SpringBoot开机启动与@Order注解
package com.example.zcw.runner;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Order(2)
@Slf4j
@Component
public class BootApplicationRunner implements ApplicationRunner {
@Override
public void run(ApplicationArguments args) throws Exception {
log.info("This is BootApplicationRunner ...");
}
}
package com.example.zcw.runner;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Order(1)
@Slf4j
@Component
public class BootCommandLineRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
log.info("This is BootCommandLineRunner ...");
}
}
spring @Order标记
@Order标记定义了组件的加载顺序
@Order标记从spring 2.0出现，但是在spring 4.0之前，@Order标记只支持AspectJ的切面排序。spring 4.0对@Order做了增强，它开始支持对装载在诸如Lists和Arrays容器中的自动包装（auto-wired）组件的排序。
在spring内部，对基于spring xml的应用，spring使用OrderComparator类来实现排序。对基于注解的应用，spring采用AnnotationAwareOrderComparator来实现排序。
@Order 标记定义如下：
@Retention(value=RUNTIME)
@Target(value={TYPE,METHOD,FIELD})
@Documented
public @interface Order这个标记包含一个value属性。属性接受整形值。如：1,2 等等。值越小拥有越高的优先级。
下面让我们来看一个
使用spring 3.x 和spring 4.x 的例子
Ranks.java
package com.javapapers.spring3.autowire.collection;
public interface Ranks {
}
RankOne.java
package com.javapapers.spring3.autowire.collection;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
public class RankOne implements Ranks{
private String rank = "RankOne";
public String toString(){
return this.rank;
}
}
RankTwo.java
package com.javapapers.spring3.autowire.collection;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
public class RankTwo implements Ranks{
private String rank = "RankTwo";
public String toString(){
return this.rank;
}
}
RankThree.java
package com.javapapers.spring3.autowire.collection;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
@Component
public class RankThree implements Ranks{
private String rank = "RankThree";
public String toString(){
return this.rank;
}
}
Results.java
Component to hold student ranks in a collection as shown below.
package com.javapapers.spring3.autowire.collection;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class Results {
@Autowired
private List ranks ;
@Override
public String toString(){
return ranks.toString();
}
}
beans.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:annotation-config />
<context:component-scan base-package="com.javapapers.spring3"/>
</beans>
RanksClient.java
package com.javapapers.spring3.autowire.collection;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class RanksClient {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
Results results = (Results)context.getBean("results");
System.out.println(results);
}
}
输出结果：
[RankOne, RankThree, RankTwo]
从结果可以看出，结果是没有顺序的。因为spring 3.x不支持对自动包装组件的排序。
接下来，我升级spring的版本至4.x， 并对RanOne,RankTwo和RankThree加上order标记，值做相应的调整。
@Component
@Order(1)
public class RankOne implements Ranks{
private String rank = "RankOne";
public String toString(){
return this.rank;
}
}输出结果如下：
[RankOne, RankTwo, RankThree]
参考文章： http://javapapers.com/spring/spring-order-annotation/
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
