# Com / Fujitsu / Futurity / Web

## Overview

The `com.fujitsu.futurity.web` package is the web-facing layer of the Fujitsu Futurity application. It provides the entry points through which the Java EE servlet container interacts with the application's business logic — handling HTTP request routing, character encoding, and application lifecycle management.

This module represents the boundary between the servlet container (e.g. Tomcat, WebSphere) and the application's internal layers. Its primary responsibility is to establish well-defined integration points — servlet filters for request processing and context listeners for startup/shutdown hooks — so that cross-cutting concerns can be applied uniformly across all HTTP requests and the application's shared resources can be cleanly initialized and torn down.

**Current status: scaffolding / stub.** The module currently contains a single sub-module (`x33`) whose classes are structural placeholders. The filter is a pass-through no-op, and the context listener is an empty class shell. This appears to be a migration or legacy scaffold, where the real functionality may have been replaced by container-managed defaults or moved to a shared library.

## Sub-module Guide

The web module delegates its concrete implementations to the `x33` sub-module, which corresponds to the Fujitsu JV (Java Version) platform branch. Within `x33`, two sub-packages serve orthogonal axes of the servlet lifecycle:

### Filter: `com.fujitsu.futurity.web.x33.filter`

`X33JVRequestEncodingSjisFilter` implements `javax.servlet.Filter` and sits in the request pipeline. The class name signals its original intent: to set the HTTP request character encoding to SJIS (Shift JIS), the Japanese encoding used by Fujitsu's JV platform. As of now, the filter performs no processing — every request passes through unmodified via a bare `chain.doFilter()` call.

This filter would be the natural place to add cross-cutting request logic such as encoding enforcement, request validation, logging, or header manipulation — all without modifying individual servlets.

### Listener: `com.fujitsu.futurity.web.x33.listener`

`X33AppContextListener` is an empty class scaffolded to implement `ServletContextListener`. Once populated, it would manage application-scoped resources: initializing configuration, connection pools, and services at startup (`contextInitialized`), and cleaning them up at shutdown (`contextDestroyed`). It currently has no registration in the web descriptor, so it does not receive any lifecycle callbacks.

### How they relate

The filter and listener together form the two classic servlet-lifecycle extension points:

- **Request flow (horizontal):** Every HTTP request passes through the filter, which can inspect, modify, or reject the request before it reaches a servlet.
- **Lifecycle flow (vertical):** The listener fires once at application start and once at shutdown, managing resources that outlive individual requests.

```
                    +---------------------------+
                    |   X33 Web Application     |
                    |                           |
Lifecycle  ------>  [X33AppContextListener]    |  Lifecycle management
                    |     at startup/shutdown   |
                    |                           |
                    |                           |
Request    ------>  [X33JVRequestEncodingFilter] |  Request pipeline
                    |     (filter chain entry)   |
                    +---------------------------+
```

While orthogonal in timing (per-request vs. once-per-application), both serve a common architectural purpose: establishing the X33 application's boundaries with the web container and providing hooks for cross-cutting concerns.

## Key Patterns and Architecture

### Servlet Filter Chain

The filter follows the standard Java EE servlet filter lifecycle:

1. The container instantiates the filter once and calls `init(FilterConfig)` during deployment.
2. For each matching request (as defined by `<filter-mapping>` in `web-full.xml`), the container invokes `doFilter()`.
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.

### Servlet Context Listener

The listener follows the `ServletContextListener` pattern:

1. The container instantiates the listener during deployment.
2. `contextInitialized(ServletContextEvent)` fires when the web application is ready.
3. The application runs.
4. `contextDestroyed(ServletContextEvent)` fires during undeployment.

This is the canonical place for application-scoped initialization — operations that should happen exactly once and be cleaned up on shutdown.

### Stub Architecture

Both classes share a defining characteristic: they are stubs. The filter is a pass-through implementation; the listener is an empty class. This suggests:

- X33 may be an older or migrating branch where the encoding logic was extracted elsewhere.
- The 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.

## 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
```

### Configuration Flow

```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
```

## 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.