java class 需要一个 bean，但找到了 2 个：
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class required a single bean, but 2 were found:
提问by Jeff
I have the below interface:
我有以下界面：
public interface MailSender {
void sender(String to, String subject,String body);
}
With 2 imlementation of it:
有2个实现：
public class SmtpkMailSender implements MailSender {
static Log log=LogFactory.getLog(MailSender.class);
public void sender(String to, String subject,String body){
log.info("SMTP To: "+to);
log.info("SMTP Subjecy: "+subject);
log.info("SMTP body: "+body);
}
}
and the second one is:
第二个是：
@Primary
public class MockMailSender implements MailSender {
static Log log=LogFactory.getLog(MailSender.class);
public void sender(String to, String subject,String body){
log.info("To: "+to);
log.info("Subject: "+subject);
log.info("body: "+body);
}
}
I used the dependency injection into the controller class which is as following:
我在控制器类中使用了依赖注入，如下所示：
@RestController
public class MailController {
@Autowired
private MailSender smtpkMailSender;
@RequestMapping("/send")
public String send(){
smtpkMailSender.sender("Person", "Important", "Take Care");
return "mail is sent";
}
}
At the end i have a configuration class which contains my Beans:
最后，我有一个包含我的 Bean 的配置类：
@Configuration
public class MailConfig {
@Bean
public SmtpkMailSender getSmtpkMailSender(){
return new SmtpkMailSender();
}
@Bean
public MockMailSender getMockMailSender(){
return new MockMailSender();
}
}
Unfortunatly, when i run my application it complains with:
不幸的是，当我运行我的应用程序时，它抱怨：
Description:
Field smtpkMailSender in com.example.demo.MailController required a single bean, but 2 were found:
- getSmtpkMailSender: defined by method 'getSmtpkMailSender' in class path resource [com/example/mail/MailConfig.class]
- getMockMailSender: defined by method 'getMockMailSender' in class path resource [com/example/mail/MailConfig.class]
Action:
Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed
As you see, although i have specified the MockMailSenderas Primary the spring still complains, and cannot identify it
如您所见，尽管我已将其指定MockMailSender为 Primary，但 spring 仍会抱怨，并且无法识别它
采纳答案by Leffchik
Since you're using java config you should mark config method with @Primaryannotation, and not a class:
由于您使用的是 java config，您应该用@Primary注释标记 config 方法，而不是类：
@Configuration
public class MailConfig {
@Bean
public SmtpkMailSender getSmtpkMailSender(){
return new SmtpkMailSender();
}
@Bean
@Primary
public MockMailSender getMockMailSender(){
return new MockMailSender();
}
}
回答by Yogi
You can use @Qualifier annotation for specify which specific type of your implementation, you want to autowire.
您可以使用 @Qualifier 注释来指定要自动装配的具体实现类型。
@RestController
public class MailController {
@Autowired
@Qualifier("smtpkMailSender")
private MailSender smtpkMailSender;
@RequestMapping("/send")
public String send(){
smtpkMailSender.sender("Person", "Important", "Take Care");
return "mail is sent";
}
}
}
回答by iAbhinav
You may simply name your bean using
您可以简单地使用命名您的 bean
@Bean(name="mockMailSender")
public MockMailSender getMockMailSender() { }
and then decorate the autowired field with
然后用
@Autowired
@Qualifier("mockMailSender")
private MailSender smtpkMailSender;
