gateway：增加访问日志，待优化~

yudao-gateway/src/main/java/cn/iocoder/yudao/gateway/filter/logging/GatewayLog.java

+package cn.iocoder.yudao.gateway.filter.logging;
+
+import lombok.Data;
+
+import java.util.Date;
+
+@Data
+public class GatewayLog {
+    /**访问实例*/
+    private String targetServer;
+    /**请求路径*/
+    private String requestPath;
+    /**请求方法*/
+    private String requestMethod;
+    /**协议 */
+    private String schema;
+    /**请求体*/
+    private String requestBody;
+    /**响应体*/
+    private String responseData;
+    /**请求ip*/
+    private String ip;
+ /**请求时间*/
+    private Date requestTime;
+ /**响应时间*/
+    private Date responseTime;
+    /**执行时间*/
+    private long executeTime;
+}

yudao-gateway/src/main/java/cn/iocoder/yudao/gateway/filter/web/CacheRequestBodyFilter.java

+package cn.iocoder.yudao.gateway.filter.web;
+
+import cn.hutool.core.util.ReflectUtil;
+import org.springframework.cloud.gateway.filter.GatewayFilterChain;
+import org.springframework.cloud.gateway.filter.GlobalFilter;
+import org.springframework.cloud.gateway.filter.factory.rewrite.CachedBodyOutputMessage;
+import org.springframework.cloud.gateway.support.BodyInserterContext;
+import org.springframework.core.Ordered;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.codec.HttpMessageReader;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
+import org.springframework.stereotype.Component;
+import org.springframework.web.reactive.function.BodyInserter;
+import org.springframework.web.reactive.function.BodyInserters;
+import org.springframework.web.reactive.function.server.HandlerStrategies;
+import org.springframework.web.reactive.function.server.ServerRequest;
+import org.springframework.web.server.ServerWebExchange;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.util.List;
+import java.util.function.Function;
+
+/**
+ * 缓存 Request Body 和 的过滤器
+ *
+ * 小知识：Request Body 都是无法重复读取的，所以需要实现一个缓存的。
+ * 从功能上，它类似 yudao-spring-boot-starter-web 的 CacheRequestBodyFilter 过滤器
+ *
+ * 实现基本是拷贝 {@link org.springframework.cloud.gateway.filter.factory.rewrite.ModifyRequestBodyGatewayFilterFactory} 类
+ *
+ * @author 芋道源码
+ */
+@Component
+public class CacheRequestBodyFilter implements GlobalFilter, Ordered {
+
+    private final List<HttpMessageReader<?>> messageReaders = HandlerStrategies.withDefaults().messageReaders();
+
+    @Override
+    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
+        ServerRequest serverRequest = ServerRequest.create(exchange, messageReaders);
+
+        // TODO: flux or mono
+        Mono<String> modifiedBody = serverRequest.bodyToMono(String.class);
+//                .flatMap()
+//                .switchIfEmpty(Mono.just(""));
+
+        BodyInserter bodyInserter = BodyInserters.fromPublisher(modifiedBody, String.class);
+        HttpHeaders headers = new HttpHeaders();
+        headers.putAll(exchange.getRequest().getHeaders());
+
+        // the new content type will be computed by bodyInserter
+        // and then set in the request decorator
+        headers.remove(HttpHeaders.CONTENT_LENGTH);
+
+        CachedBodyOutputMessage outputMessage = new CachedBodyOutputMessage(exchange, headers);
+        return bodyInserter.insert(outputMessage, new BodyInserterContext())
+                // .log("modify_request", Level.INFO)
+                .then(Mono.defer(() -> {
+                    ServerHttpRequest decorator = decorate(exchange, headers, outputMessage);
+                    return chain.filter(exchange.mutate().request(decorator).build());
+                })).onErrorResume((Function<Throwable, Mono<Void>>) throwable -> release(exchange,
+                        outputMessage, throwable));
+    }
+
+    @Override
+    public int getOrder() {
+        // 必须小于等于 -2，否则无法获取响应结果. 因为 WebClientWriteResponseFilter 和 NettyWriteResponseFilter 是 -1，优先级要高于它们
+        return -2;
+    }
+
+    protected Mono<Void> release(ServerWebExchange exchange, CachedBodyOutputMessage outputMessage,
+                                 Throwable throwable) {
+        // add by 芋道源码：由于 CachedBodyOutputMessage 的 isCached 非 public 方法，所以只能反射调用
+        if ((boolean) ReflectUtil.getFieldValue(outputMessage, "cached")) {
+            return outputMessage.getBody().map(DataBufferUtils::release).then(Mono.error(throwable));
+        }
+        return Mono.error(throwable);
+    }
+
+    ServerHttpRequestDecorator decorate(ServerWebExchange exchange, HttpHeaders headers,
+                                        CachedBodyOutputMessage outputMessage) {
+        return new ServerHttpRequestDecorator(exchange.getRequest()) {
+
+            @Override
+            public HttpHeaders getHeaders() {
+                long contentLength = headers.getContentLength();
+                HttpHeaders httpHeaders = new HttpHeaders();
+                httpHeaders.putAll(headers);
+                if (contentLength > 0) {
+                    httpHeaders.setContentLength(contentLength);
+                }
+                else {
+                    // TODO: this causes a 'HTTP/1.1 411 Length Required' // on
+                    // httpbin.org
+                    httpHeaders.set(HttpHeaders.TRANSFER_ENCODING, "chunked");
+                }
+                return httpHeaders;
+            }
+
+            @Override
+            public Flux<DataBuffer> getBody() {
+                return outputMessage.getBody();
+            }
+        };
+    }
+
+}