摘要
spring 的 qualifier 平常使用一般直接是使用id 来限定,不过spring给我们提供了更强大的功能。
@Qualifier
中限定bean的id@Qualifier
来指定后续使用的value
,然后在注入处使用指定的值Example:
public interface OrderService {
String createOrder(String name);
}
@Component
@Qualifier(value = "whatever")
public class EmptyOrderService implements OrderService {
private Logger logger = LoggerFactory.getLogger(EmptyOrderService.class);
@Override
public String createOrder(String name) {
logger.info("empty order service " + name);
return "empty";
}
}
@Qualifier
除了可以注解在类上,属性上,还可以注解在 annotation上,这样我们可以创造自己的qualifier(在xml里可以使用<qualifier>
)。
Example: id 有时候不明确,我们需要按自己的条件来创造qualifier
@Target(value = {ElementType.TYPE, ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Qualifier
@Documented
public @interface OrderQualifier {
String orderName() default"default";
int orderType() default 0;
}
然后就可以使用@OrderQualifier
来指定和注入bean了。
@Component
@OrderQualifier(orderName = "kill", orderType = 2)
public class KillOrderService implements OrderService {
private Logger logger = LoggerFactory.getLogger(KillOrderService.class);
@Override
public String createOrder(String name) {
logger.info("kill order service " + name);
return "kill";
}
}
@Component
@OrderQualifier(orderName = "normal", orderType = 1)
public class NormalOrderService implements OrderService {
private Logger logger = LoggerFactory.getLogger(NormalOrderService.class);
@Override
public String createOrder(String name) {
logger.info("normal create order " + name);
return "normal";
}
}
使用时直接注入:
@RestController
@RequestMapping("order")
public class OrderResource {
@Autowired
@OrderQualifier(orderName = "kill", orderType = 2)
OrderService orderService;
@Autowired
@OrderQualifier(orderName = "normal", orderType = 1)
OrderService normalOrderService;
@Autowired
@Qualifier("whatever")
OrderService emptyOrderService;
@GetMapping("kill")
public String print(String name) {
return orderService.createOrder(name);
}
@GetMapping("normal")
public String normal(String name) {
return normalOrderService.createOrder(name);
}
@GetMapping("empty")
public String empty(String name) {
return emptyOrderService.createOrder(name);
}
}
测试一下,分别调用回返回了各自的值。