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

        
            org.springframework.boot
            spring-boot-starter-webflux
        

ExceptionHandler

由于webflux也支持传统spring mvc的大部分注解，因此原来的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();
    }
}

启动的时候可以看到日志

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:
 * 

 * 
{@code @InitBinder}
 * 
{@code @ModelAttribute}
 * 
{@code @RequestMapping}
 * 
{@code @ExceptionHandler}
 * 
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
class ControllerMethodResolver {

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


    private final List initBinderResolvers;

    private final List modelAttributeResolvers;

    private final List requestMappingResolvers;

    private final List exceptionHandlerResolvers;

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

可以看到支持InitBinder，ModelAttribute，RequestMapping，ExceptionHandler这几个注解。

实例

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

与传统mvc不同的是，除了直接throw异常外，Mono或Flux可以直接error一个异常，在exceptionHandlers都可以被接收处理

小结

webflux支持mvc的注解，是一个非常便利的功能，相比较于RouteFunction，自动扫描注册比较省事。异常处理可以沿用ExceptionHandler。