@Order是
控制配置类的加载顺序,还能控制List<XXX> 里面放的XXX的实现注入的顺序,下面介绍使用Spring下的@Order和@Primary与javax.annotation-api下@Priority【Spring4.1后,参考:https://jira.spring.io/browse/SPR-10548】控制多实现的依赖注入,因为在项目中可能会遇到接口多实现的问题,那么要具体注入那个接口的实现就需要我们来控制了,那么如何控制,请看下面的例子示例:
示例一:
public interface XStrategyService {
}
@Service
@Priority(1)
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service
@Priority(2)
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Autowired
private XStrategyService xStrategyService; // XStrategyServiceImpl01将被选择
示例二:
public interface XStrategyService {
}
@Service
@Primary
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Autowired
private XStrategyService xStrategyService; // XStrategyServiceImpl01将被选择
示例三:
public interface XStrategyService {
}
@Service
@Order(1)
@Primary
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service
@Order(2)
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Autowired
private XStrategyService xStrategyService; // XStrategyServiceImpl01将被选择
注意,下面的是不能注入的,就是单独使用@Order(1), @Order(2) Order注解仅仅用于控制组件的加载顺序,不能控制注入优先级
public interface XStrategyService {
}
@Service
@Order(1)
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service
@Order(2)
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Autowired
private XStrategyService xStrategyService; // Error
一些其他方法完成多实现的注入,使用@Qualifier限定符
public interface XStrategyService {
}
@Service
@Qualifier("defaultStrategyService")
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Autowired
@Qualifier("defaultStrategyService")
private XStrategyService xStrategyService; // XStrategyServiceImpl01将被选择
使用@Resource,通过Bean的名称限定选择,和@Qualifier限定符类似
public interface XStrategyService {
}
@Service("xStrategyServiceImpl01")
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service("xStrategyServiceImpl02")
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Resource(name = "xStrategyServiceImpl01")
private XStrategyService xStrategyService; // XStrategyServiceImpl01将被选择
特例:Spring4.0后的新特性,就是根据泛型类型可以自动选择注入
public interface XStrategyService<T> {
}
@Service
public class XStrategyServiceImpl01 implements XStrategyService<XXX> {
}
@Service
public class XStrategyServiceImpl02 implements XStrategyService<YYY> {
}
@Autowired
private XStrategyService<XXX> xStrategyService; // XStrategyServiceImpl01将被选择
补充@Order结合@Bean的用法:
public interface XStrategyService {
}
@Service
public class XStrategyServiceImpl01 implements XStrategyService {
}
@Service
public class XStrategyServiceImpl02 implements XStrategyService {
}
@Bean
@Order(1)
XStrategyServiceImpl01 xStrategyServiceImpl01() {
return new XStrategyServiceImpl01();
}
@Bean
@Order(2)
XStrategyServiceImpl02 xStrategyServiceImpl02() {
return new XStrategyServiceImpl02();
}
@Autowired
private List<XStrategyService> xStrategyServices; // XStrategyServiceImpl01 first
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