By Mandip Dhakal
When developing a RESTful API, it’s crucial to handle exceptions gracefully and provide meaningful information in error responses to clients. Spring Boot 3 introduces ProblemDetail specification, which allows us to create standardized and structured error responses. In this post, we will explore how to use the ProblemDetail specification in Spring Boot 3 to handle exceptions and provide custom error responses.
Step 1: Create an Exception Class
The first step is to create an exception class that extends RuntimeException class. This custom exception class will represent a specific error scenario. Let's create a NotFoundException class as an example:
By extending RuntimeException, we ensure that our exception can be thrown and caught like any other runtime exception.
Step 2: Create a RestControllerAdvice
Next, we need to create a RestControllerAdvice class that handles the exception and transforms it into a ProblemDetail response. This advice class will be responsible for catching the NotFoundException and converting it into a ProblemDetail response. Here's an example:
In the handleNotFoundException method, we create a ProblemDetail object using the ProblemDetail.forStatusAndDetail factory method, specifying the HTTP status and the error message. This method will be invoked when NotFoundException is thrown, allowing us to customize the error response.
Additionally, you can set other properties for the ProblemDetail object. For example, you can set a title, type, or even custom properties:
By setting these properties, you can provide more detailed information about the error, such as a title, a link to additional resources, or any custom data relevant to the error.
Step 3: Enable ProblemDetail
Latest version of Spring Boot auto enables ProblemDetail, but we can also add it manually using the following options:
Extend the ResponseEntityExceptionHandler class with your RestControllerAdvice class:
Or add the following line to your application.properties file:
Enabling ProblemDetail ensures that Spring Boot uses ProblemDetail specification to handle exceptions and generate appropriate error responses.
Step 4: Throwing and Handling Exceptions
Now that we have our exception class and advice in place, we can throw and handle exceptions to test our error response handling.
Using a Try-Catch Block
You can throw a NotFoundException by using a try-catch block. For example:
By catching the exception and re-throwing it with an appropriate error message, the RestExceptionHandlerAdvice will intercept it and transform it into a ProblemDetail response.
Throwing an Exception from the Service Layer
In this approach, the exception is thrown from the service layer, and the RestController class relies on the RestExceptionHandlerAdvice to handle it. Let's assume we have a SomeResource class with a method that retrieves something by ID:
Inside the service layer (SomeService.java), we can throw NotFoundException if the requested resource is not found:
If the requested resource is not found, NotFoundException will be thrown, and RestExceptionHandlerAdvice will handle it accordingly.
Result of NotFound exception:
Conclusion
By following these steps, you can leverage ProblemDetail specification in Spring Boot 3 to handle error responses in a standardized and structured manner. With the ProblemDetail class and a dedicated RestControllerAdvice, you can customize and provide detailed error information to your API clients.
Handling error responses effectively is essential for building robust and user-friendly APIs. The ProblemDetail specification in Spring Boot 3 empowers developers to provide well-defined and consistent error responses, improving the overall experience for API consumers.
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