SpringBoot开机启动与@Order注解
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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;/** * @Classname BootApplicationRunner * @Description TODO * @Date 2020/3/6 13:06 * @Created by zhaocunwei */@Order(2)@Slf4j@Componentpublic class BootApplicationRunner implements ApplicationRunner { @Override public void run(ApplicationArguments args) throws Exception { log.info("This is BootApplicationRunner ..."); }} |
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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;/** * @Classname BootCommandLineRunner * @Description TODO * @Date 2020/3/6 13:09 * @Created by zhaocunwei */@Order(1)@Slf4j@Componentpublic 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：
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@Retention(value=RUNTIME)@Target(value={TYPE,METHOD,FIELD})@Documentedpublic @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
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package com.javapapers.spring3.autowire.collection;public interface Ranks { } |
RankOne.java
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package com.javapapers.spring3.autowire.collection;import org.springframework.core.annotation.Order;import org.springframework.stereotype.Component;@Componentpublic class RankOne implements Ranks{ private String rank = "RankOne"; public String toString(){ return this.rank; } } |
RankTwo.java
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package com.javapapers.spring3.autowire.collection;import org.springframework.core.annotation.Order;import org.springframework.stereotype.Component;@Componentpublic class RankTwo implements Ranks{ private String rank = "RankTwo"; public String toString(){ return this.rank; }} |
RankThree.java
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package com.javapapers.spring3.autowire.collection;import org.springframework.core.annotation.Order;import org.springframework.stereotype.Component;@Componentpublic class RankThree implements Ranks{ private String rank = "RankThree"; public String toString(){ return this.rank; }} |
Results.java
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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;@Componentpublic class Results { @Autowired private List ranks ; @Override public String toString(){ return ranks.toString(); }} |
beans.xml
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<?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
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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。
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@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服务器之家。
原文链接：https://zhaocunwei.blog.csdn.net/article/details/104694000
