應用場景：

　　使用者服務實現使用者登入將資訊儲存到session中，訂單服務需要獲取使用者登入的session物件進行其他操作

使用者服務中，驗證密碼輸入正確進去首頁

1、加入redis的session共享依賴

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<!-- session共享的依賴 -->
 

<dependency>
    <groupId>org.springframework.session</groupId>
    <artifactId>spring-session-data-redis</artifactId>
</dependency>

2、儲存在session中

session.setAttribute("user",user);

發現在其他服務中拿不到用一個session值

解決方法：

在建立session服務的服務中：

1、加入session共享依賴

2、配置redis伺服器的配置

spring:
 

  #redis相關的資訊
  redis:
    host: 127.0.0.1
    port: 6381
  main:
    allow-bean-definition-overriding: true

3、在啟動類中加入註解

@EnableRedisHttpSession(redisFlushMode= RedisFlushMode.IMMEDIATE)
public class StockUserApplication {。。。}

4、在服務中加入這個 FeignClientsConfigurationCustom配置類

@Configuration
@EnableFeignClients
 
public class FeignClientsConfigurationCustom implements RequestInterceptor {
    @Override
    public void apply(RequestTemplate template) {

        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        if (requestAttributes == null) {
            return;
        }

        HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest();
        Enumeration<String> headerNames = request.getHeaderNames();
        if (headerNames != null) {
            while (headerNames.hasMoreElements()) {
                String name = headerNames.nextElement();
                Enumeration<String> values = request.getHeaders(name);
                while (values.hasMoreElements()) {
                    String value = values.nextElement();
                    template.header(name, value);
                }
            }
        }
        String sessionId = request.getSession().getId();
        if (sessionId != null) {
            template.header("Cookie", "SESSION=" + base64Encode(request.getSession().getId()));
        }
    }
    @Bean
    public FeignHystrixConcurrencyStrategy feignHystrixConcurrencyStrategy() {
        return new FeignHystrixConcurrencyStrategy();
    }

    public static String base64Encode(String value) {
        byte[] encodedCookieBytes = Base64.getEncoder().encode(value.getBytes());
        return new String(encodedCookieBytes);

    }

在加上這個類：

/**
 * 熔斷機制會導致feign之間session失效,使用此策略來解決問題
 */
public class FeignHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy {
    private static final Logger log = LoggerFactory.getLogger(FeignHystrixConcurrencyStrategy.class);
    private HystrixConcurrencyStrategy delegate;

    public FeignHystrixConcurrencyStrategy() {
        try {
            this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();
            if (this.delegate instanceof FeignHystrixConcurrencyStrategy) {
                // 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();
            }
        }
    }

在呼叫session服務的服務中：

　　做相同的配置即可拿到同一個sessionId

//從session域裡獲取到使用者所有資訊
T_user sessionUser = (T_user) session.getAttribute("user");