基于SpringBoot开机启动与@Order注解

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;/** * @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 ...");    }}
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 ...");    }}

龙方网络

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})@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

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;@Componentpublic 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;@Componentpublic 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;@Componentpublic 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;@Componentpublic 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龙方网络。

郑重声明:本文版权包含图片归原作者所有,转载文章仅为传播更多信息之目的,如作者信息标记有误,请第一时间联系我们(delete@yzlfxy.com)修改或删除,多谢。

郑重声明:本文版权归原作者所有,转载文章仅为传播更多信息之目的,如作者信息标记有误,请第一时间联系我们修改或删除,多谢。

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