Java-Invoice-Generator

Java-based invoice generation system with client-server model, SQLite DB, and A–Z business reports (OOPs mini project).

InvoiceGenerator — Project Reports A to Z

Overview

This repository implements a simple invoice generation system (client, server, UI, DB, PDF/text export). This README focuses on the reports that the project produces or should produce — an A-to-Z catalogue of reports, what each report is for, input filters, typical output columns, example SQL to obtain the data, scheduling suggestions, and security/access notes.

Reports are intended to be generated from the application's SQLite database file invoice_db.db at the project root (or from MySQL if you change DBConnection). Generated report files should be stored under resources/reports/ (create this folder if you want to persist outputs).

Quick run (Windows PowerShell)

• Compile (from project root):

javac -cp "lib\*;src" src\invoicegenerator\**\*.java

• Start server (background/minimized):

Start-Process java -ArgumentList '-cp','src;lib\sqlite-jdbc.jar;lib\mysql-connector-java.jar;lib\itextpdf.jar','invoicegenerator.server.InvoiceServer' -WindowStyle Minimized

• Launch UI:

java -cp "src;lib\sqlite-jdbc.jar;lib\mysql-connector-java.jar;lib\itextpdf.jar" invoicegenerator.ui.InvoiceUI

Dependencies

• Java 11+ (recommended)
• lib/sqlite-jdbc.jar (if using embedded SQLite)
• lib/mysql-connector-java.jar (if using MySQL)
• lib/itextpdf.jar (optional, for PDF generation if switched back to iText)

Reports A → Z

For each report below you'll find: Purpose • Typical filters/inputs • Typical output columns • Example SQL (SQLite style, adapt for MySQL) • Schedule & output format • Notes / access.

A — Aged Receivables Report

• Purpose: Shows outstanding invoice balances grouped by ageing buckets (0-30, 31-60, 61-90, 90+ days).
• Inputs: End date, customer filter (optional).
• Output: customer_id, customer_name, invoice_id, due_date, balance, bucket.
• Example SQL (simplified):

  SELECT c.customer_id, c.name, i.invoice_id, i.invoice_date, i.total - coalesce(p.paid,0) AS balance
  FROM invoices i JOIN customers c ON i.customer_id=c.customer_id
  LEFT JOIN (SELECT invoice_id, SUM(amount) AS paid FROM payments GROUP BY invoice_id) p USING(invoice_id)
  WHERE (i.total - coalesce(p.paid,0)) > 0;

• Schedule: Daily or weekly.
• Format: CSV / PDF.
• Access: Finance team.

B — Billing Summary (Period)

• Purpose: Summary of billed amounts over a period.
• Inputs: Start date, end date, customer/product filters.
• Output: invoice_count, subtotal_sum, tax_sum, total_sum.
• Example SQL:

  SELECT COUNT(*) AS invoice_count, SUM(subtotal) AS subtotal, SUM(tax) AS tax, SUM(total) AS total
  FROM invoices WHERE invoice_date BETWEEN ? AND ?;

• Schedule: Monthly.
• Format: CSV / PDF.

C — Customer Ledger (Detailed)

• Purpose: Full transaction list per customer (invoices, payments, credit notes).
• Inputs: customer_id, date range.
• Output: date, type (invoice/payment), ref_id, description, debit, credit, running_balance.
• Example SQL: combine invoices, payments.
• Schedule: On-demand.
• Format: PDF/CSV.

D — Daily Sales Report

• Purpose: Sales totals per day.
• Inputs: Date or date range.
• Output: date, invoice_count, subtotal, tax, total.
• Example SQL:

  SELECT invoice_date, COUNT(*) AS invoices, SUM(total) AS total FROM invoices GROUP BY invoice_date;

• Schedule: Daily.

E — Expense Summary

• Purpose: If vendor/expense tracking added — shows expenses by category.
• Inputs: Category, date range.
• Output: category, amount, count.
• Schedule: Monthly.

F — Financial Summary (P&L snapshot)

• Purpose: High-level Profit & Loss (requires revenue & expense entries).
• Inputs: period (month, quarter).
• Output: revenue, cogs, gross_profit, operating_expenses, net_income.

G — GST / VAT Returns

• Purpose: Tax reporting (e.g., GST collected and payable).
• Inputs: Period (month/quarter).
• Output: taxable_sales, tax_collected, tax_paid, net_tax_due.
• Example SQL:

  SELECT SUM(subtotal) AS taxable, SUM(tax) AS tax FROM invoices WHERE invoice_date BETWEEN ? AND ?;

• Schedule: Monthly/Quarterly.
• Notes: Ensure tax rounding and jurisdiction rules.

H — Hourly Sales (if tracked)

• Purpose: Sales by hour-of-day (useful for retail/time-bound services).
• Inputs: date range.
• Output: hour, subtotal, total.

I — Invoice Detail Report

• Purpose: Detailed invoice (line-items) for audit or customer service.
• Inputs: invoice_id or range.
• Output: invoice header + item lines (description, qty, price, amount).
• Format: PDF or HTML template (resources/invoice_template.html).

J — Journal Entries (if present)

• Purpose: Shows accounting journal entries if integrated.
• Inputs: date range, account filter.

K — KPI Dashboard Data Extract

• Purpose: Data feed for KPI dashboards: MTD revenue, AR days, conversion rates.
• Inputs: timeframe.
• Output: key metric values.

L — Late Payments Report

• Purpose: Invoices past due, sorted by days overdue.
• Inputs: min days overdue, customer filter.
• Output: invoice_id, customer, due_date, days_overdue, balance.
• Schedule: Weekly.

M — Monthly Sales by Product/Service

• Purpose: Revenue breakdown by product/service.
• Inputs: month, product filter.
• Output: product_id, name, qty_sold, revenue.

N — Notes & Comments Extract

• Purpose: Export internal invoice notes/comments for review.
• Inputs: date range, user filter.
• Output: invoice_id, note_text, user, timestamp.

O — Outstanding Balances by Customer

• Purpose: Total unpaid per customer.
• Inputs: none or date cutoff.
• Output: customer_id, customer_name, outstanding_total.

P — Payment History

• Purpose: All payments received (useful for reconciliation).
• Inputs: date range.
• Output: payment_id, invoice_id, amount, date, method.

Q — Quarterly Tax Summary

• Purpose: Consolidated quarterly tax report for filing.
• Inputs: quarter/year.
• Output: taxable_sales, tax_collected, input_tax_credits (if applicable).

R — Revenue by Product / Category

• Purpose: Revenue grouped by product or category.
• Inputs: date range.
• Output: product/category, revenue, units_sold.

S — Sales by Region / Location

• Purpose: Geography-based sales breakdown (requires customer region data).
• Inputs: date range.
• Output: region, revenue, invoices.

T — Tax Summary (per jurisdiction)

• Purpose: Tax collected, broken down by tax rate or jurisdiction.
• Inputs: date range.
• Output: tax_rate, taxable_amount, tax_amount.

U — Unpaid Invoices (open items)

• Purpose: List of all invoices with outstanding balances.
• Inputs: none or aging cutoff.
• Output: invoice_id, customer, outstanding.

V — Vendor / Supplier Report (if vendors tracked)

• Purpose: Payables, outstanding supplier balances.
• Inputs: date range.
• Output: vendor_id, outstanding_payables.

W — Weekly Sales Trend

• Purpose: Sales trend over rolling week(s).
• Inputs: week range.
• Output: week_start, revenue, invoices.

X — eXception & Error Log

• Purpose: App-level errors/exceptions (useful for ops).
• Inputs: date range.
• Output: timestamp, component, error_message, stack_trace (restricted access).

Y — Yearly Summary / Fiscal Year Rollup

• Purpose: Annual totals for revenue, tax, net revenue.
• Inputs: fiscal year.
• Output: year, revenue, tax, net.

Z — ZIP / Postal Code Breakdown

• Purpose: Sales grouped by postal code for demographic analysis.
• Inputs: date range.
• Output: postal_code, revenue, customers_count.

---

Implementation notes

• Report SQL examples above are intentionally simplified. Production queries should use parameterized prepared statements and proper joins and aggregation.
• Create a resources/reports/ folder. When generating reports from the UI or server, write CSV/JSON/PDF files to that folder and present a download link in the UI.
• For scheduled reports, integrate a lightweight scheduler (e.g., java.util.concurrent.ScheduledExecutorService in InvoiceServer) or an external scheduler (Windows Task Scheduler / cron) that calls a report generator.
• For PDF output, you can re-enable iText usage by adding lib/itextpdf.jar to the classpath and replacing the current text-based PDFGenerator with the iText-based implementation already in the code (be mindful of iText license if using later iText versions).
• Access control: restrict sensitive reports (tax returns, exceptions) to authorized roles only.

How to add a new report

1. Decide the data source (which tables/views).
2. Add a method in invoicegenerator.service (e.g., ReportService.java) to execute the query and transform results into DTOs.
3. Add an endpoint or a UI action in InvoiceUI to call the service and either stream the CSV/PDF to disk or to the UI.
4. Add unit tests for the SQL logic and integration tests if possible.

Where to look in this repo

• Java sources: src/invoicegenerator/ (models, database, service, ui, util, server, client)
• DB connection settings: src/invoicegenerator/database/DBConnection.java (switch between SQLite and MySQL here)
• Report templates: resources/invoice_template.html (HTML invoice template)
• Output folder suggestion: resources/reports/

Contact & Next steps

If you'd like, I can:

• Implement a ReportService class and a few example reports (e.g., Daily Sales, Outstanding Invoices, Invoice Detail).
• Add a UI menu to generate the most-used reports and save to resources/reports/.
• Add scheduled report support to InvoiceServer.

Please tell me which reports (A–Z) you want implemented first or if you want me to create the resources/reports/ folder and wire a simple CSV reporter for Daily Sales, Unpaid Invoices, and Invoice Detail now.