springCloud-gateway按照服务名动态路由的改造(二)

从上一篇文章中，我们分析知道，按照服务名动态路由无非是构造RouteDefenition的过程不同，是根据从注册中心获取到的服务来动态构造RouteDefenition的各个属性，包括id,uri,Predicate,Filter这几个属性。

每个RouteDefenition对应后端的一个服务。当网关接收到一个请求后，会根据RouteDefenition的Predicate校验结果来决定是否路由到该RouteDefenition对应服务上，如果校验结果为true则路由，否则不路由。

Predicate自定义

现在回来看下我们的需求，在springCloud-gateway按照服务名动态路由的改造(一) 中提到过。不难看出我们只要实现我们自己的Predicate就可以了，下面是Predicate的校验流程图：

实现的代码如下：其中ApiGatewayProperties 里边是一个map，存放的是路由正则和服务名的映射关系。

@Slf4j
@Component
public class CustomerRoutePredicateFactory extends
        AbstractRoutePredicateFactory<CustomerRoutePredicateFactory.Config> {

    @Autowired
    ApiGatewayProperties gatewayProperties;

    public CustomerRoutePredicateFactory() {
        super(Config.class);
    }

    @Override
    public Predicate<ServerWebExchange> apply(Config config) {

        return new GatewayPredicate() {
            @Override
            public boolean test(ServerWebExchange exchange) {
                List<PathPattern> pathPatterns = gatewayProperties.getPathPatterns();
                String routeId = exchange.getRequiredAttribute(ServerWebExchangeUtils.GATEWAY_PREDICATE_ROUTE_ATTR);
                String serviceName = routeId.split("_")[1];
                PathContainer path = parsePath(
                        exchange.getRequest().getURI().getRawPath());

                PathPattern match = null;
                for (int i = 0; i < pathPatterns.size(); i++) {
                    PathPattern pathPattern = pathPatterns.get(i);
                    if (pathPattern.matches(path) &&
                            StringUtils.equals(serviceName, gatewayProperties.getPathServiceMap().get(pathPattern.getPatternString()))) {
                        if (Objects.isNull(match) || match.getPatternString().length() < pathPattern.getPatternString().length()) {
                            match = pathPattern;
                        }
                    }
                }

                if (match != null) {
                    config.getPatterns().clear();
                    config.getPatterns().add(match.getPatternString());
                    traceMatch("Pattern", match.getPatternString(), path, true);
                    PathPattern.PathMatchInfo pathMatchInfo = match.matchAndExtract(path);
                    putUriTemplateVariables(exchange, pathMatchInfo.getUriVariables());
                    return true;
                } else {
                    traceMatch("Pattern", gatewayProperties.getPathServiceMap().keySet(), path, false);
                    return false;
                }
            }

            @Override
            public String toString() {
                return String.format("Paths: %s, match trailing slash: %b",
                        config.getPatterns(), true);
            }
        };
    }

    private static void traceMatch(String prefix, Object desired, Object actual,
                                   boolean match) {
        if (log.isTraceEnabled()) {
            String message = String.format("%s \"%s\" %s against value \"%s\"", prefix,
                    desired, match ? "matches" : "does not match", actual);
            log.trace(message);
        }
    }

    @Getter
    @Setter
    public static class Config {
        private List<String> patterns = new ArrayList<>();
    }
}

filter自定义

由于原来的filter会去掉路径的第一级，但是我们的需求是不需要去掉，直接转发到下游服务，所以我实现了个啥都不干的filter来覆盖默认的filter。

@Component
public class CustomerGatewayFilterFactory extends
        AbstractGatewayFilterFactory<CustomerGatewayFilterFactory.Config> {

    public CustomerGatewayFilterFactory() {
        super(Config.class);
    }

    @Override
    public GatewayFilter apply(Config config) {
        return new GatewayFilter() {

            @Override
            public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
                return chain.filter(exchange);
            }

            @Override
            public String toString() {
                return filterToStringCreator(CustomerGatewayFilterFactory.this)
                        .append("do nothing").toString();
            }
        };

    }

    @Getter
    @Setter
    public static class Config {
    }
}

配置文件

最后需要把我们上面自定义的实现配置到文件里来覆盖默认的实现，如下图：

cloud:
    gateway:
      discovery:
        locator:
          enabled: true  #开启根据微服务名称自动转发
          lower-case-service-id: true  #微服务名称以小写形式呈现
          predicates:
            - name: Customer
          filters:
            - name: Customer

最后启动网关服务，通过网关的端点看下具体的路由