SpringCloud Gateway自定义全局过滤器

项目需要处理网络请求异常 404 等异常，可以通过自定义全局过滤器来处理响应结果。还可以对相应结果进行二次封装，修改内容响应最新修改过的内容。

自定义全局过滤器：

• 实现 GlobalFilter 接口
• 实现 Ordered 接口，可以自定义过滤器顺序

添加自定义全局过滤器类

import com.alibaba.fastjson.JSON;
import com.google.common.base.Joiner;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
import com.tigerkin.util.ApiResult;
import org.reactivestreams.Publisher;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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.DataBufferFactory;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.nio.charset.Charset;
import java.util.List;

/**
 * @ClassName CustomGlobalFilter
 * @Description 自定义全局过滤器
 * @Author tigerkin
 * @Date 2022/3/14 17:03
 */
@Component
public class CustomGlobalFilter implements GlobalFilter, Ordered {

    private final Logger log = LoggerFactory.getLogger(this.getClass());

    private static Joiner joiner = Joiner.on("");

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        log.info("========> 请求进入全局过滤器");
        ServerHttpResponse originalResponse = exchange.getResponse();
        DataBufferFactory bufferFactory = originalResponse.bufferFactory();
        ServerHttpResponseDecorator response = new ServerHttpResponseDecorator(originalResponse) {
            @Override
            public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                if (!(body instanceof Flux)) {
                    return super.writeWith(body);
                }

                HttpStatus statusCode = getStatusCode();
                if (statusCode.equals(HttpStatus.OK)) {
                    // return readAndWrite(body); // 读取响应结果，可以对响应结果做二次处理再返回
                    return super.writeWith(body); // 直接返回响应结果
                } else { // 对非正常状态码的请求，封装统一响应信息，不弹出错误页面
                    Flux<? extends DataBuffer> fluxBody = Flux.from(body);
                    return super.writeWith(fluxBody.buffer().map(dataBuffers -> {
                        ApiResult result;
                        if (statusCode.equals(HttpStatus.NOT_FOUND)) {
                            result = ApiResult.error(HttpStatus.NOT_FOUND, "访问服务资源不存在");
                        } else {
                            result = ApiResult.error(statusCode, statusCode.name());
                        }
                        String resultJson = JSON.toJSONString(result);

                        byte[] uppedContent = new String(resultJson.getBytes(), Charset.forName("UTF-8")).getBytes();
                        originalResponse.setStatusCode(HttpStatus.OK); // 设置状态码
                        originalResponse.getHeaders().setContentLength(uppedContent.length); // 设置内容长度
                        originalResponse.getHeaders().setContentType(MediaType.APPLICATION_JSON); // 设置内容类型
                        return bufferFactory.wrap(uppedContent);
                    }));
                }
            }

            /**
             * 读取和写入Response响应内容
             * @param body
             * @return
             */
            private Mono<Void> readAndWrite(Publisher<? extends DataBuffer> body) {
                Flux<? extends DataBuffer> fluxBody = Flux.from(body);
                return super.writeWith(fluxBody.buffer().map(dataBuffers -> {
                    List<String> list = Lists.newArrayList();
                    dataBuffers.forEach(dataBuffer -> {
                        try {
                            byte[] content = new byte[dataBuffer.readableByteCount()];
                            dataBuffer.read(content);
                            DataBufferUtils.release(dataBuffer);
                            list.add(new String(content, "UTF-8"));
                        } catch (Exception e) {
                            log.info("加载Response字节流异常，失败原因：{}", Throwables.getStackTraceAsString(e));
                        }
                    });
                    String responseData = joiner.join(list);
                    System.out.println("responseData：" + responseData);

                    byte[] uppedContent = new String(responseData.getBytes(), Charset.forName("UTF-8")).getBytes();
                    originalResponse.getHeaders().setContentLength(uppedContent.length);
                    originalResponse.getHeaders().setContentType(MediaType.APPLICATION_JSON);
                    return bufferFactory.wrap(uppedContent);
                }));
            }

            @Override
            public Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body) {
                return writeWith(Flux.from(body).flatMapSequential(p -> p));
            }
        };
        return chain.filter(exchange.mutate().response(response).build());
    }

    /**
     * 定义全局过滤器顺序
     *
     * @return
     */
    @Override
    public int getOrder() {
        return -1;
    }
}