1. 前言
不知道你有没有接到这种需求，项目启动后立马执行一些逻辑。比如缓存预热，或者上线后的广播之类等等。可能现在没有但是将来会有的。想想你可能的操作， 写个接口上线我调一次行吗？NO！NO！NO！这种初级菜鸟才干的事。今天告诉你个骚操作使得你的代码更加优雅，逼格更高。
2. CommandLineRunner 接口
package org.springframework.boot;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
/**
* Interface used to indicate that a bean should <em>run</em> when it is contained within
* a {@link SpringApplication}. Multiple {@link CommandLineRunner} beans can be defined
* within the same application context and can be ordered using the {@link Ordered}
* interface or {@link Order @Order} annotation.
* <p>
* If you need access to {@link ApplicationArguments} instead of the raw String array
* consider using {@link ApplicationRunner}.
*
* @author Dave Syer
* @see ApplicationRunner
*/
@FunctionalInterface
public interface CommandLineRunner {
/**
* Callback used to run the bean.
* @param args incoming main method arguments
* @throws Exception on error
*/
void run(String... args) throws Exception;
}复制代码
CommandLineRunner
作用是当springApplication 启动后，在同一应用上下文中定义的多个
CommandLineRunner
类型的
Spring Bean
按照标记顺序执行。如果你想替代以数组方式接收
args
参数 可以用 另一个接口代替
org.springframework.boot.ApplicationRunner
。
talk is cheap show your code 下面我就来操作一波演示一下。
2.1 优先级比较高的
CommandLineRunner
实现
package cn.felord.begin;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.Ordered;
import org.springframework.stereotype.Component;
/**
* 优先级比较高 通过实现接口{@link Ordered}的方式 来指定优先级
* 命令行测试参数 --foo=bar --dev.name=码农小胖哥 java,springboot
* @author Felordcn
* @since 2019/6/17 23:06
*/
@Slf4j
@Component
public class HighOrderCommandLineRunner implements CommandLineRunner , Ordered {
@Override
public void run(String... args) throws Exception {
log.info("i am highOrderRunner");
}
@Override
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE;
}
} 复制代码
2.2 优先级比较低的
CommandLineRunner
实现:
package cn.felord.begin;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
/**
* 优先级比较低 通过注解{@link Order}方式来指定优先级
* 比最优大64 说明会在 {@link HighOrderCommandLineRunner} 之后执行
*
* @author Felord
* @since 2019/6/17 23:07
*/
@Slf4j
@Order(Ordered.HIGHEST_PRECEDENCE + 64)
@Component
public class LowOrderCommandLineRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
log.info("i am lowOrderRunner");
}
}复制代码
2.3 用
ApplicationRunner
实现最低优先级:
package cn.felord.begin;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.core.Ordered;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;
import java.util.List;
/**
* 优先级最低的实现
* @author Felordcn
* @since 2019/6/18 22:13
*/
@Slf4j
@Component
public class DefaultApplicationRunner implements ApplicationRunner, Ordered {
@Override
public void run(ApplicationArguments args) throws Exception {
log.info("i am applicationRunner");
}
@Override
public int getOrder() {
return Ordered.HIGHEST_PRECEDENCE+65;
}
}复制代码启动springboot 后控制台打印出了执行结果：
2019-11-02 21:18:14.603 INFO 10244 --- [ main] c.f.begin.HighOrderCommandLineRunner : i am highOrderRunner
2019-11-02 21:18:14.604 INFO 10244 --- [ main] c.f.begin.LowOrderCommandLineRunner : i am lowOrderRunner
2019-11-02 21:18:14.604 INFO 10244 --- [ main] c.f.begin.DefaultApplicationRunner : i am applicationRunner复制代码
