The Problem Spring Web library provides seamless integration of application problem handling within your Spring MVC and Spring WebFlux applications. It simplifies the process of creating standardized JSON responses for various types of errors, aiding in the overall robustness of your application.

What You Need Before Getting Started

• Java 17
• Any build tool that uses Maven Central, or you can download it directly
• For Problem Spring Web:
• A Servlet Container
• For Problem Spring WebFlux:
• A Reactive, non-blocking runtime
• Spring 6 (or Spring Boot 3) to use version 0.28.0
• Spring 5 (or Spring Boot 2) to use version 0.27.0
• Spring 4 (or Spring Boot 1.5) to use version 0.23.0

Installation and Configuration

To set up the Problem Spring Web library, choose between:

• Spring Web MVC
• Spring WebFlux

How It Works: The Analogy of a Restaurant Menu

Imagine the Problem Spring Web library as a restaurant that specializes in serving delectable dishes representing various error conditions. Each dish (or error response) is crafted from fresh ingredients (or features) that the library offers.

The restaurant allows customers (developers) to select specific dishes they want (advice traits) without being forced into a fixed menu (inheritance). This flexibility means you can combine different advice traits to create the perfect error response tailored to your needs.

Instead of worrying about the details of cooking (error-handling logic), the library takes care of it for you, letting you focus on serving the best experience to your patrons (users of your application).

Customizing Problem Handling

You can customize how problems are handled by implementing the appropriate advice trait interfaces. Here are a few areas you can tailor:

Aspect	Method(s)	Default
Creation	AdviceTrait.create(..)	N/A
Logging	AdviceTrait.log(..)	4xx as WARN, 5xx as ERROR with stack trace
Content Negotiation	AdviceTrait.negotiate(..)	application/json, application/*+json, application/problem+json, application/x.problem+json
Fallback	AdviceTrait.fallback(..)	application/problem+json
Post-Processing	AdviceTrait.process(..)	N/A

Sample Code for Customization

Here’s a quick example of how to customize the error handling for a missing request parameter:

@ControllerAdvice
public class MissingRequestParameterExceptionHandler implements MissingServletRequestParameterAdviceTrait {
    @Override
    public ProblemBuilder prepare(Throwable throwable, StatusType status, URI type) {
        var exception = (MissingServletRequestParameterException) throwable;
        return Problem.builder()
                .withTitle(status.getReasonPhrase())
                .withStatus(status)
                .withDetail(exception.getMessage())
                .with("parameter", exception.getParameterName());
    }
}

Usage Example

Consider a controller designed to handle product requests:

@RestController
@RequestMapping("/products")
class ProductsResource {
    @RequestMapping(method = GET, value = "/{productId}", produces = APPLICATION_JSON_VALUE)
    public Product getProduct(@PathVariable String productId) {
        // TODO implement
        return null;
    }

    @RequestMapping(method = PUT, value = "/{productId}", consumes = APPLICATION_JSON_VALUE)
    public Product updateProduct(@PathVariable String productId, @RequestBody Product product) {
        // TODO implement
        throw new UnsupportedOperationException();
    }
}

When you send various HTTP requests to this controller, your application will respond with informative error messages in a problem-centric JSON format, ensuring that users of your API understand what went wrong.

Troubleshooting Common Issues

• If you run into issues regarding exception handling methods not being triggered, ensure that your @ControllerAdvice is not overly restricted by using the assignableTypes attribute.
• Stack traces and causal chains may require additional configuration; refer to the documentation for enabling them.
• To seamlessly integrate your setup, make sure all dependencies are correctly aligned with your project version.

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Conclusion

At fxis.ai, we believe that such advancements are crucial for the future of AI, as they enable more comprehensive and effective solutions. Our team is continually exploring new methodologies to push the envelope in artificial intelligence, ensuring that our clients benefit from the latest technological innovations.