# Com / Fujitsu / Futurity / Web / X33

## Overview

The `com.fujitsu.futurity.web.x33` package resides at the web layer of the Fujitsu Futurity application, forming the X33 module's servlet-tier entry points. It provides the foundational web infrastructure hooks — request filtering and application context lifecycle listening — that the X33 feature relies on during deployment and runtime.

As of the current state of the codebase, this package is in a scaffolding phase. Both of its classes exist as structural placeholders rather than fully implemented components. The filter and listener are wired into the deployment descriptor (`web-full.xml`), establishing the skeleton for the X33 module's integration with the servlet container, but neither contains operational logic today. This suggests the X33 module is either a newly introduced feature area or one whose web-layer concerns are pending final implementation.

The package's responsibility can be summarized in two areas:

1. **Request processing** — intercepting and potentially transforming incoming HTTP requests via a Servlet Filter.
2. **Application lifecycle** — reacting to web-container startup and shutdown events via a Servlet Context Listener.

Together, these form the X33 module's touchpoints with the servlet container's request handling and lifecycle management systems.

## Sub-module Guide

### Filter — X33JVRequestEncodingSjisFilter

**Source:** [X33JVRequestEncodingSjisFilter.java](full-fixture-codebase/src/java/com/fujitsu/futurity/web/x33/filter/X33JVRequestEncodingSjisFilter.java)

The filter sits at the front of the X33 module's HTTP request pipeline. It is mapped in `web-full.xml` and implements `javax.servlet.Filter`, giving it access to every request that matches its URL pattern.

Despite its name, which indicates Shift-JIS (SJIS) encoding handling for Japanese input, the filter is currently a no-op. It implements all three standard `Filter` lifecycle methods (`doFilter`, `init`, `destroy`) but none of them perform any work. `doFilter` simply delegates the request and response directly to the next filter or servlet in the chain without setting character encoding, modifying headers, or performing any logging.

**Why this matters for the system:** The filter's placement in the web configuration means it is an intentional design decision — the X33 module expected to participate in the request processing pipeline. The naming suggests that character encoding (likely Shift-JIS / CP932 for Japanese locales) was intended to be handled at this layer. If Japanese-language input is required for X33, the encoding logic will need to be added here, and the filter must be ordered early in the chain so that encoding is set before any downstream component reads the request body.

See the [filter submodule documentation](filter.md) for full method-level detail.

### Listener — X33AppContextListener

**Source:** [X33AppContextListener.java](full-fixture-codebase/src/java/com/fujitsu/futurity/web/x33/listener/X33AppContextListener.java)

The listener is a stub class located under the `web.x33.listener` sub-package. Its name follows the standard Java EE convention for `ServletContextListener` implementations — the `AppContextListener` suffix signals that this class is expected to manage application-scope resources during container startup and shutdown.

As written, the class declares no methods, fields, or annotations. It does not implement `ServletContextListener` and extends nothing beyond `java.lang.Object`. It is a structural placeholder intended for future expansion, likely to house initialization logic (cache preloading, resource configuration, data initialization) and cleanup hooks that the X33 module will need when it becomes operational.

**Why this matters for the system:** The listener establishes the X33 module's intended touchpoint with the servlet lifecycle. When implemented, `contextInitialized` will be the natural place to set up any X33-specific services, caches, or configuration that the application needs from startup. Conversely, `contextDestroyed` will handle graceful shutdown of those resources. The package placement under `web.x33` suggests these lifecycle hooks will interact with the broader X33 web-layer components (including the filter and any future controllers or services).

See the [listener submodule documentation](listener.md) for full detail.

### How the Sub-modules Relate

Both the filter and the listener serve as the X33 module's integration points with the servlet container, but they operate at different stages of the request lifecycle:

- **Startup phase:** The `X33AppContextListener` fires first, during `contextInitialized`. Any initialization it performs (once implemented) will prepare the X33 module's resources before the first request arrives.
- **Runtime phase:** The `X33JVRequestEncodingSjisFilter` activates on each incoming HTTP request, passing requests through the filter chain. This is where encoding transformation or request preprocessing would occur.
- **Shutdown phase:** The `X33AppContextListener` fires again during `contextDestroyed`, allowing the X33 module to release resources and perform cleanup.

The filter and listener do not directly communicate with each other — they are independent container-managed components. However, they are co-located in the same package and wired through the same deployment descriptor, making them conceptually unified as the X33 module's web-layer facade. When the X33 module is fully implemented, the listener's initialization logic will likely configure resources that the filter (and other X33 web components) consume at runtime.

## Key Patterns and Architecture

### Container-Managed Component Pattern

Both classes follow the standard Java EE servlet container lifecycle pattern. They are instantiated and managed by the servlet container, not by an application framework like Spring. The container:

1. Instantiates the filter and listener once per deployment.
2. Invokes `init()` on the filter and `contextInitialized()` on the listener during application startup.
3. Dispatches each HTTP request through the filter's `doFilter()` method.
4. Invokes `destroy()` on the filter and `contextDestroyed()` on the listener during shutdown.

This pattern is lightweight and framework-agnostic, but it requires careful attention to thread safety, since the container reuses the same instance for all requests.

### No-op / Stub Architecture

Both classes are currently no-ops, which indicates this is a scaffolded module. The pattern here — empty but present classes wired into the deployment descriptor — suggests the X33 feature was designed and its web-layer touchpoints were identified upfront, with the expectation that implementation would follow. This is a reasonable approach for greenfield development where the module's integration points are known but its business logic is still being defined.

### Data Flow

```mermaid
flowchart TD
    WC["Web Container"] -->|startup| L["X33AppContextListener.contextInitialized()"]
    L -->|prepares| RES["X33 resources / services"]
    WC -->|HTTP request| FM["web-full.xml filter mapping"]
    FM -->|dispatches| F["X33JVRequestEncodingSjisFilter.doFilter()"]
    F -->|passes through| FC["FilterChain / downstream servlet"]
    WC -->|shutdown| LS["X33AppContextListener.contextDestroyed()"]
    LS -->|releases| RES
```

### Filter Chain Positioning

The filter's position in `web-full.xml` determines when it executes relative to other filters. Since its name implies encoding setup, it should ideally be positioned early in the chain — before any filter or servlet that reads request parameters, form data, or JSON bodies. The encoding must be set before the body is consumed, so filter ordering is a critical configuration concern when this filter is implemented.

## Dependencies and Integration

### External Dependencies

| Dependency | Purpose |
|------------|---------|
| `javax.servlet.Filter` | Implemented by `X33JVRequestEncodingSjisFilter` for request processing |
| `javax.servlet.ServletContextListener` (expected) | Will be implemented by `X33AppContextListener` for lifecycle management |
| `web-full.xml` | Deployment descriptor that registers both components in the servlet container |

### Internal Dependencies

No inbound callers have been detected — no other Java packages in the codebase import or reference classes from `com.fujitsu.futurity.web.x33`. This reinforces that the X33 module is either newly introduced or isolated from other parts of the system. The filter is invoked purely through XML-based servlet container configuration rather than Java-level references.

### Integration with the Broader System

The X33 web module is designed to integrate with the rest of the Futurity application through standard servlet mechanisms:

- **Filter chain:** The filter delegates to the downstream chain, which eventually reaches X33's servlets, controllers, or other web components (not yet present in the module).
- **ServletContext:** The listener will have access to the application's `ServletContext`, which is the standard mechanism for sharing application-scoped attributes and resources across components.
- **Deployment descriptor:** Both components are wired through `web-full.xml`, which is the canonical configuration point for servlet container components.

## Notes for Developers

1. **Both classes are stubs.** Neither filter nor listener contains operational logic today. This is not a bug — it is a scaffolded module awaiting implementation.

2. **Implementing the filter:** When adding encoding logic, cast the `ServletRequest` to `HttpServletRequest`, call `setCharacterEncoding("SJIS")` (or `"CP932"`) before `chain.doFilter()`, and consider making the encoding configurable via a servlet init-param or context-param rather than hardcoding it.

3. **Implementing the listener:** Add `javax.servlet.ServletContextListener` as an implemented interface and provide `contextInitialized` and `contextDestroyed` methods. Coordinate with the X33 team on initialization ordering and resource lifecycle to avoid conflicts with other application components.

4. **Filter ordering is critical.** If the filter is used for encoding, it must appear early in the `<filter-mapping>` order in `web-full.xml`, before any component that reads request parameters.

5. **Thread safety.** As singleton container-managed components, both classes are instantiated once and handle all requests/lifecycle events on shared instances. Any future state must be read-only after initialization, or protected by synchronization.

6. **No other module depends on this package.** Changes to these classes have limited blast radius within the existing codebase, but any future X33 web components that reference the listener's initialization output will need to be considered.

7. **Encoding choice matters for Japanese locales.** If this filter is intended to handle Japanese input, verify whether the application requires Shift-JIS (`"SJIS"` / `"CP932"`) or has migrated to UTF-8. Modern applications typically use UTF-8, but legacy Japanese enterprise systems often require Shift-JIS for form data compatibility.

## Component Diagram

```mermaid
flowchart LR
    WC["Web Container"] -->|reads| WM["web-full.xml"]
    WM -->|registers| SF["X33JVRequestEncodingSjisFilter"]
    WM -->|registers| CL["X33AppContextListener"]
    SF -->|implements| FI["javax.servlet.Filter"]
    CL -->|will implement| SL["javax.servlet.ServletContextListener"]
    SF -->|passes through| CH["downstream filter chain"]
    CL -->|contextInitialized| IC["app startup hooks"]
    CL -->|contextDestroyed| DC["app shutdown hooks"]