# Com

## Overview

The `com` package serves as the top-level Java namespace root for the project's **Fujitsu Futurity** application. It contains no classes of its own — instead, it functions as a **namespace container** that groups all application code under a single organization-level prefix (`com.fujitsu`).

This is a leaf namespace at the `com` level: every class, interface, and method in the application lives beneath `com.fujitsu.*`. The `com` package itself is a declaration of ownership and packaging convention, following the reverse-domain-name convention used by Java for organizational namespaces.

## Sub-module Guide

The `com` package currently has one documented child namespace:

### `com.fujitsu` — Fujitsu Futurity Application

The `com.fujitsu` package is the root of the Futurity application's Java codebase. It contains a single sub-package:

- **`com.fujitsu.futurity.web`** — The web-tier integration layer that handles all HTTP-level concerns (request dispatching, character encoding, lifecycle management) before traffic reaches backend subsystems.

Within the `futurity.web` hierarchy, the `x33` sub-package is the only currently implemented slice — a Japanese-facing component requiring Shift-JIS (MS932) character encoding on incoming requests.

### How the hierarchy relates

The `com` namespace acts as the organizational boundary, with all meaningful application code nested beneath `com.fujitsu`. There is a single chain of delegation from top to bottom:

```mermaid
flowchart TD
    A["com — organization root"] --> B["com.fujitsu — Fujitsu application"]
    B --> C["com.fujitsu.futurity.web — web tier"]
    C --> D["com.fujitsu.futurity.web.x33 — X33 subsystem"]
    D --> E["com.fujitsu.futurity.web.x33.filter — request encoding"]
    D --> F["com.fujitsu.futurity.web.x33.listener — lifecycle"]
```

At this level, `com` is a flat namespace with a single branch (`com.fujitsu`). If new products or divisions were to join the project, they would each receive their own sub-package beneath `com` (e.g., `com.acme`), keeping each product's code isolated and versionable.

## Key Patterns and Architecture

### Namespace Convention

All application code follows the standard Java reverse-domain naming convention (`com.fujitsu...`). This ensures uniqueness of class names across the organization and separates Fujitsu-owned code from third-party libraries (which typically use different top-level packages like `org`, `javax`, `java`, etc.).

### Web-Tier-First Structure

The only implemented slice of code exists at `com.fujitsu.futurity.web.x33`, which means the application currently exposes a **single web endpoint group** — the X33 JV subsystem. The architecture places web-tier concerns (servlet filters, context listeners, deployment descriptors) at the outermost layer of the `com` tree, with the expectation that backend business logic would be nested deeper in packages not yet implemented.

### Filter + Listener Lifecycle Model

The `x33` sub-package defines the application's request processing model using two complementary components:

| Component | Scope | Role |
|---|---|---|
| `X33JVRequestEncodingSjisFilter` | Per-request | Ensures Shift-JIS encoding on incoming HTTP requests |
| `X33AppContextListener` | Application-wide | (Planned) Manages startup/shutdown lifecycle |

Together, they represent the two fundamental axes of any servlet-based application: **initialization** (listener) and **per-request processing** (filter). The `web-full.xml` deployment descriptor is the glue that wires both into the servlet container.

## Dependencies and Integration

### External Dependencies

All external dependencies come from the `javax.servlet` API:

| Dependency | Role |
|---|---|
| `javax.servlet.Filter` | Interface implemented by `X33JVRequestEncodingSjisFilter` |
| `javax.servlet.ServletRequest` / `ServletResponse` | Request/response types in `doFilter()` |
| `javax.servlet.FilterChain` | Chain delegation in filter processing |
| `javax.servlet.ServletContext` | (Planned) Lifecycle management via listener |

### Internal Relationships

No internal application dependencies have been detected. The `com` package and all its children are **leaf modules** — they receive external traffic and delegate inward, but do not import or reference any classes from other parts of the codebase. This is expected for an early-stage or greenfield application where the web tier scaffolding was built before the backend layers.

### Integration with the Servlet Container

The application uses a **traditional Java EE declarative model**: `web-full.xml` acts as the source of truth for servlet wiring, rather than Spring or annotation-based auto-discovery. The filter is registered in this deployment descriptor and mapped to URL patterns. If the listener is implemented, it would be declared similarly (or annotated with `@WebListener`).

## Notes for Developers

### This Module Is Empty by Design

The `com` package and the root of `com.fujitsu` contain no classes. All implemented code lives in the `x33` web tier. Before writing new code, understand that the existing structure is **scaffolding** — the architectural skeleton has been laid down, but the substantive business logic is not yet implemented.

### Encoding Is a Priority Concern

The `X33JVRequestEncodingSjisFilter` does not currently apply any character encoding. For a Japanese-facing endpoint, this means incoming multi-byte characters may be silently corrupted. This should be addressed before production deployment. The fix would be straightforward — calling `req.setCharacterEncoding("MS932")` before `chain.doFilter(...)` in the `doFilter()` method.

### New Code Should Follow XML-Declarative Wiring

Any new classes added to the `com.fujitsu` tree should use the existing XML-declarative deployment model for consistency. Do not introduce annotation-based wiring (Spring components, `@WebServlet`, etc.) unless the team decides to migrate the application model.

### Future Extensibility

The `com` namespace is currently a single-branch tree. If new products, APIs, or divisions are added to the project, they would each receive their own top-level sub-package (e.g., `com.fujitsu.anotherproduct`). The `com.fujitsu` namespace convention makes it straightforward to isolate new products beneath `com` without affecting existing code.

### Codebase Maturity

The `com.fujitsu.futurity.web.x33` module follows a **placeholder (scaffold) pattern** — package structure, class names, and registrations are in place, but behavior is not yet implemented. This suggests one of:

1. The X33 web integration work was started but not completed.
2. The encoding and listener concerns may be handled elsewhere (e.g., a global character encoding filter), making these X33-specific placeholders temporary.
3. The backend business layers have not been designed or implemented yet.

Before investing effort in implementation, coordinate with the team to clarify the current development status and priorities.