目录
本文章主要了解在spring容器执行refreshed之前的一个回调接口：ApplicationContextInitializer，
在容器启动成功后的最后一步回调（类似开机自启动)的接口:CommandLineRunner和ApplicationRunner。
脑图如下:
一、ApplicationContextInitializer
该接口是接口是在spring容器执行refreshed之前的一个回调。
①使用步骤:
1： 写一个类： 实现AApplicationContextInitializer接口
2： 注册ApplicationContextInitializer
②注册方法3种:
1.app.addInitializers
2:通过配置项context.initializer.classes指定
3.可以通过spring.factories机制(注册listener监听器也可以使用这种方式)
演示 1.app.addInitializers方式
写个实现类
public class MyAppliationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { @Override public void initialize(ConfigurableApplicationContext applicationContext) { System.out.println("bean count: " + applicationContext.getBeanDefinitionCount()); } }
在入口中注册和调用:
@SpringBootApplication public class Demo8Application { public static void main(String[] args) { SpringApplication app = new SpringApplication(Demo8Application.class); app.addInitializers(new MyAppliationContextInitializer()); ConfigurableApplicationContext context = app.run(args); context.close(); } }
测试
:
测试已经注入！
演示 2:通过配置项context.initializer.classes指定
public class MyAppliationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { @Override public void initialize(ConfigurableApplicationContext applicationContext) { System.out.println("bean count: " + applicationContext.getBeanDefinitionCount()); } }
public class MyAppliationContextInitializer2 implements ApplicationContextInitializer<ConfigurableApplicationContext> { @Override public void initialize(ConfigurableApplicationContext applicationContext) { System.out.println(applicationContext.getDisplayName()); } }
application.properties,写了2个实现类:
context.initializer.classes=com.springboot.demo8.MyAppliationContextInitializer,com.springboot.demo8.MyAppliationContextInitializer2
@SpringBootApplication public class Demo8Application { public static void main(String[] args) { SpringApplication app = new SpringApplication(Demo8Application.class); ConfigurableApplicationContext context = app.run(args); context.close(); }
运行结果ok:
3.spring.factories机制(注册listener监听器也可以使用这种方式)
新建一个项目intializer:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.2.5.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.springboot</groupId> <artifactId>intializer</artifactId> <version>0.0.1-SNAPSHOT</version> <name>intializer</name> <description>Demo project for Spring Boot</description> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> </dependencies> </project>
public class EchoAppliationContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { @Override public void initialize(ConfigurableApplicationContext applicationContext) { System.out.println("=========EchoAppliationContextInitializer=========="); } }
intializer\src\main\resources\META-INF\spring.factories： org.springframework.context.ApplicationContextInitializer=com.springboot.intializer.EchoAppliationContextInitializer
将该项目引入原来的项目:
<dependency> <groupId>com.springboot</groupId> <artifactId>intializer</artifactId> <version>0.0.1-SNAPSHOT</version> </dependency>
测试:
@SpringBootApplication public class Demo8Application { public static void main(String[] args) { SpringApplication app = new SpringApplication(Demo8Application.class); ConfigurableApplicationContext context = app.run(args); context.close(); } }
运行结果：
结果显示已经注入！！
二、CommandLineRunner
该接口是在容器启动成功后的最后一步回调（类似开机自启动），可以在应用启动时打印一些东西之类的。
①使用步骤:
1.写一个类，实现CommandLineRunner 接口
2 把该类纳入到spring的容器管理中
注意：可以通过@Order注解或者Ordered接口来控制执行顺序。order值小的优先
演示一下
@Order(1) @Component public class ServerSuccessReport implements CommandLineRunner { @Override public void run(String... args) throws Exception { System.out.println("=====应用已经成功的启动============" + Arrays.asList(args)); } }
@Order(2) @Component public class ServerStartedReport implements CommandLineRunner { @Override public void run(String... args) throws Exception { System.out.println("=====应用启动后的时间是:============"+ LocalDateTime.now().toString()); } }
以上2个类都实现了CommandLineRunner 接口，并用@Compoent,并通过order控制优先级，值小的优先执行，注入spring:
测试下:
@SpringBootApplication public class Demo8Application { public static void main(String[] args) { SpringApplication app = new SpringApplication(Demo8Application.class); ConfigurableApplicationContext context = app.run(args); context.close(); } }
运行结果:
三、ApplicationRunner
CommandLineRunner,ApplicationRunner 区别
区别在于方法的参数不一样
CommandLineRunner的参数是最原始的参数，没有做任务处理
ApplicationRunner的参数是ApplicationArguments，是对原始参数做了进一步的封装
举例说明:
看下CommandLineRunner的获取参数代码:
@Component public class ServerSuccessReport implements CommandLineRunner { @Override public void run(String... args) throws Exception { System.out.println("=====应用已经成功的启动============" + Arrays.asList(args)); } }
看戏ApplicationRunner的获取参数代码:
import java.util.Arrays; @Component public class StartedApplicationRunner implements ApplicationRunner { @Override public void run(ApplicationArguments args) throws Exception { System.out.println("应用已经启动，参数为:" + Arrays.asList(args.getSourceArgs())); } }
运行结果:
都获取了程序的参数，这里我们看不出来区别，继续改造：
先设置启动参数:
ApplicationRunner 获取的是一个ApplicationArguments对象，我们来通过参数对象打印看下:
public static void main(String[] args) { SpringApplication app = new SpringApplication(Demo8Application.class); ConfigurableApplicationContext context = app.run(args); ApplicationArguments arg = context.getBean(ApplicationArguments.class); System.out.println(arg.getSourceArgs().length); System.out.println(arg.getOptionNames()); System.out.println(arg.getOptionValues("myname")); context.close(); }
运行结果：
可以看到通过ApplicationArguments可以使用其提供的getOptionNames，getOptionValues方法很方便的获取参数值，而CommandLineRunner 只能获取到--myname=admin这样的字符串，我们获取key或者value需要使用split切割很麻烦，而且ApplicationArguments还有好多实用的方法:
这就是CommandLineRunner,ApplicationRunner 区别 : 方法的参数类型不一样.
本文讲了主要是springboot容器2个常用接口:在spring容器执行refreshed之前的一个回调接口：ApplicationContextInitializer，
在容器启动成功后的最后一步回调（类似开机自启动)的接口:CommandLineRunner和ApplicationRunner,和这2个接口的区别.
