SpringCloud(六):Zuul的Fallback回退机制

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;
              }
          };
      }
  }