# Com / Fujitsu

## Overview

The `com.fujitsu` package is the root namespace for the Fujitsu application platform within the X33 product line. It serves as the top-level entry point for the Futurity web application — a Java EE / Jakarta EE platform built in the mid-to-late 2000s era, characterized by its XML-driven servlet deployment model rather than annotation-based discovery.

This module occupies the outermost boundary of the X33 system, handling two foundational responsibilities that every HTTP request flowing through the platform depends on:

1. **Application lifecycle management** — one-time startup and shutdown hooks registered with the servlet container.
2. **Request preprocessing** — inbound HTTP interception for cross-cutting concerns like character encoding normalization.

As of the current index, the module's components exist primarily as structural stubs — scaffolded classes implementing the correct Java EE interfaces but containing no operational logic. This suggests the web layer is in a transitional state, possibly during a framework migration, or has delegated its actual business logic to higher-level components elsewhere in the application.

## Sub-module Guide

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

The `futurity` sub-package is the sole child of `com.fujitsu` and serves as the web entry point for the entire Fujitsu application platform. It provides the foundational servlet infrastructure that sits between HTTP clients and the rest of the Futurity system, organized in a layered hierarchy that follows the Java EE servlet model.

#### Web Layer Hierarchy

Under `futurity`, the web infrastructure is organized into three progressively scoped packages:

| Package | Role |
|---------|------|
| `com.fujitsu.futurity` | Top-level package — defines the servlet infrastructure boundary and deployment registration |
| `com.fujitsu.futurity.web` | Root web package — the servlet-based entry point for the platform, organizing components by application variant |
| `com.fujitsu.futurity.web.x33` | X33 application web layer — the only documented application-specific child, scoped to the Japanese (`JV`) build |

#### x33 Sub-package Components

The `x33` package contains two complementary stub components that form the backbone of the X33 request handling pipeline:

**`X33AppContextListener`** (in the `listener` sub-package) — A `ServletContextListener` stub intended to perform one-time application startup and shutdown tasks. In a fully implemented version, it would load configuration, register shared beans, and establish application-wide state during `contextInitialized()`, then clean up resources in `contextDestroyed()`. As a stub, it contains no fields, constructors, or methods.

**`X33JVRequestEncodingSjisFilter`** (in the `filter` sub-package) — A `javax.servlet.Filter` designed to intercept incoming HTTP requests and set the character encoding to Shift JIS (SJIS) before forwarding to the target servlet. The `X33JV` prefix indicates Japanese build scoping, suggesting this filter may be a relic of a Japanese-specific deployment no longer actively maintained. Its `doFilter()` method is a no-op stub that immediately passes the request down the chain without modifying it.

#### How the Sub-modules Relate

The sub-packages form a layered hierarchy where each level narrows the scope:

- The **`futurity`** top-level package defines the platform boundary and registers servlet components via `web-full.xml`.
- The **`web`** package structures the servlet entry point, organizing components by application variant.
- The **`x33`** package contains the actual listener and filter implementations scoped to the X33 build.

At the component level, the listener and filter serve complementary phases of the HTTP request lifecycle:

- The **listener** operates at the application scope, running once at server startup to set up the context that all subsequent components depend on.
- The **filter** operates at the request scope, running on every incoming HTTP request to ensure correct character encoding before the request reaches business logic.

Together they form the outermost layer of the X33 request pipeline: the listener boots the application and prepares the context, and the filter ensures each request is processed with the correct encoding before it is handed off to the target servlet or JSP.

## Key Patterns and Architecture

### Servlet Lifecycle Pattern

The Fujitsu web layer adheres to the standard Java Servlet API lifecycle, which provides container-managed hooks for application-scoped and request-scoped operations:

- **`ServletContextListener`** — Provides `contextInitialized()` and `contextDestroyed()` for one-time application start and stop, used by the `listener` sub-package.
- **`javax.servlet.Filter`** — Provides `init()`, `doFilter()`, and `destroy()` for per-request interception, used by the `filter` sub-package.

These patterns are well-established in the Java EE specification and provide predictable, container-managed entry points for infrastructure concerns.

### Configuration-Driven Registration

All listener and filter components are registered via `web-full.xml`, the centralized deployment descriptor. Listener registration uses the `<listener>` element, while filter registration uses `<filter>` and `<filter-mapping>` elements with URL patterns controlling interception scope. This XML-based approach (as opposed to `@WebListener` and `@WebFilter` annotations) provides explicit, order-controllable registration typical of enterprise Java deployments, but means adding new servlet components requires XML changes rather than being a purely code-level operation.

### Request Processing Pipeline

The filter sits at the front of the request pipeline, acting as a gatekeeper before requests reach downstream handlers:

```
HTTP Request --> FilterChain --> Target Servlet / JSP
```

In the X33 case, the filter's intended role is to set character encoding to SJIS before propagation, which is critical for Japanese-language web applications where input may arrive in Shift JIS rather than UTF-8.

### Stub-First Development

A notable architectural pattern in this module is the use of structural scaffolding. Both sub-modules were created as placeholders implementing the correct interfaces but containing no operational logic. This pattern suggests one or more of the following scenarios:

1. **Framework migration** — Original logic may have been removed during a migration (e.g., from Struts to Spring) and delegated to framework-level equivalents, leaving the servlet components as dead stubs.
2. **Incremental development** — Stubs were left intentionally so developers can populate them as features are implemented.
3. **Build differentiation** — The `X33JV` prefix indicates the filter was scoped to a Japanese-specific deployment that may no longer be supported.

This pattern has implications for developers: any logic that appears to be missing may have already been moved elsewhere, and removing these stubs should be done only after confirming they are not still registered in the deployment descriptor or referenced by other components.

## Module Interaction Diagram

The following diagram shows how the sub-modules interact within the Fujitsu web layer:

```mermaid
flowchart TD
    subgraph Fujitsu["com.fujitsu - Fujitsu Application Platform"]
        direction LR
        Futurity["com.fujitsu.futurity
Web Entry Point"]
    end
    Futurity -->|lifecycle| Listener["X33AppContextListener
ServletContextListener"]
    Futurity -->|request preprocessing| Filter["X33JVRequestEncodingSjisFilter
javax.servlet.Filter"]
    XML["web-full.xml
Deployment Descriptor"] -.->|registers| Filter
    XML -.->|registers| Listener
    Filter -->|chain.doFilter| Servlet["Target Servlet / JSP"]
    Listener -->|initializes| Context["ServletContext"]
    Context --> Filter
```

The listener initializes the `ServletContext` at startup, and the filter intercepts each HTTP request, setting character encoding before forwarding it to the target servlet. Both are (or were intended to be) registered via `web-full.xml`.

## Dependencies and Integration

### Inbound Dependencies

| Source | What it does |
|--------|-------------|
| `web-full.xml` | Registers `X33AppContextListener` (via `<listener>`) and `X33JVRequestEncodingSjisFilter` (via `<filter>` / `<filter-mapping>`) in the servlet container. |

### Outbound Dependencies

| Dependency | Sub-module | Reason |
|------------|-----------|--------|
| `javax.servlet.*` | `listener` | `X33AppContextListener` was designed to implement `javax.servlet.ServletContextListener` (currently not implemented). |
| `javax.servlet.*` | `filter` | `X33JVRequestEncodingSjisFilter` implements `javax.servlet.Filter`, `FilterConfig`, `FilterChain`, `ServletRequest`, and `ServletResponse`. |

No internal Futurity package dependencies are declared within either sub-module. This is consistent with their current state as no-op stubs that do not interact with other parts of the Futurity application.

### Integration with the Rest of the System

This module occupies the entry point of the X33 web layer. All HTTP requests targeting the X33 application flow through its filter chain, and all application-scoped state is initialized by its listener. Any changes to these components affect every request handled by X33, making them high-impact areas that should be modified with care and thorough validation.

## Notes for Developers

### Current State: Stub Components

All child sub-modules in this package contain placeholder implementations. Before making any changes:

- **Verify registration** — Check `web-full.xml` to confirm whether `X33AppContextListener` and `X33JVRequestEncodingSjisFilter` are still referenced. If not, they are dead code.
- **Verify logic delegation** — If the application needs character encoding handling or application-scoped initialization, confirm whether that logic has been moved to another component (e.g., a Spring filter or `@Configuration` class). Do not assume the stubs are the only place this logic exists.
- **Verify build scope** — The `X33JV` prefix strongly suggests Japanese build scoping. If the Japanese build is no longer supported, these components may be safe to remove.

### Implementing the Filter

If the SJIS encoding behavior is still required, a minimal implementation of `X33JVRequestEncodingSjisFilter` would look like:

```java
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
        throws IOException, ServletException {
    req.setCharacterEncoding("SJIS");
    chain.doFilter(req, res);
}
```

For a configurable approach (reading encoding from XML init-params):

```java
private String encoding;

public void init(FilterConfig config) {
    encoding = config.getInitParameter("encoding");
    if (encoding == null) encoding = "SJIS";
}

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
        throws IOException, ServletException {
    req.setCharacterEncoding(encoding);
    chain.doFilter(req, res);
}
```

### Implementing the Listener

If `X33AppContextListener` is still the intended initialization entry point, it should:

1. Implement `javax.servlet.ServletContextListener`.
2. Override `contextInitialized()` to perform startup tasks (load configuration, register beans, etc.).
3. Override `contextDestroyed()` to clean up resources on shutdown.
4. Be registered in `web-full.xml` via a `<listener>` element, or annotated with `@WebListener`.

### Adding New Web Components

This package is the root of the web module hierarchy. New web-related components for X33 (additional filters, listeners, or context initializer classes) should be added to the appropriate sub-package (`filter` or `listener`) within `com.fujitsu.futurity.web.x33` unless there is a clear domain reason to create a new sub-package under `web`.