SpringCloud Finchley Gateway 统一异常处理

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1 . 问题：使用SpringCloud Gateway时，会出现各种系统级异常，默认返回HTML.

2 . Finchley版本的Gateway，使用WebFlux形式作为底层框架，而不是Servlet容器，所以常规的异常处理无法使用

翻阅源码，默认是使用DefaultErrorWebExceptionHandler这个类实现结构如下：

图片描述

可以实现参考DefaultErrorWebExceptionHandler和AbstractErrorWebExceptionHandler自定义实现ErrorWebExceptionHandler，然后，注册为Bean到Spring容器中即可（Bean Name:"errorWebExceptionHandler"）

具体实现代码如下：

package pro.chenggang.example.spring.cloud.gateway.support;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;import org.springframework.cloud.gateway.support.NotFoundException;import org.springframework.http.HttpStatus;import org.springframework.http.MediaType;import org.springframework.http.codec.HttpMessageReader;import org.springframework.http.codec.HttpMessageWriter;import org.springframework.http.server.reactive.ServerHttpRequest;import org.springframework.util.Assert;import org.springframework.web.reactive.function.BodyInserters;import org.springframework.web.reactive.function.server.RequestPredicates;import org.springframework.web.reactive.function.server.RouterFunctions;import org.springframework.web.reactive.function.server.ServerRequest;import org.springframework.web.reactive.function.server.ServerResponse;import org.springframework.web.reactive.result.view.ViewResolver;import org.springframework.web.server.ResponseStatusException;import org.springframework.web.server.ServerWebExchange;import reactor.core.publisher.Mono;import java.util.Collections;import java.util.HashMap;import java.util.List;import java.util.Map;/** * @classDesc: 统一异常处理,参考{@link org.springframework.web.server.AbstractErrorWebExceptionHandler}修改 * @author: chenggang * @createTime: 2018/10/30 */public class JsonExceptionHandler implements ErrorWebExceptionHandler {    private static final Logger log = LoggerFactory.getLogger(JsonExceptionHandler.class);    /**     * MessageReader     */    private List
    
     > messageReaders = Collections.emptyList();    /**     * MessageWriter     */    private List
     
      > messageWriters = Collections.emptyList();    /**     * ViewResolvers     */    private List
      
        viewResolvers = Collections.emptyList();    /**     * 存储处理异常后的信息     */    private ThreadLocal
       
        
         > exceptionHandlerResult = new ThreadLocal<>();    /**     * 参考AbstractErrorWebExceptionHandler     * @param messageReaders     */    public void setMessageReaders(List
         
          > messageReaders) { Assert.notNull(messageReaders, "'messageReaders' must not be null"); this.messageReaders = messageReaders; } /** * 参考AbstractErrorWebExceptionHandler * @param viewResolvers */ public void setViewResolvers(List
          
            viewResolvers) { this.viewResolvers = viewResolvers; } /** * 参考AbstractErrorWebExceptionHandler * @param messageWriters */ public void setMessageWriters(List
           
            > messageWriters) { Assert.notNull(messageWriters, "'messageWriters' must not be null"); this.messageWriters = messageWriters; } @Override public Mono
            
              handle(ServerWebExchange exchange, Throwable ex) { /** * 按照异常类型进行处理 */ HttpStatus httpStatus; String body; if (ex instanceof NotFoundException) { httpStatus = HttpStatus.NOT_FOUND; body = "Service Not Found"; }else if(ex instanceof ResponseStatusException) { ResponseStatusException responseStatusException = (ResponseStatusException) ex; httpStatus = responseStatusException.getStatus(); body = responseStatusException.getMessage(); }else{ httpStatus = HttpStatus.INTERNAL_SERVER_ERROR; body ="Internal Server Error"; } /** * 封装响应体,此body可修改为自己的jsonBody */ Map
             
               result = new HashMap<>(2,1); result.put("httpStatus",httpStatus); result.put("body",body); /** * 错误记录 */ ServerHttpRequest request = exchange.getRequest(); log.error("[全局异常处理]异常请求路径:{},记录异常信息:{}",request.getPath(),ex.getMessage()); /** * 参考AbstractErrorWebExceptionHandler */ if (exchange.getResponse().isCommitted()) { return Mono.error(ex); } exceptionHandlerResult.set(result); ServerRequest newRequest = ServerRequest.create(exchange, this.messageReaders); return RouterFunctions.route(RequestPredicates.all(), this::renderErrorResponse).route(newRequest) .switchIfEmpty(Mono.error(ex)) .flatMap((handler) -> handler.handle(newRequest)) .flatMap((response) -> write(exchange, response)); } /** * 参考DefaultErrorWebExceptionHandler * @param request * @return */ protected Mono
              
                renderErrorResponse(ServerRequest request) { Map
               
                 result = exceptionHandlerResult.get(); return ServerResponse.status((HttpStatus) result.get("httpStatus")) .contentType(MediaType.APPLICATION_JSON_UTF8) .body(BodyInserters.fromObject(result.get("body"))); } /** * 参考AbstractErrorWebExceptionHandler * @param exchange * @param response * @return */ private Mono
                 write(ServerWebExchange exchange, ServerResponse response) { exchange.getResponse().getHeaders() .setContentType(response.headers().getContentType()); return response.writeTo(exchange, new ResponseContext()); } /** * 参考AbstractErrorWebExceptionHandler */ private class ResponseContext implements ServerResponse.Context { @Override public List
                
                 > messageWriters() { return JsonExceptionHandler.this.messageWriters; } @Override public List
                 
                   viewResolvers() { return JsonExceptionHandler.this.viewResolvers; } }}

注册Bean

/**     * 自定义异常处理[@@]注册Bean时依赖的Bean，会从容器中直接获取，所以直接注入即可     * @param viewResolversProvider     * @param serverCodecConfigurer     * @return     */    @Primary    @Bean    @Order(Ordered.HIGHEST_PRECEDENCE)    public ErrorWebExceptionHandler errorWebExceptionHandler(ObjectProvider
    
     
      > viewResolversProvider,                                                             ServerCodecConfigurer serverCodecConfigurer) {        JsonExceptionHandler jsonExceptionHandler = new JsonExceptionHandler();        jsonExceptionHandler.setViewResolvers(viewResolversProvider.getIfAvailable(Collections::emptyList));        jsonExceptionHandler.setMessageWriters(serverCodecConfigurer.getWriters());        jsonExceptionHandler.setMessageReaders(serverCodecConfigurer.getReaders());        log.debug("Init Json Exception Handler Instead Default ErrorWebExceptionHandler Success");        return jsonExceptionHandler;    }