastError)	No support for capturing call state
Available as Maven and Gradle plugin	Available as a separate tool