重写webFlux中的webFilter，随意跳转到指定的过滤器，其实很简单

背景：由于webFlux中的webFilter没有对指定请求路径进行分流功能，因为过滤器就像一根管道，默认情况下过滤器执行的顺序是已经固定好了的，谁也不能插队，所以我希望过滤器可以通过我的请求来分发到不同的过滤器来执行。

原理：重写 webFlux中的 DefaultWebFilterChain.java实现类与 WebFilterChain.java接口

DefaultWebFilterChain.java代码如下：

/** Copyright 2002-2017 the original author or authors.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**      http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package org.springframework.web.server.handler;import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;import lombok.extern.slf4j.Slf4j;
import reactor.core.publisher.Mono;import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
import org.springframework.web.server.WebHandler;/*** Default implementation of {@link WebFilterChain}.** @author Rossen Stoyanchev* @since 5.0*/
@Slf4j
public class DefaultWebFilterChain implements WebFilterChain {private final List<WebFilter> filters;private final WebHandler handler;private final int index;public DefaultWebFilterChain(WebHandler handler, WebFilter... filters) {Assert.notNull(handler, "WebHandler is required");this.filters = ObjectUtils.isEmpty(filters) ? Collections.emptyList() : Arrays.asList(filters);this.handler = handler;this.index = 0;}private DefaultWebFilterChain(DefaultWebFilterChain parent, int index) {this.filters = parent.getFilters();this.handler = parent.getHandler();this.index = index;}public List<WebFilter> getFilters() {return this.filters;}public WebHandler getHandler() {return this.handler;}@Overridepublic Mono<Void> filter(ServerWebExchange exchange) {return Mono.defer(() -> {if (this.index < this.filters.size()) {WebFilter filter = this.filters.get(this.index);WebFilterChain chain = new DefaultWebFilterChain(this, this.index + 1);return filter.filter(exchange, chain);} else {return this.handler.handle(exchange);}});}/*** 通过索引确定过滤器* @param exchange the current server exchange* @param index the filter index,you can choose filter to execute* @return*/@Overridepublic Mono<Void> filter(ServerWebExchange exchange, int index) {return Mono.defer(() -> {if (index < this.filters.size()) {WebFilter filter = this.filters.get(index);WebFilterChain chain = new DefaultWebFilterChain(this, index + 1);return filter.filter(exchange, chain);} else {return this.handler.handle(exchange);}});}/*** 通过指定过滤器执行* @param exchange the current server exchange* @param cls appoint one filter to execute* @return*/@Overridepublic Mono<Void> filter(ServerWebExchange exchange, Class cls) {WebFilter filter = null;int index = 0;try {for (int i = 0; i < this.filters.size(); i++) {Class targetCls = Class.forName(this.filters.get(i).getClass().getName());if (cls.isAssignableFrom(targetCls)) {filter = this.filters.get(i);index = i;}}} catch (Exception e) {log.error("get filter is error,please contact with administrator!");}if (Objects.nonNull(filter)) {WebFilterChain chain = new DefaultWebFilterChain(this, index + 1);return filter.filter(exchange, chain);} else {return this.handler.handle(exchange);}}
}

WebFilterChain.java代码如下：

/** Copyright 2002-2015 the original author or authors.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**      http://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package org.springframework.web.server;import reactor.core.publisher.Mono;/*** Contract to allow a {@link WebFilter} to delegate to the next in the chain.** @author Rossen Stoyanchev* @since 5.0*/
public interface WebFilterChain {/*** Delegate to the next {@code WebFilter} in the chain.* @param exchange the current server exchange* @return {@code Mono<Void>} to indicate when request handling is complete*/Mono<Void> filter(ServerWebExchange exchange);/*** Delegate to the next {@code WebFilter} in the chain.* @param exchange the current server exchange* @param index the filter index,you can choose filter to execute* @return {@code Mono<Void>} to indicate when request handling is complete*/Mono<Void> filter(ServerWebExchange exchange,int index);/*** Delegate to the next {@code WebFilter} in the chain.* @param exchange the current server exchange* @param cls appoint one filter to execute* @return {@code Mono<Void>} to indicate when request handling is complete*/Mono<Void> filter(ServerWebExchange exchange, Class cls);}

接下来，编写自己的过滤器，主要包括三部分：

1、入口的过滤器（DispatcherFilter.java），主要用于分发到不同的过滤器

2、业务过滤器（checkFilter.java,自己随意编写）

3、底层过滤器（BaseFilter.java）

一、BaseFilter.java代码如下：

package com.test.filter;

import io.netty.buffer.ByteBufAllocator;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
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.HttpHeaders;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
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;

/**
*
*/
@Slf4j
@Component
public abstract class BaseFilter implements WebFilter, Ordered {

protected String bodyData="";

protected void readRequestData(ServerHttpRequest serverHttpRequest)
   {
       String method = serverHttpRequest.getMethodValue();
       if ("POST".equals(method)) {
           bodyData=resolveBodyFromRequest(serverHttpRequest);
       }
       else if("GET".equals(method))
       {
           bodyData=getContentByGetRequest(serverHttpRequest);
       }
   }

public void after(ServerWebExchange exchange) {
   }

@Override
   public Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {
       System.out.println("BaseFilter is comming");
       ServerHttpRequest serverHttpRequest = exchange.getRequest();
       ServerHttpResponse response = exchange.getResponse();

String method = serverHttpRequest.getMethodValue();
       if ("POST".equals(method)) {
           //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(bodyData);
           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)) {
           return chain.filter(exchange);
       }
       return chain.filter(exchange);
   }

private String getContentByGetRequest(ServerHttpRequest serverHttpRequest) {
       Map requestQueryParams = serverHttpRequest.getQueryParams().toSingleValueMap();
       StringBuffer s = new StringBuffer();
       String content = "";
       requestQueryParams.forEach((k, v) -> {
           System.out.println(k + " v:" + v);
           s.append(k + "=" + v + "&");
       });
       if (StringUtils.isNotEmpty(s.toString())) {
           content = s.toString().substring(0, s.toString().lastIndexOf('&'));
       }
       return content;
   }

/**
   * 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;
   }

}

二，DispatcherFilter.java分流过滤器

package org.test.filter
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilterChain;
import reactor.core.publisher.Mono;

@Slf4j
@Component
public class DispatcherFilter extends BaseFilter {@Overridepublic int getOrder() {//数值越小，优先级越高return Integer.MIN_VALUE;}@Overridepublic Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {super.readRequestData(exchange.getRequest());List<String> signUrls = cantaloupeConfig.getCheckSignWhiteUrls();List<String> cacheUrls = cantaloupeConfig.getUpdateCacheWhiteUrls();//根据不同的请求分流到不同的过滤器if (checkUrl(exchange,signUrls)) {return chain.filter(exchange,CheckSignFilter.class);}else if (checkUrl(exchange,cacheUrls)){return chain.filter(exchange,UpdateCacheFilter.class);}return super.filter(exchange,chain);}

}

三，各业务过滤器，举个栗子，CheckSignFilter.java

package com.test.filter;import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilterChain;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;import java.util.List;/*** 验证签名过滤器*/
@Slf4j
@Component
public class CheckSignFilter extends BaseFilter {@Overridepublic Mono<Void> filter(ServerWebExchange exchange, WebFilterChain chain) {//to doreturn super.filter(exchange,chain);}@Overridepublic void after(ServerWebExchange exchange) {}@Overridepublic int getOrder() {return -100;}
}

是不是很简单的就可以让过滤器听你的话，亲测无误，如有问题，请留言！

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