Answering REST API Questions: A Comprehensive Guide

Atomic Answer: To answer REST API questions accurately, developers must locate the precise routing configuration and controller resources in the source code. Instead of relying on outdated documentation or broad searches, you should inspect files like web.xml or application routers to discover the exact HTTP methods, expected payloads, and security models.

The /api/* surface of modern applications is often vast and grows organically. When developers or AI agents need to interact with a system, finding the correct endpoints can be a major hurdle.

• Most engineers over-rely on broad text searches or outdated documentation.
• The truth is often much closer to the source code.

1. The Source of Truth: Web Configurations

Atomic Answer: Web configuration files are the definitive source of truth for API routing. By inspecting files such as web.xml in Java applications, developers can reliably match URL patterns to their specific implementation classes. This guarantees that you find the exact endpoint needed for operations without guessing paths.

When a user asks something that should be a single curl call, but you cannot name the endpoint in advance, always look to the application's core routing configuration.

For Java/Spring/Servlet architectures, wikantik-war/src/main/webapp/WEB-INF/web.xml (or its equivalent Application.java routing file) is the strict contract.

• Every servlet (e.g., *Resource.java) has a declaration and a mapping.
• The mapping defines the exact URL pattern.
• The declaration points to the exact implementation class.
• Actionable Insight: These files answer the question "does an endpoint for X exist?" with absolute certainty.

2. Analyzing the Resource Classes

Atomic Answer: Once you locate the resource class, it provides the exact HTTP method shapes, payload structures, and permission models. Examining annotations like @GET or @POST, alongside data transfer objects and parameter bindings, ensures you fully understand how to format requests and securely access the correct endpoints.

Once the routing file points you to a specific Resource class (e.g., wikantik-rest/.../*Resource.java), that class becomes your source-of-truth. It reveals the HTTP method shape, payload structure, and permission model.

• HTTP Methods: Look for @GET, @POST, @PUT, @DELETE annotations to confirm what actions are supported.
• Permission Models: Endpoint security is often handled via annotations or parent-class helpers (e.g., RestServletBase providing methods like checkPagePermission).
• Payloads: Look at the method signatures to see if they expect query parameters (@QueryParam), path variables (@PathParam), or JSON body payloads (parsed via helpers like parseJsonBody).

3. The Canonical Walkthrough

Atomic Answer: Executing an unfamiliar API request requires a strict, methodical approach. You must first find the route in configuration files, verify HTTP methods and permissions in the controller class, and analyze the required JSON payload structure. Only then should you formulate and send the actual network request.

When tasked with executing a REST API call without prior knowledge, follow this strict, ordered procedure:

• Locate the Route: Inspect the routing configuration (web.xml, routes.rb, urls.py, etc.) to find if the endpoint exists.
• Inspect the Controller/Resource: Read the implementation class to verify the required HTTP method and the permission constraints.
• Analyze the Payload: Check the data transfer objects (DTOs) or parameter bindings to understand exactly what JSON shape the endpoint expects.
• Execute: Formulate the curl or client request only after confirming the above three steps.

4. Common Pitfalls and Traps

Atomic Answer: Developers often fall into traps by assuming API mutations share read permissions or strictly adhere to RESTful purity. Always verify exact permission annotations and interceptors. Do not assume standard HTTP methods are used, and remember to include necessary custom headers to prevent silent failures and unauthorized access.

• Permission-by-Analogy: The most common mistake. Developers see that a GET /api/resource/view works for a user, and falsely assume that a DELETE /api/resource/delete will also work for that same user. Always verify the specific permission annotation on the mutation endpoint.
• Assuming RESTful Purity: Real-world APIs are rarely purely RESTful. Do not assume that updating a resource is a PUT or PATCH—it might be a POST to an RPC-style URL like /api/resource/updateStatus. Always verify the source code.
• Ignoring Headers: Many APIs fail silently or return 403s because a custom header (like X-CSRF-Token or Accept: application/json) was omitted. Check the base controller class for required interceptors.