rabbitmq消费者消费json格式的String，出现无限循环抛出No method found for class [B 这个异常

男娘i 2022-01-28 03:43 207阅读 0赞

rabbitmq消费者消费json格式的String，出现无限循环抛出org.springframework.amqp.AmqpException: No method found for class \[B 这个异常

原因：

There are two conversions in the @RabbitListener pipeline.
    The first converts from a Spring AMQP Message to a spring-messaging Message.
    There is currently no way to change the first converter from SimpleMessageConverter which handles String, Serializable and passes everything else as byte[].
    The second converter converts the message payload to the method parameter type (if necessary).
    With method-level @RabbitListeners there is a tight binding between the handler and the method.
    With class-level @RabbitListener s, the message payload from the first conversion is used to select which method to invoke. Only then, is the argument conversion attempted.
    This mechanism works fine with Java Serializable objects since the payload has already been converted before the method is selected.
    However, with JSON, the first conversion returns a byte[] and hence we find no matching @RabbitHandler.
    We need a mechanism such that the first converter is settable so that the payload is converted early enough in the pipeline to select the appropriate handler method.
    A ContentTypeDelegatingMessageConverter is probably most appropriate.
    And, as stated in AMQP-574, we need to clearly document the conversion needs for a @RabbitListener, especially when using JSON or a custom conversion.

解决方案:  
1.新增RabbItConfig,完成JSON格式的String转成字节码

@Configuration
    public class RabbitConfig { 
    
        @Bean
        public RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory) { 
            RabbitTemplate template = new RabbitTemplate(connectionFactory);
            template.setMessageConverter(new Jackson2JsonMessageConverter());
            return template;
        }
    
        @Bean
        public SimpleRabbitListenerContainerFactory rabbitListenerContainerFactory(ConnectionFactory connectionFactory) { 
            SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
            factory.setConnectionFactory(connectionFactory);
            factory.setMessageConverter(new Jackson2JsonMessageConverter());
            return factory;
        }
    }

2.用字节码数组接收，并转换为String，用JSONArray解析

@Component
    public class ResultReceiver { 
        @RabbitHandler
        @RabbitListener(queues="队列名",containerFactory="rabbitListenerContainerFactory") //监听器监听指定的queues
        public void process(byte[] result) { 
            String result1 = new String(result,"UTF-8");
            JSONArray jsonArray = JSONArray.fromObject(result1);
            for(int i = 0 ;i < jsonArray.size() ; i++){  
            }  
        }
    }