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@ -1,6 +1,370 @@
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***************************
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# spring-cloud-zuul
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## 一、zuul简介
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### 1.1 API 网关
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api 网关是整个微服务系统的门面，所有的外部访问需要通过网关进行调度和过滤。它实现了请求转发、负载均衡、校验过滤、错误熔断、服务聚合等功能。
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下图是直观的显示api Gateway 在微服务网关中的作用（图片引用自spring boot 官网）。
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### 1.2 zuul
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spring cloud 中提供了基础Net flix Zuul 实现的网关组件，这就是Zuul,它除了实现负载均衡、错误熔断、路由转发等功能，还能与spring 其他组件无缝配合使用。
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## 二、项目结构
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[spring-cloud-feign](https://github.com/heibaiying/spring-samples-for-all/tree/master/spring-cloud/spring-cloud-feign)用例已经实现通过feign实现服务间的调用，且提供了两个业务服务单元(consumer、producer)，可以方便直观的测试zuul的路由、负载均衡、和错误熔断等功能，所以本用例在其基础上进行zuul的整合。
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+ common: 公共的接口和实体类；
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+ consumer: 服务的消费者，采用feign调用产品服务；
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+ producer：服务的提供者；
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+ eureka: 注册中心；
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+ zuul: api网关。
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聚合项目目录如下：
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/spring-cloud-zuul.png"/> </div>
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zuul 项目目录如下：
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul.png"/> </div>
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## 三、构建api 网关 zuul
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#### 3.1 引入依赖
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主要的依赖是 spring-cloud-starter-netflix-zuul
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-parent</artifactId>
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<version>2.0.8.RELEASE</version>
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<relativePath/>
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</parent>
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<artifactId>zuul</artifactId>
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<properties>
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<java.version>1.8</java.version>
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<spring-cloud.version>Finchley.SR2</spring-cloud.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-web</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-freemarker</artifactId>
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</dependency>
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<dependency>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-starter-test</artifactId>
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<scope>test</scope>
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</dependency>
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<!--eureka-client-->
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<dependency>
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<groupId>org.springframework.cloud</groupId>
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<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
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</dependency>
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<!--zuul-->
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<dependency>
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<groupId>org.springframework.cloud</groupId>
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<artifactId>spring-cloud-starter-netflix-zuul</artifactId>
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</dependency>
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</dependencies>
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<build>
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<plugins>
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<plugin>
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<groupId>org.springframework.boot</groupId>
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<artifactId>spring-boot-maven-plugin</artifactId>
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</plugin>
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</plugins>
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</build>
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<dependencyManagement>
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<dependencies>
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<dependency>
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<groupId>org.springframework.cloud</groupId>
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<artifactId>spring-cloud-dependencies</artifactId>
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<version>${spring-cloud.version}</version>
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<type>pom</type>
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<scope>import</scope>
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</dependency>
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</dependencies>
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</dependencyManagement>
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</project>
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```
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#### 3.2 在启动类上添加注解@EnableZuulProxy和@EnableDiscoveryClient
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@EnableZuulProxy会自动设置Zuul服务器端点并在其中开启一些反向代理过滤器，以便将请求转发到后端服务器。
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```java
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@SpringBootApplication
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@EnableZuulProxy
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@EnableDiscoveryClient
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public class ZuulApplication {
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public static void main(String[] args) {
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SpringApplication.run(ZuulApplication.class, args);
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}
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}
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```
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#### 3.3 指定注册中心、配置网关的路由规则
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zuul 需要指定注册中心的地址，zuul 会从eureka获取其他微服务的实例信息，然后按照指定的路由规则进行请求转发。
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```yaml
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server:
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port: 8090
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# 指定服务命名
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spring:
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application:
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name: zuul
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# 指定注册中心地址
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eureka:
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client:
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serviceUrl:
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defaultZone: http://localhost:8010/eureka/
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# 网关的路由
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zuul:
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routes:
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xxxx: #这个地方的值是可以任意的字符串
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path: /producer/**
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serviceId: producer
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consumer:
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path: /consumer/**
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serviceId: consumer
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```
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#### 3.4 启动eureka、producer、consumer、zuul服务，访问 localhost:8090/consumer/sell/product
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-consumer.png"/> </div>
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## 四、错误熔断
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#### 4.1 zuul 默认整合了 hystrix ，不用导入其他额外依赖
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-hystrix.png"/> </div>
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#### 4.2 创建 CustomZuulFallbackProvider并实现FallbackProvider 接口，同时用@Component声明为spring 组件，即可实现熔断时候的回退服务
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```java
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/**
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* @author : heibaiying
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* @description : zuul 的熔断器
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*/
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@Component
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public class CustomZuulFallbackProvider implements FallbackProvider {
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/*
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* 定义熔断将用于哪些路由的服务
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*/
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@Override
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public String getRoute() {
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return "consumer";
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}
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@Override
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public ClientHttpResponse fallbackResponse(String route, Throwable cause) {
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return new ClientHttpResponse() {
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/**
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* 返回响应的HTTP状态代码
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*/
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@Override
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public HttpStatus getStatusCode() throws IOException {
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return HttpStatus.SERVICE_UNAVAILABLE;
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}
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/**
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* 返回HTTP状态代码
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*/
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@Override
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public int getRawStatusCode() throws IOException {
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return HttpStatus.SERVICE_UNAVAILABLE.value();
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}
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/**
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* 返回响应的HTTP状态文本
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*/
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@Override
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public String getStatusText() throws IOException {
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return HttpStatus.SERVICE_UNAVAILABLE.getReasonPhrase();
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}
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@Override
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public void close() {
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}
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/**
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* 将消息正文作为输入流返回
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*/
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@Override
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public InputStream getBody() throws IOException {
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return new ByteArrayInputStream("商城崩溃了,请稍后重试！".getBytes());
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}
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/**
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* 将消息正文作为输入流返回
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*/
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@Override
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public HttpHeaders getHeaders() {
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HttpHeaders httpHeaders = new HttpHeaders();
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httpHeaders.setContentType(MediaType.APPLICATION_JSON_UTF8);
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return httpHeaders;
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}
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};
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}
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}
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```
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正确返回了内容、同时返回的http状态码也和我们设置的一样。
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-broker.png"/> </div>
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## 五、zuul 过滤器
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创建自定义过滤器继承自CustomZuulFilter，当我们访问网关的时候，如果判断session 中没有对应的 code,则跳转到我们自定义的登录页面。
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```java
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/**
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* @author : heibaiying
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* @description : 自定义filter过滤器
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*/
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@Component
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public class CustomZuulFilter extends ZuulFilter {
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/**
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* 返回过滤器的类型
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*/
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@Override
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public String filterType() {
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return FilterConstants.PRE_TYPE;
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}
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/**
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* 返回过滤器的优先级顺序
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*/
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@Override
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public int filterOrder() {
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return 0;
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}
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/**
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* 从此方法返回“true”意味着应该调用下面的 run（）方法
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*/
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@Override
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public boolean shouldFilter() {
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return true;
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}
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/**
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* ZuulFilter的核心校验方法
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*/
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@Override
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public Object run() throws ZuulException {
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RequestContext currentContext = RequestContext.getCurrentContext();
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HttpServletRequest request = currentContext.getRequest();
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String code = (String)request.getSession().getAttribute("code");
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if (StringUtils.isEmpty(code)){
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// 设置值为false 不将请求转发到对应的服务上
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currentContext.setSendZuulResponse(false);
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// 设置返回的状态码
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currentContext.setResponseStatusCode(HttpStatus.NON_AUTHORITATIVE_INFORMATION.value());
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HttpServletResponse response = currentContext.getResponse();
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try {
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// 跳转到登录页面
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response.sendRedirect("/index");
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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return null;
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}
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}
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```
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index.ftl:
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```html
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<!doctype html>
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<html lang="en">
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<head>
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<title>Title</title>
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</head>
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<body>
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<form action="/login" method="post">
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<input name="username" type="text">
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<button id="btn">输入临时用户名后登录！</button>
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</form>
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</body>
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</html>
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```
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## 六、负载均衡
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#### zuul 默认集成了ribbon 实现了负载均衡。只要启动多个实例即可查看到负载均衡的效果。
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-ribbon.png"/> </div>
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#### 这里我们直接在idea 中启动多个实例来测试：
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-config.png"/> </div>
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#### 负载均衡测试结果：
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-consumer.png"/> </div>
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-consumer-8040.png"/> </div>
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<div align="center"> <img src="https://github.com/heibaiying/spring-samples-for-all/blob/master/pictures/zuul-consumer-8030.png"/> </div>
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## 七、附：关于版本问题可能导致的 zuul 启动失败
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如果出现以下错误导致启动失败，是 spring boot 版本不兼容导致的错误，Finchley SR2版本 spring cloud 中的 zuul 和 spring boot 2.1.x 版本存在不兼容。如果出现这个问题，则将 spring boot 将至 2.0.x 的版本即可，用例中采用的是 2.0.8 版本。在实际的开发中应该严格遵循spring 官方的版本依赖说明。
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```java
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APPLICATION FAILED TO START
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***************************
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---
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Description:
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@ -8,4 +372,17 @@ The bean 'counterFactory', defined in class path resource [org/springframework/c
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Action:
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Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true
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Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true
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```
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**spring cloud 版本说明**：
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| Release Train | Boot Version |
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| ------------- | ------------ |
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| Greenwich | 2.1.x |
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| Finchley | 2.0.x |
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| Edgware | 1.5.x |
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| Dalston | 1.5.x |
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更多组件的版本说明可以在[spring cloud overview](https://spring.io/projects/spring-cloud#overview) 页面查看。
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