Vert.x 3.1 has (re-) introduced the redeploy feature. This blog post explains how to use this feature in the Eclipse IDE. However, you can easily adapt the content to your IDE.

How does redeploy work

How is implemented the redeploy is not as you may expect. First, the redeploy does not rely on a build tool, but is integrated in vert.x. However you can plug your build tools with the redeploy feature. This feature is offered by the io.vertx.core.Launcher class. The redeployment process is actually very simple:

1. the application is launched in redeploy mode.
2. it listens for file changes
3. when a matching file is changed, it stops the application
4. it executes the on-redeploy actions if any
5. it restarts the application
6. back to (2)

Initially the application is launched in redeploy mode. The application is actually launched in background, in a separated process. Vert.x listens for file changes. You give it a set of (Ant-style) patterns and every time a matching file changes, Vert.x stops the whole application and restarts it. Optionally you can configure a on-redeploy action to plug in your build tools.

To integrate this process in Eclipse (or in your IDE), you just need to configure the set of listened files, and let the Launcher class starts and stops your application.

Redeploy in Eclipse

The following screencast explains how you configure a vert.x application to be run in Eclipse and how to configure the redeploy:

To summarize the last configuration:

• it’s a Java application configuration
• it uses io.vertx.core.Launcher as main class
• In the Program arguments (Arguments tab), write: run org.acme.verticle.MyMainVerticle --redeploy="src/**/*.java" --launcher-class=io.vertx.core.Launcher

Redeploy with your own Main class

Let’s now imagine that you have your own Main class, starting your application. For instance, it can be something like:

package org.acme.vertx;

import io.vertx.core.Vertx;

public class Main {

    public static void main(String[] args) {
        Vertx vertx = Vertx.vertx();
        vertx.deployVerticle(MyMainVerticle.class.getName());
    }

}

The redeploy feature from vert.x lets you use your own Main class:

1. Create another Run configuration
2. Set the Main-Class to io.vertx.core.Launcher (yes, the one from vert.x not yours)
3. In the application parameter add: run --redeploy="src/**/*.java" --launcher-class=org.acme.vertx.Main

With this configuration, the application is launched in background using your own Main class, and will restart the application every time you change your source code (you can even change the source code of your Main class).