10 Spring Boot Exception Handling Best Practices

Spring Boot provides a great way to handle exceptions. By default, it provides a generic error page that shows the stack trace and the reason for the exception. However, this is not very user-friendly. In this article, we will discuss 10 best practices for exception handling in Spring Boot.

1. Use @ControllerAdvice for global exception handling

@ControllerAdvice is a Spring annotation that provides a mechanism to treat exceptions globally. It can be used with any Spring component, but it’s most commonly used with @RestController and @ControllerAdvice.

When you use @ControllerAdvice, all exceptions thrown by the controller are handled by the advice. This includes exceptions thrown by methods annotated with @RequestMapping, @ExceptionHandler, or @InitBinder.

The @ControllerAdvice annotation has two attributes:

• basePackages: The base package of the controllers. All controllers in this package and its sub-packages are included.

• assignableTypes: The specific classes of controllers. Only these controllers are included.

You can use either attribute, but not both. If you don’t specify either attribute, all controllers are included.

2. Define a common base package for Controller classes

When you have a large number of Controller classes, it can be difficult to keep track of which exceptions are handled by each class. By defining a common base package, you can easily see which exceptions are handled by each class, and this makes it easier to maintain your codebase.

Furthermore, when you’re defining exception handling logic in your Controller classes, it’s often helpful to reuse existing ExceptionHandlers. By keeping your Controller classes in the same base package, you can easily reuse these ExceptionHandlers without having to duplicate code.

3. Global Exception handler methods

Exception handler methods are like a catch block in Java. They allow you to handle exceptions in a centralized way and provide a consistent response to the client, whether it’s an error message or some other data.

If you don’t have global exception handler methods, then each controller will need to handle exceptions individually. This can lead to duplicated code and inconsistent responses.

It’s much better to have a single place to handle all exceptions, so that’s why global exception handler methods are a best practice.

4. Catch exceptions using @ExceptionHandler annotation

The @ExceptionHandler annotation is used to specify a method that will handle a particular type of exception. This is useful if you want to centralize your exception handling logic in one place.

For example, suppose you have a controller with two methods, and each method can throw different types of exceptions. You can use the @ExceptionHandler annotation on a single method to handle both types of exceptions.

@ExceptionHandler(Exception.class)
public void handleException(Exception e) {
// …
}

This method will be invoked whenever any exception is thrown by either of the controller methods.

One advantage of using the @ExceptionHandler annotation is that it makes your code more readable and maintainable. It’s also easier to unit test because you can mock the exception and test the handler method separately.

5. Customize Response body

When an exception is thrown, the default response body includes the stack trace. This is not only unnecessary information for the client, but it can also be a security risk. By customizing the response body, you can include only the information that’s necessary and relevant to the client, while keeping the rest of the information hidden.

To customize the response body, you need to create a class that implements the HandlerExceptionResolver interface. In this class, you can specify the status code, headers, and body of the response.

For example, here’s how you would customize the response body for a NotFoundException:

@Override
public ModelAndView resolveException(HttpServletRequest request,
HttpServletResponse response,
Object handler,
Exception ex) {
response.setStatus(HttpStatus.NOT_FOUND.value());
Map body = new LinkedHashMap<>();
body.put(“timestamp”, LocalDateTime.now());
body.put(“message”, “Not found”);
return new ModelAndView(“error”, body);
}

6. Return response entity in json format

When an exception is thrown, the default response entity returned by Spring Boot is in html format. This can be problematic for two reasons.

Firstly, if the client making the request is not expecting html format, it can cause issues. Secondly, even if the client is expecting html format, the html response returned by Spring Boot can be very basic and uninformative.

Returning response entity in json format solves both of these problems. Firstly, it means that the client will always receive the data in the format they are expecting. Secondly, it allows you to return more informative error messages in the json response.

To return response entity in json format, you need to configure Spring Boot to use a different message converter. One option is to use the Jackson2JsonMessageConverter. This message converter will automatically convert any response entity with a @ResponseBody annotation into json format.

7. Specify the HTTP Status code

When an exception is thrown, the default response code is 500 Internal Server Error. This status code indicates that something went wrong on the server side, and the client cannot do anything about it.

While this might be accurate in some cases, most of the time it’s not. For example, if a user tries to access a resource that doesn’t exist, it would make more sense to return a 404 Not Found status code. This way, the client knows that the issue is not on their end, and they can take appropriate action (e.g., try a different resource).

Similarly, if a user tries to submit a form with invalid data, it would be more helpful to return a 400 Bad Request status code. This way, the client knows that the issue is on their end, and they can fix it before resubmitting the form.

Specifying the HTTP Status code is important because it helps the client understand what went wrong and what they can do about it. It also makes your API more self-documenting, which is always a good thing.

8. Handle specific Exceptions

When you’re handling exceptions, you want to be as specific as possible. This way, you can give your users the most accurate information about what went wrong and how they can fix it.

For example, let’s say you have a controller that handles two different types of Exceptions: InvalidArgumentException and ResourceNotFoundException.

If you were to handle these Exception in the same way, you would end up with a generic error message that doesn’t really help your users. However, if you handle each Exception separately, you can give your users more specific instructions on what went wrong and how to fix it.

This is just one example of why it’s important to handle specific Exceptions. By doing so, you can ensure that your users receive the most accurate and helpful information possible.

9. Create custom exceptions

Creating custom exceptions gives you more control over the error handling process. By creating your own exception class, you can add additional information that might be helpful for debugging, such as the time of the error or the user’s ID.

Custom exceptions also make it easier to handle errors in a specific way. For example, you can choose to log all instances of a particular custom exception, or send an email notification to the administrator.

Overall, custom exceptions provide a more flexible and customizable approach to exception handling, which can be very useful in a Spring Boot application.

10. Add logs to trace application flow

When an exception is thrown, it can be difficult to determine the root cause of the problem without looking at the application logs. By adding logs at key points in the code, you can get a better understanding of what went wrong and why.

For example, let’s say you have a controller that handles requests for a user’s profile. If an exception is thrown when trying to retrieve the user’s data from the database, you can add a log statement in the controller to print out the SQL query that was executed. This will give you valuable information about what went wrong and help you fix the issue.

Adding logs is a simple way to improve the spring boot exception handling in your application. It’s important to remember, however, that too many logs can clutter the output and make it more difficult to find the relevant information. Therefore, it’s important to strike a balance and only add logs when they will be genuinely useful.