# Com / Fujitsu / Futurity

## Overview

The `com.fujitsu.futurity` package is the root package for the Fujitsu Futurity application — a Java EE application built on Fujitsu's proprietary JV (Java Version) platform. This package serves as the top-level namespace that contains the web-facing entry points for the application, which act as the boundary between the servlet container (such as Tomcat or WebSphere) and the application's internal business logic layers.

Futurity appears to be a Japanese enterprise application, given its use of SJIS (Shift JIS) character encoding and the Fujitsu-specific X33 platform branch. The module's current state suggests it is either in early development, undergoing migration, or serves as a legacy scaffold where the substantive logic lives in shared libraries or container-managed defaults rather than within the package itself.

**Current status: scaffolding / stub.** The module's concrete implementations are structural placeholders — pass-through filters and empty listener classes — indicating that real functionality may have been extracted elsewhere or is pending implementation.

## Sub-module Guide

### `web` — Web-Facing Entry Points

The `web` package is the sole child sub-module and provides the HTTP-facing layer of the Futurity application. It is responsible for two key servlet lifecycle extension points:

- **Request filter** (`X33JVRequestEncodingSjisFilter`) — intercepts every HTTP request to potentially set character encoding (originally SJIS) before the request reaches any servlet. Currently a pass-through no-op.
- **Context listener** (`X33AppContextListener`) — intended to manage application-scoped resources at startup and shutdown. Currently an empty class shell.

These two extension points work orthogonally: the filter handles the **horizontal** axis of request flow (per-request processing), while the listener handles the **vertical** axis of application lifecycle (once-per-application initialization and cleanup). Together they form the canonical servlet integration boundary.

Both are currently stubs, but the filter is the more immediately useful extension point for adding cross-cutting concerns like request logging, validation, or header manipulation — without touching individual servlets.

## Key Patterns and Architecture

### Servlet Filter Chain Pattern

The filter follows the standard Java EE servlet filter lifecycle:

1. The container instantiates the filter once during deployment and calls `init(FilterConfig)`.
2. For each matching HTTP request (as defined in `web-full.xml`), `doFilter()` is invoked.
3. The filter delegates to `chain.doFilter()`, passing control to the next element in the chain.
4. On shutdown, `destroy()` is called.

This pattern is ideal for cross-cutting concerns because it intercepts all matching requests uniformly, before they reach any servlet. The current implementation is a bare pass-through, but the scaffold is in place for future encoding or request-processing logic.

### Servlet Context Listener Pattern

The listener follows the `ServletContextListener` pattern, with callbacks at application startup (`contextInitialized`) and shutdown (`contextDestroyed`). This is the canonical place for application-scoped initialization — connection pools, configuration loading, service bootstrapping — that should happen exactly once and be cleaned up on undeployment. The current class is empty and not yet registered in the web descriptor, so it receives no lifecycle callbacks today.

### Stub Architecture

Both sub-modules share a defining characteristic: they are stubs. The filter performs no processing; the listener is an empty class. This architecture suggests:

- X33 may be an older or migrating branch where encoding logic was extracted to a shared library.
- SJIS encoding handling may now be managed by a different filter higher in the chain, making this filter redundant.
- The application may be in early development or migration, with these scaffolds marking where integration points will eventually live.

**This appears to be a migration or legacy scaffold** — the naming convention (X33JV, SJIS) points to Fujitsu's proprietary Java platform, and the pass-through implementations suggest the real functionality has been replaced by container-managed defaults or moved to a shared library.

## Module Interaction

```mermaid
flowchart TD
    PARENT["com.fujitsu.futurity<br/>Parent Module"]
    WEB["web<br/>Web Layer"]
    PARENT --> WEB

    WEB --> FILTER["X33JVRequestEncodingSjisFilter<br/>Request Filter"]
    WEB --> LISTENER["X33AppContextListener<br/>Context Listener"]
    WEB --> CONFIG["web-full.xml<br/>Configuration"]

    FILTER --> CHAIN["FilterChain<br/>Forward to next"]
    LISTENER --> LIFECYCLE["ServletContext<br/>Startup / Shutdown"]

    style PARENT fill:#e1f5fe
    style WEB fill:#f3e5f5
    style FILTER fill:#fff3e0
    style LISTENER fill:#fff3e0
    style CONFIG fill:#e8f5e9
    style CHAIN fill:#e8f5e9
    style LIFECYCLE fill:#e8f5e9
```

```mermaid
flowchart TD
    A["web-full.xml<br/>Configuration"] --> B["X33JVRequestEncodingSjisFilter<br/>Request Filter"]
    A --> C["X33AppContextListener<br/>Context Listener"]
    B --> D["FilterChain<br/>Next Servlet / Filter"]
    C --> E["ServletContext Lifecycle<br/>Startup / Shutdown"]
    style A fill:#e1f5fe
    style B fill:#fff3e0
    style C fill:#fff3e0
    style D fill:#e8f5e9
    style E fill:#e8f5e9
```

## Dependencies and Integration

### Internal Dependencies

| Dependency | How It's Used |
|---|---|
| `web-full.xml` | Declares the filter's URL mapping and would be the registration point for the context listener. |

### External Dependencies

| Dependency | How It's Used |
|---|---|
| `javax.servlet.Filter` | Implemented by `X33JVRequestEncodingSjisFilter`. |
| `javax.servlet.FilterChain` | Used in `doFilter()` to forward requests. |
| `javax.servlet.ServletRequest`, `ServletResponse` | The request/response types processed by the filter. |
| `javax.servlet.FilterConfig` | Configuration passed to `init()`. |
| *(future)* `javax.servlet.ServletContextListener` | Intended interface for `X33AppContextListener`. |
| *(future)* `javax.servlet.ServletContextEvent` | Event type for lifecycle callbacks. |

### Module Structure

```mermaid
flowchart LR
    WEB["com.fujitsu.futurity.web<br/>Web Module"] --> X33["x33<br/>X33 Branch"]
    X33 --> FILTER["x33/filter<br/>X33JVRequestEncodingSjisFilter"]
    X33 --> LISTENER["x33/listener<br/>X33AppContextListener"]
    FILTER --> CHAIN["FilterChain<br/>Forward to next"]
    LISTENER --> LIFECYCLE["ServletContext<br/>Startup/Shutdown"]
    style WEB fill:#e1f5fe
    style X33 fill:#f3e5f5
    style FILTER fill:#fff3e0
    style LISTENER fill:#fff3e0
```

## Notes for Developers

- **Both sub-modules are stubs.** Neither filter logic nor listener initialization has been implemented. If you are adding functionality here, start by implementing the expected interfaces.
- **Encoding awareness.** The filter's name (`X33JVRequestEncodingSjisFilter`) signals that SJIS encoding is important for this application. If encoding logic is added, remember that `setCharacterEncoding()` must be called *before* the request body is read (i.e., before `chain.doFilter()` and before any servlet reads parameters).
- **Registration requirement.** `X33AppContextListener` will not be invoked by the servlet container until it is registered — either via `web.xml` `<listener>` element or via `@WebListener` annotation. Simply creating the class is not enough.
- **Thread safety.** Servlet context listeners execute in the container's deployment thread. Avoid blocking operations in `contextInitialized()` to prevent slow application startup.
- **Error handling in listeners.** Exceptions thrown from `contextInitialized()` typically cause the entire web application to fail to start. Any initialization code should include try-catch blocks with clear error messages.
- **Extension opportunity.** The filter is a natural place to add new cross-cutting concerns (logging, request tracing, header manipulation) without modifying individual servlets.
- **No tests.** There are no test files in either sub-module. Tests would be valuable once real logic is added.