A simple Quarkus demo

Useful IDE shortcuts

• ⌘⌥L to format
• ⇧⌘T to flip between tests and implementation
• fn-cmd-F1 to switch screen mirroring on and off

Scaffolding the app

1. Go to https://code.quarkus.io
2. Just choose the top option, Rest
3. Show that the template doesn't have much in it, except for maven, because can't make less maven less verbose. :)
4. Copy the folder path from the Downloads folder
5. In a terminal run

idea <path>

Touring the generated code

1. MAKE THE FONT BIGGER
2. Show the generated dockerfiles, because Quarkus is Kubernetes-native.
3. Explain that actually we prefer jib because it's easier to keep it up to date, compared to a file which is generated once.

Running the application

1. Launch in dev mode

mvn quarkus:dev

1. Click ‘r’ to run tests

2. Visit http://localhost:8080, which will show a get static page

3. Navigate to the Dev UI

4. Show the configuration and continuous testing tabs

5. I didn't write this code, what even is my endpoint?

6. Find the endpoint by viewing the Rest Easy extension panel's endpoint scores

7. Visit http://localhost:8080/hello. It should work!

Live coding

1. Make a change. Try changing the greeting, using a hello live template.
2. Can we make it more exciting? Add a queryparam in GreetingResource (a query live template is useful for this, and also a greeting live template for hello in other languages)

public String hello(@QueryParam("name") String name) {
return "Hello " + name;
}

1. Visit http://localhost:8080/hello?name=yourname
2. If you forget the space first time, no worries! It shows the reload when fixed.

Continuous testing

1. We got so excited by the UI, we did not notice a test is failing. Fix it using

.body(containsString("Hello"));

Adding persistence

1. To add the persistence libraries, run

quarkus ext add hibernate-orm-panache jdbc-postgresql

1. Now do some persistence. Make a greeting:

@Entity
public class Greeting extends PanacheEntity {
String name;
}

2. This is using Panache, a layer on top of hibernate. PanacheEntity allows us to use the active record pattern and eliminate a lot of boilerplate.
3. Then change the Get method to persist it. Construct the entity, add @Transactional and persist.

We're aiming for the following:

@GET
@Transactional
@Produces(MediaType.TEXT_PLAIN)
public String hello(@QueryParam("name") String name) {
   Greeting greeting = new Greeting();
   greeting.name = name;
   greeting.persist();
   return "Hello " + name;
}

Normally you wouldn't use a GET to persist something to the database, but we're being lazy. Let's pretend it's monitoring.

1. Is the data going in? Add a second method. It needs to be in two steps to avoid a cast. Use a names live template.

@GET
@Path("names")
@Produces(MediaType.TEXT_PLAIN)
public String names() {
List<Greeting> greetings = Greeting.listAll();
   String names = greetings.stream().map(g-> g.name)
   .collect(Collectors.joining (", "));
   return "I've seen " + names;
}

Dev services

1. This is being stored in a database, but we didn’t set one up.
2. Run podman ps
3. Kill the container running the database.
4. Quarkus is unhappy, but everything comes back if Quarkus is restarted.
5. Run podman ps again to show it’s back

Initialising services

What if we want the database not to be empty on a restart?

1. Let’s make it look like we have more friends.

2. Make a src/main/resources/import.sql file.

3. Populate it with the following:

INSERT INTO Greeting(id, name)
VALUES (nextval('Greeting_SEQ'), 'Alice');
INSERT INTO Greeting(id, name)
VALUES (nextval('Greeting_SEQ'), 'Bob');

(An IntelliJ live template called sql is handy for this.)

1. The data will update without a restart.
2. We can also go to the dev UI, and navigate to hibernate, persistence units, and then click on it, to get a create script.

Building a native app

To build a native application, we can run

quarkus build --native -DskipTests

Then use tab complete for target/code-with-quarkus-1.0.0-SNAPSHOT-runner

However, this would fail at runtime, because no database is configured.