@Order 通常和 spring boot | 接口 CommandLineRunner 还有 spring | 注解 @component @Repository @Service @Controller 一起使用。
注解 @Order 或者接口 Ordered 的作用是定义 Spring IOC 容器中 Bean 的执行顺序的优先级，而不是定义 Bean 的加载顺序，Bean的加载顺序不受 @Order 或 Ordered 接口的影响；
@Order源码
1
2
3
4
5
6
7
8
9
10
11
| @Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE, ElementType.METHOD, ElementType.FIELD})
@Documented
public @interface Order {
int value() default Ordered.LOWEST_PRECEDENCE;
}
|
- 注解可以作用在类(接口、枚举)、方法、字段声明（包括枚举常量）；
- 注解有一个int类型的参数，可以不传，默认是最低优先级；
- 通过常量类的值我们可以推测参数值越小优先级越高；
Order 接口类
1
2
3
4
5
6
7
8
| package org.springframework.core;
public interface Ordered {
int HIGHEST_PRECEDENCE = -2147483648;
int LOWEST_PRECEDENCE = 2147483647;
int getOrder();
}
|
使用
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
| @Component
@Order(1)
public class BlackPersion implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("----BlackPersion----");
}
}
@Component
@Order(0)
public class YellowPersion implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("----YellowPersion----");
}
}
|
输出
我们可以通过调整@Order的值来调整类执行顺序的优先级，即执行的先后；当然也可以将@Order注解更换为Ordered接口，效果是一样的
注入顺序
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
| package com.lou.springboot;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;
import javax.annotation.Resource;
import java.util.List;
interface ComponentConsumer<T> {
boolean deal(T t);
}
@Component
@Order(2)
class EatComponent implements ComponentConsumer<Message> {
private static final Logger logger = LoggerFactory.getLogger(Component.class);
@Override
public boolean deal(Message message) {
return message.getEat();
}
}
@Component
@Order(3)
class SleepComponent implements ComponentConsumer<Message> {
private static final Logger logger = LoggerFactory.getLogger(Component.class);
@Override
public boolean deal(Message message) {
return message.getSleep();
}
}
@Component
@Order(1)
class PlayComponent implements ComponentConsumer<Message> {
private static final Logger logger = LoggerFactory.getLogger(Component.class);
@Override
public boolean deal(Message message) {
return message.getPlay();
}
}
@Service
public class ServiceImpl {
@Resource
List<ComponentConsumer> componentConsumerList;
}
|
componentConsumerList 的注入顺序是
