Spring Cloud网关之Zuul

微服务有服务之间的相互调用，客户端请求也会请求各个不同的服务，如果此时要统计网站pv，uv等数据，会变得很复杂，如果有一个统一的请求入口，将请求进行转发，则会大大简化业务。为此，spring cloud zuul应运而生。
Zuul是Netflix开源的微服务网关，通过网关可以完成请求过滤，转发，身份认证，流量统一入口等。根据配置，zuul可将对应的请求转发到对应的服务，同时，zuul也作为一个客户端注册到eureka中。
创建一个zuul服务spring-cloud-zuul
pom.xml内容如下

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>spring-cloud-zuul</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-cloud-zuul</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.10.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <spring-cloud.version>Edgware.SR2</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- 配置中心客户端依赖 -->
        <!-- 如果需要读取配置中心的配置，添加此依赖 -->
        <!--
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
        </dependency>
        -->
        <!-- eureka服务发现客户端依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <!-- zuul依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-zuul</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-start-webflux</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>

在SpringCloudZuulApplication自动类加上@EnableZuulServer @EnableDiscoveryClient注解，@EnableZuulServer表示此功能是一个zuul服务端。

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.zuul.EnableZuulServer;

@SpringBootApplication
@EnableZuulServer
@EnableDiscoveryClient
public class SpringCloudZuulApplication {

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

配置文件：

#应用名称
spring.application.name=spring-cloud-zuul
#应用端口号，默认为8080
server.port=8889

#配置中心
#如果需要读取配置中心的配置，添加此配置项
#spring.cloud.config.discovery.enabled=true
#spring.cloud.config.discovery.service-id=spring-cloud-zuul

#eureka服务发现相关
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/
eureka.instance.prefer-ip-address=true
eureka.instance.instance-id=${spring.cloud.client.ipAddress}:${server.port}

#api路由配置
zuul.routes.api-a.path=/api-a/**
zuul.routes.api-a.service-id=service-A
zuul.routes.api-a.sensitive-headers=*
zuul.routes.api-b.path=/api-b/**
zuul.routes.api-b.service-id=service-B

注：如果需要读取配置中心的配置，配置文件名用bootstrap.yml或者bootstrap.properties，因为bootstrap*是在application*之前加载。
根据路由配置，http://ip:port/api-a/的请求都会转发到service-A服务下，service-A为服务注册到eureka注册中心的实例名。同理，http://ip:port/api-b/的请求都会转发到service-B服务下。
如果想在zuul网关下做一些业务处理，比如特殊字符过滤，身份认证等，可以集成ZuulFilter。

import com.netflix.zuul.ZuulFilter;
import org.springframework.stereotype.Component;

@Component
public class RequestFilter extends ZuulFilter {
    
    

    /**
     * 过滤器类型
     * pre:路由之前；routing:路由之时；post:路由之后；error:发送错误调用；
     * @return
     */
    @Override
    public String filterType() {
        return "pre";
    }

    /**
     * 过滤的顺序
     * @return
     */
    @Override
    public int filterOrder() {
        return 0;
    }

    /**
     *可写逻辑判断，是否过滤，true代表永久过滤
     * @return
     */
    @Override
    public boolean shouldFilter() {
        return false;
    }

    /**
     * 过滤器的具体逻辑
     * @return
     */
    @Override
    public Object run() {
        return null;
    }
}