# Com / Fujitsu / Futurity / Web / X33

## Overview

The `com.fujitsu.futurity.web.x33` package sits at the top of the X33 web layer within the Fujitsu Futurity application framework. It provides the foundational web infrastructure that the X33 application — originally scoped to the Japanese (`JV`) build — needs to receive HTTP requests and initialize its runtime context.

Currently, this package contains two sub-packages that serve complementary roles in the servlet lifecycle:

- **`listener`** — Application-scoped lifecycle management (`X33AppContextListener`)
- **`filter`** — Per-request request preprocessing (`X33JVRequestEncodingSjisFilter`)

Both components are currently placeholders: the filter delegates pass-through (implemented but inactive), and the listener is an empty skeleton. They 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.

## Sub-module Guide

### listener — Application Lifecycle Listener

The listener sub-package (`com.fujitsu.futurity.web.x33.listener`) contains `X33AppContextListener`, a class intended to function as a `ServletContextListener`. Its purpose is to perform one-time initialization when the web application starts (and cleanup when it shuts down), such as bootstrapping configuration, registering shared beans into the servlet context, or setting up application-wide state.

At present, the class body is completely empty — no fields, no constructor, no methods, and no interface implementation. This means it is not registered with the servlet container and has no runtime effect. The class exists as a structural placeholder, and the `web-full.xml` deployment descriptor may or may not reference it.

Before building out initialization logic, developers should verify whether `X33AppContextListener` is still the intended entry point, or if that responsibility has been delegated elsewhere (e.g., Spring `@Configuration` classes, `@Bean` definitions, or an alternative listener).

### filter — Request Encoding Filter

The filter sub-package (`com.fujitsu.futurity.web.x33.filter`) contains `X33JVRequestEncodingSjisFilter`, a servlet `Filter` that was designed to intercept HTTP requests and set the character encoding to SJIS (Shift JIS) — a common encoding for Japanese-language web applications — before forwarding them to the target servlet.

Unlike the listener, the filter class is structurally complete: it implements `javax.servlet.Filter` and provides `doFilter()`, `init()`, and `destroy()` methods. However, `doFilter()` is a no-op stub — it immediately calls `chain.doFilter(req, res)` without setting any encoding. The class is registered in `web-full.xml` via `<filter>` and `<filter-mapping>` entries, but its presence in the chain has no practical effect.

The `X33JV` prefix in the class name indicates this was originally scoped to the Japanese build of the X33 platform. If a non-JV build exists, there may be a corresponding filter with a different encoding (e.g., UTF-8) in another package, or this class may be included but never activated.

### How the Sub-modules Relate

Both sub-packages address the two fundamental phases of a servlet-based web application:

1. **Startup (listener)** — The `X33AppContextListener` is expected to set up the application context once when the web container starts. Any configuration, bean registration, or shared state initialized here would be available to all components that handle requests.
2. **Per-request (filter)** — The `X33JVRequestEncodingSjisFilter` intercepts every incoming HTTP request matching its URL pattern, sets the character encoding, and then passes the request down the filter chain to the target servlet.

In a fully implemented system, the listener would establish the runtime environment that the filter and subsequent servlets depend on. For example, the listener might load locale-specific configuration (including the encoding to use), and the filter would read that configuration during its `init()` phase and apply it to each request. As it stands today, neither component performs any actionable logic.

## Key Patterns and Architecture

### Servlet Lifecycle Pattern

Both classes follow the standard Java Servlet API lifecycle pattern:

- **`ServletContextListener` (listener)** — `contextInitialized()` / `contextDestroyed()` for application-scoped start and stop hooks.
- **`javax.servlet.Filter` (filter)** — `init()` / `doFilter()` / `destroy()` for per-request interception and cleanup.

These are both well-established patterns in the Java EE servlet specification, providing predictable hooks that the container calls automatically.

### Request Processing Pipeline

The filter is designed to sit at the front of the request processing pipeline, acting as a gatekeeper before the request reaches any servlet or JSP. The typical flow is:

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

The filter's role is to transform or annotate the request before it propagates. In this case, the intended transformation is character encoding, which is critical for Japanese-language applications where input data may arrive in Shift JIS rather than UTF-8.

### Configuration-Driven Registration

Both components are registered via `web-full.xml`, the centralized deployment descriptor. This means:

- The listener is registered via a `<listener>` element.
- The filter is registered via `<filter>` and `<filter-mapping>` elements, with URL patterns controlling which requests it intercepts.

This is the traditional Servlet 2.x / 3.x approach. In newer Java EE / Jakarta EE applications, `@WebListener` and `@WebFilter` annotations can replace XML-based registration, but the X33 module currently uses the XML approach exclusively.

### Stub-to-Production Transition

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

1. **Framework migration** — The original logic may have been removed during a migration (e.g., from Struts to Spring) and replaced with framework-level equivalents, leaving the servlet-level components as dead stubs.
2. **Incremental development** — The stubs were left intentionally so developers could populate them as features are implemented.
3. **Build differentiation** — The `X33JV` prefix indicates the filter was built for a Japanese-specific deployment. If that build is no longer supported, the filter may be a relic.

## Dependencies and Integration

### Inbound Dependencies

| Source | What it does |
|--------|-------------|
| `web-full.xml` | Registers both `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. The filter and listener do not import classes from other packages in the `com.fujitsu.futurity.web` hierarchy, which is consistent with their current state as no-op stubs.

### Integration with the Rest of the System

This package occupies the entry point of the X33 web layer. All HTTP requests targeting the X33 application flow through the filter chain, and all application-scoped state is initialized by the listener. As such:

- **Downstream impact** — Any changes to these components affect every request handled by X33. The filter's URL mapping determines which paths are intercepted, and the listener's initialization logic determines what state is available to downstream servlets.
- **Deployment dependency** — Both components are only active if referenced in `web-full.xml` (or annotated with `@WebListener` / `@WebFilter`). If the deployment descriptor omits them, they have no effect regardless of their code.

## Notes for Developers

### Current State: Stub Components

Both sub-packages contain placeholder implementations. Before making changes:

- **Verify registration** — Check `web-full.xml` to confirm whether `X33AppContextListener` and `X33JVRequestEncodingSjisFilter` are still referenced. If they are not, they are dead code.
- **Verify logic delegation** — If the application needs character encoding (filter) or application-scoped initialization (listener), confirm whether that logic has been moved to another component (e.g., a Spring filter or a `@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 the 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`.

### Package Structure

This package is the deepest sub-package in the `x33` web layer — it has no child modules of its own. New web-related components for X33 (additional filters, listeners, or context initializer classes) should be added to the appropriate sub-package (`filter` or `listener`) unless there is a clear domain reason to create a new sub-package.

### Diagram: Module Interaction

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

```mermaid
flowchart TD
    subgraph Web["Web Layer: com.fujitsu.futurity.web.x33"]
        direction LR
        L["X33AppContextListener
ServletContext stub"] --- R["X33JVRequestEncodingSjisFilter
doFilter no-op"]
    end
    XMLConfig["web-full.xml
Deployment Descriptor"] -.->|registers| R
    R --> Chain["FilterChain.doFilter()"]
    Chain --> Servlet["Target Servlet / JSP"]
    L -->|initializes| Context["ServletContext"]
    Context --> R
```

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`.