Quarkus - Reactive SQL Clients

Installing
- Reactive PostgreSQL Client extension
- JSON Binding
Configuring
Database schema and seed data
Using
Database Clients details
Configuration Reference

The Reactive SQL Clients have a straightforward API focusing on scalability and low-overhead. Currently, the following database servers are supported:

PostgreSQL
MariaDB/MySQL

In this guide, you will learn how to implement a simple CRUD application exposing data stored in PostgreSQL over a RESTful API.

Extension and connection pool class names for each client can be found at the bottom of this document.

If you are not familiar with the Quarkus Vert.x extension, consider reading the Using Eclipse Vert.x guide first.

The application shall manage fruit entities:

public class Fruit {

    public Long id;

    public String name;

    public Fruit() {
    }

    public Fruit(String name) {
        this.name = name;
    }

    public Fruit(Long id, String name) {
        this.id = id;
        this.name = name;
    }
}

Do you need a ready-to-use PostgreSQL server to try out the examples?

docker run --ulimit memlock=-1:-1 -it --rm=true --memory-swappiness=0 --name quarkus_test -e POSTGRES_USER=quarkus_test -e POSTGRES_PASSWORD=quarkus_test -e POSTGRES_DB=quarkus_test -p 5432:5432 postgres:10.5

Installing

Reactive PostgreSQL Client extension

First, make sure your project has the quarkus-reactive-pg-client extension enabled. If you are creating a new project, set the extensions parameter as follows:

mvn io.quarkus:quarkus-maven-plugin:1.3.1.Final:create \
    -DprojectGroupId=org.acme \
    -DprojectArtifactId=reactive-pg-client-quickstart \
    -Dextensions="reactive-pg-client"
cd reactive-pg-client-quickstart

If you have an already created project, the reactive-pg-client extension can be added to an existing Quarkus project with the add-extension command:

./mvnw quarkus:add-extension -Dextensions="reactive-pg-client"

Otherwise, you can manually add this to the dependencies section of your pom.xml file:

<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-reactive-pg-client</artifactId>
</dependency>

In this guide, we will use the Axle API of the Reactive PostgreSQL Client. Read the Using Eclipse Vert.x guide to understand the differences between the callback, Mutiny, RxJava and Axle based APIs. The RxJava and Axle API are deprecated, and are planned for removal. It is recommended to switch to Mutiny.

Mutiny

The recommended API uses Mutiny reactive types, if you’re not familiar with them, read the Getting Started with Reactive guide first.

JSON Binding

We will expose Fruit instances over HTTP in the JSON format. Consequently, you also need to add the quarkus-resteasy-jsonb extension:

./mvnw quarkus:add-extension -Dextensions="resteasy-jsonb"

If you prefer not to use the command line, manually add this to the dependencies section of your pom.xml file:

<dependency>
    <groupId>io.quarkus</groupId>
    <artifactId>quarkus-resteasy-jsonb</artifactId>
</dependency>

Of course, this is only a requirement for this guide, not any application using the Reactive PostgreSQL Client.

Configuring

The Reactive PostgreSQL Client can be configured with standard Quarkus datasource properties and a reactive URL:

src/main/resources/application.properties

quarkus.datasource.db-kind=postgresql
quarkus.datasource.username=quarkus_test
quarkus.datasource.password=quarkus_test
quarkus.datasource.reactive.url=postgresql://localhost:5432/quarkus_test

With that you may create your FruitResource skeleton and @Inject a io.vertx.mutiny.pgclient.PgPool instance:

src/main/java/org/acme/vertx/FruitResource.java

@Path("fruits")
@Produces(MediaType.APPLICATION_JSON)
@Consumes(MediaType.APPLICATION_JSON)
public class FruitResource {

    @Inject
    io.vertx.mutiny.pgclient.PgPool client;
}

Database schema and seed data

Before we implement the REST endpoint and data management code, we need to setup the database schema. It would also be convenient to have some data inserted upfront.

For production we would recommend to use something like the Flyway database migration tool. But for development we can simply drop and create the tables on startup, and then insert a few fruits.

src/main/java/org/acme/vertx/FruitResource.java

    @Inject
    @ConfigProperty(name = "myapp.schema.create", defaultValue = "true") (1)
    boolean schemaCreate;

    @PostConstruct
    void config() {
        if (schemaCreate) {
            initdb();
        }
    }

    private void initdb() {
        // TODO
    }
}

You may override the default value of the myapp.schema.create property in the application.properties file.

Almost ready! To initialize the DB in development mode, we will use the client simple query method. It returns a Uni and thus can be composed to execute queries sequentially:

 client.query("DROP TABLE IF EXISTS fruits")
    .flatMap(r -> client.query("CREATE TABLE fruits (id SERIAL PRIMARY KEY, name TEXT NOT NULL)"))
    .flatMap(r -> client.query("INSERT INTO fruits (name) VALUES ('Orange')"))
    .flatMap(r -> client.query("INSERT INTO fruits (name) VALUES ('Pear')"))
    .flatMap(r -> client.query("INSERT INTO fruits (name) VALUES ('Apple')"))
    .await().indefinitely();

Wondering why we need block until the latest query is completed? This code is part of a @PostConstruct method and Quarkus invokes it synchronously. As a consequence, returning prematurely could lead to serving requests while the database is not ready yet.

That’s it! So far we have seen how to configure a pooled client and execute simple queries. We are now ready to develop the data management code and implement our RESTful endpoint.

Using

Query results traversal

In development mode, the database is set up with a few rows in the fruits table. To retrieve all the data, we will use the query method again:

Uni<RowSet> rowSet = client.query("SELECT id, name FROM fruits ORDER BY name ASC");

When the operation completes, we will get a RowSet that has all the rows buffered in memory. As an java.lang.Iterable<Row>, it can be traversed with a for-each loop:

Uni<List<Fruit>> fruits = rowSet
    .map(pgRowSet -> {
        List<Fruit> list = new ArrayList<>(pgRowSet.size());
        for (Row row : pgRowSet) {
            list.add(from(row));
        }
        return list;
    });

The from method converts a Row instance to a Fruit instance. It is extracted as a convenience for the implementation of the other data management methods:

src/main/java/org/acme/vertx/Fruit.java

private static Fruit from(Row row) {
    return new Fruit(row.getLong("id"), row.getString("name"));
}

Putting it all together, the Fruit.findAll method looks like:

src/main/java/org/acme/vertx/Fruit.java

    public static Uni<List<Fruit>> findAll(PgPool client) {
        return client.query("SELECT id, name FROM fruits ORDER BY name ASC")
            .map(pgRowSet -> {
                List<Fruit> list = new ArrayList<>(pgRowSet.size());
                for (Row row : pgRowSet) {
                    list.add(from(row));
                }
                return list;
            });
    }

And the endpoint to get all fruits from the backend:

src/main/java/org/acme/vertx/FruitResource.java

@GET
public Uni<Response> get() {
    return Fruit.findAll(client)
            .map(Response::ok)
            .map(ResponseBuilder::build);
}

Now start Quarkus in dev mode with:

./mvnw compile quarkus:dev

Lastly, open your browser and navigate to http://localhost:8080/fruits, you should see:

[{"id":3,"name":"Apple"},{"id":1,"name":"Orange"},{"id":2,"name":"Pear"}]

Prepared queries

The Reactive PostgreSQL Client can also prepare queries and take parameters that are replaced in the SQL statement at execution time:

client.preparedQuery("SELECT name FROM fruits WHERE id = $1", Tuple.of(id))

The SQL string can refer to parameters by position, using $1, $2, …etc.

Like the simple query method, preparedQuery returns an instance of Uni<RowSet>. Equipped with this tooling, we are able to safely use an id provided by the user to get the details of a particular fruit:

src/main/java/org/acme/vertx/Fruit.java

public static Uni<Fruit> findById(PgPool client, Long id) {
    return client.preparedQuery("SELECT id, name FROM fruits WHERE id = $1", Tuple.of(id)) (1)
            .map(RowSet::iterator) (2)
            .map(iterator -> iterator.hasNext() ? from(iterator.next()) : null); (3)
}

1	Create a `Tuple` to hold the prepared query parameters.
2	Get an `Iterator` for the `RowSet` result.
3	Create a `Fruit` instance from the `Row` if an entity was found.

And in the JAX-RS resource:

src/main/java/org/acme/vertx/FruitResource.java

@GET
@Path("{id}")
public Uni<Response> getSingle(@PathParam Long id) {
    return Fruit.findById(client, id)
            .map(fruit -> fruit != null ? Response.ok(fruit) : Response.status(Status.NOT_FOUND)) (1)
            .map(ResponseBuilder::build); (2)
}

1	Prepare a JAX-RS response with either the `Fruit` instance if found or the `404` status code.
2	Build and send the response.

The same logic applies when saving a Fruit:

src/main/java/org/acme/vertx/Fruit.java

public Uni<Long> save(PgPool client) {
    return client.preparedQuery("INSERT INTO fruits (name) VALUES ($1) RETURNING (id)", Tuple.of(name))
            .map(pgRowSet -> pgRowSet.iterator().next().getLong("id"));
}

And in the web resource we handle the POST request:

src/main/java/org/acme/vertx/FruitResource.java

@POST
public Uni<Response> create(Fruit fruit) {
    return fruit.save(client)
            .map(id -> URI.create("/fruits/" + id))
            .map(uri -> Response.created(uri).build());
}

Result metadata

A RowSet does not only hold your data in memory, it also gives you some information about the data itself, such as:

the number of rows affected by the query (inserted/deleted/updated/retrieved depending on the query type),
the column names.

Let’s use this to support removal of fruits in the database:

src/main/java/org/acme/vertx/Fruit.java

public static Uni<Boolean> delete(PgPool client, Long id) {
    return client.preparedQuery("DELETE FROM fruits WHERE id = $1", Tuple.of(id))
            .map(pgRowSet -> pgRowSet.rowCount() == 1); (1)
}

1	Inspect metadata to determine if a fruit has been actually deleted.

And to handle the HTTP DELETE method in the web resource:

src/main/java/org/acme/vertx/FruitResource.java

@DELETE
@Path("{id}")
public Uni<Response> delete(@PathParam Long id) {
    return Fruit.delete(client, id)
            .map(deleted -> deleted ? Status.NO_CONTENT : Status.NOT_FOUND)
            .map(status -> Response.status(status).build());
}

With GET, POST and DELETE methods implemented, we may now create a minimal web page to try the RESTful application out. We will use jQuery to simplify interactions with the backend:

<!doctype html>
<html>
<head>
    <meta charset="utf-8"/>
    <title>Reactive PostgreSQL Client - Quarkus</title>
    <script src="https://code.jquery.com/jquery-3.3.1.min.js"
            integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8=" crossorigin="anonymous"></script>
    <script type="application/javascript" src="fruits.js"></script>
</head>
<body>

<h1>Fruits API Testing</h1>

<h2>All fruits</h2>
<div id="all-fruits"></div>

<h2>Create Fruit</h2>
<input id="fruit-name" type="text">
<button id="create-fruit-button" type="button">Create</button>
<div id="create-fruit"></div>

</body>
</html>

In the Javascript code, we need a function to refresh the list of fruits when:

the page is loaded, or
a fruit is added, or
a fruit is deleted.

function refresh() {
    $.get('/fruits', function (fruits) {
        var list = '';
        (fruits || []).forEach(function (fruit) { (1)
            list = list
                + '<tr>'
                + '<td>' + fruit.id + '</td>'
                + '<td>' + fruit.name + '</td>'
                + '<td><a href="#" onclick="deleteFruit(' + fruit.id + ')">Delete</a></td>'
                + '</tr>'
        });
        if (list.length > 0) {
            list = ''
                + '<table><thead><th>Id</th><th>Name</th><th></th></thead>'
                + list
                + '</table>';
        } else {
            list = "No fruits in database"
        }
        $('#all-fruits').html(list);
    });
}

function deleteFruit(id) {
    $.ajax('/fruits/' + id, {method: 'DELETE'}).then(refresh);
}

$(document).ready(function () {

    $('#create-fruit-button').click(function () {
        var fruitName = $('#fruit-name').val();
        $.post({
            url: '/fruits',
            contentType: 'application/json',
            data: JSON.stringify({name: fruitName})
        }).then(refresh);
    });

    refresh();
});

1	The `fruits` parameter is not defined when the database is empty.

All done! Navigate to http://localhost:8080/fruits.html and read/create/delete some fruits.

Database Clients details

Database Extension name Pool class name

Database	Extension name	Pool class name
PostgreSQL	`quarkus-reactive-pg-client`	`io.vertx.mutiny.pgclient.PgPool`
MariaDB/MySQL	`quarkus-reactive-mysql-client`	`io.vertx.mutiny.mysqlclient.MySQLPool`

PostgreSQL

quarkus-reactive-pg-client

io.vertx.mutiny.pgclient.PgPool

MariaDB/MySQL

quarkus-reactive-mysql-client

io.vertx.mutiny.mysqlclient.MySQLPool

Configuration Reference

Common Datasource

Configuration property fixed at build time - All other configuration properties are overridable at runtime

Configuration property	Type	Default
`quarkus.datasource.db-kind` The kind of database we will connect to (e.g. h2, postgresql…).	string
`quarkus.datasource.health.enabled` Whether or not an health check is published in case the smallrye-health extension is present. This is a global setting and is not specific to a datasource.	boolean	`true`
`quarkus.datasource.metrics.enabled` Whether or not datasource metrics are published in case the smallrye-metrics extension is present. This is a global setting and is not specific to a datasource. NOTE: This is different from the "jdbc.enable-metrics" property that needs to be set on the JDBC datasource level to enable collection of metrics for that datasource.	boolean	`false`
`quarkus.datasource.username` The datasource username	string
`quarkus.datasource.password` The datasource password	string
`quarkus.datasource.credentials-provider` The credentials provider name	string
`quarkus.datasource.credentials-provider-type` The credentials provider type. It is the `@Named` value of the credentials provider bean. It is used to discriminate if multiple CredentialsProvider beans are available. For Vault it is: vault-credentials-provider. Not necessary if there is only one credentials provider available.	string
`quarkus.datasource.max-size`	int	`20`
Additional named datasources	Type	Default
`quarkus.datasource."datasource-name".db-kind` The kind of database we will connect to (e.g. h2, postgresql…).	string
`quarkus.datasource."datasource-name".username` The datasource username	string
`quarkus.datasource."datasource-name".password` The datasource password	string
`quarkus.datasource."datasource-name".credentials-provider` The credentials provider name	string
`quarkus.datasource."datasource-name".credentials-provider-type` The credentials provider type. It is the `@Named` value of the credentials provider bean. It is used to discriminate if multiple CredentialsProvider beans are available. For Vault it is: vault-credentials-provider. Not necessary if there is only one credentials provider available.	string
`quarkus.datasource."datasource-name".max-size`	int	`20`

Configuration property

Type

Default

quarkus.datasource.db-kind

The kind of database we will connect to (e.g. h2, postgresql…).

string

quarkus.datasource.health.enabled

Whether or not an health check is published in case the smallrye-health extension is present. This is a global setting and is not specific to a datasource.

boolean

true

quarkus.datasource.metrics.enabled

Whether or not datasource metrics are published in case the smallrye-metrics extension is present. This is a global setting and is not specific to a datasource. NOTE: This is different from the "jdbc.enable-metrics" property that needs to be set on the JDBC datasource level to enable collection of metrics for that datasource.

boolean

false

quarkus.datasource.username

The datasource username

string

quarkus.datasource.password

The datasource password

string

quarkus.datasource.credentials-provider

The credentials provider name

string

quarkus.datasource.credentials-provider-type

The credentials provider type. It is the @Named value of the credentials provider bean. It is used to discriminate if multiple CredentialsProvider beans are available. For Vault it is: vault-credentials-provider. Not necessary if there is only one credentials provider available.

string

quarkus.datasource.max-size

int

20

Additional named datasources

Type

Default

quarkus.datasource."datasource-name".db-kind

The kind of database we will connect to (e.g. h2, postgresql…).

string

quarkus.datasource."datasource-name".username

The datasource username

string

quarkus.datasource."datasource-name".password

The datasource password

string

quarkus.datasource."datasource-name".credentials-provider

The credentials provider name

string

quarkus.datasource."datasource-name".credentials-provider-type

string

quarkus.datasource."datasource-name".max-size

int

20

Reactive Datasource

Configuration property fixed at build time - All other configuration properties are overridable at runtime

Configuration property	Type	Default
`quarkus.datasource.reactive` If we create a Reactive datasource for this datasource.	boolean	`true`
`quarkus.datasource.reactive.url` The datasource URL.	string
`quarkus.datasource.reactive.max-size` The datasource pool maximum size.	int

Configuration property

Type

Default

quarkus.datasource.reactive

If we create a Reactive datasource for this datasource.

boolean

true

quarkus.datasource.reactive.url

The datasource URL.

string

quarkus.datasource.reactive.max-size

The datasource pool maximum size.

int

MariaDB/MySQL

Configuration property fixed at build time - All other configuration properties are overridable at runtime

Configuration property	Type	Default
`quarkus.datasource.reactive.mysql.cache-prepared-statements` Whether prepared statements should be cached on the client side.	boolean
`quarkus.datasource.reactive.mysql.charset` Charset for connections.	string
`quarkus.datasource.reactive.mysql.collation` Collation for connections.	string

Configuration property

Type

Default

quarkus.datasource.reactive.mysql.cache-prepared-statements

Whether prepared statements should be cached on the client side.

boolean

quarkus.datasource.reactive.mysql.charset

Charset for connections.

string

quarkus.datasource.reactive.mysql.collation

Collation for connections.

string

PostgreSQL

Configuration property fixed at build time - All other configuration properties are overridable at runtime

Configuration property	Type	Default
`quarkus.datasource.reactive.postgresql.cache-prepared-statements` Whether prepared statements should be cached on the client side.	boolean
`quarkus.datasource.reactive.postgresql.pipelining-limit` The maximum number of inflight database commands that can be pipelined.	int

Configuration property

Type

Default

quarkus.datasource.reactive.postgresql.cache-prepared-statements

Whether prepared statements should be cached on the client side.

boolean

quarkus.datasource.reactive.postgresql.pipelining-limit

The maximum number of inflight database commands that can be pipelined.

int