Escrevendo uma aplicação com acoplamento zero no Mentawai

O suporte do Mentawai a POJO Actions , junto com seus poderosos filtros, permite que você escreva a sua aplicação web com desacoplamento total do framework.

Para um exemplo completo, sinta-se à vontade para baixar as duas implementações da aplicação MyBooks: (use o arquivo mybooks.sql, incluso no arquivo zip, para criar o database MySQL do MyBooks).

MyBooks-ACTION.zip - As Actions e modelos de negócio estão separados. As Actions estão acopladas ao Mentawai. O modelo de negócio não está acoplado.

MyBooks-POJO.zip - As Actions e modelos de negócio estão todos juntos em uma única classe, totalmente desacoplada do framework Mentawai.

Dê uma olhada nos códigos abaixo:

ACTION version:

MyBooks-ACTION ApplicationManager.java

package org.mentawai.mybooks;

// imports aqui...

public class ApplicationManager extends org.mentawai.core.ApplicationManager {
   
   private ConnectionHandler connHandler = null;

public void init(Context application) {

// ligando o modo de debug
      setDebugMode(true);

// ConnectionPool (ConnectionHandler)
      this.connHandler = new C3P0ConnectionHandler("com.mysql.jdbc.Driver", "jdbc:mysql://localhost/mybooks?autoReconnect=true", "mybooks", "mybooks");

}

@Override
   public void loadActions() {
      
      filter(new ExceptionFilter());
      on(EXCEPTION, fwd("/error.jsp"));

// Authentication for all actions (exceto para aqueles que implementam AuthenticationFree)
      filter(new AuthenticationFilter());
      on(LOGIN, redir("/login.jsp")); // global consequence

// Validação para todas as actions que implementam Validatable
      filter(new ValidatorFilter());
      
      // Connection Pooling
      filter(new ConnectionFilter("connection", connHandler));

// IoC (Inversion of Control)
      filter(new IoCFilter());
      
      // IoC services (Business Model)
      ioc("userService", UserService.class);
      ioc("bookService", BookService.class);
      ioc("loginService", LoginService.class);
      ioc("registrationService", RegistrationService.class);
      
      // IoC components (DAOs)
      ioc("userDAO", MySQLUserDAO.class);
      ioc("bookDAO", MySQLBookDAO.class);
      ioc("userBooksDAO", MySQLUserBooksDAO.class);
      ioc("transaction", JdbcTransaction.class);

// Auto-wiring
      filter(new DIFilter());
      
      // Dependências
      di("connection", Connection.class); // DAOs dependem de Connection
      
      di("userDAO", UserDAO.class); // Services dependem de DAOs
      di("bookDAO", BookDAO.class);
      di("userBooksDAO", UserBooksDAO.class);

// Injection
      filter(new InjectionFilter());
      
      // LoginAction
      action(LoginAction.class, "login")
         .on(SUCCESS, redir("/welcome.jsp"))
         .on(ERROR, fwd("/login.jsp"));

// RegistrationAction
      action(RegistrationAction.class, "register")
         .on(SUCCESS, redir("/welcome.jsp"))
         .on(ERROR, fwd("/registration.jsp"));
      
      // BookAction.searchToAdd
      action(BookAction.class, "searchToAdd")
         .on(SUCCESS, fwd("/book/showbooks.jsp"))
         .on(NOBOOKS, fwd("/book/createbook.jsp"))
         .on(ERROR, fwd("/welcome.jsp"));

// BookAction.search
      action(BookAction.class, "search")
         .on(SUCCESS, fwd("/book/search.jsp"));

// BookAction.addToUser
      action(BookAction.class, "addToUser")
         .on(SUCCESS, fwd("/welcome.jsp"))
         .on(ERROR, fwd("/book/showbooks.jsp"))
         .on(ALREADYHASBOOK, fwd("/welcome.jsp"));

// BookAction.create
      action(BookAction.class, "create")
         .on(SUCCESS, fwd("/book/createbook.jsp"))
         .on(ERROR, redir("/welcome.jsp"));

// BookAction.createAndAddToUser
      action(BookAction.class, "createAndAddToUser")
         .on(SUCCESS, fwd("/welcome.jsp"))
         .on(ERROR, fwd("/book/createbook.jsp"))
         .on(BOOKALREADYCREATED, fwd("/welcome.jsp"))
         .filter(new TransactionFilter("transaction")); // make this action atomic...

// BookAction.show
      action(BookAction.class, "show")
         .on(SUCCESS, fwd("/book/show.jsp"))
         .on(ERROR, redir("/"));

// BookAction.remove
      action(BookAction.class, "remove")
         .on(ERROR, redir("/welcome.jsp"))
         .on(SUCCESS, fwd("/welcome.jsp"));
      
      // UserAction.search
      action(UserAction.class, "search")
         .on(SUCCESS, fwd("/user/search.jsp"));

// UserAction.show
      action(UserAction.class, "show")
         .on(SUCCESS, fwd("/user/show.jsp"))
         .on(ERROR, redir("/"));

// LogoutAction
      action(LogoutAction.class)
         .on(SUCCESS, redir("/"));
      
   }
}

MyBooks-ACTION BookAction.java

package org.mentawai.mybooks.action;

// imports aqui...

public class BookAction extends BaseAction implements Validatable {

public static final String NOBOOKS = "nobooks";
   public static final String ALREADYHASBOOK = "alreadyhasbook";
   public static final String BOOKALREADYCREATED = "bookalreadycreated";

private BookService bookService;
   
   public void setBookService(BookService bookService) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.bookService = bookService;
   }

public String searchToAdd(String title) throws Exception {

List<Book> books = bookService.searchBooks(title);
      
      if (books == null || books.isEmpty()) {
         
         output.setValue("title", title);
         
         return NOBOOKS;
      }

output.setValue("title", title);
      output.setValue("books", books);

saveLastSearch(title, books);
      
      return SUCCESS;
   }

public String search(String keywords) throws Exception {
      
      List<Book> books = bookService.searchBooks(keywords);
      
      output.setValue("keywords", keywords);
      
      output.setValue("books", books);
      
      return SUCCESS;
   }

public String create(String title) throws Exception {
      
      if (title == null || title.trim().equals("")) {
         
         return ERROR;
         
      }
      
      output.setValue("title", title);
      
      return SUCCESS;
   }

private void resendLastSearch() {
      
      List<Book> books = (List<Book>) session.getAttribute("lastSearchToAdd");
      
      if (books != null && books.size() > 0) {
         
         output.setValue("books", books);
         
      }
      
      String title = (String) session.getAttribute("title");
      
      if (title != null) {
         
         output.setValue("title", title);
         
      }
   }

private void removeLastSearch() {
      
      session.removeAttribute("lastSearchToAdd");
      
      session.removeAttribute("title");
      
   }
   
   private void saveLastSearch(String title, List<Book> books) {
      
      session.setAttribute("title", title);
      
      session.setAttribute("lastSearchToAdd", books);
   }

public String addToUser(int book_id) throws Exception {
      
      if (book_id <= 0) {
         
         addError(CHOOSE_ANOTHER_BOOK);
         
         resendLastSearch();
         
         return ERROR;
         
      }
      
      User user = (User) getUserSession();
      
      if (!bookService.addBookToUser(book_id, user)) {
         
         addError(ALREADY_HAS_THIS_BOOK);
         
         resendLastSearch();
         
         return ALREADYHASBOOK;
         
      } else {
         
         addMessage(BOOK_ADDED);
         
         removeLastSearch();
         
         return SUCCESS;
      }
   }

public String createAndAddToUser(Book book) throws Exception {
      
      User user = (User) getUserSession();
      
      if (user.checkBookByName(book)) {
         
         addError(BOOK_ALREADY_CREATED);
         
         return BOOKALREADYCREATED;
         
      } else {
         
         bookService.createAndAddBookToUser(book, user);
         
         addMessage(BOOK_CREATED);
         
         removeLastSearch();
         
         return SUCCESS;
      }
   }

public String show(int book_id) throws Exception {
      
      if (book_id <= 0) return ERROR;
      
      Book book = bookService.loadBook(book_id);
         
      if (book == null) return ERROR;
         
      output.setValue("book", book);
      
      return SUCCESS;
   }

public String remove(int book_id) throws Exception {
      
      if (book_id <= 0) return ERROR;
      
      User user = (User) getUserSession();
      
      bookService.removeBookFromUser(book_id, user);
      
      addMessage(BOOK_REMOVED);
      
      return SUCCESS;
   }

public void prepareValidator(Validator val, String innerAction) {

if (innerAction != null && innerAction.equals("createAndAddToUser")) {

val.add("author", RequiredRule.getInstance(), FIELD_REQUIRED);
         val.add("author", StringRule.getInstance(4, 50), INVALID_LENGTH);
         val.add("author", RegexRule.getInstance(NAME_PATTERN), INVALID_CHARACTERS);

val.add("languageId", RequiredRule.getInstance(), FIELD_REQUIRED);
         val.add("languageId", IntegerRule.getInstance(1, 100), FIELD_REQUIRED);

val.add("amazonLink", RegexRule.getInstance(LINK_PATTERN), INVALID_CHARACTERS);
         val.add("submarinoLink", RegexRule.getInstance(LINK_PATTERN), INVALID_CHARACTERS);

} else if (innerAction != null && innerAction.equals("searchToAdd")) {

val.add("title", RequiredRule.getInstance(), FIELD_REQUIRED);
         val.add("title", StringRule.getInstance(3, 50), INVALID_LENGTH);
      }

}

private static final String LINK_PATTERN = "^[^\\s]+$";
   private static final String NAME_PATTERN = "^[a-zA-Z\\-\\. ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝàáâãäåæçèéêëìíîïðñòóôõöùúûüýÿŠšŸ]+$";

private static final String FIELD_REQUIRED = "Campo obrigatório não-preenchido!";
   private static final String INVALID_LENGTH = "Esse campo deve ter entre %min% e %max% caracteres!";
   private static final String INVALID_CHARACTERS = "Você digitou caracteres inválidos para esse campo!";
   
   private static final String CHOOSE_ANOTHER_BOOK = "Favor escolher um livro!";
   private static final String ALREADY_HAS_THIS_BOOK = "Você já possui esse livro!";
   private static final String BOOK_ALREADY_CREATED = "Esse livro já foi criado!";
   private static final String BOOK_ADDED = "Livro adicionado com sucesso!";
   private static final String BOOK_CREATED = "Livro criado com sucesso!";
   private static final String BOOK_REMOVED = "Livro removido com sucesso!";

}

MyBooks-ACTION BookService.java

package org.mentawai.mybooks.service;

// imports aqui...

public class BookService {
   
   private static final int MAX_RESULTS = 100;

private BookDAO bookDAO = null;
   private UserBooksDAO userBooksDAO = null;

public void setBookDAO(BookDAO bookDAO) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.bookDAO = bookDAO;
   }
   
   public void setUserBooksDAO(UserBooksDAO userBooksDAO) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.userBooksDAO = userBooksDAO;
   }

private void removeSmallWords(List<String> tokens) {
      
      Iterator<String> iter = tokens.iterator();
      
      while (iter.hasNext()) {
         
         String token = iter.next();
         
         if (token.equals("the") || token.length() < 3) {
            
            iter.remove();
         }
      }
   }

public List<Book> searchBooks(String title) throws Exception {
      
      String[] s = title.split("\\s+");
      
      List<String> tokens = new ArrayList<String>(s.length);
      
      for(String token: s) {
         
         tokens.add(token.toLowerCase());
      }
      
      Set<Book> results = new HashSet<Book>();

// tente primeiro o título inteiro
      List<String> temp = new ArrayList<String>(1);
      temp.add(title);
      List<Book> list = bookDAO.searchBooksByName(temp, true, MAX_RESULTS);
      results.addAll(list);

// tente com todas as palavras
      list = bookDAO.searchBooksByName(tokens, true, MAX_RESULTS);
      results.addAll(list);

removeSmallWords(tokens);

if (tokens.size() > 0) {
         // tente com todas as palavras, sem considerar palavras pequenas
         list = bookDAO.searchBooksByName(temp, true, MAX_RESULTS);
         results.addAll(list);

// tente com todas as palavras, sem considerar palavras pequenas
         list = bookDAO.searchBooksByName(temp, false, MAX_RESULTS);
         results.addAll(list);
      }

return list;
   }

public boolean addBookToUser(int book_id, User user) throws Exception {
      
      Book book = bookDAO.loadById(book_id);
      
      if (book == null) return false;
      
      if (user.checkBook(book)) {
         
         // já tem esse livro
         
         return false;
      }
      
      userBooksDAO.addBookToUser(book.getId(), user.getId());
      
      user.addBook(book);
      
      return true;
      
   }

public void removeBookFromUser(int book_id, User user) throws Exception {
      
      userBooksDAO.removeBookFromUser(book_id, user.getId());
      
      user.delBook(book_id);
   }

public void createAndAddBookToUser(Book book, User user) throws Exception {
      
      bookDAO.insert(book);
      
      userBooksDAO.addBookToUser(book.getId(),user.getId());
      
      user.addBook(book);
   }

public Book loadBook(int book_id) throws Exception {
      
      Book book = bookDAO.loadById(book_id);
         
      if (book != null && book.getUsers() == null) {
         
         List<User> users = userBooksDAO.loadUsersByBookId(book.getId());
         
         book.setUsers(users);
         
      }
      
      return book;
   }
}

Agora, a versão com POJO Actions:

MyBooks-POJO ApplicationManager.java

package org.mentawai.mybooks;

// imports aqui...

public class ApplicationManager extends org.mentawai.core.ApplicationManager {
   
   private ConnectionHandler connHandler = null;

public void init(Context application) {

// Ligando o modo debug
      setDebugMode(true);

// ConnectionPool (ConnectionHandler)
      this.connHandler = new C3P0ConnectionHandler("com.mysql.jdbc.Driver", "jdbc:mysql://localhost/mybooks?autoReconnect=true", "mybooks", "mybooks");

}

@Override
   public void loadActions() {
      
      filter(new ExceptionFilter());
      on(EXCEPTION, fwd("/error.jsp"));

// Autenticação para todas as actions (com exceção das que implementam AuthenticationFree)
      filter(new AuthenticationFilter());
      on(LOGIN, redir("/login.jsp")); // global consequence
      
      // Pojo Action Filter Stack
      filter(PojoAction.getFilterStack());

// Connection Pooling
      filter(new ConnectionFilter("connection", connHandler));

// IoC (Inversion of Control)
      filter(new IoCFilter());
      
      // IoC components (DAOs)
      ioc("userDAO", MySQLUserDAO.class);
      ioc("bookDAO", MySQLBookDAO.class);
      ioc("userBooksDAO", MySQLUserBooksDAO.class);
      ioc("transaction", JdbcTransaction.class);

// Auto-wiring
      filter(new DIFilter());
      
      // Dependências
      di("connection", Connection.class); // DAOs depend on Connection
      
      // Injection
      filter(new InjectionFilter());
      
      // LoginAction
      action("/LoginAction", LoginService.class, "login")
         .filter(new AuthenticationFreeMarkerFilter())
         .filter(new LoginServiceValidation())
         .on(SUCCESS, redir("/welcome.jsp"))
         .on(ERROR, fwd("/login.jsp"));

// RegistrationAction
      action("/RegistrationAction", RegistrationService.class, "register")
         .filter(new RegistrationServiceValidation())
         .filter(new AuthenticationFreeMarkerFilter())
         .on(SUCCESS, redir("/welcome.jsp"))
         .on(ERROR, fwd("/registration.jsp"));
      
      // BookAction.searchToAdd
      action("/BookAction", BookService.class, "searchToAdd")
         .filter(new BookServiceValidation())
         .on(SUCCESS, fwd("/book/showbooks.jsp"))
         .on(NOBOOKS, fwd("/book/createbook.jsp"))
         .on(ERROR, fwd("/welcome.jsp"));

// BookAction.search
      action("/BookAction", BookService.class, "search")
         .on(SUCCESS, fwd("/book/search.jsp"));

// BookAction.addToUser
      action("/BookAction", BookService.class, "addToUser")
         .on(SUCCESS, fwd("/welcome.jsp"))
         .on(ERROR, fwd("/book/showbooks.jsp"))
         .on(ALREADYHASBOOK, fwd("/welcome.jsp"));

// BookAction.create
      action("/BookAction", BookService.class, "create")
         .on(SUCCESS, fwd("/book/createbook.jsp"))
         .on(ERROR, redir("/welcome.jsp"));

// BookAction.createAndAddToUser
      action("/BookAction", BookService.class, "createAndAddToUser")
         .filter(new BookServiceValidation())
         .on(SUCCESS, fwd("/welcome.jsp"))
         .on(ERROR, fwd("/book/createbook.jsp"))
         .on(BOOKALREADYCREATED, fwd("/welcome.jsp"))
         .filter(new TransactionFilter("transaction")); // faz essa action ser atômica

// BookAction.show
      action("/BookAction", BookService.class, "show")
         .on(SUCCESS, fwd("/book/show.jsp"))
         .on(ERROR, redir("/"));

// BookAction.remove
      action("/BookAction", BookService.class, "remove")
         .on(ERROR, redir("/welcome.jsp"))
         .on(SUCCESS, fwd("/welcome.jsp"));
      
      // UserAction.search
      action("/UserAction", UserService.class, "search")
         .on(SUCCESS, fwd("/user/search.jsp"));

// UserAction.show
      action("/UserAction", UserService.class, "show")
         .on(SUCCESS, fwd("/user/show.jsp"))
         .on(ERROR, redir("/"));

// LogoutAction
      action(LogoutAction.class)
         .on(SUCCESS, redir("/"));
      
   }
}

MyBooks-POJO BookService.java

package org.mentawai.mybooks.service;

// imports aqui...

public class BookService {
   
   private static final int MAX_RESULTS = 100;

public static final String NOBOOKS = "nobooks";
   public static final String ALREADYHASBOOK = "alreadyhasbook";
   public static final String BOOKALREADYCREATED = "bookalreadycreated";
   
   private Map<String, Object> output;
   private Map<String, Object> session;
   private List<String> errors;
   private List<String> messages;
   
   private BookDAO bookDAO = null;
   private UserBooksDAO userBooksDAO = null;

public void setBookDAO(BookDAO bookDAO) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.bookDAO = bookDAO;
   }
   
   public void setUserBooksDAO(UserBooksDAO userBooksDAO) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.userBooksDAO = userBooksDAO;
   }

public void setOutput(Map<String, Object> output) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.output = output;
   }
   
   public void setSession(Map<String, Object> session) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.session = session;
   }
   
   public void setErrors(List<String> errors) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.errors = errors;
   }
   
   public void setMessages(List<String> messages) {
      
      // Não precisa do setter, mas é uma boa prática.
      
      this.messages = messages;
   }

public String searchToAdd(String title) throws Exception {

List<Book> books = searchBooks(title);
      
      if (books == null || books.isEmpty()) {
         
         output.put("title", title);
         
         return NOBOOKS;
      }

output.put("title", title);
      output.put("books", books);

saveLastSearch(title, books);
      
      return SUCCESS;
   }

public String search(String keywords) throws Exception {
      
      List<Book> books = searchBooks(keywords);
      
      output.put("keywords", keywords);
      
      output.put("books", books);
      
      return SUCCESS;
   }

public String create(String title) throws Exception {
      
      if (title == null || title.trim().equals("")) {
         
         return ERROR;
         
      }
      
      output.put("title", title);
      
      return SUCCESS;
   }

private void resendLastSearch() {
      
      List<Book> books = (List<Book>) session.get("lastSearchToAdd");
      
      if (books != null && books.size() > 0) {
         
         output.put("books", books);
         
      }
      
      String title = (String) session.get("title");
      
      if (title != null) {
         
         output.put("title", title);
         
      }
   }

private void removeLastSearch() {
      
      session.remove("lastSearchToAdd");
      
      session.remove("title");
      
   }
   
   private void saveLastSearch(String title, List<Book> books) {
      
      session.put("title", title);
      
      session.put("lastSearchToAdd", books);
   }

public String addToUser(int book_id) throws Exception {
      
      if (book_id <= 0) {
         
         errors.add(CHOOSE_ANOTHER_BOOK);
         
         resendLastSearch();
         
         return ERROR;
         
      }
      
      User user = getUserSession();
      
      if (!addBookToUser(book_id, user)) {
         
         errors.add(ALREADY_HAS_THIS_BOOK);
         
         resendLastSearch();
         
         return ALREADYHASBOOK;
         
      } else {
         
         messages.add(BOOK_ADDED);
         
         removeLastSearch();
         
         return SUCCESS;
      }
   }

public String createAndAddToUser(Book book) throws Exception {
      
      User user = getUserSession();
      
      if (user.checkBookByName(book)) {
         
         errors.add(BOOK_ALREADY_CREATED);
         
         return BOOKALREADYCREATED;
         
      } else {
         
         createAndAddBookToUser(book, user);
         
         messages.add(BOOK_CREATED);
         
         removeLastSearch();
         
         return SUCCESS;
      }
   }

public String show(int book_id) throws Exception {
      
      if (book_id <= 0) return ERROR;
      
      Book book = loadBook(book_id);
         
      if (book == null) return ERROR;
         
      output.put("book", book);
      
      return SUCCESS;
   }

public String remove(int book_id) throws Exception {
      
      if (book_id <= 0) return ERROR;
      
      User user = getUserSession();
      
      removeBookFromUser(book_id, user);
      
      messages.add(BOOK_REMOVED);
      
      return SUCCESS;
   }
   
   private void removeSmallWords(List<String> tokens) {
      
      Iterator<String> iter = tokens.iterator();
      
      while (iter.hasNext()) {
         
         String token = iter.next();
         
         if (token.equals("the") || token.length() < 3) {
            
            iter.remove();
         }
      }
   }

public List<Book> searchBooks(String title) throws Exception {
      
      String[] s = title.split("\\s+");
      
      List<String> tokens = new ArrayList<String>(s.length);
      
      for(String token: s) {
         
         tokens.add(token.toLowerCase());
      }
      
      Set<Book> results = new HashSet<Book>();

// tente primeiro o título inteiro
      List<String> temp = new ArrayList<String>(1);
      temp.add(title);
      List<Book> list = bookDAO.searchBooksByName(temp, true, MAX_RESULTS);
      results.addAll(list);

// tente com todas as palavras
      list = bookDAO.searchBooksByName(tokens, true, MAX_RESULTS);
      results.addAll(list);

removeSmallWords(tokens);

if (tokens.size() > 0) {
         // tente com todas as palavras, mas sem considerar as palavras pequenas
         list = bookDAO.searchBooksByName(temp, true, MAX_RESULTS);
         results.addAll(list);

// tente com todas as apalvras, mas sem considerar as palavras pequenas
         list = bookDAO.searchBooksByName(temp, false, MAX_RESULTS);
         results.addAll(list);
      }

return list;
   }

public boolean addBookToUser(int book_id, User user) throws Exception {
      
      Book book = bookDAO.loadById(book_id);
      
      if (book == null) return false;
      
      if (user.checkBook(book)) {
         
         // já tem essa livro.
         
         return false;
      }
      
      userBooksDAO.addBookToUser(book.getId(), user.getId());
      
      user.addBook(book);
      
      return true;
      
   }

public void removeBookFromUser(int book_id, User user) throws Exception {
      
      userBooksDAO.removeBookFromUser(book_id, user.getId());
      
      user.delBook(book_id);
   }

public void createAndAddBookToUser(Book book, User user) throws Exception {
      
      bookDAO.insert(book);
      
      userBooksDAO.addBookToUser(book.getId(),user.getId());
      
      user.addBook(book);
   }

public Book loadBook(int book_id) throws Exception {
      
      Book book = bookDAO.loadById(book_id);
         
      if (book != null && book.getUsers() == null) {
         
         List<User> users = userBooksDAO.loadUsersByBookId(book.getId());
         
         book.setUsers(users);
         
      }
      
      return book;
   }
   
   private User getUserSession() {
      
      return (User) session.get("user");
   }

private static final String CHOOSE_ANOTHER_BOOK = "Favor escolher um livro!";
   private static final String ALREADY_HAS_THIS_BOOK = "Você já possui esse livro!";
   private static final String BOOK_ALREADY_CREATED = "Esse livro já foi criado!";
   private static final String BOOK_ADDED = "Livro adicionado com sucesso!";
   private static final String BOOK_CREATED = "Livro criado com sucesso!";
   private static final String BOOK_REMOVED = "Livro removido com sucesso!";

}