# Com / Fujitsu

## Overview

The `com.fujitsu` package is the root Java namespace for Fujitsu's enterprise application ecosystem. It serves as the top-level organizational scaffold — a package container that groups platform-level systems without containing direct source code. Under it sits the Futurity platform (`com.fujitsu.futurity`), which is the primary concrete subsystem.

Futurity appears to be a multi-regional, Jakarta EE-based web application platform designed to support region-specific variants (notably a Japan-targeted variant called X33). The architecture follows a standard layered model — web, domain, infrastructure — with regional customization expressed through package-scoped subsystems rather than monolithic forks.

At the module level, no source files are indexed directly under `com.fujitsu`. This is expected: the package functions as a namespace root, delegating all substantive code to its children. The first and currently only child with concrete implementation is the Futurity platform, and within Futurity, the X33 Japan variant holds the sole web-tier components.

## Sub-module Guide

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

Futurity (`com.fujitsu.futurity`) is the sole direct child of `com.fujitsu`. It is itself a namespace container rather than a code-bearing package. Its purpose is to aggregate the web-tier and, potentially in the future, domain and infrastructure tiers of the application. The platform is designed for multi-regional deployment, with region-specific logic organized as sub-packages (e.g. `x33` for Japan).

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 (parent → platform → web → regional variant → filter/listener), reflecting a stub-first development approach where intermediate layers exist purely for organizational clarity.

**How they relate:** The hierarchy is strictly vertical. `com.fujitsu` → `com.fujitsu.futurity` → `com.fujitsu.futurity.web` → `com.fujitsu.futurity.web.x33` → (`filter`, `listener`). Each level narrows the scope: from enterprise namespace → application platform → web boundary → regional variant → lifecycle components. There are no sibling relationships at this depth — 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

The `com.fujitsu` package and its Futurity child 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 the 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 the compile level 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 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.