關於Spring bean 注入時有多個候選bean的解決方案

Error Message

org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'javax.jms.ConnectionFactory' available: expected single matching bean but found 2: activeMQConnectionFactory,springFactory

今天使用springboot Demo ActiveMQ過程當中，注入ConnectionFactory時，SpringBoot 自動配置時發現由於多個候選bean注入失敗，解決此問題有兩個方法:

// 1. 當bean定義階段和bean注入階段代碼均可以修改時優先採用@Qualifier註解在bean注入階段解決，使用以前須要先得到bean的名稱;

   @Autowired
   @Qualifier(value = "activeMQConnectionFactory")
   public ActiveMQConnectionFactory mqConnectionFactory;
   
   @Bean(name = "activeMQConnectionFactory")
   public ActiveMQConnectionFactory activeMQConnectionFactory(){
	  ActiveMQConnectionFactory activeMQConnectionFactory = new ActiveMQConnectionFactory();
	  activeMQConnectionFactory.setBrokerURL(BROKERURL);
	  activeMQConnectionFactory.setUserName(USERNAME);
	  activeMQConnectionFactory.setPassword(PASSWORD);
	  activeMQConnectionFactory.setTrustAllPackages(true);
	  return activeMQConnectionFactory;
   }
   
   @Bean(name = "springFactory")
//   @Primary
   public CachingConnectionFactory connectionFactory(){
      CachingConnectionFactory  factory = new CachingConnectionFactory(mqConnectionFactory);
      factory.setSessionCacheSize(100);
      factory.setCacheConsumers(true);
      factory.setCacheProducers(true);
      return factory;
   }
   
// 2. 但遇到像springboot自動配置這種狀況，沒法改動@AutoWired階段的代碼，因此只能採起在@Bean階段加上註解配置@primary
  @Bean(name = "springFactory")
  @Primary // 默認優先調用該bean
   public CachingConnectionFactory connectionFactory(){
      CachingConnectionFactory  factory = new CachingConnectionFactory(mqConnectionFactory);
      factory.setSessionCacheSize(100);
      factory.setCacheConsumers(true);
      factory.setCacheProducers(true);
      return factory;
   }