讲讲我和Spring创始级程序员共同review代码的故事

@Resourceprivate RocketMQTemplate rocketMQTemplate;
...
SendResult sendResult = rocketMQTemplate.syncSend(xxxTopic, "Hello, World!");

@Service@RocketMQMessageListener(topic = "xxx", consumerGroup = "xxx_consumer")
public class StringConsumer implements RocketMQListener<String> {
   @Override   public void onMessage(String message) {
       System.out.printf("------- StringConsumer received: %s \n", message);
   }
}

@Configuration
@EnableConfigurationProperties(RocketMQProperties.class)
@ConditionalOnClass(MQClientAPIImpl.class)
@Order  ~~春波特: 这个类里使用Order很不合理呵，不建议使用，完全可以通过其他方式控制runtime是Bean的构建顺序
@Slf4j
public class RocketMQAutoConfiguration {
   @Bean
   @ConditionalOnClass(DefaultMQProducer.class) ~~春波特: 属性直接使用类是不科学的，需要用(name="类全名") 方式，这样在类不在classpath时，不会抛出CNFE
   @ConditionalOnMissingBean(DefaultMQProducer.class)
   @ConditionalOnProperty(prefix = "spring.rocketmq", value = {"nameServer", "producer.group"}) ~~春波特: nameServer属性名要写成name-server [1]
   @Order(1) ~~春波特: 删掉呵   public DefaultMQProducer mqProducer(RocketMQProperties rocketMQProperties) {
       ...
   }
   @Bean
   @ConditionalOnClass(ObjectMapper.class)
   @ConditionalOnMissingBean(name = "rocketMQMessageObjectMapper") ~~春波特: 不建议与具体的实例名绑定，设计的意图是使用系统中已经存在的ObjectMapper, 如果没有，则在这里实例化一个，需要改成
    @ConditionalOnMissingBean(ObjectMapper.class)
   public ObjectMapper rocketMQMessageObjectMapper() {
       return new ObjectMapper();
   }
   @Bean(destroyMethod = "destroy")
   @ConditionalOnBean(DefaultMQProducer.class)
   @ConditionalOnMissingBean(name = "rocketMQTemplate") ~~春波特: 与上面一样
   @Order(2) ~~春波特: 删掉呵 
   public RocketMQTemplate rocketMQTemplate(DefaultMQProducer mqProducer,
       @Autowired(required = false)              ~~春波特: 删掉
       @Qualifier("rocketMQMessageObjectMapper") ~~春波特: 删掉，不要与具体实例绑定              
          ObjectMapper objectMapper) {
       RocketMQTemplate rocketMQTemplate = new RocketMQTemplate();
       rocketMQTemplate.setProducer(mqProducer);
       if (Objects.nonNull(objectMapper)) {
           rocketMQTemplate.setObjectMapper(objectMapper);
       }
       return rocketMQTemplate;
   }
   @Bean(name = RocketMQConfigUtils.ROCKETMQ_TRANSACTION_ANNOTATION_PROCESSOR_BEAN_NAME)
   @ConditionalOnBean(TransactionHandlerRegistry.class)
   @Role(BeanDefinition.ROLE_INFRASTRUCTURE) ~~春波特: 这个bean（RocketMQTransactionAnnotationProcessor）建议声明成static的，因为这个RocketMQTransactionAnnotationProcessor实现了BeanPostProcessor接口,接口里方法在调用的时候（创建Transaction相关的Bean的时候）可以直接使用这个static实例，而不要等到这个Configuration类的其他的Bean都构建好 [2]
   public RocketMQTransactionAnnotationProcessor transactionAnnotationProcessor(     
   TransactionHandlerRegistry transactionHandlerRegistry) {
     return new RocketMQTransactionAnnotationProcessor(transactionHandlerRegistry);
  }
   @Configuration  ~~春波特: 这个内嵌的Configuration类比较复杂，建议独立成一个顶级类，并且使用
   @Import在主Configuration类中引入 
   @ConditionalOnClass(DefaultMQPushConsumer.class)
   @EnableConfigurationProperties(RocketMQProperties.class)
   @ConditionalOnProperty(prefix = "spring.rocketmq", value = "nameServer") ~~春波特: name-server
   public static class ListenerContainerConfiguration implements ApplicationContextAware, InitializingBean {
      ...
      @Resource ~~春波特: 删掉这个annotation, 这个field injection的方式不推荐，建议使用setter或者构造参数的方式初始化成员变量
      private StandardEnvironment environment;
       @Autowired(required = false)  ~~春波特: 这个注解是不需要的
       public ListenerContainerConfiguration(
           @Qualifier("rocketMQMessageObjectMapper") ObjectMapper objectMapper) { ~~春波特: @Qualifier 不需要
           this.objectMapper = objectMapper;
       }

@Configuration
public class ListenerContainerConfiguration implements ApplicationContextAware, SmartInitializingSingleton {
    private ObjectMapper objectMapper = new ObjectMapper(); ~~春波特: 性能上考虑，不要初始化这个成员变量，既然这个成员是在构造/setter方法里设置的，就不要在这里初始化，尤其是当它的构造成本很高的时候。
   private void registerContainer(String beanName, Object bean) {   Class<?> clazz = AopUtils.getTargetClass(bean);
   if(!RocketMQListener.class.isAssignableFrom(bean.getClass())){
       throw new IllegalStateException(clazz + " is not instance of " + RocketMQListener.class.getName());
   }
   RocketMQListener rocketMQListener = (RocketMQListener) bean;     RocketMQMessageListener annotation = clazz.getAnnotation(RocketMQMessageListener.class);
   validate(annotation);   ~~春波特: 下面的这种手工注册Bean的方式是Spring 4.x里提供能，可以考虑使用Spring5.0 里提供的 GenericApplicationContext.registerBean的方法,通过supplier调用new来构造Bean实例 [3]
    BeanDefinitionBuilder beanBuilder = BeanDefinitionBuilder.rootBeanDefinition(DefaultRocketMQListenerContainer.class);
   beanBuilder.addPropertyValue(PROP_NAMESERVER, rocketMQProperties.getNameServer());
   ...
   beanBuilder.setDestroyMethodName(METHOD_DESTROY);
   String containerBeanName = String.format("%s_%s", DefaultRocketMQListenerContainer.class.getName(), counter.incrementAndGet());
   DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) applicationContext.getBeanFactory();
   beanFactory.registerBeanDefinition(containerBeanName, beanBuilder.getBeanDefinition());
   DefaultRocketMQListenerContainer container = beanFactory.getBean(containerBeanName, DefaultRocketMQListenerContainer.class);   ~~春波特: 你这里的启动方法是通过 afterPropertiesSet() 调用的，这个是不建议的，应该实现SmartLifecycle来定义启停方法，这样在ApplicationContext刷新时能够自动启动；并且避免了context初始化时由于底层资源问题导致的挂住(stuck)的危险
   if (!container.isStarted()) {
       try {
           container.start();
       } catch (Exception e) {
         log.error("started container failed. {}", container, e);           throw new RuntimeException(e);
       }
   }
   ...
 }
}

import org.springframework.util.Assert;
...
Assert.hasText(nameServer, "[rocketmq.name-server] must not be null");

public class RocketMQAutoConfigurationTest {
   private ApplicationContextRunner runner = new ApplicationContextRunner()           .withConfiguration(AutoConfigurations.of(RocketMQAutoConfiguration.class));


   @Test(expected = NoSuchBeanDefinitionException.class)   public void testRocketMQAutoConfigurationNotCreatedByDefault() {
       runner.run(context -> context.getBean(RocketMQAutoConfiguration.class));   }
   @Test
   public void testDefaultMQProducerWithRelaxPropertyName() {
       runner.withPropertyValues("rocketmq.name-server=127.0.0.1:9876",               "rocketmq.producer.group=spring_rocketmq").
               run((context) -> {
                   assertThat(context).hasSingleBean(DefaultMQProducer.class);                   assertThat(context).hasSingleBean(RocketMQProperties.class);               });
   }