一、序言

我們都知道Spring Cloud Gateway是一個(gè)基于Spring Boot、Spring WebFlux、Project Reactor構(gòu)建的高性能網(wǎng)關(guān)驰弄，旨在提供簡(jiǎn)單、高效的API路由速客。

Spring Cloud Gateway基于Netty運(yùn)行戚篙，因此在傳統(tǒng)Servlet容器中或者打成war包是不能正常運(yùn)行的。

二溺职、代碼示例

這里我們注冊(cè)中心選型的是Nacos已球，如果還沒(méi)有安裝Nacos，請(qǐng)參考：Nacos快速安裝部署辅愿。

1、父工程spring-cloud-gateway-learning

    <modules>
            <module>spring-cloud-api-gateway</module>
            <module>spring-cloud-user-service</module>
            <module>spring-cloud-message-service</module>
    </modules>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring.boot.version>2.3.7.RELEASE</spring.boot.version>
        <spring.cloud.version>Hoxton.SR12</spring.cloud.version>
        <spring.cloud.alibaba.version>2.2.6.RELEASE</spring.cloud.alibaba.version>
        <commons.lang3.version>3.12.0</commons.lang3.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>${commons.lang3.version}</version>
        </dependency>
    </dependencies>

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

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

備注：具體==Spring Cloud==各版本說(shuō)明請(qǐng)參考Spring Cloud Alibaba版本說(shuō)明忆某。

2点待、子工程spring-cloud-api-gateway

(1) pom.xml

<parent>
        <groupId>com.universe</groupId>
        <artifactId>spring-cloud-gateway-learning</artifactId>
        <version>1.0-SNAPSHOT</version>
</parent>

<dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-gateway</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
</dependencies>

(2) 配置文件和代碼示例

1. bootstrap.yml

spring:
  application:
    name: api-gateway
server:
  port: 9000

2. application.yml

spring:
  cloud:
    gateway:
      routes:
        - id: user-service
          uri: lb://user-service
          predicates:
            - Path=/user/**
        - id: message-service
          uri: lb://message-service
          predicates:
            - Path=/message/**
    nacos:
      discovery:
        server-addr: localhost:8848

如果URI以==lb==開頭，比如如上配置中的lb://user-service弃舒，Spring Cloud Gateway會(huì)用ReactiveLoadBalancerClientFilter解析服務(wù)名為user-service的實(shí)例對(duì)應(yīng)的實(shí)際host和端口癞埠，并做集群負(fù)載均衡。

這項(xiàng)功能通過(guò)全局過(guò)濾器ReactiveLoadBalancerClientFilter實(shí)現(xiàn)聋呢，官網(wǎng)描述如下：
[圖片上傳失敗...(image-b13395-1655546589820)]

3. RouteRecordGlobalFilter

@Slf4j
@Component
public class RouteRecordGlobalFilter implements GlobalFilter, Ordered {

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        // RouteToRequestUrlFilter會(huì)把實(shí)際路由的URL通過(guò)該屬性保存
        URI proxyRequestUri = exchange.getAttribute(ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR);
        long start = System.currentTimeMillis();

        return chain.filter(exchange).then(Mono.fromRunnable(() -> {
            long end = System.currentTimeMillis();
            log.info("實(shí)際調(diào)用地址為：{}苗踪，調(diào)用耗時(shí)為：{}ms", proxyRequestUri, (end - start));
        }));
    }

    @Override
    public int getOrder() {
        // 優(yōu)先級(jí)設(shè)為最低，先讓RouteToRequestUrlFilter先調(diào)用
        return Ordered.LOWEST_PRECEDENCE;
    }
}

RouteRecordGlobalFilter 這個(gè)全局過(guò)濾器我們主要用來(lái)記錄路由后的實(shí)際代理地址削锰，以及調(diào)用耗時(shí)通铲。

我們看下RouteToRequestUrlFilter的描述會(huì)發(fā)現(xiàn)實(shí)際路由地址會(huì)通過(guò)ServerWebExchange中名為ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR的屬性保存。

[圖片上傳失敗...(image-a33940-1655546589820)]

關(guān)于RouteToRequestUrlFilter的部分源碼如下：

@Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);
        if (route == null) {
            return chain.filter(exchange);
        }
        log.trace("RouteToRequestUrlFilter start");
        URI uri = exchange.getRequest().getURI();
        boolean encoded = containsEncodedParts(uri);
        URI routeUri = route.getUri();

        if (hasAnotherScheme(routeUri)) {
            // this is a special url, save scheme to special attribute
            // replace routeUri with schemeSpecificPart
            exchange.getAttributes().put(GATEWAY_SCHEME_PREFIX_ATTR,
                    routeUri.getScheme());
            routeUri = URI.create(routeUri.getSchemeSpecificPart());
        }

        if ("lb".equalsIgnoreCase(routeUri.getScheme()) && routeUri.getHost() == null) {
            // Load balanced URIs should always have a host. If the host is null it is
            // most
            // likely because the host name was invalid (for example included an
            // underscore)
            throw new IllegalStateException("Invalid host: " + routeUri.toString());
        }

        URI mergedUrl = UriComponentsBuilder.fromUri(uri)
                // .uri(routeUri)
                .scheme(routeUri.getScheme()).host(routeUri.getHost())
                .port(routeUri.getPort()).build(encoded).toUri();
        exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, mergedUrl);
        return chain.filter(exchange);
    }

備注：更多關(guān)于全局過(guò)濾器的介紹請(qǐng)參考 Spring Cloud Gateway全局過(guò)濾器器贩。

3颅夺、子工程spring-cloud-user-service

(1) pom.xml

<parent>
        <groupId>com.universe</groupId>
        <artifactId>spring-cloud-gateway-learning</artifactId>
        <version>1.0-SNAPSHOT</version>
</parent>

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
</dependencies>

(2) 配置文件

1. bootstrap.yml

spring:
  application:
    name: user-service
server:
  servlet:
    context-path: /user

---
spring:
  profiles: user-service-master
server:
  port: 9091

---
spring:
  profiles: user-service-slave
server:
  port: 9092

2. application.yml

spring:
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848

3. UserController

@RestController
public class UserController {

    @GetMapping("/info")
    public Map<String, Object> getUserInfo() {
    Random random = new Random();
        int waitTime = random.nextInt(1000);
        LockSupport.parkNanos(1000 * 1000 * waitTime);
        
        Map<String, Object> result = new HashMap<>();
        result.put("name", "Nick");
        result.put("age", 25);
        return result;
    }
}

4、子工程spring-cloud-message-service

(1) pom.xml

<parent>
        <groupId>com.universe</groupId>
        <artifactId>spring-cloud-gateway-learning</artifactId>
        <version>1.0-SNAPSHOT</version>
</parent>

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>
</dependencies>

(2) 配置文件和代碼示例

1. bootstrap.yml

spring:
  application:
    name: message-service
server:
  servlet:
    context-path: /message

---
spring:
  profiles: message-service-master
server:
  port: 9093

---
spring:
  profiles: message-service-slave
server:
  port: 9094

2. application.yml

spring:
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848

3. MessageController

@RestController
public class MessageController {

    @GetMapping("/info")
    public Map<String, Object> getMessageInfo() {
    Random random = new Random();
        int waitTime = random.nextInt(1000);
        LockSupport.parkNanos(1000 * 1000 * waitTime);
    
        Map<String, Object> result = new HashMap<>();
        result.put("id", 1);
        result.put("title", "我愛(ài)中國(guó)");
        return result;
    }
}

三蛹稍、測(cè)試結(jié)果

分別啟動(dòng)api-gateway吧黄、指定概要文件啟動(dòng)兩個(gè)user-service服務(wù)實(shí)例、和兩個(gè)message-service服務(wù)實(shí)例唆姐，查看Nacos控制臺(tái)拗慨。
[圖片上傳失敗...(image-34bdc6-1655546589820)]

可以看到，api-gateway啟動(dòng)了一個(gè)服務(wù)實(shí)例，user-service和message-service都啟動(dòng)了兩個(gè)服務(wù)實(shí)例赵抢。

備注：IDEA運(yùn)行時(shí)指定Active Profiles即可剧蹂。

1、集群負(fù)載均衡測(cè)試

連續(xù)訪問(wèn)http://localhost:9000/user/info昌讲，可以看到user-service集群服務(wù)實(shí)例被輪詢調(diào)用国夜。

image.png

2、服務(wù)路由測(cè)試

分別訪問(wèn) http://localhost:9000/user/info短绸、http://localhost:9000/message/info车吹，我們可以看到基于路徑匹配的服務(wù)路由分發(fā)是成功的。

image.png