8: Do it yourself

Back to school! First, you learn the theory, then you apply it to something new. What would authors be without books! (Maybe bloggers, but anyways...)

After having completed the last chapter where we split of our domain interaction layer, we need to update our domain model:

Domain Model Diagram

UPDATE DOMAIN MODEL TO CONTAIN CORRECT METHODS

The API

In this chapter you will need to apply what you have learned so far and create two new commands in our API spec that will allow an author to write a book and afterwards publish it (publishing is part of the next chapter).

### DONE
POST /authors/commands/register HTTP/1.1
Host: localhost:8080
Content-Type: application/json

{
  "firstName": "PLACE_YOUR_FIRST_NAME",
  "lastName": "PLACE_YOUR_LAST_NAME"
}

### TODO in this assignment
POST /authors/10001/commands/writeBook HTTP/1.1
Host: localhost:8080
Content-Type: application/json

{
  "title": "PLACE_YOUR_TILE",
  "genre": "HORROR"
}

### TODO in this assignment
GET /books?title= HTTP/1.1
Accept: application/json
Host: localhost:8080

The assignment

Your new assignment is to enable authors to write a book. Try to find out which steps you need to take in order to do so. Try to backtrace the steps we have taken so far.

To not get hung up on Database evolution, here is the liquibase script you will need:

• Update src/main/resources/db/db.changelog-master.xml

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-latest.xsd">
    <include file="changelog/01_create_author_seq.xml" relativeToChangelogFile="true"/>
    <include file="changelog/02_create_author_table.xml" relativeToChangelogFile="true"/>
    <include file="changelog/03_create_book_seq.xml" relativeToChangelogFile="true"/>
    <include file="changelog/04_create_book_table.xml" relativeToChangelogFile="true"/>
</databaseChangeLog>

• Add file changelog/03_create_book_seq.xml

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.6.xsd">

    <changeSet id="03-create-book-sequence" author="Maik Kingma">
        <comment>Create Book sequence</comment>
        <createSequence sequenceName="book_seq" minValue="10001"/>
    </changeSet>
</databaseChangeLog>

• Add file changelog/04_create_book_table.xml

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog
        xmlns="http://www.liquibase.org/xml/ns/dbchangelog"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://www.liquibase.org/xml/ns/dbchangelog http://www.liquibase.org/xml/ns/dbchangelog/dbchangelog-3.6.xsd">

  <changeSet id="04-create-book-table" author="Maik Kingma">
    <comment>Create book table</comment>
    <createTable tableName="book">
      <column name="id" type="bigint">
        <constraints primaryKey="true" primaryKeyName="book_id_pk" nullable="false"/>
      </column>
      <column name="title" type="text">
        <constraints nullable="false"/>
      </column>
      <column name="author_id" type="bigint">
        <constraints nullable="false"/>
      </column>
      <column name="genre" type="text">
        <constraints nullable="false"/>
      </column>
      <column name="published" type="boolean" defaultValue="false"/>
      <column name="publisher_id" type="uuid"/>
      <column name="isbn" type="text"/>
    </createTable>

    <addForeignKeyConstraint
            baseColumnNames="author_id"
            baseTableName="book"
            constraintName="FK_AUTHOR_BOOK"
            deferrable="false"
            initiallyDeferred="false"
            onDelete="RESTRICT"
            onUpdate="RESTRICT"
            referencedColumnNames="id"
            referencedTableName="author"
            validate="true"/>
  </changeSet>
</databaseChangeLog>

Let's assume we have 4 genres available: 'FANTASY','HORROR', 'CRIME' and 'ROMANCE'. Make sure to add the enum in the code accordingly.

Now try to complete the rest!

Some things to watch our for

• Remember that an entity in DDD is not the same as an entity in the ORM sense. So the OneToMany and ManyToOne relation annotations need to be placed on the JPA data model classes only.

The following code snippets might prove useful:

    @OneToMany(mappedBy = "authorJPA", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private Set<BookJPA> books;

and

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "author_id")
    private AuthorJPA author;

TIP: If you are stuck, TDD can be practiced with the code from the validate paragraph?

GOOD LUCK!

Validate

Done? Let's test your implementation:

• the test for the creation of books:

@SpringBootTest
@AutoConfigureMockMvc
class AuthorActionCommandsTest {

  @Autowired
  private MockMvc mockMvc;

  @Autowired
  private ObjectMapper objectMapper;

  @Autowired
  private BookRepository bookRepository;

  @Autowired
  private EntityManager entityManager;

  @BeforeEach
  void beforeAll() {
    entityManager.createNativeQuery("DELETE FROM author where true; DELETE FROM book where true;")
            .executeUpdate();
  }

  @Test
  @Transactional
  void writeBook() throws Exception {
    // given
    entityManager.createNativeQuery(
                    "INSERT INTO author (id, first_name, last_name) VALUES (?,?,?)")
            .setParameter(1, 1)
            .setParameter(2, "firstName")
            .setParameter(3, "lastName")
            .executeUpdate();

    var writeBookDTOJson = objectMapper.writeValueAsString(new WriteBookPayload("title", "CRIME"));
    var expected = BookJPA.builder()
            .title("title")
            .genre("CRIME")
            .published(false)
            .author(AuthorJPA.builder().id(1L).firstName("firstName").lastName("lastName").build())
            .build();
    // when
    mockMvc.perform(post("/authors/1/commands/writeBook")
                    .contentType(MediaType.APPLICATION_JSON)
                    .content(writeBookDTOJson))
            .andExpect(status().isAccepted());
    entityManager.flush();
    // then
    List<BookJPA> books = bookRepository.findAll();
    assertThat(books.size()).isEqualTo(1);
    assertThat(books.get(0)).usingRecursiveComparison().ignoringFields("id").isEqualTo(expected);
  }
}

• the test for the querying of books:

@SpringBootTest
@AutoConfigureMockMvc
class BookQueriesTest {

  @Autowired
  private MockMvc mockMvc;

  @Autowired
  private ObjectMapper objectMapper;

  @Autowired
  private EntityManager entityManager;

  @BeforeEach
  void beforeEach() {
    entityManager.createNativeQuery("DELETE FROM author where true; DELETE FROM book where true;")
            .executeUpdate();
  }

  @Test
  @Transactional
  void shouldFindBooksWithNoQueryParam() throws Exception {
    // given
    entityManager.createNativeQuery(
                    "INSERT INTO author (id, first_name, last_name) VALUES (?,?,?)")
            .setParameter(1, 1)
            .setParameter(2, "firstName")
            .setParameter(3, "lastName")
            .executeUpdate();
    var book1 = BookJPA.builder()
            .author(AuthorJPA.builder().id(1L).build())
            .genre("HORROR")
            .title("horror-book")
            .build();
    var book2 = BookJPA.builder()
            .author(AuthorJPA.builder().id(1L).build())
            .genre("ROMANCE")
            .title("romance-book")
            .build();
    var expectedBookView1 = new BookView("horror-book", "HORROR", "firstName lastName");
    var expectedBookView2 = new BookView("romance-book", "ROMANCE", "firstName lastName");

    entityManager.persist(book1);
    entityManager.persist(book2);
    entityManager.flush();
    // when
    MvcResult result = mockMvc.perform(get("/books")
                    .accept(MediaType.APPLICATION_JSON))
            .andExpect(status().isOk())
            .andReturn();
    // then
    var resultingBookViews = objectMapper.readValue(
            result.getResponse().getContentAsString(), new TypeReference<List<BookView>>() {
            });
    assertThat(resultingBookViews).hasSize(2);
    assertThat(resultingBookViews).usingRecursiveFieldByFieldElementComparatorIgnoringFields("id")
            .containsExactlyInAnyOrder(expectedBookView1, expectedBookView2);
  }

  @Test
  @Transactional
  void shouldFindBooksFilteredByQueryParamTitle() throws Exception {
    // given
    entityManager.createNativeQuery(
                    "INSERT INTO author (id, first_name, last_name) VALUES (?,?,?)")
            .setParameter(1, 1)
            .setParameter(2, "firstName")
            .setParameter(3, "lastName")
            .executeUpdate();
    var book1 = BookJPA.builder()
            .author(AuthorJPA.builder().id(1L).build())
            .genre("HORROR")
            .title("horror-book")
            .build();
    var book2 = BookJPA.builder()
            .author(AuthorJPA.builder().id(1L).build())
            .genre("ROMANCE")
            .title("romance-book")
            .build();
    var expectedBookView = new BookView("horror-book", "HORROR", "firstName lastName");

    entityManager.persist(book1);
    entityManager.persist(book2);
    entityManager.flush();
    // when
    MvcResult result = mockMvc.perform(get("/books")
                    .accept(MediaType.APPLICATION_JSON)
                    .queryParam("title", "orror-"))
            .andExpect(status().isOk())
            .andReturn();
    // then
    var resultingBookViews = objectMapper.readValue(
            result.getResponse().getContentAsString(), new TypeReference<List<BookView>>() { });
    assertThat(resultingBookViews).hasSize(1);
    assertThat(resultingBookViews).usingRecursiveFieldByFieldElementComparatorIgnoringFields("id")
            .containsExactly(expectedBookView);
  }
}

Good job! You now know how to apply the Clean Hexagonal Onion yourself. Once again:

if (allTestsGreen == true) {
    log.info("DONE! Let's move on to the next topic: The ACL adapter")}
else{
    log.error("Shout for help!") || (git stash && git checkout 8-do-it-yourself-done)
}