gateway里面可以自定义普通filter，也可以创建自定义的GlobalFilter。

GlobalFilter实际上还是比较常用的，譬如可以在GlobalFilter里做日志处理、认证鉴权等，这里就涉及一个获取到请求参数的问题。

用户发起Get、Post请求，经过网关gateway，gateway的GlobalFilter进行拦截——获取参数——处理并包装——转到下一级，我们就来看看该怎么获取请求的参数。

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.6.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>Finchley.SR1</spring-cloud.version>
    </properties>

Get请求

/**
 * @author wuweifeng wrote on 2018/10/24.
 */
@Component
public class AuthSignFilter implements GlobalFilter, Ordered {
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        String token = exchange.getRequest().getQueryParams().getFirst("authToken");
        if (token == null || token.isEmpty()) {
            exchange.getResponse().setStatusCode(HttpStatus.UNAUTHORIZED);
            return exchange.getResponse().setComplete();
        }
        return chain.filter(exchange);

    }

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

这里定义了一个GlobalFilter，如果是Get请求，就可以通过getQueryParams().getFirst("你的key")的方式来获取。

可以看到已经获取到了Get请求的参数，如果有多个请求参数，就可以通过遍历exchange.getRequest().getQueryParams()来获取。

Post请求

post请求的传参获取相对比较麻烦一些，gateway采用了webflux的方式来封装的请求体。

我们知道post常用的两种传参content-type是application/x-www-form-urlencoded和application/json，这两种方式还是有区别的。

下面来看一下获取Post请求体的方法，关于webflux获取内容的教程请看上一篇。

package com.example.gateway.filter;

import io.netty.buffer.ByteBufAllocator;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.core.io.buffer.NettyDataBufferFactory;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.net.URI;
import java.nio.CharBuffer;
import java.nio.charset.StandardCharsets;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;

/**
 * @author wuweifeng wrote on 2018/10/24.
 */
@Component
public class AuthSignFilter implements GlobalFilter, Ordered {
    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpRequest serverHttpRequest = exchange.getRequest();
        String method = serverHttpRequest.getMethodValue();
        if ("POST".equals(method)) {
            //从请求里获取Post请求体
            String bodyStr = resolveBodyFromRequest(serverHttpRequest);
            //TODO 得到Post请求的请求参数后，做你想做的事

            //下面的将请求体再次封装写回到request里，传到下一级，否则，由于请求体已被消费，后续的服务将取不到值
            URI uri = serverHttpRequest.getURI();
            ServerHttpRequest request = serverHttpRequest.mutate().uri(uri).build();
            DataBuffer bodyDataBuffer = stringBuffer(bodyStr);
            Flux<DataBuffer> bodyFlux = Flux.just(bodyDataBuffer);

            request = new ServerHttpRequestDecorator(request) {
                @Override
                public Flux<DataBuffer> getBody() {
                    return bodyFlux;
                }
            };
            //封装request，传给下一级
            return chain.filter(exchange.mutate().request(request).build());
        } else if ("GET".equals(method)) {
            Map requestQueryParams = serverHttpRequest.getQueryParams();
            //TODO 得到Get请求的请求参数后，做你想做的事

            return chain.filter(exchange);
        }
        return chain.filter(exchange);
    }

    /**
     * 从Flux<DataBuffer>中获取字符串的方法
     * @return 请求体
     */
    private String resolveBodyFromRequest(ServerHttpRequest serverHttpRequest) {
        //获取请求体
        Flux<DataBuffer> body = serverHttpRequest.getBody();

        AtomicReference<String> bodyRef = new AtomicReference<>();
        body.subscribe(buffer -> {
            CharBuffer charBuffer = StandardCharsets.UTF_8.decode(buffer.asByteBuffer());
            DataBufferUtils.release(buffer);
            bodyRef.set(charBuffer.toString());
        });
        //获取request body
        return bodyRef.get();
    }

    private DataBuffer stringBuffer(String value) {
        byte[] bytes = value.getBytes(StandardCharsets.UTF_8);

        NettyDataBufferFactory nettyDataBufferFactory = new NettyDataBufferFactory(ByteBufAllocator.DEFAULT);
        DataBuffer buffer = nettyDataBufferFactory.allocateBuffer(bytes.length);
        buffer.write(bytes);
        return buffer;
    }

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

这里有详细的获取Post请求体的方法，无论是application/x-www-form-urlencoded和application/json都可以通过上面的方式。

看结果：

下面是@RequestBody形式的

这是后端消费的服务代码

也能正常接收@RequestBody请求并解析。