1.问题
当一个接口有2个不同实现时,使用@Autowired注解时会报org.springframework.beans.factory.NoUniqueBeanDefinitionException异常信息
2.方案1-@Qualifier
使用Qualifier注解，选择一个对象的名称,通常比较常用
3. 方案2-@Primary
Primary可以理解为默认优先选择,同时不可以同时设置多个,
内部实质是设置BeanDefinition的primary属性
示例
@Component("metalSinger") // 加注解，让spring识别 public class MetalSinger implements Singer{ @Override public String sing(String lyrics) { return "I am singing with DIO voice: "+lyrics; } } @Primary @Component("operaSinger") public class OperaSinger implements Singer { @Override public String sing(String lyrics) { return "I am singing in Bocelli voice: "+lyrics; } } public interface Singer { String sing(String lyrics); } @Component public class SingerService { private static final Logger logger = LoggerFactory.getLogger(SingerService.class); @Autowired @Qualifier private Singer singer; public String sing(){ return singer.sing("song lyrics"); } public static void main(String[] args) { ApplicationContext context = new AnnotationConfigApplicationContext("context.annotation.primary"); SingerService singerService = context.getBean(SingerService.class); System.out.println(singerService.sing()); } }