rder的规则：
order的值越小，优先级越高
order如果不标注数字，默认最低优先级，因为其默认值是int最大值
该注解等同于实现Ordered接口getOrder方法，并返回数字。
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD, ElementType.FIELD})
@Documented
public @interface Order {
int value() default 2147483647;
}
例子：
OrderRunner1.java
@Component
@Order(1)
public class OrderRunner1 implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("The OrderRunner1 start to initialize ...");
}
}
OrderRunner2.java
@Component
@Order(2)
public class OrderRunner2 implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("The OrderRunner2 start to initialize ...");
}
}
启动日志：
…
…
The OrderRunner1 start to initialize …
The OrderRunner2 start to initialize …
