6.1 重试机制
RetryGatewayFilter 是 Spring Cloud Gateway 对请求重试提供的一个 GatewayFilter Factory。配置方式如下所示。
# 路由定义
routes:
- id: baidu
uri: http://localhost:8080/
predicates:
- Path=/baidu/**
filters:
- name: Retry
args:
retries: 1
series: SERVER_ERROR
上述代码中具体参数含义如下：
- retries：重试次数，默认值是 3 次。
- series：状态码配置（分段），符合某段状态码才会进行重试逻辑，默认值是 SERVER_ERROR，值是 5，也就是 5XX（5 开头的状态码），共有 5 个值，代码如下所示。
public enum Series {
INFORMATIONAL(1), SUCCESSFUL(2), REDIRECTION(3), CLIENT_ERROR(4), SERVER_ERROR(5);
}
模拟测试：
我们不启动8080端口的服务，所以会有500错误。访问：http://localhost:8888/baidu返回时长8.18秒，如果不加重试机制返回时长约2.7秒。
6.2 统一异常处理
Spring Cloud Gateway 中的全局异常处理不能直接使用@ControllerAdvice，可以通过跟踪异常信息的抛出，找到对应的源码，自定义一些处理逻辑来匹配业务的需求。
网关是给接口做代理转发的，后端对应的是 REST API，返回数据格式是 JSON。如果不做处理，当发生异常时，Gateway 默认给出的错误信息是html页面，不方便前端进行异常处理。
所以我们需要对异常信息进行处理，并返回 JSON 格式的数据给客户端。下面先看实现的代码。
自定义异常处理逻辑，JsonExceptionHandler代码如下所示：
package com.erbadagang.gateway.exception;
import lombok.extern.slf4j.Slf4j;
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;
/**
* @description 自定义异常errorWebExceptionHandler的配置类, 使用我们自定义的JsonExceptionHandler处理异常。
* @ClassName: JsonExceptionHandler
* @author: 郭秀志 jbcode@126.com
* @date: 2020/8/1 18:51
* @Copyright:
*/
@Slf4j
public class JsonExceptionHandler implements ErrorWebExceptionHandler {
/**
* MessageReader
*/
private List<HttpMessageReader<?>> messageReaders = Collections.emptyList();
/**
* MessageWriter
*/
private List<HttpMessageWriter<?>> messageWriters = Collections.emptyList();
/**
* ViewResolvers
*/
private List<ViewResolver> viewResolvers = Collections.emptyList();
/**
* 存储处理异常后的信息
*/
private ThreadLocal<Map<String, Object>> exceptionHandlerResult = new ThreadLocal<>();
/**
* 参考AbstractErrorWebExceptionHandler
*/
public void setMessageReaders(List<HttpMessageReader<?>> messageReaders) {
Assert.notNull(messageReaders, "'messageReaders' must not be null");
this.messageReaders = messageReaders;
}
/**
* 参考AbstractErrorWebExceptionHandler
*/
public void setViewResolvers(List<ViewResolver> viewResolvers) {
this.viewResolvers = viewResolvers;
}
/**
* 参考AbstractErrorWebExceptionHandler
*/
public void setMessageWriters(List<HttpMessageWriter<?>> messageWriters) {
Assert.notNull(messageWriters, "'messageWriters' must not be null");
this.messageWriters = messageWriters;
}
@Override
public Mono<Void> 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<String, Object> result = new HashMap<>(2, 1);
result.put("httpStatus", httpStatus);
String msg = "{\"code\":" + httpStatus + ",\"message\": \"" + body + "\"}";
result.put("body", msg);
//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
*/
protected Mono<ServerResponse> renderErrorResponse(ServerRequest request) {
Map<String, Object> result = exceptionHandlerResult.get();
return ServerResponse.status((HttpStatus) result.get("httpStatus"))
.contentType(MediaType.APPLICATION_JSON_UTF8)
.body(BodyInserters.fromObject(result.get("body")));
}
/**
* 参考AbstractErrorWebExceptionHandler
*/
private Mono<? extends Void> 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<HttpMessageWriter<?>> messageWriters() {
return JsonExceptionHandler.this.messageWriters;
}
@Override
public List<ViewResolver> viewResolvers() {
return JsonExceptionHandler.this.viewResolvers;
}
}
}
ExceptionConfig.java
package com.erbadagang.gateway.exception;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.boot.web.reactive.error.ErrorWebExceptionHandler;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.http.codec.ServerCodecConfigurer;
import org.springframework.web.reactive.result.view.ViewResolver;
import java.util.Collections;
import java.util.List;
@Configuration
public class ExceptionConfig {
/**
* 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
*/
@Primary
@Bean
@Order(Ordered.HIGHEST_PRECEDENCE)
public ErrorWebExceptionHandler errorWebExceptionHandler(ObjectProvider<List<ViewResolver>> viewResolversProvider,
ServerCodecConfigurer serverCodecConfigurer) {
JsonExceptionHandler jsonExceptionHandler = new JsonExceptionHandler();
jsonExceptionHandler.setViewResolvers(viewResolversProvider.getIfAvailable(Collections::emptyList));
jsonExceptionHandler.setMessageWriters(serverCodecConfigurer.getWriters());
jsonExceptionHandler.setMessageReaders(serverCodecConfigurer.getReaders());
return jsonExceptionHandler;
}
}
这两个文件就可以满足我们Gateway全局监听的需求，当在Gateway发生错误时，会进行拦截并格式化信息，返回给客户端。
处理前返回错误：
<html><body><h1>Whitelabel Error Page</h1><p>This application has no configured error view, so you are seeing this as a fallback.</p><div id='created'>Sat Aug 01 17:43:05 CST 2020</div><div>[64a4a1ca-2] There was an unexpected error (type=Internal Server Error, status=500).</div><div></div></body></html>
处理后返回错误：
{"code":500 INTERNAL_SERVER_ERROR,"message": "Internal Server Error"}
