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Alazani

Table of Contents

Database

  • DB Interface 
    public interface DB {
    // Queries
    String createTableQuery(String tableName, Map<String, Object> fields);
    String createDatabaseQuery();
    String insertQuery(String tableName, Map<String, Object> fields);
    String updateQuery(String tableName, int id, Map<String, Object> fields);
    String getAllQuery(String tableName);
    String getQuery(String tableName, int id);

    // Execute queries
    void createTable(String tableName, Map<String, Object> fields) throws SQLException;
    void createDatabase() throws SQLException;
    int insert(String tableName, Map<String, Object> fields) throws SQLException;
    void deleteRow(String tableName, int  id) throws SQLException;
    void update(String tableName, int id, Map<String, Object> fields) throws SQLException;
    Map<String, String> get(String tableName, int id) throws SQLException;
    List<Map<String, String>> getAll(String tableName) throws SQLException;
}

  • MySQL Singleton Class (Implements DB Interface) 
    public class MySQL implements DB {
    private Connection connection;
    private static MySQL mysql_single_instance = null;

    private MySQL() throws SQLException, ClassNotFoundException {
        connectToDatabase();
    }

    // Singleton Class
    public static MySQL getInstance() throws SQLException, ClassNotFoundException {
        if (mysql_single_instance == null)
            mysql_single_instance = new MySQL();
        return mysql_single_instance;
    }
    
    private void connectToDatabase() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        connection = DriverManager.getConnection(Environment.URL, Environment.USER, Environment.PASSWORD);
        createDatabase();
    }
    
    ...
    /* Overrides of DB Interface */
    ...
}

  • Migrations:

    • Table Creation/Dummy Data Initialization
    public class Migration {
    public static void createTables(DB db) throws SQLException {
        db.createTable(User.TABLE_NAME, User.FIELDS);
        db.createTable(Product.TABLE_NAME, Product.FIELDS);
        ...
    }

    public static void createStartingData() {
        UserSeeder.Seed();
        ProductSeeder.Seed();
        ...
    }
}
    • On Server Start:
    @WebListener()
public class ServerListener implements ServletContextListener,HttpSessionListener, HttpSessionAttributeListener {
    ...
    public void contextInitialized(ServletContextEvent sce) {
        DB db = MySQL.getInstance();
        Migration.createTables(db);
        Migration.createStartingData();
    }
    ...
}

  • Seeders:

    Project includes a simple method of seeding your database with test data using seed classes. See example below:

    public class UserSeeder {
    public static void Seed() {
        new User("Test", "User", BCrypt.hashpw("test"), "test", "[email protected]").save();
        new User("Admin", "Admin", BCrypt.hashpw("admin451"), "GM", "[email protected]").save();
        ...
    }
}

    • In the end we have the following hierarchy DB_Graph

  • Models

    • BaseModel

    Any model that needs to be added should extend Basemodel class. Extending this class, describe DB fields and implementing JavaToDB and DBToJava will allow user's model to have all CRUD operations right away, without needing to affect and write DB queries.

    public class BaseModel {
    ...
    /* Constructors and util functions*/
    ...
    
    /* CRUD Operations */
    // Create object in Database
    public Object save() {...}

    // Read Object from Database
    public static Map<String, String> getGeneric(String table_name, int id) {...}

    // Update Object in Database
    public boolean update() {...}

    // Delete Object's record from Database
    public void deleteRow() {...}

    // Get all of Objects from Database
    public static List<Map<String, String>> getAllGeneric(String table_name) {...}
}
    • User Model (example)

    User Model should:

    1. extend BaseModel
    2. Describe DB Fields
    3. Implement JavaToDB
    4. Implement DBToJava
    // 1. extend BaseModel
public class User extends BaseModel {
    public static final String TABLE_NAME = "users";
    
    // 2. Describe DB Fields
    public static final Map<String, Object> FIELDS = new LinkedHashMap<>();
    static {
        FIELDS.put("id", Fields.ID);
        FIELDS.put("first_name", Fields.varchar(30));
        FIELDS.put("last_name", Fields.varchar(30));
        FIELDS.put("password", Fields.varchar(512));
        FIELDS.put("username", Fields.varchar(32));
        FIELDS.put("email", Fields.varchar(256));
    }
    
    // 3. Implement JavaToDB
    public Map<String, Object> JavaToDB() {
        return new LinkedHashMap<String, Object>() {
            {
                put("first_name", firstName);
                put("last_name", lastName);
                put("password", password);
                put("username", username);
                put("email", email);
            }
        };
    }

    // 4. Implement DBToJava
    public static User DBToJava(Map<String, String> fields) {
        User user = new User(fields.get("first_name"),
                fields.get("last_name"),
                fields.get("password"),
                fields.get("username"),
                fields.get("email"));
        user.setId(Integer.parseInt(fields.get("id")));
        return user;
    }
}

    • In the end we have the following hierarchy DB_Graph