spring 5 webflux異常處理

序

本文主要研究一下spring 5 webflux的異常處理

maven

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>

ExceptionHandler

因爲webflux也支持傳統spring mvc的大部分註解，所以原來的ExceptionHandler也是支持的。

@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();
    }
}

啓動的時候能夠看到日誌

2018-02-12 19:26:03.249  INFO 7053 --- [           main] o.s.w.r.r.m.a.ControllerMethodResolver   : Looking for @ControllerAdvice: org.springframework.boot.web.reactive.context.AnnotationConfigReactiveWebServerApplicationContext@65d09a04: startup date [Mon Feb 12 19:25:59 CST 2018]; root of context hierarchy
2018-02-12 19:26:03.281  INFO 7053 --- [           main] o.s.w.r.r.m.a.ControllerMethodResolver   : Detected @ExceptionHandler methods in exceptionHandlers

spring-webflux-5.0.2.RELEASE-sources.jar!/org/springframework/web/reactive/result/method/annotation/ControllerMethodResolver.java

/**
 * Package-private class to assist {@link RequestMappingHandlerAdapter} with
 * resolving, initializing, and caching annotated methods declared in
 * {@code @Controller} and {@code @ControllerAdvice} components:
 * <ul>
 * <li>{@code @InitBinder}
 * <li>{@code @ModelAttribute}
 * <li>{@code @RequestMapping}
 * <li>{@code @ExceptionHandler}
 * </ul>
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
class ControllerMethodResolver {

    private static Log logger = LogFactory.getLog(ControllerMethodResolver.class);


    private final List<SyncHandlerMethodArgumentResolver> initBinderResolvers;

    private final List<HandlerMethodArgumentResolver> modelAttributeResolvers;

    private final List<HandlerMethodArgumentResolver> requestMappingResolvers;

    private final List<HandlerMethodArgumentResolver> exceptionHandlerResolvers;

    private final ReactiveAdapterRegistry reactiveAdapterRegistry;
    //......
}

能夠看到支持InitBinder，ModelAttribute，RequestMapping，ExceptionHandler這幾個註解。

實例

@GetMapping(value = "/error",produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public Mono<String> exceptionReturn(){
//        throw new RuntimeException("hello");
        return Mono.error(new RuntimeException("test error"));
    }

與傳統mvc不一樣的是，除了直接throw異常外，Mono或Flux能夠直接error一個異常，在exceptionHandlers均可以被接收處理

小結

webflux支持mvc的註解，是一個很是便利的功能，相比較於RouteFunction，自動掃描註冊比較省事。異常處理能夠沿用ExceptionHandler。