# Com

## Overview

The `com` package is the root Java namespace for the codebase — the top-level organizational scaffold that holds the `com.fujitsu` enterprise application ecosystem. As a package root with no direct source files, its sole purpose is to provide a hierarchical namespace that groups platform-level systems and supports future growth across multiple Fujitsu-branded applications and regions.

All substantive code lives beneath `com.fujitsu`, which contains the Futurity platform. This is a multi-regional, Jakarta EE-based web application designed with a layered architecture (web, domain, infrastructure) and regional customization expressed through package-scoped subsystems rather than monolithic forks.

## Sub-module Guide

### com.fujitsu — Fujitsu Enterprise Namespace

`com.fujitsu` is a hollow namespace root — it contains no indexed source files and serves purely as the organizational parent for the Futurity platform and any future Fujitsu-branded systems. Its role is namespace isolation and structural clarity at the enterprise level.

### com.fujitsu.futurity — The Futurity Platform

Beneath the Fujitsu namespace sits the Futurity platform (`com.fujitsu.futurity`), itself also a namespace container rather than a code-bearing package. Futurity aggregates the web-tier (and potentially future domain and infrastructure tiers) of the application. It is designed for multi-regional deployment, with region-specific logic organized as sub-packages.

Currently, Futurity's only child with substantive code is `com.fujitsu.futurity.web.x33` — the X33 Japan regional variant. This package lives deep in the hierarchy:

```
com.fujitsu
  └── com.fujitsu.futurity
        └── com.fujitsu.futurity.web
              └── com.fujitsu.futurity.web.x33
                    ├── filter
                    └── listener
```

Each level narrows the scope: enterprise namespace → application platform → web boundary → regional variant → lifecycle components. X33 is the sole regional variant, and its `filter` and `listener` packages are leaf nodes with no further children.

## Key Patterns and Architecture

### Namespace-hollow hierarchy

Both `com.fujitsu` and `com.fujitsu.futurity` are hollow — they contain no indexed source files. All implementation lives in the deepest leaf packages. This is a common pattern in large enterprise Java projects where top-level packages exist solely for namespace isolation and to support future growth (additional platforms beyond Futurity, additional regions beyond X33).

### Stub-first development

Both X33 components — `X33AppContextListener` and `X33JVRequestEncodingSjisFilter` — are class declarations with empty bodies. They exist in the correct packages with correct interfaces and naming, but implement no logic. This suggests the subsystem was scaffolded in anticipation of requirements, likely to establish the contract (filter chain integration, listener lifecycle) before business logic is added.

### Regional variant through package scoping

Rather than using feature flags or runtime configuration to distinguish the Japan variant, X33 is expressed through its own package (`x33`) and class naming convention (`X33JV`). This makes the variant's boundaries explicit at compile time and supports clean separation between shared platform code and region-specific logic.

### Jakarta EE servlet lifecycle pattern

The X33 web layer follows the standard Jakarta EE bootstrap-and-filter pattern:

- **Listener** (`ServletContextListener` / `ApplicationListener`): Runs once at deployment time to initialize shared resources, configuration, and locale settings.
- **Filter** (`javax.servlet.Filter`): Runs for every HTTP request to apply cross-cutting transformations (currently intended: Shift-JIS encoding).
- **Delegation**: The filter delegates to the next link in the chain, and the listener's bootstrap work primes the context that downstream components consume.

```mermaid
flowchart TD
    subgraph Fujitsu["com.fujitsu (Fujitsu Enterprise Namespace)"]
        direction TB
        subgraph Futurity["com.fujitsu.futurity (Futurity Platform)"]
            direction TB
            Web["com.fujitsu.futurity.web (Web Tier)"] --> X33["com.fujitsu.futurity.web.x33 (X33 Japan Variant)"]
            subgraph X33Sub["X33 Subsystem"]
                Listener["X33AppContextListener"] -->|contextInitialized| Bootstrap["Bootstrap: config, locale, shared resources"]
                Filter["X33JVRequestEncodingSjisFilter"] -->|doFilter| Encoding["setCharacterEncoding Shift_JIS"]
                Encoding -->|chain.doFilter| Target["Target Servlet / Controller"]
                Bootstrap --> Filter
            end
        end
        Listener -->|implements| ListenerIF["ServletContextListener / ApplicationListener"]
        Filter -->|implements| FilterIF["javax.servlet.Filter"]
        FilterIF -->|registered in| WebXML["web-full.xml deployment descriptor"]
    end
```

## Dependencies and Integration

### Internal

- No source files are indexed at the `com.fujitsu` level — the package is purely organizational.
- Futurity is the only direct child and is itself a namespace container.
- X33 is the only sub-module with substantive code, comprising two leaf packages (`filter`, `listener`) under `web.x33`.

### External

- **Jakarta Servlet API** (`javax.servlet.Filter`, `javax.servlet.ServletContextListener`): Required by both X33 components. Provided at runtime by the servlet container.
- **Spring Framework (potential)**: If the listener implements Spring's `ApplicationListener`, it introduces a dependency on the Spring context.
- **Deployment descriptor** (`web-full.xml`): Wires the filter into the servlet container's request processing pipeline.

### Integration with the broader system

The X33 web layer is the HTTP-facing entry point for Japanese-language Futurity operations. The Shift-JIS encoding requirement in the filter name (`X33JVRequestEncodingSjisFilter`) indicates integration with Japanese legacy UIs or enterprise systems that expect Shift-JIS-encoded form data. The listener's bootstrap role suggests it may wire up encoding configuration, locale settings, or regional features consumed by other X33 domain components that exist outside the web tier (and are not yet indexed).

When fully implemented, the pipeline for any Japanese request to Futurity flows: incoming HTTP request → `X33JVRequestEncodingSjisFilter` (Shift-JIS decode) → target servlet/controller → downstream domain logic. The listener ensures shared resources are initialized before the first request arrives.

## Notes for Developers

- **No source files are indexed under `com.fujitsu`.** The package is a namespace root. All code lives in children.
- **The Futurity platform is currently a scaffold.** Its only concrete implementation is the X33 Japan variant under `com.fujitsu.futurity.web.x33`.
- **Both X33 components are stubs.** `X33JVRequestEncodingSjisFilter.doFilter()` is a no-op passthrough; `X33AppContextListener` has an empty class body. These are the entry points for implementing X33 functionality.
- **To enable Shift-JIS encoding**, the filter should cast the request to `HttpServletRequest` and call `request.setCharacterEncoding("Shift_JIS")` before delegating via `chain.doFilter(req, res)`.
- **To wire the listener**, implement the appropriate lifecycle interface (`ServletContextListener` or Spring `ApplicationListener`) and register it in `web-full.xml` or via Spring component scanning.
- **Thread safety**: The filter holds no instance state and is thread-safe by design. If state is added later, consider synchronization.
- **Shift-JIS migration consideration**: If the application is moving away from legacy encodings, evaluate whether the filter should use UTF-8 instead of Shift-JIS, and what impact this has on compatibility with Japanese legacy systems.