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Spring Cloud Gateway 聚合 swagger 3.0.0

前言

网上关于zuul聚合各个微服务的swagger已经有很多文章了, 但是没有一个完整的关于spring cloud gateway的聚合教程.
研究了一天, 写了个demo, 然后写篇文章记录一下.

Swagger引入

Springfox现在已经更新到3.0.0了, 并且也支持了starter方式.
直接引入, 不需要加任何注解.

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<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-boot-starter</artifactId>
<version>3.0.0</version>
</dependency>

聚合Swagger

zuul的套路一样, 我们要实现SwaggerResourcesProvider接口, 然后根据各个服务的服务名拼接uri.

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@Primary
@Configuration(proxyBeanMethods = false)
public class SwaggerConfig implements SwaggerResourcesProvider {

@Autowired
private RouteDefinitionLocator routeDefinitionLocator; // 获取路由定义

@Override
public List<SwaggerResource> get() {
List<SwaggerResource> swaggerResourceList = new ArrayList<>();
routeDefinitionLocator.getRouteDefinitions()
.map(this::swaggerResource) // 转化为 SwaggerResource 对象
.subscribe(swaggerResourceList::add); // Flux 转化为 List 对象
return swaggerResourceList;
}

private SwaggerResource swaggerResource(RouteDefinition definition) {
String location = definition.getPredicates().stream()
.filter(predicate -> "Path".equalsIgnoreCase(predicate.getName()))
.findFirst() // 获取第一个名为 Path 的 predicate, 里面含有路由规则
.map(PredicateDefinition::getArgs)
// 如果是从注册中心的路由规则, key 就是 pattern, 否则就是 _genkey_0
.map(map -> map.getOrDefault("pattern", map.get(NameUtils.GENERATED_NAME_PREFIX + "0")))
// 拼接 url
.map(pattern -> StringUtils.substringBefore(pattern, "*"))
.map(pattern -> pattern + "v2/api-docs")
.orElse(null);

SwaggerResource swaggerResource = new SwaggerResource();
swaggerResource.setName(definition.getId());
swaggerResource.setLocation(location);
return swaggerResource;
}
}

整个执行流程很简单, 就是从路由定义里面获取路由规则, 拼接成swagger的地址, 丢到SwaggerResource里面.
但是中间有一些比较坑的地方.

Flux 转化为 List 对象

不懂MonoFlux的去搜索, 自己实现一个webfluxhello world程序.
MonoFlux都是支持泛型的类. 可以简单地认为, Mono是包装了一个对象的对象, Flux是包装了一堆对象的集合.
要进行转换有两种方法

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List<SwaggerResource> swaggerResourceList1 = new ArrayList<>();
routeDefinitionLocator.getRouteDefinitions()
.map(this::swaggerResource)
.subscribe(swaggerResourceList1::add);

List<SwaggerResource> swaggerResourceList2 = routeDefinitionLocator.getRouteDefinitions()
.map(this::swaggerResource)
.collectList()
.block(Duration.ofSeconds(10));

但是我们只能用第一种, 第二种方法会抛出IllegalStateException异常.

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// reactor.core.publisher.Mono
public abstract class Mono<T> implements CorePublisher<T> {
public T block(Duration timeout) {
BlockingMonoSubscriber<T> subscriber = new BlockingMonoSubscriber<>();
subscribe((Subscriber<T>) subscriber);
return subscriber.blockingGet(timeout.toMillis(), TimeUnit.MILLISECONDS);
}
}

// reactor.core.publisher.BlockingSingleSubscriber
abstract class BlockingSingleSubscriber<T> extends CountDownLatch implements InnerConsumer<T>, Disposable {
final T blockingGet(long timeout, TimeUnit unit) {
if (Schedulers.isInNonBlockingThread()) {
throw new IllegalStateException("block()/blockFirst()/blockLast() are blocking, which is not supported in thread " + Thread.currentThread().getName());
}
}
}

// reactor.core.scheduler.Schedulers
public abstract class Schedulers {
public static boolean isInNonBlockingThread() {
return Thread.currentThread() instanceof NonBlocking;
}
}

获取路由规则

gateway会从注册中心获取服务的相关信息, 初始化路由规则.
GatewayDiscoveryClientAutoConfiguration会为DiscoveryLocatorProperties属性生成一个初始化的PredicateDefinition集合, 有点像原型模式.

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@Configuration(proxyBeanMethods = false)
public class GatewayDiscoveryClientAutoConfiguration {

public static List<PredicateDefinition> initPredicates() {
ArrayList<PredicateDefinition> definitions = new ArrayList<>();
// TODO: add a predicate that matches the url at /serviceId?

// add a predicate that matches the url at /serviceId/**
PredicateDefinition predicate = new PredicateDefinition();
predicate.setName("Path"); // 所以上面才要根据 Path 进行过滤
predicate.addArg("pattern", "'/'+serviceId+'/**'"); // 所以上面才要根据 pattern 进行过滤
definitions.add(predicate);
return definitions;
}

@Bean
public DiscoveryLocatorProperties discoveryLocatorProperties() {
DiscoveryLocatorProperties properties = new DiscoveryLocatorProperties();
properties.setPredicates(initPredicates());
properties.setFilters(initFilters());
return properties;
}
}

// org.springframework.cloud.gateway.discovery.DiscoveryClientRouteDefinitionLocator
public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
@Override
public Flux<RouteDefinition> getRouteDefinitions() {
// 省略部分代码
return serviceInstances.filter(instances -> !instances.isEmpty())
.map(instances -> instances.get(0)).filter(includePredicate)
.map(instance -> {
// 1. 获取服务名
String serviceId = instance.getServiceId();

RouteDefinition routeDefinition = new RouteDefinition();
routeDefinition.setId(this.routeIdPrefix + serviceId);
String uri = urlExpr.getValue(evalCtxt, instance, String.class);
routeDefinition.setUri(URI.create(uri));

final ServiceInstance instanceForEval = new DelegatingServiceInstance(instance, properties);

// 2. 获取 GatewayDiscoveryClientAutoConfiguration 初始化的默认 Predicate
for (PredicateDefinition original : this.properties.getPredicates()) {
// 3. 为服务初始化它自己的 Predicate 定义. 包括路由规则
PredicateDefinition predicate = new PredicateDefinition();
predicate.setName(original.getName());
for (Map.Entry<String, String> entry : original.getArgs().entrySet()) {
// 将 '/'+serviceId+'/**' 表达式替换成真正的路由规则
String value = parser.parseExpression(entry.getValue()).getValue(evalCtxt, instanceForEval, String.class);
predicate.addArg(entry.getKey(), value);
}
routeDefinition.getPredicates().add(predicate);
}

return routeDefinition;
});
}
}

_genkey_0是从哪来的?

在上面的源码分析里已经看到了pattern这个key是从哪里生成的了.
但是为什么还有一个_genkey_0呢?

因为如果是手动在配置文件里面配置服务的话, gateway会自动生成key.

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// org.springframework.cloud.gateway.support.NameUtils
public final class NameUtils {
public static final String GENERATED_NAME_PREFIX = "_genkey_";
public static String generateName(int i) {
return GENERATED_NAME_PREFIX + i;
}
}

// org.springframework.cloud.gateway.handler.predicate.PredicateDefinition
public class PredicateDefinition {
public PredicateDefinition(String text) { // 解析配置文件里的规则, 如 Path=/api/**
int eqIdx = text.indexOf('=');
if (eqIdx <= 0) {
throw new ValidationException("Unable to parse PredicateDefinition text '" + text + "'" + ", must be of the form name=value");
}
setName(text.substring(0, eqIdx));

String[] args = tokenizeToStringArray(text.substring(eqIdx + 1), ",");
for (int i = 0; i < args.length; i++) {
// 注意这里
this.args.put(NameUtils.generateName(i), args[i]);
}
}
}

看到这, 你就会发现, 我写的代码其实有一个问题, 如果配置文件里有多个predicate.
那么一定要保证Path是第0个, 否则就获取不到路由规则. 目前也没想到什么好办法, 就这样将就用吧.

服务id特别长怎么办

有的同学会发现, 注册中心生成的服务id特别长, 不美观.
我只想安安静静做一个美男子
我只想要显示服务名, 可以把前缀都去掉吗?

答案是不行.
在配置文件中加入配置项spring.cloud.gateway.discovery.locator.route-id-prefix: "你想要的前缀"即可.
但是不能填空字符串.

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// org.springframework.cloud.gateway.discovery.DiscoveryClientRouteDefinitionLocator
public class DiscoveryClientRouteDefinitionLocator implements RouteDefinitionLocator {
private DiscoveryClientRouteDefinitionLocator(String discoveryClientName, DiscoveryLocatorProperties properties) {
this.properties = properties;
// 如果判断是空字符串, 就用默认的前缀了
if (StringUtils.hasText(properties.getRouteIdPrefix())) {
routeIdPrefix = properties.getRouteIdPrefix();
} else {
// 默认的 discoveryClientName 是 discoveryClient.getClass().getSimpleName()
routeIdPrefix = discoveryClientName + "_";
}
evalCtxt = SimpleEvaluationContext.forReadOnlyDataBinding().withInstanceMethods().build();
}
}

总结

实际的例子可以看我在github上的项目ahao-spring-cloud-gateway

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