spring 5 webflux异常处理

序

本文主要研究一下spring 5 webflux的异常处理

maven

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

ExceptionHandler

因为webflux也支持传统spring mvc的大部分注解，所以原来的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();
    }
}

启动的时候能够看到日志

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;
    //......
}

能够看到支持InitBinder，ModelAttribute，RequestMapping，ExceptionHandler这几个注解。

实例

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

与传统mvc不一样的是，除了直接throw异常外，Mono或Flux能够直接error一个异常，在exceptionHandlers均可以被接收处理

小结

webflux支持mvc的注解，是一个很是便利的功能，相比较于RouteFunction，自动扫描注册比较省事。异常处理能够沿用ExceptionHandler。