exercise5

Exercise 5

Connect to and use a Database!

In this exercise, we will use Panache, a feature of Quarkus that allows fast and smooth database integration!

0. Start Quarkus in Dev mode

./mvnw quarkus:dev

keep this running in a separate terminal window throughout this exercise!

1. Configure database access

We've already configured for you a in-memory H2 database in resources/application.properties. We'll connect to a postgres DB in the next exercise.

quarkus.datasource.url = jdbc:h2:mem:blog
quarkus.datasource.driver = org.h2.Driver
quarkus.hibernate-orm.database.generation=drop-and-create
quarkus.hibernate-orm.log.sql=true

2. Look at the code for a Panache entity bean

Have a look at: org.example.exercise5/Tag.java

You can see we've extended PanacheEntity, and have the standard JPA @Entity annotation on it. This PanacheEntity uses Hibernate underneath the hood as the ORM engine.

Also have a look at: org.example.exercise5/TagResource.java

This is our RESTful endpoint for the Tag database-aware object.

Fire up Quarkus in dev mode if you haven't already:

./mvnw quarkus:dev

then go to:

http://localhost:8080/tag

We've pre-seeded the database with some initial entries using the resources/import.sql file.

3. Implement a new Entity class called Article

Create a new Entity object called Article. Add these persistent fields to it:

  @NotBlank
  public String title;
  public String subtitle;
  public String linktotweet;
  public String coverImage;
  public int likes;
  @NotBlank
  public String asciidocsource;

As we are using an im-memory H2 database, and have set the underlying JPA impl to drop-and-create it will create the database table/fields when you restart quarkus.

4. Write a new RESTful endpoint called ArticleResource

Create a new file ArticleResource.java and create some RESTful endpoints to use the Article entity object. Refer to the code fragment below and the guide link below to get going. Name your RESTful endpoint "/article". Have a look at TagResource.java for some inspiration!

Here is the RESTful endpoint to get one Article entity object to get you started:

  @GET
  @Path("/{id}")
  public Response getOne(@PathParam("id") Long id) {
    Article entity = Article.findById(id);
    if (entity == null) {
      return Response
        .status(Response.Status.NOT_FOUND)
        .build();
    }

    return Response
      .status(Response.Status.OK)
      .entity(entity)
      .build();
  }

And a RESTful endpoint to create an Article object:

  @POST
  @Transactional
  public Response create(Article article) {
    article.persist();
    return Response.status(Response.Status.CREATED).entity(article).build();
  }

Go to: http://localhost:8080/article to test out your Resource and Entity!

Here's a curl command to add an Article per the above datamodel:

curl -H "Content-type: application/json" -d "{"title":"Quarkus test", "asciidocsource":"https://somesource/\"}" -X POST http://localhost:8080/article

Quarkus Panache Guide

5. Add more RESTful endpoints to complete the ArticleResource and exercise the JPA object

Add these into ArticleResource:

public List<Article> getAll ...
public Response update ...
public Response deleteOne ...

EXTRA CREDIT

Write some unit tests! Below you'll see a sample test for the Tag entity. Create one to test the CRUD operations for Article.

@QuarkusTest
@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
public class TagEntityTest {

  public boolean somevar = false;

  @Test
  @Order(0)
  @Transactional
  public void testAddAndGetTags() {
    Tag tag = new Tag();
    tag.name ="BIG DATA";
    tag.persist();
    assertEquals(tag.name, "BIG DATA");

    List<Tag> foundTags = Tag.listAll();
    assertEquals(foundTags.size(), 8);

    foundTags = Tag.list("order by id");
    assertEquals(foundTags.get(0).name, "Java");
  }

}

EXTRA EXTRA CREDIT

Create a many-to-many relationship between Article and Tag. Think of a blog article where you want to have multiple tags, and a tag can be linked to multiple Articles. Below is some code to make it happen - don't forget to amend import.sql with some seed data once you have it all coded.

// Article owns the relationship
  @ManyToMany(cascade = { CascadeType.PERSIST,
    CascadeType.MERGE }, fetch = FetchType.EAGER)
  @JoinTable(
    name = "article_tag",
    joinColumns = { @JoinColumn(name = "article_id") },
    inverseJoinColumns = { @JoinColumn(name = "tag_id") }
  )
  public Set<Tag> tags = new HashSet<>();


// Tag refers back to Article
  @ManyToMany(mappedBy = "tags", fetch = FetchType.LAZY)
  Set<Article> articles = new HashSet<>();

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