010-Spring Boot 扩展分析-ApplicationContextInitializer、CommandLineRunner

一、常见的两个扩展点

1、ApplicationContextInitializer

1.1、作用实现

作用：接口实在Spring容器执行refresh之前的一个回调。

Callback interface for initializing a Spring {@link ConfigurableApplicationContext}

实现：

package com.lhx.spring.springboot_enableauto;

import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

@Component
public class ServerSuccessReport implements CommandLineRunner {

@Override
public void run(String... args) throws Exception {
System.out.println("----CommandLineRunner执行-----");
}

}

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注意同类接口

ApplicationRunner，

void run(ApplicationArguments args)

只是参数不一样

CommandLineRunner是原始参数，没有任何处理

ApplicationRunner是ApplicationArguments 对象，是对原始参数进一步的封装

3.ApplicationArguments

是对参数（main方法）进一步重载

可以解析--name=value的，可以通过name获取value

package com.lhx.spring.springboot_enableauto;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication
public class App {
public static void main(String[] args) {
SpringApplication application = new SpringApplication(App.class);
ConfigurableApplicationContext context = application.run(args);

ApplicationArguments arguments = context.getBean(ApplicationArguments.class);
System.out.println(arguments.getSourceArgs().length);
System.out.println(arguments.getOptionNames());
System.out.println(arguments.getOptionValues("name"));

context.close();
}
}