Spring Cloud教程五：Zuul

前一篇讲了Spring Cloud断路器组件，本篇文章基于上一篇文章的项目开展，没看过上篇的先去上一篇文章了解一下。这篇文章我们讲一下智能路由Zuul的使用。

Zuul简介

Zuul的主要功能是路由转发和过滤器。路由功能是微服务的一部分，比如/api/user转发到到user服务，/api/shop转发到到shop服务。zuul默认和Ribbon结合实现了负载均衡的功能。

Netflix Zuul有以下功能：

Authentication
Insights
Stress Testing
Canary Testing
Dynamic Routing
Service Migration
Load Shedding
Security
Static Response handling
Active/Active traffic management

准备工作

在之前工程的基础上，启动eureka-server，端口为9090；启动eureka-client, 端口为8040；启动ribbon-service, 端口为8050；启动feign-service, 端口为8080；

温馨提示：这篇文章要启动5个项目，如果个人电脑内存有限，可以设置一下项目启动参数，加入-Xms256m -Xmx256m

创建zuul-service项目

使用Spring Initializr新建一个Moudle，取名为zuul-service, 在Spring Cloud Discovery中勾选Eureka Discovery Client，在Spring Cloud Routing中勾选Zuul，在Web中勾选Spring Web:

其pom.xml文件如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.noodles.mars</groupId>
    <artifactId>zuul-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>zuul-service</name>
    <description>Zuul Service</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.SR3</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

zuul-service配置注册服务中心地址、应用名、端口、路由信息，配置文件内容：

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:9090/eureka/
server:
  port: 8090
spring:
  application:
    name: zuul-service
zuul:
  routes:
    feign-api:
      path: /feign-api/**
      serviceId: feign-service
    ribbon-api:
      path: /ribbon-api/**
      serviceId: ribbon-service

其他的配置前面文章都讲过，这里重点讲一下zuul的配置，以/feign-api/ 开头的请求都转发给feign-service服务；以/ribbon-api/开头的请求都转发给ribbon-service服务。
在项目启动类上注解@EnableZuulProxy, 开启Zuul的功能；

package com.noodles.mars.zuulservice;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;

@EnableZuulProxy
@EnableEurekaClient
@SpringBootApplication
public class ZuulServiceApplication {

    public static void main(String[] args) {
        SpringApplication.run(ZuulServiceApplication.class, args);
    }

}

启动Zuul项目，浏览器访问：http://localhost:8090/feign-api/hello?name=Mars

1	Hello, My name is Mars, I'm from port: 8040

再打开一个窗口访问：http://localhost:8090/ribbon-api/hello?name=Mars

这说明zuul起到了路由的作用

过滤功能

Zuul不仅仅只有路由功能，他还可以过滤，做一些安全校验。

package com.noodles.mars.zuulservice;

import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.util.ObjectUtils;

import javax.servlet.http.HttpServletRequest;
import java.io.IOException;


@Component
public class ValidateTokenFilter extends ZuulFilter {
    
    private final static String VALIDATE_TOKEN_FILTER_TYPE = "pre"; 
    
    private final static String TOKEN_PARAM_NAME = "token";
    
    private final Logger logger = LoggerFactory.getLogger(ValidateTokenFilter.class);
    
    @Override
    public String filterType() {
        return VALIDATE_TOKEN_FILTER_TYPE;
    }

    @Override
    public int filterOrder() {
        return 0;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() {
        RequestContext ctx = RequestContext.getCurrentContext();

        HttpServletRequest request = ctx.getRequest();
        logger.info("Request info: method {{}} url {{}}", request.getMethod(), request.getRequestURL().toString());
        
        String token = request.getParameter(TOKEN_PARAM_NAME);
        
        if(ObjectUtils.isEmpty(token)) {
            logger.warn("Token in request is empty.");
            ctx.setSendZuulResponse(false);
            ctx.setResponseStatusCode(401);

            try {
                ctx.getResponse().getWriter().write("Token can not be empty!");
            } catch (IOException e) {
                return null;
            }
        }
        logger.info("Validate via...");
        return null;
    }
}

filterType：返回一个字符串代表过滤器的类型，在zuul中定义了四种不同生命周期的过滤器类型，具体如下：
- pre：路由之前
- routing：路由之时
- post：路由之后
- error：发送错误调用
filterOrder：过滤的顺序
shouldFilter：这里可以写逻辑判断，是否要过滤，本文true,永远过滤。
run：过滤器的具体逻辑。可用很复杂，包括查sql，nosql去判断该请求到底有没有权限访问。

重启项目，继续访问：http://localhost:8090/feign-api/hello?name=Mars