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 @Component public 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 @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:
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@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
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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; @Component public 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; @Component public 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; @Component public 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; @Component public 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