How to Filter URL Patterns in Java Based on Request Parameters?

What is the method to filter URL patterns in a Java application based on specific request parameters?

@WebServlet("/example")
public class ExampleServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String paramName = request.getParameter("name");
        if (paramName != null && paramName.equals("test")) {
            // Process request
        } else {
            // Handle invalid request
            response.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid parameter!");
        }
    }
}

To filter URL patterns based on request parameters in Java, you can utilize servlets or filters in a Spring application. This approach allows you to capture incoming requests and conditionally process them based on the presence or value of specific request parameters. Here’s how you can implement this using a servlet approach.

@WebServlet("/filter")
public class FilteredServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String category = request.getParameter("category");
        if ("electronics".equals(category)) {
            // Forward to electronics handling code
        } else if ("clothing".equals(category)) {
            // Forward to clothing handling code
        } else {
            response.sendError(HttpServletResponse.SC_NOT_FOUND, "Category not found!");
        }
    }
}

Causes

• Not validating request parameters properly can lead to security vulnerabilities.
• No mechanisms in place to handle requests without specified parameters.
• Inefficient routing that does not account for varying request parameter values.

Solutions

• Use servlet filters to intercept requests and evaluate parameters before processing.
• Implement error handling to manage requests with unexpected parameters.
• Utilize annotations in Spring to map specific methods to certain URL patterns with conditions based on parameters.

Mistake: Forgetting to check if request parameters are null before processing.

Solution: Always validate request parameters to ensure they are present and meaningful before use.

Mistake: Not sending appropriate HTTP status codes on errors.

Solution: Make sure to use HTTP status codes like 400 for bad requests and 404 for not found.

Mistake: Hardcoding values instead of using enums or constants for parameter checks.

Solution: Define constants for parameter names and expected values to avoid magic strings.