Run a Project

Enabling Hotswap
Project Configuration

You can run and debug your Vaadin application in NetBeans as you would any other Java application. Start by selecting File › Project Properties. Select the Run category and specify your Main Class, like this:

Click OK to close the dialog. Next, click the Debug button on the toolbar, indicated by a red circle in this screenshot:

The application starts up and you can access it at http://localhost:8080. Hot deploy of the frontend files is enabled automatically. However, to enable Java hotswap, you have to take some additional actions.

Enabling Hotswap

Enabling hotswap manually consists of three steps:

Download and install JetBrains Runtime;
Download HotswapAgent and install it into JetBrains Runtime; and
Create a launch configuration for VS Code that runs the application with JetBrain Runtime and additional JVM parameters.

JetBrains Runtime

You can download the latest version from the JetBrains GitHub release page. Be sure to select the correct architecture. Use JetBrains Runtime to execute your application, not necessarily your IDE.

HotswapAgent

You can download HotswapAgent from the HotswapAgent GitHub release page. You’ll need version 1.4.2 or later.

Download the JAR file and place it inside the JetBrains Runtime installation directory as lib/hotswap/hotswap-agent.jar. You’ll need to create the hotswap folder, and rename the downloaded file to hotswap-agent.jar.

If you want to know more about the features of HotswapAgent, the documentation in the HotswapAgent webpage is a good resource.

Project Configuration

Select File › Project Properties. If the menu item is disabled, your application is likely running and you have to stop it. Then go to the Build › Compile category.

Under JDK Settings, click Manage and locate the JetBrains Runtime. Then select it as your Java Platform.

Next, go to the Run category. In the VM Options field, copy-paste the following:

-XX:+AllowEnhancedClassRedefinition -XX:+ClassUnloading -XX:HotswapAgent=fatjar

Click OK to close the dialog, then start the application again. The application starts up.

Open the application in a browser and verify that everything is working through Vaadin Copilot. Move your mouse pointer over the Copilot button at the bottom-right corner:

Vaadin Copilot menu visible in a browser

Important

The Copilot button is only available when the application is running in development mode. It is not available in production mode.

Now click Development workflow. Your browser should look something like this:

Vaadin Copilot development workflow dialog

The first item is orange because Vaadin does not have an official plugin for NetBeans. However, Java hotswap is enabled.

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