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Handle exceptions in a rest controller in Spring Boot

I create REST web-service with Spring Boot.
I would like to know what is a better way to handle exceptions in a controller. I have seen other questions and didn’t found an answer.
My controller:
#GetMapping
public ResponseEntity<?> saveMyUser(){
MyUser myUser = new MyUser(“Anna”);
//throws SQLException
MyUserDetails userDetails = userService.saveMyUser(myUser);
//if successful
return ResponseBody.ok(userDetails);
}
saveMyUser() method of UserService:
public MyUserDetails saveUser(MyUser) throws SQLException {...}
So at this point I have at least 2 simple options:
Add exception to method signature.
Here I may rely on Spring Boot to pass all information about exception and status code to a client. However do not know if it is a reliable approach.
Surround with try/catch and pass all information about exceptions manually.
What is a better simple way?

You can create an additional class with #ControllerAdivce annotation and later you will be able to write custom response logic for each exception e.g:
#ControllerAdvice
public class GlobalExceptionHandler {
#ExceptionHandler({SQLException.class})
public ResponseEntity<Object> sqlError(Exception ex) {
return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Some SQL exception occured");
}
}
Also, you can extend ResponseEntityExceptionHandler and override the default behavior for mapping from exceptions to HTTP response.
Also, take a look at this, it holds very usefull information for your case.

Spring Boot #ExceptionHandler working on dev server but not locally

I know this is usually an issue that happens the other way around, so I am caught a little of guard here :D
I have built a user-management backend that provides a UI with data. When this architecture is deployed on our dev-server, everything works beautifully. However, as soon as I try to run the integration tests (which we do using a maven cargo tomcat) or if I use the war file in a local tomcat, the exception handlers aren't used at all. Spring simply displays a standard 500 response with the exception transformed into the body.
Perusing SO for similar issues has only resulted in the advice that I should use #EnableWebMVC, but that is neither applicable to what my backend is trying to accomplish, nor does it change anything.
How should I go about looking for the solution to this issue? Specifically, can I somehow observe if my controlleradvice is even scanned, and is there a reason why it might not be?
EDIT: These are the relevant files:
SpringConfiguration:
#Configuration
#ComponentScan(basePackageClasses = {UserManagementSpringConfiguration.class})
#EnableWebSecurity
public class UserManagementSpringConfiguration {
#Configuration
public static class ResourceMappingConfig implements WebMvcConfigurer {
#Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/ui/*/usermanagement").setViewName("forward:/usermanagement-ui/index.html");
// registry.addViewController("/ui/*/*/generator/").setViewName("forward:/generator-ui/index.html");
registry.addViewController("/ui/*/usermanagement/*").setViewName("forward:/usermanagement-ui/index.html");
}
#Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
// cache setting, otherwise fonts are not loaded in IE over https
CacheControl cacheControl = CacheControl.noCache().mustRevalidate();
registry.addResourceHandler("/ui/**/*").addResourceLocations("/usermanagement-ui/")
.setCacheControl(cacheControl);
}
}
}
ControllerAdvice:
#ControllerAdvice
public class CustomResponseEntityExceptionHandler {
public static final Logger LOG = EISLoggerFactory.getLogger(CustomResponseEntityExceptionHandler.class);
#PostConstruct
public void postConstruct() {
LOG.debug("CustomExceptionHandler loaded and ready for use");
}
#ExceptionHandler(PasswordMismatchException.class)
public final ResponseEntity<ErrorDetails> handlePasswordChangeMismatch(
PasswordMismatchException ex,
WebRequest request) {
ErrorDetails errorDetails = new ErrorDetails(
new Date(),
ex.getMessage(),
request.getDescription(false),
MessageKeys.mismatchedPassword);
return new ResponseEntity<>(errorDetails, HttpStatus.BAD_REQUEST);
}
}

It turns out that one of the modules that we wrote and that my project contains defines an ExceptionHandler for Throwable.class. On my machine, this ControllerAdvice is registered before my own ControllerAdvice, which causes Spring to look there first. Since Throwable fits the bill, Spring asks no further questions and just uses that handler.
The solution to my immediate problem was to add #Order(Ordered.HIGHEST_PRECEDENCE) to my ControllerAdvice. Since the exceptions I define within are quite specific, this will not cause any issues.
I have yet to find an explanation for why the order in which the two ControllerAdvice classes are registered is so consistently different between my machine and our dev server. Will update if I find anything. For now, I consider this issue to be answered.
This SO question was essential to solving this particular problem. Perhaps it helps someone in the future to link it here: Setting Precedence of Multiple #ControllerAdvice #ExceptionHandlers
Thanks to ValentinCarnu for pointing me to it!

How could we use #ExceptionHandler with spring web flux?

In spring web we could use annotation #ExceptionHandler for handling server and client errors for controllers.
I've tried to use this annotation with web-flux controller and it still worked for me, but after some investigation I've found out here
The situation with Spring Web Reactive is more complicated. Because
the reactive streams are evaluted by a different thread than the one
that executes the controllers method, the exceptions won’t be
propagated to the controller thread automatically. This means that the
#ExceptionHandler method will work only for exceptions that are thrown
in the thread that handles the request directly. Exceptions thrown in
the stream will have to be propagated back to the thread if we want to
use the #ExceptionHandler feature. This seems like a bit of a let down
but at the time of writing this Spring 5 is still not released so
error handling might still get better.
So my question is how to propagate back exception to the thread. Is there a good example or article about using #ExceptionHandler and Spring web flux?
Updated:
From spring.io it looks like it's supported, but still lack general understanding
Thanks,

Now it is possible to use the #ExceptionHandler as well as #RestControllerAdvice or even #ControllerAdvice in Spring WebFlux.
Example:
Add the webflux dependency
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
Create your class ExceptionHandler
#RestControllerAdvice
public class ExceptionHandlers {
private static final Logger LOGGER = LoggerFactory.getLogger(ExceptionHandlers.class);
#ExceptionHandler(Exception.class)
#ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
public String serverExceptionHandler(Exception ex) {
LOGGER.error(ex.getMessage(), ex);
return ex.getMessage();
}
}
Create a Controller
#GetMapping(value = "/error", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
public Mono<String> exceptionReturn() {
return Mono.error(new RuntimeException("test error"));
}
Example extracted here:
https://ddcode.net/2019/06/21/spring-5-webflux-exception-handling/

You can use #ExceptionHandler annotated methods to handle errors that happen within the execution of a WebFlux handler (e.g., your controller method). With MVC you can indeed also handle errors happening during the mapping phase, but this is not the case with WebFlux.
Back to your exception propagation question, the article you're sharing is not accurate.
In reactive applications, the request processing can indeed hop from one thread to another at any time, so you can't rely on the "one thread per request" model anymore (think: ThreadLocal).
You don't have to think about exception propagation or how threads are managed, really. For example, the following samples should be equivalent:
#GetMapping("/test")
public Mono<User> showUser() {
throw new IllegalStateException("error message!");
}
#GetMapping("/test")
public Mono<User> showUser() {
return Mono.error(new IllegalStateException("error message!"));
}
Reactor will send those Exceptions as error signals as expected in the Reactive Streams contract (see the "error handling" documentation section for more on that).

not an exact answer to the original question, but a quick way to map your exceptions to http response status is to throw org.springframework.web.server.ResponseStatusException / or create your own subclasses...
Full control over http response status + spring will add a response body with the option to add a reason.
{
"timestamp": 1529138182607,
"path": "/api/notes/f7b.491bc-5c86-4fe6-9ad7-111",
"status": 400,
"error": "Bad Request",
"message": "For input string: \"f7b.491bc\""
}

The following global error handler did the trick for me:
import org.springframework.web.server.ResponseStatusException;
#Slf4j
#RestControllerAdvice
#ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)
public class MyCustomReactiveErrorHandling {
#ExceptionHandler(MyCustomNotFoundException.class)
public void handleMyCustomException(MyCustomNotFoundException ex) {
throw new ResponseStatusException(404, "Data not found!", ex);
}
}
Throwing my exceptions returns the correct http status code at the rest service.

Configure Spring interceptor for controllers only

I'm trying to configure a Spring interceptor for controllers only in the following way. For the beginning I want to exclude all the requests starting with /swagger. I try to do it in the following way:
registry.addInterceptor(myInterceptor).addPathPatterns("/**").excludePathPatterns("/swagger**");
However, interceptor gets fired. Where is a mistake?
Maybe, there is an alternative solution with #ControllerAdvice. But I need to get request headers, so I guess it doesn't fit my needs.
Thanks for any help!

Try to use "/swagger*/**" or "/swagger*" instead of "/swagger**"

I solved the problem in the following way:
#ControllerAdvice
public class SomeAdvice {
#ModelAttribute
public void token(HttpServletRequest request) {
// getting headers and setting the attribute in the request
request.setAttribute("theAttribute", new SomeObject());
}
}
And then I get the request attribute in a controller this way:
public void someMethod(#RequestAttribute("theAttribute") SomeObject someObject) {
// some logic goes here
}
P.S. And one more note. If you're using Swagger you'll get into the trouble as Swagger will consider this attribute as controller method parameter. To ignore it you can use the following snapshot of configuration:
.ignoredParameterTypes(SomeObject.class);

REST resource exception interceptor

I am trying to determine if it is possible to setup an interceptor like solution on a REST resource such that if an exception is thrown I can log the exception and change the response returned. I basically don't want to wrap all my REST resources with try/catch blocks. If a REST resource was managed I would just use an #Interceptor on all of my calls but since it is not managed that seems to be out of the question.

You can use an implementation javax.ws.rs.ext.ExceptionMapper. Let's suppose that your code might throw a YourFancyException from the resources. Then you can use the following mapper:
#Provider
public class YourFancyExceptionMapper
implements ExceptionMapper <YourFancyException> {
#Override
public Response toResponse(YourFancyException exception) {
return Response.status(Response.Status.BAD_REQUEST)
.entity(exception.getMessage()).build();
}
}
Don't forget to annotate the mapper with #Provider and to make your resources methods to throw YourFancyException.