Read: 13 - Related Resources and Integration Testing

• Important Note all code copied is resourced.

  Working with Relationships in Spring Data REST

  how to create relationships in spring mvc.

  One-to-One Relationship

  1. the data mode:
  • @OneToOne allow me to associate a relation between 2 classes 1 to 1 (I will be using the example from the read).
• and can have the optional @RestResource annotation to customize the association resource. class Library :

  @OneToOne
    @JoinColumn(name = "address_id")
    @RestResource(path = "libraryAddress", rel="address")
    private Address address;
  

class Address

 @OneToOne(mappedBy = "address")
  private Library library;

• explination: the example create a relation 1 to 1 between adress and library.
  • example used the address id column to add it inside library as column that refer to address entity inside adress class.
  • and inside the Address class added mappedby to tell the springMVC I am making 1 to 1 relation to library.
• Important Note: We must be careful to have different names for each association resource. Otherwise, will encounter a JsonMappingException with the message: “Detected multiple association links with same relation type! Disambiguate association”.

1. The Repositories:: now I will create repository for each class and extended it from CrudRepository so they are exposed as resources

One-to-many Relationship

• A one-to-many relationship is created using the @OneToMany and @ManyToOne annotations.
• and can have the optional @RestResource annotation to customize the association resource.
  1. The Data Model
• example (also from read to save time):

@ManyToOne
    @JoinColumn(name="library_id")
    private Library library;

@OneToMany(mappedBy = "library")
    private List<Book> books;

• explination:
  • Book entity that will represent the many end of a relationship with the Library entity:

1. The Repository
   • public interface BookRepository extends CrudRepository<Book, Long> { }
   • the book resource entity also exposed to make the relation of many books inside our library in the db.

Many-to-Many Relationship

1. data model
   • A many-to-many relationship is extablished with @ManyToMany annotation.
   • example :

@ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "book_author", 
      joinColumns = @JoinColumn(name = "book_id", referencedColumnName = "id"), 
      inverseJoinColumns = @JoinColumn(name = "author_id", 
      referencedColumnName = "id"))
    private List<Book> books;

@ManyToMany(mappedBy = "books")
    private List<Author> authors;

• explination : the relation between authors and books a book can have many authors and vice versa.

1. The Repository
   • public interface AuthorRepository extends CrudRepository<Author, Long> { }
   • expose the authors resource to establish the relationship

     Integration Testing in Spring

   • we use it to test the controllers behaviour
2. Preparation
   • required dependencies junit-jupiter-engine, junit-jupiter-api, and Spring test.
   • for asserting results : Hamcrest and JSON path
3. Spring MVC Test Configuration
   1. Enable Spring in Tests with JUnit 5.
      1. JUnit defines an extension interface through which classes can integrate with the JUnit test.
      2. adding the @ExtendWith annotation to test classes and specifying the extension class to load. To run the Spring test, use SpringExtension.class.
      3. @ContextConfiguration provide the ApplicationConfig.class config class, which loads the configuration needed for test test.
      4. @WebAppConfiguration, will load the web application context, it search from root and to override it i provide value=""
      5. example :

         @ExtendWith(SpringExtension.class)
         @ContextConfiguration(classes = { ApplicationConfig.class })
         @WebAppConfiguration
         public class GreetControllerIntegrationTest {
          ....
         }
         

         resource.

4. The WebApplicationContext Object
   1. provides a web application configuration, it load app beans and controllers into context.
5. Mocking Web Context Beans
   1. encapsulate app beans and make them available for testing.
   2. usage:
   3. Note : initialize the mockMvc object in the @BeforeEach annotated method so I don’t have to initialize it inside every test.

private MockMvc mockMvc;
@BeforeEach
public void setup() throws Exception {
    this.mockMvc = MockMvcBuilders.webAppContextSetup(this.webApplicationContext).build();
}

resource

1. Verify Test Configuration

@Test
public void givenWac_whenServletContext_thenItProvidesGreetController() {
    ServletContext servletContext = webApplicationContext.getServletContext();
    
    Assert.assertNotNull(servletContext);
    Assert.assertTrue(servletContext instanceof MockServletContext);
    Assert.assertNotNull(webApplicationContext.getBean("greetController"));
}

resource.

Writing Integration Tests

@Test
public void givenHomePageURI_whenMockMVC_thenReturnsIndexJSPViewName() {
    this.mockMvc.perform(get("/homePage")).andDo(print())
      .andExpect(view().name("index"));
}

• explination:
  • perform() call a GET request, return result and then I can create assertion.
  • andDo(print()) print the request and response.
  • andExpect() expect the provided argument from requesting the url, for example on /homePage will load the inedx.html.

MockMvc Limitations

• uses a subclass of the DispatcherServlet to handle test requests.