# Com / Fujitsu / Futurity / Web

## Overview

The `com.fujitsu.futurity.web` package forms the web layer of the Fujitsu Futurity application. It sits at the top of the web module hierarchy and provides the foundational servlet-based infrastructure for receiving HTTP requests, managing the servlet lifecycle, and initializing runtime context for the Futurity platform.

This module follows the traditional Java Servlet API pattern (Java EE / Jakarta EE), using `web.xml`-style deployment descriptors (`web-full.xml`) for component registration rather than annotation-based approaches. The web layer is organized under sub-packages by application or build variant, with the `x33` sub-package being the primary documented child — originally scoped to the Japanese (`JV`) build of the X33 platform.

At present, the child sub-modules within this package consist of structural placeholders — stub implementations for servlet lifecycle listeners and request-processing filters that were designed as scaffolding for future logic. No source files have been indexed for this module, which suggests either that the codebase uses a different indexing configuration, or that the web layer's implementation logic has been delegated to a higher-level framework (e.g., Spring MVC or Struts action classes defined elsewhere).

## Sub-module Guide

### x33 — X33 Application Web Layer

The `com.fujitsu.futurity.web.x33` package is the top-level sub-package of the X33 application's web layer. It serves as the entry point for HTTP requests targeting the X33 application and provides the two fundamental servlet lifecycle hooks: application-scoped initialization and per-request preprocessing.

The x33 sub-package contains two child sub-packages that work together in the servlet request pipeline:

- **`listener`** — `X33AppContextListener`, a `ServletContextListener` stub that is intended to perform one-time application startup and shutdown tasks (e.g., loading configuration, registering shared beans, establishing application-wide state). Currently, the class body is empty with no fields, constructors, methods, or interface implementation.
- **`filter`** — `X33JVRequestEncodingSjisFilter`, a `javax.servlet.Filter` that was designed to intercept incoming HTTP requests and set the character encoding to Shift JIS (SJIS) before forwarding to the target servlet. This filter is structurally complete (it implements `Filter`, `FilterConfig`, `FilterChain`, `ServletRequest`, and `ServletResponse`) but its `doFilter()` method is a no-op stub that immediately passes the request down the chain without modifying it.

Both components are registered (or intended to be registered) in `web-full.xml`. The `X33JV` prefix on the filter indicates Japanese build scoping; if the Japanese build is no longer actively developed, this filter may be a relic or a build-time exclusion candidate.

These components were designed to form the backbone of X33's request handling pipeline: the listener bootstraps the application context at startup, and the filter ensures incoming requests are processed with the correct character encoding before reaching the target servlet. As of now, neither performs any actionable logic.

## Key Patterns and Architecture

### Servlet Lifecycle Pattern

The web layer follows the standard Java Servlet API lifecycle:

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

These are well-established patterns in the Java EE servlet specification, providing predictable container-managed hooks.

### Request Processing Pipeline

The filter sits at the front of the request processing pipeline, acting as a gatekeeper:

```
HTTP Request → FilterChain → Target Servlet / JSP
```

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

### Configuration-Driven Registration

Both listener and filter components are registered via `web-full.xml`, the centralized deployment descriptor:

- Listener registration: `<listener>` element
- Filter registration: `<filter>` and `<filter-mapping>` elements with URL patterns controlling interception scope

This is the traditional Servlet 2.x / 3.x XML-based approach. Modern applications would typically use `@WebListener` and `@WebFilter` annotations instead.

### Placeholder-First Development

A notable architectural pattern in this module is the "stub-first" approach. Both sub-modules were created as structural scaffolding and remain in that state. This suggests one or more of the following:

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 built for a Japanese-specific deployment that may no longer be supported.

## 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 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`.

### Module Interaction Diagram

The following diagram shows how the sub-modules interact within the X33 web layer:

```mermaid
flowchart TD
    subgraph Web["Web Layer: com.fujitsu.futurity.web"]
        direction LR
        X33["X33 Sub-package
com.fujitsu.futurity.web.x33
listener + filter stubs"]
        Web --> X33
    end
    X33 -->|"ServletContextListener
(lifecycle)"| Listener["X33AppContextListener"]
    X33 -->|"javax.servlet.Filter
(request encoding)"| Filter["X33JVRequestEncodingSjisFilter"]
    XML["web-full.xml
Deployment Descriptor"] -.->|"registers"| Filter
    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 currently registered (or intended to be registered) via `web-full.xml`.

### Package Structure

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`.