解决Hmily与Feign冲突报错 NullPointerException

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在项目中使用了Hmily保证分布式事务的一致性，由于Hmily会注册一个 HmilyFeignInterceptor ，并且feign会将其添加到 SynchronousMethodHandler 中的 requestInterceptors ，当feign客户端执行 HmilyFeignInterceptor 中apply方法

public void apply(final RequestTemplate requestTemplate) { 
   
        Transmiter.getInstance().transmit((x$0, xva$1) -> { 
   
            requestTemplate.header(x$0, new String[]{ 
   xva$1});
        }, HmilyTransactionContextLocal.getInstance().get());
    }

由于获取到的 HmilyTransactionContext 为 null ，所以抛出 NullPointerException 异常。

解决方法：

定义一个后置处理器，将没有被 @Hmily 注解的方法，移除 HmilyFeignInterceptor 。

package com.jz.shop.cart.service;

import com.jz.shop.commons.utils.text.StringUtils;
import feign.InvocationHandlerFactory;
import feign.ReflectiveFeign;
import feign.RequestInterceptor;
import lombok.extern.slf4j.Slf4j;
import org.dromara.hmily.annotation.Hmily;
import org.dromara.hmily.springcloud.feign.HmilyFeignInterceptor;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RestController;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.List;
import java.util.Map;

/** * @author:JZ * @date:2020/6/1 */
@Slf4j
@Component
public class ShopFeignPostProcessor implements BeanPostProcessor { 
   

    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { 
   
        return bean;
    }

    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { 
   
        // 对所有含有 @FeignClient 的bean进行处理
        if (StringUtils.isNotNull(AnnotationUtils.findAnnotation(bean.getClass(), FeignClient.class))) { 
   
            // 排除含有 @Controller 和 @RestController 注解的bean
            if (StringUtils.isNotNull(AnnotationUtils.findAnnotation(bean.getClass(), Controller.class)) ||
                    StringUtils.isNotNull(AnnotationUtils.findAnnotation(bean.getClass(), RestController.class))) { 
   
                return bean;
            }
            try { 
   
                // 获取代理类中的 FeignInvocationHandler
                Field h = bean.getClass().getSuperclass().getDeclaredField("h");
                boolean hAccessible = h.isAccessible();
                h.setAccessible(true);
                Object feignInvocationHandler = h.get(bean);
                /** * 获取 FeignInvocationHandler 中 dispatch 字段的 Map<Method, MethodHandler> dispatch 属性。 * dispatch中包含feign代理的方法 和 SynchronousMethodHandler */
                Field dispatchField = feignInvocationHandler.getClass().getDeclaredField("dispatch");
                boolean dispatchAccessible = dispatchField.isAccessible();
                dispatchField.setAccessible(true);
                Map<Method, InvocationHandlerFactory.MethodHandler> dispatch =
                        (Map<Method, InvocationHandlerFactory.MethodHandler>) dispatchField.get(feignInvocationHandler);

                /** * SynchronousMethodHandler 中的 List<RequestInterceptor> requestInterceptors 字段 * 加载了Hmily对feign的拦截器 HmilyFeignInterceptor */
                for (Map.Entry<Method, InvocationHandlerFactory.MethodHandler> entry : dispatch.entrySet()) { 
   
                    /** * 没有添加 @Hmily 注解的方法不需要被 Hmily 拦截处理， * 否则会因为加载的 HmilyTransactionContext 为 null 导致 NullPointerException */
                    if (StringUtils.isNull(AnnotationUtils.findAnnotation(entry.getKey(), Hmily.class))) { 
   
                        Field riField = entry.getValue().getClass().getDeclaredField("requestInterceptors");
                        boolean riAccessible = riField.isAccessible();
                        riField.setAccessible(true);
                        List<RequestInterceptor> requestInterceptors = (List<RequestInterceptor>) riField.get(entry.getValue());
                        for (RequestInterceptor interceptor : requestInterceptors) { 
   
                            if (interceptor instanceof HmilyFeignInterceptor) { 
   
                                requestInterceptors.remove(interceptor);
                                break;
                            }
                        }
                        riField.setAccessible(riAccessible);
                        log.info("{}.{} 方法移除 HmilyFeignInterceptor", beanName, entry.getKey().getName());
                    }
                }
                dispatchField.setAccessible(dispatchAccessible);
                h.setAccessible(hAccessible);
            } catch (Exception e) { 
   
                log.warn("{} exception", beanName);
                e.printStackTrace();
            }
        }
        return bean;
    }

}