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20-SpringBoot事件监听

忍禁 2022-07-04 阅读 44
javaspring bootspring接口zookeeperSpark大数据

20-SpringBoot事件监听

SpringBoot事件监听

Java中的事件监听机制定义了以下几个角色：

①事件：Event，继承 java.util.EventObject 类的对象

②事件源：Source ，任意对象Object

③监听器：Listener，实现 java.util.EventListener 接口 的对象

SpringBoot 在项目启动时，会对几个监听器进行回调，我们可以实现这些监听器接口，在项目启动时完成一些操作。

  • ApplicationContextInitializer、
  • SpringApplicationRunListener、
  • CommandLineRunner、
  • ApplicationRunner

案例

1.创建一个基础项目 springboot-listener


20-SpringBoot事件监听_接口

下面我们来编写实现监听器接口。

2.实现监听器接口

  • ApplicationContextInitializer、
  • SpringApplicationRunListener、
  • CommandLineRunner、
  • ApplicationRunner

20-SpringBoot事件监听_zookeeper_02

2.1 实现 ApplicationContextInitializer

package com.lijw.springbootlistener.listener;

import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.stereotype.Component;

@Component
public class MyApplicationContextInitializer implements ApplicationContextInitializer {
    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {
        System.out.println("ApplicationContextInitializer initialize...");
    }
}

2.2 实现 SpringApplicationRunListener

package com.lijw.springbootlistener.listener;

import org.springframework.boot.ConfigurableBootstrapContext;
import org.springframework.boot.SpringApplicationRunListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.stereotype.Component;

import java.time.Duration;

@Component
public class MySpringApplicationRunListener implements SpringApplicationRunListener {

    @Override
    public void starting(ConfigurableBootstrapContext bootstrapContext) {
        System.out.println("SpringApplicationRunListener starting..");
    }

    @Override
    public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext, ConfigurableEnvironment environment) {
        System.out.println("SpringApplicationRunListener environmentPrepared..");
    }

    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener contextPrepared");
    }

    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener contextLoaded");
    }

    @Override
    public void started(ConfigurableApplicationContext context, Duration timeTaken) {
        System.out.println("SpringApplicationRunListener started");
    }

    @Override
    public void ready(ConfigurableApplicationContext context, Duration timeTaken) {
        System.out.println("SpringApplicationRunListener ready");
    }

    @Override
    public void running(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener running");
    }

    @Override
    public void failed(ConfigurableApplicationContext context, Throwable exception) {
        System.out.println("SpringApplicationRunListener failed");
    }
}

2.3 实现 CommandLineRunner

package com.lijw.springbootlistener.listener;

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

@Component
public class MyCommandLineRunner implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("CommandLineRunner run");
    }
}

2.4 实现 ApplicationRunner

package com.lijw.springbootlistener.listener;

import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.stereotype.Component;

@Component
public class MyApplicationRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.println("ApplicationRunner run");
    }
}

3.测试验证


20-SpringBoot事件监听_接口_03

也就说明：MyApplicationRunner和MyCommandLineRunner都是当项目启动后执行，一般我们可以将缓存预热之类的操作放到这里执行。

那么另外的两个监听器要怎么才会启动监听呢？这个先不急，我们来看看 MyApplicationRunner和MyCommandLineRunner 的参数怎么用。

4. MyApplicationRunner和MyCommandLineRunner的参数使用

4.1 打印 MyApplicationRunner和MyCommandLineRunner 的 args 参数

// 项目启动后执行
@Component
public class MyCommandLineRunner implements CommandLineRunner {
    @Override
    public void run(String... args) throws Exception {
        System.out.println("CommandLineRunner run... args: " + Arrays.asList(args));
    }
}
// 项目启动后执行
@Component
public class MyApplicationRunner implements ApplicationRunner {
    @Override
    public void run(ApplicationArguments args) throws Exception {
        System.out.println("ApplicationRunner run... args: " + Arrays.asList(args.getSourceArgs()));
    }
}

打印信息如下：


20-SpringBoot事件监听_spring boot_04

可以看到，现在传递的参数为空数组。

如果需要传递参数，则是可以配置在项目的启动命令上。

4.2 配置项目的启动命令


20-SpringBoot事件监听_接口_0520-SpringBoot事件监听_spring boot_06

此时，再启动服务，我们来看看传递的参数如下：


20-SpringBoot事件监听_java_07

5.配置使用 MyApplicationContextInitializer 和 MySpringApplicationRunListener 的监听器

5.1 需要在 META-INF/spring.factories 配置注册两个实现类


20-SpringBoot事件监听_接口_08

org.springframework.context.ApplicationContextInitializer=com.lijw.springbootlistener.listener.MyApplicationContextInitializer

org.springframework.boot.SpringApplicationRunListener=com.lijw.springbootlistener.listener.MySpringApplicationRunListener

此时，我们再执行启动服务，可以发现报错如下：


20-SpringBoot事件监听_spring_09

// main方法中出现异常，异常由于接口MySpringApplicationRunListener实现类报错
Exception in thread "main" java.lang.IllegalArgumentException: Cannot instantiate interface org.springframework.boot.SpringApplicationRunListener : com.lijw.springbootlistener.listener.MySpringApplicationRunListener
 at org.springframework.boot.SpringApplication.createSpringFactoriesInstances(SpringApplication.java:456)
 at org.springframework.boot.SpringApplication.getSpringFactoriesInstances(SpringApplication.java:438)
 at org.springframework.boot.SpringApplication.getRunListeners(SpringApplication.java:426)
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:293)
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312)
 at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
 at com.lijw.springbootlistener.SpringbootListenerApplication.main(SpringbootListenerApplication.java:10)
// MySpringApplicationRunListener报错的类型为缺少方法，缺少了 <init>(org.springframework.boot.SpringApplication, [Ljava.lang.String;) 也就是缺少了 构造器方法。
Caused by: java.lang.NoSuchMethodException: com.lijw.springbootlistener.listener.MySpringApplicationRunListener.<init>(org.springframework.boot.SpringApplication, [Ljava.lang.String;)
 at java.lang.Class.getConstructor0(Class.java:3082)
 at java.lang.Class.getDeclaredConstructor(Class.java:2178)
 at org.springframework.boot.SpringApplication.createSpringFactoriesInstances(SpringApplication.java:451)
 ... 6 more

Process finished with exit code 1

在查看如何设置构造器的方法上，我们可以查看这个接口的其他实现类：


20-SpringBoot事件监听_spring boot_10

5.2 MySpringApplicationRunListener的使用要添加构造器


20-SpringBoot事件监听_zookeeper_1120-SpringBoot事件监听_zookeeper_12

package com.lijw.springbootlistener.listener;

import org.springframework.boot.ConfigurableBootstrapContext;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.SpringApplicationRunListener;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.env.ConfigurableEnvironment;

import java.time.Duration;

public class MySpringApplicationRunListener implements SpringApplicationRunListener {


    public MySpringApplicationRunListener(SpringApplication application, String[] args){

    }

    @Override
    public void starting(ConfigurableBootstrapContext bootstrapContext) {
        System.out.println("SpringApplicationRunListener starting..");
    }

    @Override
    public void environmentPrepared(ConfigurableBootstrapContext bootstrapContext, ConfigurableEnvironment environment) {
        System.out.println("SpringApplicationRunListener environmentPrepared..");
    }

    @Override
    public void contextPrepared(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener contextPrepared");
    }

    @Override
    public void contextLoaded(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener contextLoaded");
    }

    @Override
    public void started(ConfigurableApplicationContext context, Duration timeTaken) {
        System.out.println("SpringApplicationRunListener started");
    }

    @Override
    public void ready(ConfigurableApplicationContext context, Duration timeTaken) {
        System.out.println("SpringApplicationRunListener ready");
    }

    @Override
    public void running(ConfigurableApplicationContext context) {
        System.out.println("SpringApplicationRunListener running");
    }

    @Override
    public void failed(ConfigurableApplicationContext context, Throwable exception) {
        System.out.println("SpringApplicationRunListener failed");
    }
}

执行打印的日志：

SpringApplicationRunListener starting..
SpringApplicationRunListener environmentPrepared..

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.6.4)

ApplicationContextInitializer initialize...
SpringApplicationRunListener contextPrepared
2022-02-27 08:54:55.785  INFO 15164 --- [           main] c.l.s.SpringbootListenerApplication      : Starting SpringbootListenerApplication using Java 1.8.0_91 on regalli-NB0 with PID 15164 (D:\javaProject\maven-practice01\springboot-listener\target\classes started by lijw in D:\javaProject\maven-practice01)
2022-02-27 08:54:55.785  INFO 15164 --- [           main] c.l.s.SpringbootListenerApplication      : No active profile set, falling back to 1 default profile: "default"
SpringApplicationRunListener contextLoaded
2022-02-27 08:54:56.255  INFO 15164 --- [           main] c.l.s.SpringbootListenerApplication      : Started SpringbootListenerApplication in 0.9 seconds (JVM running for 1.838)
SpringApplicationRunListener started
ApplicationRunner run... args: [name=libai, age=32]
CommandLineRunner run... args: [name=libai, age=32]
SpringApplicationRunListener ready

Process finished with exit code 0



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