在使用spring boot 构建应用启动时，我们在工作中都是通过命令行来启动应用，有时候会需要一些特定的参数以在应用启动时，做一些初始化的操作。
spring boot 提供了 CommandLineRunner 和 ApplicationRunner 这两个接口供用户使用。
1. CommandLineRunner
1.1 声明:
@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;
}
1.2 使用:
package com.example.consoleapplication;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
@Component
public class TestRunner implements CommandLineRunner {
@Override
public void run(String... args) {
// Do something...
for(String arg: args){
System.out.println(arg);
}
System.out.print("test command runner");
}
}
1.3 运行结果
运行： java -jar build/libs/consoleapplication-0.0.1-SNAPSHOT.jar -sdfsaf sdfas,
结果如下：
2019-03-16 17:31:56.544 INFO 18679 --- [ main] c.e.consoleapplication.DemoApplication : No active profile set, falling back to default profiles: default
2019-03-16 17:31:57.195 INFO 18679 --- [ main] c.e.consoleapplication.DemoApplication : Started DemoApplication in 16.172 seconds (JVM running for 16.65)
-sdfsaf
sdfas
test command runner%
2. ApplicationRunner
2.1 声明
/**
* Interface used to indicate that a bean should <em>run</em> when it is contained within
* a {@link SpringApplication}. Multiple {@link ApplicationRunner} beans can be defined
* within the same application context and can be ordered using the {@link Ordered}
* interface or {@link Order @Order} annotation.
*
* @author Phillip Webb
* @since 1.3.0
* @see CommandLineRunner
*/
@FunctionalInterface
public interface ApplicationRunner {
/**
* Callback used to run the bean.
* @param args incoming application arguments
* @throws Exception on error
*/
void run(ApplicationArguments args) throws Exception;
}
2.2 使用
ApplicationRunner 和 CommandLineRunner 的使用是有差别的：
package com.example.consoleapplication;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;
import org.springframework.boot.ApplicationArguments;
@Component
public class TestApplicationRunner implements ApplicationRunner {
@Override
public void run(ApplicationArguments args) throws Exception {
// Do something...
System.out.println("option arg names" + args.getOptionNames());
System.out.println("non option+" + args.getNonOptionArgs());
}
}
2.3 运行结果
运行命令 java -jar build/libs/consoleapplication-0.0.1-SNAPSHOT.jar -non1 non2 --option=1， 结果为:
2019-03-16 18:08:08.528 INFO 19778 --- [ main] c.e.consoleapplication.DemoApplication : No active profile set, falling back to default profiles: default
2019-03-16 18:08:09.166 INFO 19778 --- [ main] c.e.consoleapplication.DemoApplication : Started DemoApplication in 16.059 seconds (JVM running for 16.56)
test
option arg names[option]
non option+[-non1, non2]-non1
non2
--option=1
test%
可以看到， optional 参数名有 option, non optional 参数有 -non1 和 non2
3. 小结
CommandLineRunner 和 ApplicationRunner 都能实现命令行应用启动时根据参数获取我们需要的值，做特殊的逻辑。但两者有所不同，推荐使用 ApplicationRunner 的 optional 参数, 方便扩展。
4. 参考文档
https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/reference/htmlsingle/
