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@Order 可以作用在类、方法、属性。 影响加载顺序。 若不加，spring的加载顺序是随机的。
@Primary 当注入bean冲突时，以@Primary定义的为准。
@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
原文链接：https://blog.csdn.net/weixin_42465125/article/details/88574670
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