I did a task on working with JDBC. And implemented methods based on G… #421

IgorGunder · 2024-09-30T14:42:56Z

…RUD principles!!!

mateacademy-ai-mentor

Hey there! 👋 It's great to see the effort you've put into following Java conventions and implementing the CRUD operations cleanly. However, there are a few improvements we can make to ensure your code is even more robust and maintainable. Let's enhance the exception messages to give more context when something goes wrong, and consider using PreparedStatement for all SQL queries to boost security and performance. Also, let's try to reduce code duplication by refactoring common logic into separate methods. Remember to manage resources like database connections carefully using try-with-resources, and keep sensitive information like database credentials out of the source code. Lastly, double-check that your database URL is complete. These changes will make your codebase solid and professional. Keep up the great work, and with these adjustments, your project will be top-notch! 🚀💻

✨ Please rate this review in the Platform's notification center. I will be grateful for your feedback! ✨

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/ConnectionUtil.java

+import mate.academy.exception.DataProcessingException;
+
+public class ConnectionUtil {
+    private static final String DB_URL = "jdbc:mysql://localhost:3306/test";


It looks like the DB_URL is not fully defined here. Make sure to provide the complete database URL string.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/ConnectionUtil.java

+        DB_PROPERTIES.put("user", "root");
+        DB_PROPERTIES.put("password", "Root1234");


Storing credentials in code is a security risk. Consider using environment variables or a configuration file to keep sensitive information out of the source code.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/ConnectionUtil.java

+    public static Connection getConnection() throws SQLException {
+        return DriverManager.getConnection(DB_URL, DB_PROPERTIES);
+    }


According to the best practices, it's recommended to use try-with-resources for getting the Connection to ensure that it is closed properly. This can prevent potential resource leaks.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+                book.setId(resultSet.getLong("id"));
+                book.setTitle(resultSet.getString("title"));
+                book.setPrice(resultSet.getBigDecimal("price"));


You are using setters to set the properties of the Book object after using the default constructor. According to the checklist, it is recommended to use either setters or the constructor to set all properties, but not both. Consider creating a constructor in the Book class that takes all the properties as parameters, or use the default constructor and setters consistently.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+                Book book = new Book();
+                book.setId(resultSet.getLong("id"));
+                book.setTitle(resultSet.getString("title"));
+                book.setPrice(resultSet.getBigDecimal("price"));


The code duplicates the logic of converting a ResultSet to a Book object which is present in both 'findById' and 'findAll' methods. To avoid code duplication, you could move this logic into a separate private method that constructs a Book object from a ResultSet and then call this method in both 'findById' and 'findAll'.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    public List<Book> findAll() {
+        List<Book> books = new ArrayList<>();
+        try (Connection connection = ConnectionUtil.getConnection();
+                Statement statement = connection.createStatement()) {


Use PreparedStatement instead of Statement for the 'findAll' method, even if the query does not have parameters. This is a best practice for several reasons, including better performance and security against SQL injection attacks.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+                return Optional.of(book);
+            }
+        } catch (SQLException e) {
+            throw new DataProcessingException("Can't get book by ID", e);


The exception message is not informative enough. According to the checklist, it's recommended to include the id of the book that failed to be retrieved. For example, 'Can't get book by id ' + id.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+            int rowsAffected = statement.executeUpdate();
+            return rowsAffected > 0;
+        } catch (SQLException e) {
+            throw new DataProcessingException("Can't delete book by ID", e);


Similarly, the exception message when deleting a book is not informative enough. Include the id of the book that failed to be deleted, for example, 'Can't delete book by ID ' + id.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+            return book;
+
+        } catch (SQLException e) {
+            throw new DataProcessingException("Can't insert book into DB", e);


The exception message when inserting a book should be more informative. Include the book object that failed to be inserted, for example, 'Can't insert book ' + book + ' into DB'.

mateacademy-ai-mentor · 2024-09-30T14:43:31Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+            statement.executeUpdate();
+            return book;
+        } catch (SQLException e) {
+            throw new DataProcessingException("Can't update book", e);


The exception message when updating a book should also be more informative. Include the book object that failed to be updated, for example, 'Can't update book ' + book.

…RUD principles!!!

mateacademy-ai-mentor

Thank you for your efforts so far! 😊 However, there are a few critical issues that need to be addressed before the pull request can be approved. Specifically, the handling of the DB_URL needs correction to prevent connection issues, and the handling of the Book ID generation should be left to the database to ensure uniqueness. Also, please ensure that database credentials are securely managed and not hardcoded. Keep up the good work, and with a few adjustments, your code will be ready to go! 👍

✨ Please rate this review in the Platform's notification center. I will be grateful for your feedback! ✨

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/ConnectionUtil.java

+import mate.academy.exception.DataProcessingException;
+
+public class ConnectionUtil {
+    private static final String DB_URL = "jdbc:mysql://localhost:3306/test";


The DB_URL is incomplete, which will cause a SQLException when attempting to connect to the database. Make sure to provide the full JDBC URL in the format jdbc:mysql://<host>:<port>/<database_name>.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/ConnectionUtil.java

+        DB_PROPERTIES.put("user", "root");
+        DB_PROPERTIES.put("password", "Root1234");


Hardcoding the database credentials in the source code is not a secure practice. It's better to load these values from an external configuration file or environment variables.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/ConnectionUtil.java

+        try {
+            Class.forName("com.mysql.cj.jdbc.Driver");
+        } catch (ClassNotFoundException e) {
+            throw new DataProcessingException("Can not load JDBC driver", e);


While it's good to load the JDBC driver class, consider adding an informative message about the JDBC driver that was not found to make the exception more helpful.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/ConnectionUtil.java

+        }
+    }
+
+    public static Connection getConnection() throws SQLException {


Do not use schema's name in the DB_URL as you are configuring it while establishing a connection with the database. Ensure that the schema is specified in the URL if necessary, or configured through the DB_PROPERTIES.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/Main.java

+        Book book = new Book(1L, "Java Programming", new BigDecimal("29.99"));
+        Book book1 = new Book(2L, "Java", new BigDecimal("30.25"));


It's not recommended to set the ID for the Book object manually when creating a new Book. The ID should be auto-generated by the database to ensure uniqueness and to prevent conflicts. Consider removing the ID parameter from the Book constructor and letting the database handle the ID generation.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    @Override
+    public Book create(Book book) {
+        try (Connection connection = ConnectionUtil.getConnection();
+                PreparedStatement statement =
+                        connection.prepareStatement(CREATE_BOOK_QUERY,
+                                Statement.RETURN_GENERATED_KEYS)) {
+
+            statement.setString(1, book.getTitle());
+            statement.setBigDecimal(2, book.getPrice());
+            statement.executeUpdate();
+
+            ResultSet resultSet = statement.getGeneratedKeys();
+            if (resultSet.next()) {
+                book.setId(resultSet.getLong(1));
+            }
+            return book;
+
+        } catch (SQLException e) {
+            throw new DataProcessingException("Failed to insert book " + book + " into DB", e);
+        }
+    }


Use PreparedStatement over Statement for the CREATE_BOOK_QUERY. Also, consider using Statement.RETURN_GENERATED_KEYS only in the create statement, which you are already doing correctly, but remember that it's not needed in other methods.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    public Optional<Book> findById(Long id) {
+        try (Connection connection = ConnectionUtil.getConnection();
+                PreparedStatement statement = connection.prepareStatement(FIND_BY_ID_QUERY)) {
+            statement.setLong(1, id);
+            ResultSet resultSet = statement.executeQuery();
+            if (resultSet.next()) {
+                Book book = mapToBook(resultSet);
+                return Optional.of(book);
+            }
+        } catch (SQLException e) {
+            throw new DataProcessingException("Failed to retrieve book with id " + id, e);
+        }
+        return Optional.empty();


Use if or while with resultSet.next() to avoid a potential NullPointerException if the result set is empty. You are doing this correctly here, but keep it in mind for consistency across all methods.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    public List<Book> findAll() {
+        List<Book> books = new ArrayList<>();
+        try (Connection connection = ConnectionUtil.getConnection();
+                PreparedStatement statement = connection.prepareStatement(FIND_ALL_QUERY);
+                ResultSet resultSet = statement.executeQuery()) {
+            while (resultSet.next()) {
+                books.add(mapToBook(resultSet));
+            }
+        } catch (SQLException e) {
+            throw new DataProcessingException("Can't get all books from DB", e);
+        }
+
+        return books;
+    }


It's good that you used PreparedStatement over Statement in the findAll() method, following the best practice.

mateacademy-ai-mentor · 2024-09-30T18:37:08Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    public boolean deleteById(Long id) {
+        try (Connection connection = ConnectionUtil.getConnection();
+                PreparedStatement statement = connection.prepareStatement(DELETE_BY_ID_QUERY)) {
+            statement.setLong(1, id);
+            int rowsAffected = statement.executeUpdate();
+            return rowsAffected > 0;
+        } catch (SQLException e) {
+            throw new DataProcessingException("Failed to delete book with id " + id, e);
+        }


Don't return true all the time in the deleteById method. You're correctly returning a boolean value depending on the preparedStatement.executeUpdate() result, which is a good practice.

mateacademy-ai-mentor · 2024-09-30T18:37:09Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    Book mapToBook(ResultSet resultSet) throws SQLException {
+        return new Book(resultSet.getLong("id"),
+                resultSet.getString("title"),
+                resultSet.getBigDecimal("price"));
+    }


When converting ResultSet to Book, it's good practice to create an object using a constructor or setters, but not both. Here, you are using the constructor, which is consistent and recommended.

…RUD principles!!!

mateacademy-ai-mentor

🌟 Great job on the progress! Remember to address the incomplete DB_URL and consider the feedback provided on using consistent object initialization, more informative exception messages, and SQL style conventions. Keep up the good work and make sure to refine your code according to the suggestions. You're doing well, and with these improvements, your code will be even better! Keep learning and coding! 🚀💻

✨ Please rate this review in the Platform's notification center. I will be grateful for your feedback! ✨

mateacademy-ai-mentor · 2024-09-30T19:46:27Z

src/main/java/mate/academy/ConnectionUtil.java

+import mate.academy.exception.DataProcessingException;
+
+public class ConnectionUtil {
+    private static final String DB_URL = "jdbc:mysql://localhost:3306/test?serverTimezone=UTC";


The DB_URL is incomplete. It needs to be a full JDBC URL. For example: jdbc:mysql://localhost:3306/yourdatabasename?serverTimezone=UTC

mateacademy-ai-mentor · 2024-09-30T19:46:27Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+    private static final String CREATE_BOOK_QUERY
+            = "INSERT INTO books (title, price) VALUES (?, ?)";
+    private static final String FIND_BY_ID_QUERY = "SELECT * FROM books WHERE id = ?";
+    private static final String FIND_ALL_QUERY = "SELECT * FROM books";
+    private static final String UPDATE_BOOK_QUERY
+            = "UPDATE books SET title = ?, price = ? WHERE id = ?";
+    private static final String DELETE_BY_ID_QUERY = "DELETE FROM books WHERE id = ?";


Remember to use uppercase for SQL keywords in your queries to follow SQL style best practices.

mateacademy-ai-mentor · 2024-09-30T19:46:27Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+        }
+    }
+
+    Book mapToBook(ResultSet resultSet) throws SQLException {


Consider moving the logic for mapping the ResultSet to a Book object into a separate private method to avoid code duplication as suggested in the checklist. This method should be used in findById and findAll methods.

mateacademy-ai-mentor · 2024-09-30T19:46:27Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+        }
+    }
+
+    Book mapToBook(ResultSet resultSet) throws SQLException {


When you are converting ResultSet to Book, it's better to use either setters or a constructor consistently rather than both. In this case, you are using the constructor to set title and price, and then using a setter to set the id. Choose one approach for consistency.

mateacademy-ai-mentor · 2024-09-30T19:46:27Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+            }
+            return book;
+
+        } catch (SQLException e) {


Use informative exception messages. Instead of 'Failed to insert book into DB', include the book details to make the exception message more informative.

mateacademy-ai-mentor · 2024-09-30T19:46:27Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+                return Optional.of(book);
+            }
+        } catch (SQLException e) {
+            throw new DataProcessingException("Failed to retrieve book with id " + id, e);


Use informative exception messages. Instead of 'Failed to retrieve book with id', include the book id to make the exception message more informative.

mateacademy-ai-mentor · 2024-09-30T19:46:28Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+            statement.executeUpdate();
+            return book;
+        } catch (SQLException e) {
+            throw new DataProcessingException("Can't update book " + book, e);


Use informative exception messages. Instead of 'Can't update book', include the book details to make the exception message more informative.

mateacademy-ai-mentor · 2024-09-30T19:46:28Z

src/main/java/mate/academy/dao/BookDaoImpl.java

+            int rowsAffected = statement.executeUpdate();
+            return rowsAffected > 0;
+        } catch (SQLException e) {
+            throw new DataProcessingException("Failed to delete book with id " + id, e);


Use informative exception messages. Instead of 'Failed to delete book with id', include the book id to make the exception message more informative.

mateacademy-ai-mentor · 2024-09-30T19:46:28Z

src/main/java/mate/academy/model/Book.java

+    public Book(String title, BigDecimal price) {
+        this.title = title;
+        this.price = price;
+    }


When you convert ResultSet to Book better create an object using setters or constructor but not both of them, because it's not consistent to use both ways of initialization of object. Since you have setters for all fields, consider removing the constructor that takes parameters and use setters instead, or add an id parameter to the constructor if you want to initialize all fields at once.

I did a task on working with JDBC. And implemented methods based on G…

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…RUD principles!!!

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I did a task on working with JDBC. And implemented methods based on G… #421

I did a task on working with JDBC. And implemented methods based on G… #421

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		DB_PROPERTIES.put("user", "root");
		DB_PROPERTIES.put("password", "Root1234");

		Book book = new Book(1L, "Java Programming", new BigDecimal("29.99"));
		Book book1 = new Book(2L, "Java", new BigDecimal("30.25"));

I did a task on working with JDBC. And implemented methods based on G… #421

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I did a task on working with JDBC. And implemented methods based on G… #421

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