# Javax / Faces / Webapp

## Overview

The `javax.faces.webapp` package sits at the intersection of the JavaServer Faces (JSF) framework and the servlet container. It provides the `FacesServlet`, which serves as the entry point for all HTTP requests that are managed by the JSF lifecycle. This package appears to be a stub placeholder within a test fixture — the `FacesServlet` class is defined but contains no implementation.

## Key Classes and Interfaces

### FacesServlet

**File:** [FacesServlet.java](full-fixture-codebase/src/java/javax/faces/webapp/FacesServlet.java)

The `FacesServlet` is a servlet that acts as the front controller for the JSF framework. When a request matches its URL pattern, it intercepts the request and delegates it into the JSF lifecycle — which processes events such as restore view, apply request values, process validations, update model values, invoke application, and render response.

```java
package javax.faces.webapp;
public class FacesServlet {}
```

In the current codebase, the class is declared but empty. In a real JSF implementation (such as Mojarra or MyFaces), this class would contain:

- A `service()` or `doGet()`/`doPost()` override that bootstraps the JSF lifecycle for each request.
- An `init()` method to look up the `FacesLifecycle` and `FacesContextFactory` from the application context.
- Support for mapping incoming requests (e.g., `*.jsf`, `/faces/*`, or the default `/faces/faces Servlet`) to the JSF request processing pipeline.
- Handling of non-GET/POST HTTP methods and passing them through unchanged (a servlet filter would handle those cases instead).

The class is referenced by two web deployment descriptors:

- `web-full.xml`
- `web.xml`

These configurations register the servlet and define its URL mapping, ensuring the servlet container routes matching requests to JSF processing.

## How It Works

### Request Flow (Conceptual)

In a fully implemented JSF application, the request flow through this servlet follows a standard pattern:

```mermaid
flowchart TD
    A["Browser Request"] --> B["Servlet Container
(web.xml mapping)"]
    B --> C["FacesServlet.service()"]
    C --> D["Faces Lifecycle
1. Restore View"]
    D --> E["2. Apply Request Values"]
    E --> F["3. Process Validations"]
    F --> G["4. Update Model Values"]
    G --> H["5. Invoke Application"]
    H --> I["6. Render Response"]
    I --> J["HTML returned to Browser"]
```

Since this `FacesServlet` is currently an empty stub, no actual lifecycle processing occurs. The module is functional in structure (correct package, correct class name, wired into `web.xml` and `web-full.xml`) but deferred in implementation.

### Configuration Integration

The servlet is wired up through standard Java EE deployment descriptors:

| Descriptor     | Role                                       |
|----------------|--------------------------------------------|
| `web.xml`      | Standard servlet registration and mapping  |
| `web-full.xml` | Full Java EE profile variant of config     |

Both files reference `FacesServlet`, likely defining a URL pattern (such as `*.jsf` or `/faces/*`) that causes the container to dispatch matching requests to this servlet.

## Data Model

No data model classes, DTOs, or entities are defined within this package. The `FacesServlet` in its current form carries no fields or state.

## Dependencies and Integration

### Inbound Dependencies

Other modules depend on this one by referencing `FacesServlet`:

- **`web-full.xml`** — Full Java EE web.xml variant, declares the servlet
- **`web.xml`** — Standard web.xml, declares the servlet

These XML files are the external consumers of this module. The servlet container reads these descriptors at startup to register and map the servlet.

### Framework Integration

`FacesServlet` is the core integration point between the servlet API (`javax.servlet`) and the JSF framework (`javax.faces`). In a complete implementation, it would depend on:

- `javax.servlet` — for request/response handling
- `javax.faces.context` — for creating the `FacesContext`
- `javax.faces.lifecycle` — for invoking the JSF lifecycle phases

## Notes for Developers

1. **This is a stub.** The `FacesServlet` class body is empty. Any production code relying on JSF request processing through this servlet will need the implementation filled in.

2. **URL mapping matters.** The behavior of this servlet is governed by its URL pattern in `web.xml`. Common patterns include `*.jsf`, `*.faces`, or `/faces/*`. Changing the pattern changes which requests enter the JSF lifecycle.

3. **Only GET and POST are handled.** A real `FacesServlet` typically processes only GET and POST requests; other HTTP methods (PUT, DELETE, etc.) are passed through unchanged, leaving them to be handled by filters or the servlet's default behavior.

4. **Single instance.** Like all servlets, `FacesServlet` is instantiated once per web application and handles all matching requests concurrently. Any state stored as instance variables must be thread-safe.

5. **Multiple configuration files.** The presence of both `web.xml` and `web-full.xml` suggests this project supports both standard and full Java EE profiles. Ensure both files define consistent servlet mappings.