How-to-develop-Qt-in-Java.md

How to develop with QtJambi

Add qtjambi-5.15.jar/qtjambi-6.2.jar to the classpath of your Java project containing the most essential Qt Core, Gui and Widgets modules. If you use Maven to build your application simply add following dependency to your project:

<dependency>
  <groupId>io.qtjambi</groupId>
  <artifactId>qtjambi</artifactId>
  <version>$VERSION</version>
</dependency>

(exchange $VERSION either by 5.15 or by 6.2).

Otherwise, download QtJambi JAR file from Maven Central Repository. Find the list of all available QtJambi modules.

Create a file Test.java containing the following code

import io.qt.widgets.*;
public class Test {
    public static void main(String[] args) {
        QApplication.initialize(args);
        QMessageBox.information(null, "QtJambi", "Hello World!");
        QApplication.shutdown();
    }
}

Compile the file:

javac -cp qtjambi-6.2.jar Test.java

For execution you need the platform dependent binaries of QtJambi. For instance, if you are working on Windows download and unpack the win64 binaries. The required DLLs are to be found in the bin folder (lib folder on Linux and macOS). Additionally, you need Qt. Use the Qt installer to install Qt on your system. Make sure you are using the same Qt version and QtJambi version (e.g. 5.15 or 6.2).

When running a QtJambi application you have to make the locations of Qt and QtJambi libraries known to Java. Therefore, use the PATH environment (LD_LIBRARY_PATH on Linux, DYLD_LIBRARY_PATH on macOS) or the Java runtime property java.library.path. The example program can be executed this way:

java -cp qtjambi-6.2.jar;qtjambi-native-windows-x64-6.2.jar;. -Djava.library.path=C:\Qt\6.2.0\msvc2019_64\bin Test

On macOS you need to use the start parameter -XstartOnFirstThread:

java -XstartOnFirstThread -cp qtjambi-6.2.jar;qtjambi-native-windows-x64-6.2.jar;. -Djava.library.path=C:\Qt\6.2.0\msvc2019_64\bin Test

In general, you can start learning how to use Qt in Java as it is introduced for C++. There are a couple of specifics for QtJambi that are introduced here. Instead of starting your program with a java command as shown above you can deploy your application as executable as described here.

See QtJambi 5.15 API Reference Documentation and QtJambi 6.2 API Reference Documentation