# Com / Fujitsu / Futurity

## Overview

The `com.fujitsu.futurity` package represents the web entry point for the Fujitsu Futurity application platform — a Java EE / Jakarta EE application originally scoped for the X33 product line. At the top of the module hierarchy, it provides the foundational servlet infrastructure that sits at the boundary between HTTP clients and the rest of the Futurity system.

This module is responsible for three core concerns:

1. **Application lifecycle management** — bootstrapping and tearing down the runtime context via `ServletContextListener` implementations.
2. **Request preprocessing** — intercepting inbound HTTP traffic through `javax.servlet.Filter` chains to handle cross-cutting concerns such as character encoding before requests reach their target servlets or JSPs.
3. **Deployment registration** — wiring servlet components into the container through `web-full.xml`, the centralized XML-based deployment descriptor.

The Futurity web layer follows the traditional Java EE servlet model (Servlet 2.x / 3.x style), using XML deployment descriptors rather than annotation-based discovery. This is a deliberate architectural choice consistent with enterprise Java applications built in the mid-to-late 2000s, where explicit XML configuration provided better control over component lifecycle ordering and deployment behavior.

As of the current index, the module's sub-modules consist of structural stubs — scaffolded classes that implement the correct interfaces but contain no operational logic. This suggests the web layer is either in a transitional state (e.g., mid-migration to a framework-level approach) or has delegated its actual business logic to higher-level components elsewhere in the application.

## Sub-module Guide

### com.fujitsu.futurity.web — The Root Web Package

The `web` package forms the root of the web module hierarchy. It defines the servlet-based entry point for the Futurity platform and organizes components by application variant. Its primary purpose is to provide the infrastructure hooks — listeners for application startup and filters for request preprocessing — that every HTTP request flowing through the X33 application passes through.

### com.fujitsu.futurity.web.x33 — X33 Application Web Layer

The `x33` sub-package is the top-level sub-package under `web` and is the only documented application-specific child of the Futurity web layer. It was scoped to the Japanese (`JV`) build of the X33 platform and contains two complementary stub components that form the backbone of X33's request handling pipeline.

#### listener — Application Lifecycle

`X33AppContextListener` is a `ServletContextListener` stub intended to perform one-time application startup and shutdown tasks. In a fully implemented version, this listener 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.

#### filter — Request Encoding

`X33JVRequestEncodingSjisFilter` is 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 filter is structurally complete — its class body references `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. The `X33JV` prefix indicates Japanese build scoping, suggesting this filter may be a relic of a Japanese-specific deployment no longer actively maintained.

#### How They Relate

These two components serve complementary phases of the HTTP request lifecycle:

- The **listener** operates at the application scope, running once at server startup. It sets up the context that the filter and all subsequent servlets depend on.
- The **filter** operates at the request scope, running on every incoming HTTP request. It transforms or annotates the request before it reaches the 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. Both are (or were intended to be) registered in `web-full.xml`.

## Key Patterns and Architecture

### Servlet Lifecycle Pattern

The Futurity 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.

### Request Processing Pipeline

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

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

In the X33 case, the filter's intended role is to set character encoding to SJIS before propagation. This is critical for Japanese-language web applications where input may arrive in Shift JIS rather than UTF-8. The filter transforms the request before it reaches downstream components, ensuring consistent encoding across all handlers.

### Configuration-Driven Registration

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

- Listener registration uses the `<listener>` element.
- 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 that is typical of enterprise Java deployments. However, it also means that adding new servlet components requires XML changes rather than being a purely code-level operation.

### 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:

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.

## 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.

## 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"]
    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 (or were intended to be) registered via `web-full.xml`.

## 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`.