Zuul回退机制

默认情况下，经过Zuul的请求都会使用Hystrix进行包裹，所以Zuul本身就具有断路器的功能。

未指定路由配置回退

• 代码示例如下：

package com.mmzs.cloud.fallback;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;

import org.springframework.cloud.netflix.zuul.filters.route.FallbackProvider;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;

import com.netflix.hystrix.exception.HystrixTimeoutException;

/**
 * @author: mmzsit
 * @date:   2018年11月14日
 * @Description: 用于定制FallBack返回的body、状态码、消息头Header
 * 博客地址：https://blog.csdn.net/MobiusStrip
 * @version V1.0
 */
@Component
public class MyFallbackProvider implements FallbackProvider {

    @Override
    public String getRoute() {
        return "microservice-provider-user";
        //微服务配了路由的话，就用配置的名称
        //return "customers";
        //如果要为所有路由提供默认回退，可以创建FallbackProvider类型的bean并使getRoute方法返回*或null
        //return "*";
    }

    @Override
    public ClientHttpResponse fallbackResponse(String route, final Throwable cause) {
        if (cause instanceof HystrixTimeoutException) {
            return response(HttpStatus.GATEWAY_TIMEOUT);
        } else {
            return response(HttpStatus.INTERNAL_SERVER_ERROR);
        }
    }

    private ClientHttpResponse response(final HttpStatus status) {
        return new ClientHttpResponse() {
            @Override
            public HttpStatus getStatusCode() throws IOException {
                //return status;
                return HttpStatus.BAD_REQUEST;
            }

            @Override
            public int getRawStatusCode() throws IOException {
                //return status.value();
                return HttpStatus.BAD_REQUEST.value();
            }

            @Override
            public String getStatusText() throws IOException {
                //return status.getReasonPhrase();
                //return HttpStatus.BAD_REQUEST.name();
                return HttpStatus.BAD_REQUEST.getReasonPhrase();
            }

            @Override
            public void close() {
            }

            @Override
            public InputStream getBody() throws IOException {
                return new ByteArrayInputStream(("fallback:"+MyFallbackProvider.this.getRoute()).getBytes());
            }

            @Override
            public HttpHeaders getHeaders() {
                HttpHeaders headers = new HttpHeaders();
                headers.setContentType(MediaType.APPLICATION_JSON);
                return headers;
            }
        };
    }
}

==[注]== 其中代理的路由如果在 application.yml中配置过，也可以有如下示例：

zuul:
  routes:
    customers: /myuser/**

为所有路由提供默认回退

如果要为所有路由提供默认回退，可以创建FallbackProvider类型的bean并使getRoute方法返回*或null

• 代码示例如下：

class MyFallbackProvider implements FallbackProvider {
    @Override
    public String getRoute() {
        return "*";
    }

    @Override
    public ClientHttpResponse fallbackResponse(String route, Throwable throwable) {
        return new ClientHttpResponse() {
            @Override
            public HttpStatus getStatusCode() throws IOException {
                return HttpStatus.OK;
            }

            @Override
            public int getRawStatusCode() throws IOException {
                return 200;
            }

            @Override
            public String getStatusText() throws IOException {
                return "OK";
            }

            @Override
            public void close() {

            }

            @Override
            public InputStream getBody() throws IOException {
                return new ByteArrayInputStream("fallback".getBytes());
            }

            @Override
            public HttpHeaders getHeaders() {
                HttpHeaders headers = new HttpHeaders();
                headers.setContentType(MediaType.APPLICATION_JSON);
                return headers;
            }
        };
    }
}