解决Hmily与Feign冲突报错 NullPointerException

心已赠人 2023-02-14 13:08 6阅读 0赞

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;
        }
    
    }