今天在使用Feign調(diào)用其他微服務(wù)的接口時(shí)，發(fā)現(xiàn)了一個(gè)問題：因?yàn)槲业捻?xiàng)目采用了無狀態(tài)登錄，token信息是存放在cookie中的，所以調(diào)用接口時(shí)，因?yàn)閏ookie中沒有token信息，我的請(qǐng)求被攔截器攔截了。

參考幾篇文章，靠譜的解決方法是：將cookie信息放到請(qǐng)求頭中，再進(jìn)行調(diào)用接口時(shí)，攔截器中可以對(duì)請(qǐng)求頭進(jìn)行解析，獲取cookie信息

服務(wù)調(diào)用方

package top.codekiller.manager.upload.config;
import feign.RequestInterceptor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;
/**
 * @author codekiller
 * @date 2020/5/26 14:22
 * 
 *   自定義的請(qǐng)求頭處理類，處理服務(wù)發(fā)送時(shí)的請(qǐng)求頭；
 *   將服務(wù)接收到的請(qǐng)求頭中的uniqueId和token字段取出來，并設(shè)置到新的請(qǐng)求頭里面去轉(zhuǎn)發(fā)給下游服務(wù)
 *   比如A服務(wù)收到一個(gè)請(qǐng)求，請(qǐng)求頭里面包含uniqueId和token字段，A處理時(shí)會(huì)使用Feign客戶端調(diào)用B服務(wù)
 *   那么uniqueId和token這兩個(gè)字段就會(huì)添加到請(qǐng)求頭中一并發(fā)給B服務(wù)；
 */
@Configuration
@Slf4j
public class FeignHeaderConfiguration {
    @Bean
    public RequestInterceptor requestInterceptor() {
        return requestTemplate -> {
            ServletRequestAttributes attrs = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
            if (attrs != null) {
                HttpServletRequest request = attrs.getRequest();
                // 如果在Cookie內(nèi)通過如下方式取
                Cookie[] cookies = request.getCookies();
                if (cookies != null && cookies.length > 0) {
                    for (Cookie cookie : cookies) {
                        requestTemplate.header(cookie.getName(), cookie.getValue());
                        System.out.println("信息"+cookie.getName()+cookie.getValue());
                    }
                } else {
                    log.warn("FeignHeadConfiguration", "獲取Cookie失?。?);
                }
                
                // 如果放在header內(nèi)通過如下方式取
                Enumeration<String> headerNames = request.getHeaderNames();
                if (headerNames != null) {
                    while (headerNames.hasMoreElements()) {
                        String name = headerNames.nextElement();
                        String value = request.getHeader(name);
                        /**
                         * 遍歷請(qǐng)求頭里面的屬性字段，將jsessionid添加到新的請(qǐng)求頭中轉(zhuǎn)發(fā)到下游服務(wù)
                         * */
                        if ("jsessionid".equalsIgnoreCase(name)) {
                            log.debug("添加自定義請(qǐng)求頭key:" + name + ",value:" + value);
                            requestTemplate.header(name, value);
                        } else {
                            log.debug("FeignHeadConfiguration", "非自定義請(qǐng)求頭key:" + name + ",value:" + value + "不需要添加!");
                        }
                    }
                } else {
                    log.warn("FeignHeadConfiguration", "獲取請(qǐng)求頭失??！");
                }
            }
        };
    }
}

服務(wù)接受方

//有些請(qǐng)求時(shí)從通過feign進(jìn)行請(qǐng)求的，這一部分請(qǐng)求時(shí)不包含cookie信息的，因此我們要從請(qǐng)求頭中獲取
            Enumeration<String> headerNames = request.getHeaderNames();
            if (headerNames != null) {
                while (headerNames.hasMoreElements()) {
                    String name = headerNames.nextElement();
                    String value = request.getHeader(name);
                    System.out.println("header的信息"+name+"::::"+value);
                    if(name.equalsIgnoreCase("MC_TOKEN")){  //注意這里變成了小寫
                        token=value;
                    }
                }
            }

運(yùn)行的時(shí)候，我發(fā)現(xiàn)請(qǐng)求還是被攔截了，看了下打印信息，發(fā)現(xiàn)我的MC_TOKEN變成了小寫，所以在字符串進(jìn)行比較的時(shí)候要忽略大小寫。

以下為擴(kuò)展，僅僅記錄一下

這樣仍然有個(gè)問題：

在開啟熔斷器之后，方法里的attrs是null，因?yàn)槿蹟嗥髂J(rèn)的隔離策略是thread，也就是線程隔離，實(shí)際上接收到的對(duì)象和這個(gè)在發(fā)送給B不是一個(gè)線程，怎么辦？

有一個(gè)辦法，修改隔離策略hystrix.command.default.execution.isolation.strategy=SEMAPHORE，改為信號(hào)量的隔離模式，但是不推薦，因?yàn)閠hread是默認(rèn)的，而且要命的是信號(hào)量模式，熔斷器不生效，比如設(shè)置了熔斷時(shí)間。

另一個(gè)辦法：重寫Feign的隔離策略

import com.netflix.hystrix.HystrixThreadPoolKey;
import com.netflix.hystrix.HystrixThreadPoolProperties;
import com.netflix.hystrix.strategy.HystrixPlugins;
import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategy;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariable;
import com.netflix.hystrix.strategy.concurrency.HystrixRequestVariableLifecycle;
import com.netflix.hystrix.strategy.eventnotifier.HystrixEventNotifier;
import com.netflix.hystrix.strategy.executionhook.HystrixCommandExecutionHook;
import com.netflix.hystrix.strategy.metrics.HystrixMetricsPublisher;
import com.netflix.hystrix.strategy.properties.HystrixPropertiesStrategy;
import com.netflix.hystrix.strategy.properties.HystrixProperty;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
 
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
 
/**
 * 自定義Feign的隔離策略;
 * 在轉(zhuǎn)發(fā)Feign的請(qǐng)求頭的時(shí)候，如果開啟了Hystrix，Hystrix的默認(rèn)隔離策略是Thread(線程隔離策略)，因此轉(zhuǎn)發(fā)攔截器內(nèi)是無法獲取到請(qǐng)求的請(qǐng)求頭信息的，可以修改默認(rèn)隔離策略為信號(hào)量模式：hystrix.command.default.execution.isolation.strategy=SEMAPHORE，這樣的話轉(zhuǎn)發(fā)線程和請(qǐng)求線程實(shí)際上是一個(gè)線程，這并不是最好的解決方法，信號(hào)量模式也不是官方最為推薦的隔離策略；另一個(gè)解決方法就是自定義Hystrix的隔離策略，思路是將現(xiàn)有的并發(fā)策略作為新并發(fā)策略的成員變量,在新并發(fā)策略中，返回現(xiàn)有并發(fā)策略的線程池、Queue；將策略加到Spring容器即可；
 *
 */
@Component
public class FeignHystrixConcurrencyStrategyIntellif extends HystrixConcurrencyStrategy {
 
    private static final Logger log = LoggerFactory.getLogger(FeignHystrixConcurrencyStrategyIntellif.class);
    private HystrixConcurrencyStrategy delegate;
 
    public FeignHystrixConcurrencyStrategyIntellif() {
        try {
            this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();
            if (this.delegate instanceof FeignHystrixConcurrencyStrategyIntellif) {
                // Welcome to singleton hell...
                return;
            }
            HystrixCommandExecutionHook commandExecutionHook =
                    HystrixPlugins.getInstance().getCommandExecutionHook();
            HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance().getEventNotifier();
            HystrixMetricsPublisher metricsPublisher = HystrixPlugins.getInstance().getMetricsPublisher();
            HystrixPropertiesStrategy propertiesStrategy =
                    HystrixPlugins.getInstance().getPropertiesStrategy();
            this.logCurrentStateOfHystrixPlugins(eventNotifier, metricsPublisher, propertiesStrategy);
            HystrixPlugins.reset();
            HystrixPlugins.getInstance().registerConcurrencyStrategy(this);
            HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook);
            HystrixPlugins.getInstance().registerEventNotifier(eventNotifier);
            HystrixPlugins.getInstance().registerMetricsPublisher(metricsPublisher);
            HystrixPlugins.getInstance().registerPropertiesStrategy(propertiesStrategy);
        } catch (Exception e) {
            log.error("Failed to register Sleuth Hystrix Concurrency Strategy", e);
        }
    }
 
    private void logCurrentStateOfHystrixPlugins(HystrixEventNotifier eventNotifier,
                                                 HystrixMetricsPublisher metricsPublisher, HystrixPropertiesStrategy propertiesStrategy) {
        if (log.isDebugEnabled()) {
            log.debug("Current Hystrix plugins configuration is [" + "concurrencyStrategy ["
                    + this.delegate + "]," + "eventNotifier [" + eventNotifier + "]," + "metricPublisher ["
                    + metricsPublisher + "]," + "propertiesStrategy [" + propertiesStrategy + "]," + "]");
            log.debug("Registering Sleuth Hystrix Concurrency Strategy.");
        }
    }
 
    @Override
    public <T> Callable<T> wrapCallable(Callable<T> callable) {
        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        return new WrappedCallable<>(callable, requestAttributes);
    }
 
    @Override
    public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
                                            HystrixProperty<Integer> corePoolSize, HystrixProperty<Integer> maximumPoolSize,
                                            HystrixProperty<Integer> keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        return this.delegate.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize, keepAliveTime,
                unit, workQueue);
    }
 
    @Override
    public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
                                            HystrixThreadPoolProperties threadPoolProperties) {
        return this.delegate.getThreadPool(threadPoolKey, threadPoolProperties);
    }
 
    @Override
    public BlockingQueue<Runnable> getBlockingQueue(int maxQueueSize) {
        return this.delegate.getBlockingQueue(maxQueueSize);
    }
 
    @Override
    public <T> HystrixRequestVariable<T> getRequestVariable(HystrixRequestVariableLifecycle<T> rv) {
        return this.delegate.getRequestVariable(rv);
    }
 
    static class WrappedCallable<T> implements Callable<T> {
        private final Callable<T> target;
        private final RequestAttributes requestAttributes;
 
        public WrappedCallable(Callable<T> target, RequestAttributes requestAttributes) {
            this.target = target;
            this.requestAttributes = requestAttributes;
        }
 
        @Override
        public T call() throws Exception {
            try {
                RequestContextHolder.setRequestAttributes(requestAttributes);
                return target.call();
            } finally {
                RequestContextHolder.resetRequestAttributes();
            }
        }
    }
}

然后使用默認(rèn)的熔斷器隔離策略，也可以在攔截器內(nèi)獲取到上游服務(wù)的請(qǐng)求頭信息了；

Feign調(diào)用存在的問題

① feign遠(yuǎn)程調(diào)用丟失請(qǐng)求頭

問題描述：

當(dāng)遠(yuǎn)程調(diào)用其他服務(wù)時(shí)，設(shè)置了攔截器判斷用戶是否登錄，但是結(jié)果是即使用戶登錄了，也會(huì)顯示用戶沒登錄，原因在于遠(yuǎn)程調(diào)用時(shí)，發(fā)送的請(qǐng)求是一個(gè)新的情求，請(qǐng)求中并不存在cookie，而原始請(qǐng)求中是攜帶cookie的。

解決方案如下：

@Configuration
public class MallFeignConfig {
    @Bean("requestInterceptor")
    public RequestInterceptor requestInterceptor() {
        RequestInterceptor requestInterceptor = template -> {
            //1、使用RequestContextHolder拿到剛進(jìn)來的請(qǐng)求數(shù)據(jù)
            ServletRequestAttributes requestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
            if (requestAttributes != null) {
                //老請(qǐng)求
                HttpServletRequest request = requestAttributes.getRequest();
                if (request != null) {
                    //2、同步請(qǐng)求頭的數(shù)據(jù)（主要是cookie）
                    //把老請(qǐng)求的cookie值放到新請(qǐng)求上來，進(jìn)行一個(gè)同步
                    String cookie = request.getHeader("Cookie");
                    template.header("Cookie", cookie);
                }
            }
        };
        return requestInterceptor;
    }
}

② 異步調(diào)用Feign丟失上下文問題

問題描述：

由于feign請(qǐng)求攔截器為新的request設(shè)置請(qǐng)求頭底層是使用ThreadLocal保存剛進(jìn)來的請(qǐng)求，所以在異步情況下，其他線程并不能獲取到主線程的ThreadLocal，所以也拿不到請(qǐng)求。

解決：

先獲取主線程的requestAttributes，再分別向其他線程中設(shè)置

RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
CompletableFuture.runAsync(() ->{
   RequestContextHolder.setRequestAttributes(requestAttributes);
});

以上為個(gè)人經(jīng)驗(yàn)，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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