Today I read Groovy Manual in 'Core' section in vertx documentation. It's a very good starting point.

Good examples: * gradle groovy example * gradle java example * gradle java embeded example * Vert.x Tutorial by Jakob Jenkov

Some facts about vertx:

The golden rule: never block event loop (like node.js);
vertx use 'future' to handle async events;
The 'verticle' is something like actor in akka;
Verticles live in event loop (standard verticle) or worker thread (worker verticle). They both live in one thread;
An 'event bus' has many 'address', which is a plain string;
A 'handler' can be registered to one or more addresses;
One or more handlers can be registered to the same address;
A 'message' can be published to an address, in which case all handlers can receive this message;
A message can be sent to an address, in which case only one handler could receive this message;
vertx use JSON as the default message format;

Run Vertical with external jars

Add these jars into the 'dependencies' section in 'build.gradle'. Then add the task 'getjars' into build.gradle:

task(getjars, type: Copy) {
    into "lib"
    from configurations.runtime
}

When develop, run gradle getjars to put all jars into 'lib' folder. Then run verticle with vertx run -cp 'lib/*' <verticle-name>. The wildcard syntax can only be used for Java 6 or later. In Java 5, you have to add all jar file names into -cp option. See How to include all the jars present at a particular directory in the CLASSPATH in one go? for details.

Web App Auto Refresh

First install Auto Refresh plugin for your browser, such as Chrome, then run:

mkdir src
cat << EOF > src/HelloServer.groovy
vertx.createHttpServer().requestHandler({ req ->
    req.response().putHeader("content-type", "text/html").
    end("<html><body><h3>Hello from vert.X!</h3></body></html>")
}).listen(8080)
EOF
vertx run --redeploy="src/**/*.*" --launcher-class=io.vertx.core.Launcher src/HelloServer.groovy

Now when any file in folder 'src' changes, the vertical will be redeployed. You can put all external jars into 'lib' folder and run the verticle with the -cp option: vertx run --redeploy="src/**/*.*" --launcher-class=io.vertx.core.Launcher -cp lib src/HelloServer.groovy. See Automatic redeployment in Eclipse IDE and vertx run --help for details.

Build Fat Jar with Gradle

Build a fat-jar including all dependencies with Gradle: gradle shadowJar. Then this app can be run with java -jar app-fat-jar.jar.

Project files:

cat << EOF > build.gradle
plugins {
  id 'java'
  id 'groovy'
  id 'application'
  id 'com.github.johnrengelman.shadow' version '1.2.3'
}

repositories {
  mavenCentral()
  maven {
    url "https://oss.sonatype.org/content/repositories/snapshots"
  }
}


version = '3.4.1'

sourceCompatibility = '1.8'
mainClassName = 'io.vertx.core.Launcher'

dependencies {
  compile "io.vertx:vertx-core:$version"
  compile "io.vertx:vertx-lang-groovy:$version"
}

processResources {
  from 'src/main/groovy'
}

shadowJar {
  classifier = 'fat'
  manifest {
    attributes 'Main-Verticle': 'groovy:MyGroovyVerticle'
  }
  mergeServiceFiles {
    include 'META-INF/services/io.vertx.core.spi.VerticleFactory'
  }
}

task wrapper(type: Wrapper) {
  gradleVersion = '3.4.1'
}
EOF
mkdir -p src/main/groovy
cat << EOF > src/main/groovy/MyGroovyVerticle.groovy
vertx.createHttpServer().requestHandler({ req ->
    req.response()
       .putHeader("content-type", "text/html")
       .end("<html><body><h1>Hello from vert.x!</h1></body></html>")
}).listen(8080)
EOF

P.S: Why you can use vertx directly in Groovy script without import or declaring it?

Because vertx is a field in class AbstractVerticle. The entrance class defined in build.gradle is io.vertx.core.Launcher, which will load AbstractVerticle somewhere at runtime (How? I didn't figure it out so far). The launcher then load your verticle (defined in Main-Verticle in build.gradle) As compared with Java verticle class, you must declare you class extends AbstractVerticle explicitly.

Vert.x Notes

Run Vertical with external jars

Web App Auto Refresh

Build Fat Jar with Gradle

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