詳解SpringBoot實現ApplicationEvent事件的監聽與發佈

<?xml version="1.0" encoding="UTF-8"?>
<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>2.7.7</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

package com.example.demo.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;


/**
 * 線程池參數配置
 **/
@EnableAsync
@Configuration
public class TaskPoolConfig {
    /**
     * 自定義線程池
     **/
    @Bean
    public Executor taskExecutor() {
        //返回可用處理器的Java虛擬機的數量 12
        int i = Runtime.getRuntime().availableProcessors();
        System.out.println("系統最大線程數  ： " + i);

        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        //核心線程池大小
        executor.setCorePoolSize(16);
        //最大線程數
        executor.setMaxPoolSize(20);
        //配置隊列容量，默認值為Integer.MAX_VALUE
        executor.setQueueCapacity(99999);
        //活躍時間
        executor.setKeepAliveSeconds(60);
        //線程名字前綴
        executor.setThreadNamePrefix("asyncServiceExecutor -");
        //設置此執行程序應該在關閉時阻止的最大秒數，以便在容器的其餘部分繼續關閉之前等待剩餘的任務完成他們的執行
        executor.setAwaitTerminationSeconds(60);
        //等待所有的任務結束後再關閉線程池
        executor.setWaitForTasksToCompleteOnShutdown(true);

        return executor;
    }
}

package com.example.demo.entity;

import lombok.Data;

@Data
public class EmailDto {
    private String email;
    private String subject;
    private String content;
}

package com.example.demo.event;

import com.example.demo.entity.EmailDto;
import org.springframework.context.ApplicationEvent;

/**
 * 自定義事件
 */
public class SendEmailEvent extends ApplicationEvent {
    private EmailDto emailDto;

    public SendEmailEvent(EmailDto emailDto) {
        super(emailDto);
        this.emailDto = emailDto;
    }

    public EmailDto getEmailDto() {
        return this.emailDto;
    }
}

package com.example.demo.listener;

import com.example.demo.entity.EmailDto;
import com.example.demo.event.SendEmailEvent;
import com.example.demo.service.SendEmailService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Component;

/**
 * 事件監聽器
 */
@Component
public class SendEmailListener implements ApplicationListener<SendEmailEvent> {
    @Autowired
    private SendEmailService sendEmailService;

    @Async
    @Override
    public void onApplicationEvent(SendEmailEvent event) {
        EmailDto emailDto = event.getEmailDto();
        this.sendEmailService.sendEmail(emailDto);
    }
}

package com.example.demo.service;

import com.example.demo.entity.EmailDto;

public interface SendEmailService {
    void sendEmail(EmailDto emailDto);
}

package com.example.demo.service.impl;

import com.example.demo.entity.EmailDto;
import com.example.demo.service.SendEmailService;
import org.springframework.stereotype.Service;

@Service
public class SendEmailServiceImpl implements SendEmailService {
    @Override
    public void sendEmail(EmailDto emailDto) {
        try {
            // 模擬耗時3秒
            Thread.sleep(3 * 1000);
        } catch (Exception e) {
            System.out.println("Email發送異常");
        }

        System.out.println("Email發送成功 " + emailDto);
    }
}

package com.example.demo.controller;

import com.example.demo.entity.EmailDto;
import com.example.demo.event.SendEmailEvent;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;


@RestController
public class IndexController {
    @Autowired
    private ApplicationEventPublisher publisher;

    @GetMapping("/sendEmail")
    public String sendEmail() {
        EmailDto emailDto = new EmailDto();
        emailDto.setEmail("[email protected]");
        emailDto.setSubject("郵件標題");
        emailDto.setContent("郵件內容");

        // 發佈事件
        publisher.publishEvent(new SendEmailEvent(emailDto));
        return "success";
    }
}