# Com / Fujitsu / Futurity / Web / X33

## Overview

The `com.fujitsu.futurity.web.x33` package is the web-tier scaffolding for the X33 sub-system within the Fujitsu Futurity application. It lives at the intersection of the Java EE servlet container and the X33 business domain, providing two standard JEE extension points — a servlet filter and a servlet context listener — both currently implemented as no-op stubs.

This area of the codebase appears to be a legacy or transitional layer. Its primary purpose is structural: it registers hooks into the servlet container's lifecycle so that X33-specific initialization, encoding, and filtering logic can be plugged in without modifying deployment descriptors. The "JV" suffix on the filter name ("JV" likely referring to Japan) suggests the original intent was to handle Japanese character encoding (Shift JIS / Windows-31J) for requests targeting X33 endpoints, but the actual encoding logic has not yet been wired up.

From an architectural standpoint, the X33 web package occupies the **request-entry boundary** of the application. All incoming HTTP requests that match its URL patterns flow through the filter chain, while application-wide startup and shutdown events are exposed through the context listener. Both are currently inert, meaning the X33 module likely delegates its request handling entirely to downstream servlets or dispatchers that reside in sibling packages.

## Sub-module Guide

The X33 web package contains two sub-modules, each responsible for a different phase of the servlet container's lifecycle:

### Filter — `X33JVRequestEncodingSjisFilter`

The filter (`com.fujitsu.futurity.web.x33.filter`) implements `javax.servlet.Filter` and is designed to sit in the request processing pipeline. Based on its name, the intended responsibility is to set the character encoding of incoming HTTP requests to **Shift JIS (SJIS / Windows-31J)** — a Japanese encoding — before the request reaches the target servlet.

**Current behavior:** The filter is a pure pass-through. Its `doFilter()` method calls `chain.doFilter(req, res)` without inspecting or modifying the request, `init()` is empty, and `destroy()` is empty. No encoding logic exists.

**Relationship to the system:** This filter would have been the first line of defense in ensuring that Japanese-language input from X33 endpoints is interpreted correctly. Without encoding logic, the filter adds no value at runtime but provides a registration point in `web.xml` and `web-full.xml` where encoding can be added later.

### Listener — `X33AppContextListener`

The listener (`com.fujitsu.futurity.web.x33.listener`) is registered in `web.xml` under the `<listener-class>` element. Its intended responsibility is to react to `ServletContext` lifecycle events — specifically application startup (`contextInitialized`) and shutdown (`contextDestroyed`) — so that X33-specific one-time initialization or cleanup can be performed.

**Current behavior:** The class body is entirely empty. It does not even implement `javax.servlet.ServletContextListener`, which means the servlet container instantiates it on startup but nothing else happens. It is a scaffold waiting for implementation.

**Relationship to the system:** This listener is the designated landing point for any X33 application-level bootstrapping (e.g., loading configuration, registering beans, warming caches) or graceful shutdown logic. Because it is already wired in the deployment descriptor, developers can add `implements ServletContextListener` and the callback methods without touching `web.xml`.

### How the sub-modules relate

Both sub-modules serve as **lifecycle extension points** into the servlet container, but they operate at different stages:

| Aspect | Filter | Listener |
|---|---|---|
| **Lifecycle phase** | Per-request | Application lifecycle (startup/shutdown) |
| **Invocation model** | Called once per matching HTTP request | Called once on container startup, once on shutdown |
| **Role in request flow** | Pre-processor before the target servlet | Setup/cleanup around the entire application lifetime |
| **Current state** | Registered, no-op pass-through | Registered, empty class body |

Together, they form a complete but inert pair of hooks: the **filter** would handle per-request concerns (encoding, authentication, logging), and the **listener** would handle application-wide concerns (initialization, teardown). Neither is functional today, but both are properly registered in the deployment descriptors, meaning the infrastructure is in place for X33-specific logic to be grafted in without deployment changes.

## Key Patterns and Architecture

### Deployment Descriptor–Driven Registration

Both components follow a **configuration-over-code** pattern. They are wired into the servlet container exclusively through `web.xml` and `web-full.xml`, with no programmatic registration via `@WebFilter` or `@WebListener` annotations. This is consistent with legacy Java EE applications that predate the servlet 3.0 annotation model, or with enterprise deployments that prefer explicit XML configuration for auditable, version-controlled lifecycles.

### No-Op Stub Pattern

Both the filter and listener follow a **stub-first, implement-later** approach. Rather than omitting registration entirely (which would require editing `web.xml`), the codebase registers placeholder classes in the descriptors and implements them incrementally. This pattern minimizes merge conflicts and deployment risk when adding X33-specific functionality.

### Request Lifecycle Flow

The following diagram shows how these components fit into the overall web request and application lifecycle:

```mermaid
flowchart TD
    Config["web.xml / web-full.xml deployment descriptors"] --> Register["Filter and Listener registration"]
    Register --> Filter["X33JVRequestEncodingSjisFilter"]
    Register --> Listener["X33AppContextListener"]
    Filter --> InitFilter["init(FilterConfig)"]
    InitFilter --> NoOpFilter["no-op: pass through"]
    Filter --> DoFilter["doFilter(ServletRequest, ServletResponse, FilterChain)"]
    DoFilter --> Chain["chain.doFilter(req, res)"]
    Chain --> Next["Next filter or target servlet"]
    Listener --> InitContext["ServletContext startup"]
    InitContext --> NoOpContext["no-op: class instantiated but empty"]
    Filter --> DestroyFilter["destroy()"]
    DestroyFilter --> NoOpFilter
    Listener --> DestroyContext["contextDestroyed(event)"]
    DestroyContext --> NoOpContext
```

### Encoding Strategy (Planned)

The filter name (`X33JVRequestEncodingSjisFilter`) strongly implies an intended encoding strategy: set the request character encoding to **Windows-31J** (the MIME-compatible alias for Shift JIS) before the request is processed. This is the standard approach in legacy Japanese enterprise applications where forms and API payloads use SJIS rather than UTF-8. The intended implementation would look like:

```java
((HttpServletRequest) req).setCharacterEncoding("Windows-31J");
chain.doFilter(req, res);
```

Until this is implemented, the filter is transparent.

## Dependencies and Integration

### External Dependencies

| Dependency | Purpose |
|---|---|
| `javax.servlet.Filter` API | Provides the `Filter` interface and `FilterChain` for the filter |
| `javax.servlet.ServletRequest` / `ServletResponse` | Request and response types passed through the filter |
| `javax.servlet.FilterConfig` / `FilterChain` | Container-provided configuration and chain management for the filter |

Both components have **no Java-level dependencies** on other classes within the `com.fujitsu.futurity` codebase. They depend solely on the standard Servlet API.

### Inbound Dependencies

| Artifact | Relationship |
|---|---|
| `web.xml` | Registers both the filter and the listener |
| `web-full.xml` | Extended/alternate deployment descriptor that also registers both components |

### Integration with the X33 Module

The X33 web package is a **leaf module** — it has no child packages and no indexed source files beyond the two stub classes. Its integration point with the rest of the X33 system is implicit: requests that pass through the filter are destined for X33-targeting servlets, controllers, or dispatchers in sibling packages (e.g., `com.fujitsu.futurity.web.x33.*` controllers or action classes). The listener, if implemented, would initialize services or resources used by those downstream components.

## Notes for Developers

- **Both components are no-ops.** If you are onboarding to the X33 web layer, be aware that the filter does not perform encoding and the listener does not run any initialization code. Functionality must be added explicitly.
- **The filter needs encoding logic.** To activate Shift JIS encoding, add `((HttpServletRequest) req).setCharacterEncoding("Windows-31J")` in `doFilter()` before `chain.doFilter(req, res)`. Consider making this conditional on the request path if only Japanese endpoints need SJIS encoding.
- **The listener needs interface implementation.** To make the listener functional, add `implements javax.servlet.ServletContextListener` and implement `contextInitialized` and optionally `contextDestroyed`.
- **Thread safety is not a concern** for the current no-op implementations, but any future initialization logic in the listener must account for the fact that `contextInitialized` runs on the container's startup thread — heavy blocking work will delay application startup.
- **Both components are registered in two descriptors.** Changes to one (`web.xml`) may need to be mirrored in the other (`web-full.xml`) depending on your deployment profile. Check your CI/CD pipeline to understand when each is used.
- **No child modules exist.** The package is a leaf — all logic lives in `X33JVRequestEncodingSjisFilter.java` and `X33AppContextListener.java`.