SOLID Principles - SRP, OCP, ISP, DIP

SOLID.java

// Contracts
interface IBookRepository{

    @Nullable
    String getBook(Long id);
      
    List<Object> getBooksByDescription(String description);
    
    List<Object> getBooksByDescriptionOrder(String description);

    Object post(Object book);
}

interface IBookApplication{
  
  @Nullable
  Object createBook(Object book);
  
  List<Object> searchBooks(String description);
    
  List<Object> searchBooks(String description);
}

interface IValidationModel{
  
    boolean isValidated(Object book);
}

// ========================================================

class BookRepository extends IBookRepository(){

    @Nullable
    public String getBook(Long id){
      // sql -> select Description, Price ... from Book where id = id ...
    }
        
    public List<Object> getBooksByDescription(String description){
      // sql -> select Description, Price ... from Book where description like description ...
    }

    public Object post(Object book){
      // sql -> insert into Book values (object) ...
    }
}

class BookValidation : IValidationModel{
  
   @Override
   public boolean isValidated(Object book){
      // ... checks if the model is correct ...
       if(book.year == 1994)
           if(book.price < 60)
               return false;
       
       if(book.year >= 2000)
           if(book.price < 80)
               return false;
       
     return true;
   }
}


class NotebookValidation : IValidationModel{
  
   @Override
   public boolean isValidated(Object notebook){
      // ... checks if the model is correct ...
       if(book.year == 2000)
           if(book.price < 90)
               return false;
       
     return true;
   }
}

@Test
public void IsModel_Correct_When_1994(){

    Object book = new Object("Desc", 1994, 34.6);
    IValidationModel validator = new BookValidation();
    assert.Equal(false, validator.isValidated(book)); 
}



@Test
public void IsModel_Correct(){

    Object book = new Object("Desc", 2000, 80);
    IValidationModel validator ;//= new BookValidation();
    assert.Equal(true, validator.isValidated(book)); 
}


@Test
public void IsModel_Correct2(){

    Object book = new Object("Uyeausdy", 1994, 70);
    IValidationModel validator = new NotebookValidation();
    assert.Equal(true, validator.isValidated(book)); 
}

// Implementation class
class BookApplication extends IBookApplication {

    private IBookRepository repository;
    private IValidationModel bookValidation;
  
    public BookApplication(IBookRepository repository, IValidationModel bookValidation){
        this.repository = repository;  
        this.bookValidation = bookValidation;
    }
  
    @Override @Nullable
    public Object createBook(Object book) {
        
        if(bookValidation.isValidated(book))
          return repository.post(book);
        else
           return null;
    }

    @Override 
    public List<Object> searchBooks(String description) {
        
        List<Object> books = new ArrayList<?>();
        
        if(!description.equals(""))        
          books = repository.getBooksByDescription(description);
      
        return books;
    }
    
    @Override 
    public List<Object> searchBooksOrder(String description) {
        
        List<Object> books = new ArrayList<?>();
        
        if(!description.equals(""))        
          books = repository.getBooksByDescription(description);
      
        return books;
    }
    
    
}

fun main(){

    // Dependencies
    IBookRepository repository = new MockBookRepository();
    IValidationModel bookValidation = new BookValidation();
    IBookApplication application = new BookApplication(repository, bookValidation);
  
    // Model
    Object myBook = new Object("The art of doing twice the work in half the time");
  
    // Create the book
    application.createBook(myBook);
  
    // Query 
    List<Objects> books = application.searchBooks("twice the work");
}