文章目录
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.
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