10-OpenFeign-实现异步调用

通常我们在使用openfeign发起服务调用时，需要同步等待调用结束。某些场景下，我们需要实现异步调用。

1、使用java8 的 CompletableFuture 异步工具

    @Resource
    OauthFeign oauthFeign;
 
 
    @GetMapping("/get")
    public Object get() {
 
        CompletableFuture<Object> completableFuture = CompletableFuture.supplyAsync(() -> {
                    return oauthFeign.openFeignApi();
                });
        return completableFuture;
    }

RequestContextHolder中是将请求信息放入ThreadLocal中的，只能取到同一个线程的数据。

2、使用RequestContextHolder 获取主线程中的header信息

RequestAttributes attributes = RequestContextHolder.getRequestAttributes();

在异步线程内部设置 RequestContextHolder.setRequestAttributes(attributes);

CompletableFuture<T> future1 = CompletableFuture.supplyAsync(() -> {
 //openfeign的调用
 return feign.remoteCall();
},executor);
 
CompletableFuture<T> future2 = CompletableFuture.supplyAsync(() -> {
 //openfeign的调用
 return feign.remoteCall();
},executor);
 
CompletableFuture.allOf(future1,future2).join();
 
.....

//获取主线程的请求信息
RequestAttributes attributes = RequestContextHolder.getRequestAttributes();
 
CompletableFuture<T> future1 = CompletableFuture.supplyAsync(() -> {
   //将主线程的请求信息设置到异步线程中，否则会丢失请求上下文，导致调用失败
   RequestContextHolder.setRequestAttributes(attributes);
    
 //openfeign的调用
 return feign.remoteCall();
},executor);
 
 
CompletableFuture<T> future2 = CompletableFuture.supplyAsync(() -> {
   //将主线程的请求信息设置到异步线程中，否则会丢失请求上下文，导致调用失败
 RequestContextHolder.setRequestAttributes(attributes);
 
    //openfeign的调用
 return feign.remoteCall();
},executor);
 
CompletableFuture.allOf(future1,future2).join();
 
.....

3、全局设置（未验证）

1. 定义一个Feign RequestInterceptor拦截器:
java
public class RequestContextInterceptor implements RequestInterceptor {
    @Override
    public void apply(RequestTemplate requestTemplate) {
        ServletRequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        if (requestAttributes != null) {
            RequestContextHolder.setRequestAttributes(requestAttributes, true);
        }
    }
} 
 
 
 
2. 在FeignClient上添加配置,使用该拦截器:
java
@FeignClient(name="hello", configuration = HelloConfiguration.class)
public interface HelloClient {
    // ...
}
 
public class HelloConfiguration { 
    @Bean
    public RequestInterceptor requestContextInterceptor() {
        return new RequestContextInterceptor();
    }
}