Question

我正在尝试使用Spring实现基于策略模式的通信服务功能。我有以下课程 -

界面 - MessageService.java

package com.xxx

public Interface MessageService{

    String sendMessage(String idOrNumber);

}

实施类 -

1）EmailService.java

package com.xxx

@Component
public class EmailService implements MessageService{

        public String sendMessage(String idOrNumber){

    // Do some operation

    return "success"

    } 

}

2）SmsService.java

package com.xxx

@Component
public class SmsService implements MessageService{

        public String sendMessage(String idOrNumber){

    // Do some operation

    return "success"

    } 

}

CommunicationFactory Class

package com.xxx

@Component
public class CommunicationFactory {

    @Resource(name ="smsService")
    private SmsService smsService 


    @Resource(name ="emailService")
    private EmailService emailService;


    public MessageService getCommunicationChannel(String channel){

    MessageService messageService = null;

    if("sms".equals(channel){

    messageService = smsService;    

    }

    if("email".equals(channel){

    messageService = emailService;

    }

   return messageService;

}

我有一个邮件服务实现类

package com.xxx

@Component
@Service
public class CommunicationServiceImpl implements CommunicationService {

      @Autowired
      private MessageService messageService;

      CommunicationFactory communicationFactory;


      @Override
      public String sendCommunication(String idOrNumber){

        //Which implementation be called - SMS or EMAIL
        messageService = communicationFactory.getCommunicationChannel(channel);

        String statusMessage = messageService.sendMessage(idOrNumber);

        }

}

运行服务器时出现以下错误。

Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: com.xxx.MessageService com.xxx.CommunicationServiceImpl.messageService; nested exception is 

org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.xxx.MessageService] is defined: expected single matching bean but found 2: smsService,emailService
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:514) [spring-beans-

3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87) [spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:285) [spring-beans-

3.2.3.RELEASE.jar:3.2.3.RELEASE]
    ... 25 more
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.xxx.MessageService] is defined: expected single matching bean but found 2: 

smsService,emailService
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:863) [spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:768) [spring-beans-3.2.3.RELEASE.jar:3.2.3.RELEASE]
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:486) [spring-beans-

3.2.3.RELEASE.jar:3.2.3.RELEASE]
    ... 27 more

我哪里错了？任何指针都会有所帮助

Answer 1

试试这个。

实施类 -

1) EmailService.java

package com.xxx

@Component("emailService")
public class EmailService implements MessageService{

        public String sendMessage(String idOrNumber){

    // Do some operation

    return "success"

    } 

}
2) SmsService.java

package com.xxx

@Component("smsService")
public class SmsService implements MessageService{

        public String sendMessage(String idOrNumber){

    // Do some operation

    return "success"

    } 

}

问题在于：

@Autowired
private MessageService messageService;

可能的解决方案是@Autowired两种服务。

@Autowired
private MessageService smsService;
@Autowired
private MessageService emailService;

或者，如果您遇到同样的问题。

@Autowired
@Qualifier("smsService")
private MessageService smsService;
@Autowired
@Qualifier("emailService")
private MessageService emailService;

Answer 2

我知道最简单的实现是依赖注入的服务列表并使用get方法来获取负责任的服务：

package com.xxx

@Component
public class CommunicationFactory {

    /**
     * This list would be ordered if the interface is implementing `org.springframework.core.Ordered` or an implementation declares `@org.springframework.core.annotation.Order`(in Spring 4)
     */
    @Autowired
    private List<MessageService> messageServices; 

    /**
     * @return the FIRST communication channel for the given channel
     */
    public MessageService getCommunicationChannel(String channel){
        for (MessageService ms : messageServices) {
            if (ms.supports(channel)) {
                return ms;
            }
        }
        return null; // or a default :)
    }

    /**
     * With this implementation you can even have multiple implementations firing a message if they support the given channel.
     * @return a list of communication channels that support the given channel
     */
    public List<MessageService> getCommunicationChannels(String channel){
        List<MessageService> supporting = new ArrayList<>();
        for (MessageService ms : messageServices) {
            if (ms.supports(channel)) {
                supporting.add(ms);
            }
        }
        return supporting;
    }
}

NoUniqueBeanDefinitionException - 具有策略模式的Spring DI

2 个答案: