fgen

Description

fgen is an application whose goal is to allow users to generate invoices emitted between registered customers on the system.

The customer can be a particular person or a company. It is identified on the system by a unique code. Then, it will be defined by some required data like the name and the TIN (Tax Identification Number). Besides, it will have optional data such as the address, the city, the province, the ZIP code and the IBAN.

Once the customer is registered on the system, the application will allow us to modify all its data (except the code). Furthermore, it also offers the possibility of removing the user, and even restoring it.

The invoice is composed by the sender and the recipient customers, the list of goods purchased or services provided, which will be called as “items”, and a set of subtotals which can alter the invoice total.

Each “item” includes the quantity, the description and the price. The subtotal can be a discount or a tax, which will be defined by a name and a percentage. Besides, the invoice will also contain additional metadata like generation datetime.

Respecting its characteristics, an invoice can have the same customer as recipient and sender at the same time. Then, its generation is based on an invoice template which can be configured. Finally, once the invoice has been created, it cannot be edited or removed.

The invoice template indicates how each invoice attribute must be filled on the generated invoice. It is composed by the mapping between each field position in the spreadsheet file and its expression, which establishes the content to show on that field. Besides, it stores the spreadsheet file to use to fill the invoice.

Finally, the generated invoice can be saved in your local computer in a spreadsheet format like Excel (XLSX) or PDF format.

Architecture & Technologies

In the first phase of the project, a monolithic architecture which will be composed by the next three layers:

• Presentation: It will responsible for showing the system information to the user. In other words, it will contain all the UI.
• Application: It will contain all the business logic with all the use cases.
• Persistence: This layer will be responsible for accessing to the data. It will interact with the database.

Then, each entity will be distinguished in a separate folder, so it is independent from the others. This will facilitate a future transition to isolated microservices. Note that common resources for all entities will be set in a shared folder.

This architecture has been chosen because it will facilitate the development and the product testing during this first project phase, as it is preferred to set more focus on the logic at this moment. Then, improvements could be made based on this first version.

Respect to the technology stack, Java will be used as the programming language because with the help of the Netbeans IDE, it will accelerate the UI development, so we can set a better focus to the logic and the system functionality, as mentioned before. The chosen programming language also has an easy learning curve and its generated applications can be executed easily on any operating system after installing Java. Besides, the Mongo database has been chosen due to its installation facility on any place (locally and cloud), scalability and flexibility on the data structure. Keep in mind that there are some entities like the customer which will have optional data. Finally, the conversion from a spreadsheet format to PDF will be done thanks to the Gembox library, which offers a free license to process 150 rows per sheet and a maximum of 5 sheets per file.

Entities & Use cases

1. Customer: It acts as an entity which emits or receives an invoice. The customer can be a particular person or a company.

   Use cases:

   • CS-1: Register a customer
   • CS-2: List customers
   • CS-3: Show customer
   • CS-4: Remove customer
   • CS-5: Restore customer
   • CS-6: Update customer

2. Invoice: It is a list of all goods purchased or services provided from one customer to another.

   Use cases:

   • INV-1: Generate invoice
   • INV-2: List all generated invoices
   • INV-3: List all generated invoices by customer
   • INV-4: Save invoice
   • INV-5: Retrieve invoice

3. Invoice item: It represents a good purchased or service provided, which is set on a specific invoice.

   Use cases:

   • INVIT-1: Add an invoice item
   • INVIT-2: Edit an invoice item
   • INVIT-3: Remove an invoice item

4. Template: It establishes the pattern to generate the invoices based on a spreadsheet file.

   Use cases:

   • TEM-1: Register template
   • TEM-2: List templates
   • TEM-3: Show template
   • TEM-4: Edit template
   • TEM-5: Remove template
   • TEM-6: Restore template

5. Template field: It sets up the mapping between a field from a template spreadsheet file field and the content to render defined by an expression. Note that the field will be only associated with one template.

   Use cases:

   • TEMFLD-1: Add template field
   • TEMFLD-2: Edit template field
   • TEMFLD-3: Remove template field

6. Subtotal: It represents a discount or a tax, which can alter an invoice total. That subtotal can be associated with any template.

   Use cases:

   • SUBT-1: Add subtotal
   • SUBT-2: List subtotals
   • SUBT-3: Edit subtotal
   • SUBT-4: Remove subtotal
   • SUBT-5: Restore subtotal
   • SUBT-6: Calculate subtotal

7. Variable: It establishes the mapping between an entity attribute with a descriptive name to add it in an expression. Variables are global, so they can be added in whatever expression.

   Use cases:

   • VAR-1: Add variable
   • VAR-2: List variables
   • VAR-3: Edit variable
   • VAR-4: Remove variable
   • VAR-5: Restore variable

Localization

The application user interface supports localization on different languages. So, the user can change the content of the interface easily.

To do that, you need to execute the next steps:

1. Create a new dictionary class in the shared.presentation.dictionary.languages package. In that class, you will define the translations for each localization key. Example:

   package shared.presentation.dictionary.languages;
   
   import shared.presentation.dictionary.Dictionary;
   import shared.presentation.localization.LocalizationKey;
   
   /**
    * Dictionary with all the translations for the English language.
    */
   public class EnglishDictionary extends Dictionary {
   
       /**
        * Constructor.
        */
       public EnglishDictionary() {
           super.setTranslation(LocalizationKey.PROGRAM_NAME, "Program name");
           super.setTranslation(LocalizationKey.ABOUT, "About");
           // Add more...
       }
   
   }
   

2. Load the dictionary on the localization class. That can be done on the main class, which is located on the shared.presentation package by replacing the localization loading with this statement:

   Localization.load(new EnglishDictionary());
   

License

A GNU General Public License v3.0 license (GNU GPLv3) has been chosen because it lets people to do whatever they want with the project, except distributing closed source versions.

Source: https://choosealicense.com/