413 lines
13 KiB
Markdown
413 lines
13 KiB
Markdown
# Spring-Cloud-Zuul
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<nav>
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<a href="#一简介">一、简介</a><br/>
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<a href="#11-API-网关">1.1 API 网关</a><br/>
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<a href="#12-Spring-Cloud-Zuul">1.2 Spring Cloud Zuul</a><br/>
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<a href="#二项目结构">二、项目结构</a><br/>
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<a href="#三Zuul-网关">三、Zuul 网关</a><br/>
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<a href="#31-引入依赖">3.1 引入依赖</a><br/>
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<a href="#32-添加注解">3.2 添加注解</a><br/>
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<a href="#33--项目配置">3.3 项目配置</a><br/>
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<a href="#34--启动服务">3.4 启动服务</a><br/>
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<a href="#四错误熔断">四、错误熔断</a><br/>
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<a href="#41--默认依赖">4.1 默认依赖</a><br/>
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<a href="#42-服务降级">4.2 服务降级</a><br/>
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<a href="#五Zuul--过滤器">五、Zuul 过滤器</a><br/>
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<a href="#六负载均衡">六、负载均衡</a><br/>
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<a href="#七常见异常">七、常见异常</a><br/>
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</nav>
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## 一、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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<div align="center"> <img src="https://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/apiGateway.png"/> </div>
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### 1.2 Spring Cloud Zuul
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Spring Cloud 基于 Net Flix Zuul 实现了网关组件，这就是 Spring Cloud 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 的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) 用例已经通过 Feign 实现服务间的调用，且提供了两个服务单元 (consumer、producer)，可以方便直观地测试 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://gitee.com/heibaiying/spring-samples-for-all/raw/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://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/zuul.png"/> </div>
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## 三、Zuul 网关
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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 添加注解
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在启动类上添加 @EnableZuulProxy和 @EnableDiscoveryClient 注解，@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 项目配置
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在配置文件中指定注册中心的地址并配置网关的路由规则。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 启动服务
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启动 eureka、producer、consumer、zuul 四个服务，访问 localhost:8090/consumer/sell/product ：
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<div align="center"> <img src="https://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/zuul-consumer.png"/> </div>
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## 四、错误熔断
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### 4.1 默认依赖
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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://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/zuul-hystrix.png"/> </div>
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### 4.2 服务降级
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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://gitee.com/heibaiying/spring-samples-for-all/raw/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 并实现了负载均衡，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://gitee.com/heibaiying/spring-samples-for-all/raw/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://gitee.com/heibaiying/spring-samples-for-all/raw/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://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/zuul-consumer.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/zuul-consumer-8040.png"/> </div>
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<div align="center"> <img src="https://gitee.com/heibaiying/spring-samples-for-all/raw/master/pictures/zuul-consumer-8030.png"/> </div>
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## 七、常见异常
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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 版本的 Zuul 组件和 Spring Boot 2.1.x 存在不兼容的情况。如果出现这个问题，则将 Spring Boot 版本降至 2.0.x 即可，本用例中采用的是 2.0.8 。
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```java
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APPLICATION FAILED TO START
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---
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Description:
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The bean 'counterFactory', defined in class path resource [org/springframework/cloud/netflix/zuul/ZuulServerAutoConfiguration$ZuulCounterFactoryConfiguration.class], could not be registered. A bean with that name has already been defined in class path resource [org/springframework/cloud/netflix/zuul/ZuulServerAutoConfiguration$ZuulMetricsConfiguration.class] and overriding is disabled.
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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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```
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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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| 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) 页面上查看。
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