feat:增加SpringBoot 线程与事件文档
This commit is contained in:
333
docs/Web/SpringBoot/SpringBoot-Thread.md
Normal file
333
docs/Web/SpringBoot/SpringBoot-Thread.md
Normal file
@@ -0,0 +1,333 @@
|
||||
---
|
||||
title: SpringBoot 线程与事件
|
||||
date: 2026-06-02
|
||||
---
|
||||
|
||||
# 一、基本概念
|
||||
  **进程**：进程是操作系统资源分配的最小单位，每个进程都有独立的内存空间（代码段、数据段、堆、栈），比如打开一个应用程序，就是一个进程。
|
||||
  **线程**：线程是 CPU 调度的最小单位，线程共享所属进程的内存空间。 比如一个HTTP请求就是一个线程。
|
||||
  **协程**：协程是 用户态的轻量级“线程”，由程序自己调度，不依赖操作系统，切换成本极低。
|
||||
  创建线程方法：
|
||||
```java
|
||||
// 继承 Thread 不推荐
|
||||
class MyThread extends Thread {
|
||||
@Override
|
||||
public void run() {
|
||||
System.out.println("线程运行中：" + Thread.currentThread().getName());
|
||||
}
|
||||
}
|
||||
|
||||
public class Test {
|
||||
public static void main(String[] args) {
|
||||
MyThread t = new MyThread();
|
||||
t.start(); // ✅ 启动线程
|
||||
}
|
||||
}
|
||||
|
||||
// 实现 Runnable
|
||||
class MyRunnable implements Runnable {
|
||||
@Override
|
||||
public void run() {
|
||||
System.out.println("线程运行中：" + Thread.currentThread().getName());
|
||||
}
|
||||
}
|
||||
|
||||
public class Test2 {
|
||||
public static void main(String[] args) {
|
||||
Thread t = new Thread(new MyRunnable());
|
||||
t.start();
|
||||
}
|
||||
}
|
||||
|
||||
// Lambda 写法
|
||||
Thread t = new Thread(() -> {
|
||||
System.out.println("Hello Thread");
|
||||
});
|
||||
t.start();
|
||||
|
||||
// 线程池
|
||||
ThreadPoolExecutor executor = new ThreadPoolExecutor(
|
||||
2, // 核心线程数
|
||||
4, // 最大线程数
|
||||
60,
|
||||
TimeUnit.SECONDS,
|
||||
new LinkedBlockingQueue<>(100),
|
||||
Executors.defaultThreadFactory(),
|
||||
new ThreadPoolExecutor.AbortPolicy()
|
||||
);
|
||||
```
|
||||
|
||||
  **SpringBoot线程池**:
|
||||
```java
|
||||
// 1. 启动类加上 @EnableAsync 注解
|
||||
@EnableAsync
|
||||
@SpringBootApplication
|
||||
public class Application {
|
||||
|
||||
}
|
||||
|
||||
// 2. 线程池配置
|
||||
@Bean
|
||||
public Executor taskExecutor() {
|
||||
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
|
||||
executor.setCorePoolSize(5);
|
||||
executor.setMaxPoolSize(10);
|
||||
executor.setQueueCapacity(20);
|
||||
executor.initialize();
|
||||
return executor;
|
||||
}
|
||||
|
||||
// 3. 调用方法上加上 @Async 注解
|
||||
@Service
|
||||
public class OrderService {
|
||||
|
||||
@Async
|
||||
public void createOrder() {
|
||||
System.out.println(Thread.currentThread().getName());
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
# 二、案例
|
||||
  案例：电商秒杀系统。
|
||||
- 资源竞争：多个用户抢同一件商品（多线程抢锁）。
|
||||
- 异步解耦：扣减库存后，需要发短信、发优惠券（多线程并行）。
|
||||
- 系统解耦：订单系统不应依赖短信系统（事件驱动）。
|
||||
|
||||
# 二、JDK原生线程通信
|
||||
- synchronized：锁住库存，防止超卖。
|
||||
- wait/notify：通知消息线程“库存已扣，可以发通知了”。
|
||||
- Thread+ ExecutorService：实现多线程并行发通知。
|
||||
|
||||
## 2.1 共享资源
|
||||
```java
|
||||
/**
|
||||
* 商品库存（共享资源）
|
||||
*/
|
||||
public class Stock {
|
||||
// 假设只有 1 件库存
|
||||
public int count = 1;
|
||||
// 信号：是否有人下单成功
|
||||
public volatile boolean ordered = false;
|
||||
}
|
||||
```
|
||||
|
||||
## 2.2 下单线程
|
||||
```java
|
||||
/**
|
||||
* 用户下单线程
|
||||
*/
|
||||
public class OrderWorker extends Thread {
|
||||
|
||||
private final Stock stock;
|
||||
|
||||
public OrderWorker(Stock stock) {
|
||||
this.stock = stock;
|
||||
}
|
||||
|
||||
@Override
|
||||
public void run() {
|
||||
// 1. 锁住库存，防止超卖
|
||||
synchronized (stock) {
|
||||
if (stock.count > 0) {
|
||||
System.out.println(Thread.currentThread().getName() + " 抢到锁，准备扣库存");
|
||||
stock.count--;
|
||||
stock.ordered = true;
|
||||
System.out.println("库存扣减成功，剩余：" + stock.count);
|
||||
stock.notifyAll(); // 通知消息线程
|
||||
} else {
|
||||
System.out.println(Thread.currentThread().getName() + " 没抢到，库存不足");
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## 2.3 消息分发线程
|
||||
```java
|
||||
/**
|
||||
* 消息分发线程
|
||||
* 负责监听下单成功信号，并启动线程池发通知
|
||||
*/
|
||||
public class MessageDispatcher extends Thread {
|
||||
|
||||
private final Stock stock;
|
||||
private final ExecutorService pool;
|
||||
|
||||
public MessageDispatcher(Stock stock, ExecutorService pool) {
|
||||
this.stock = stock;
|
||||
this.pool = pool;
|
||||
}
|
||||
|
||||
@Override
|
||||
public void run() {
|
||||
synchronized (stock) {
|
||||
try {
|
||||
while (!stock.ordered) {
|
||||
System.out.println("消息线程：等待下单信号...");
|
||||
stock.wait(); // 没下单就死等
|
||||
}
|
||||
} catch (InterruptedException e) {
|
||||
Thread.currentThread().interrupt();
|
||||
}
|
||||
|
||||
System.out.println("消息线程：收到下单成功信号，开始并行发通知！");
|
||||
|
||||
// 2. 并行执行通知任务
|
||||
pool.execute(() -> System.out.println("线程池任务：发送短信"));
|
||||
pool.execute(() -> System.out.println("线程池任务：发放优惠券"));
|
||||
pool.execute(() -> System.out.println("线程池任务：更新用户积分"));
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## 2.4 主程序
|
||||
```java
|
||||
import java.util.concurrent.ExecutorService;
|
||||
import java.util.concurrent.Executors;
|
||||
|
||||
public class TraditionalDemo {
|
||||
|
||||
public static void main(String[] args) {
|
||||
Stock stock = new Stock();
|
||||
ExecutorService pool = Executors.newFixedThreadPool(3);
|
||||
|
||||
// 消息线程先启动（等待）
|
||||
new MessageDispatcher(stock, pool).start();
|
||||
|
||||
// 模拟 3 个用户同时下单（竞争）
|
||||
new OrderWorker(stock).start();
|
||||
new OrderWorker(stock).start();
|
||||
new OrderWorker(stock).start();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
# 三、SpringBoot 异步方法
|
||||
- @Transactional：保证库存扣减的事务性。
|
||||
- @Async：将发短信、发券等耗时操作丢给线程池，立即释放 Tomcat 线程。
|
||||
|
||||
## 3.1 配置线程池
|
||||
```java
|
||||
@Configuration
|
||||
@EnableAsync
|
||||
public class AsyncConfig {
|
||||
|
||||
@Bean("orderExecutor")
|
||||
public Executor orderExecutor() {
|
||||
ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
|
||||
executor.setCorePoolSize(5);
|
||||
executor.setThreadNamePrefix("Order-Async-");
|
||||
executor.initialize();
|
||||
return executor;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## 3.2 订单服务
|
||||
```java
|
||||
@Service
|
||||
public class OrderService {
|
||||
|
||||
@Autowired
|
||||
private StockService stockService;
|
||||
@Autowired
|
||||
private NotifyService notifyService;
|
||||
|
||||
/**
|
||||
* 下单主流程
|
||||
*/
|
||||
public void createOrder() {
|
||||
// 1. 扣库存（核心，同步）
|
||||
boolean success = stockService.decreaseStock();
|
||||
if (!success) {
|
||||
throw new RuntimeException("库存不足");
|
||||
}
|
||||
|
||||
// 2. 异步通知（非核心，并行）
|
||||
notifyService.sendSms();
|
||||
notifyService.sendCoupon();
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## 3.3 通知服务
|
||||
```java
|
||||
@Service
|
||||
public class NotifyService {
|
||||
|
||||
// 指定使用哪个线程池
|
||||
@Async("orderExecutor")
|
||||
public void sendSms() {
|
||||
System.out.println(Thread.currentThread().getName() + " 发送短信");
|
||||
}
|
||||
|
||||
@Async("orderExecutor")
|
||||
public void sendCoupon() {
|
||||
System.out.println(Thread.currentThread().getName() + " 发放优惠券");
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
# 四、SpringBoot 事件机制
|
||||
- 事件（Event）：下单成功这个“事实”。
|
||||
- 发布者（Publisher）：只负责发布事件，不关心后续。
|
||||
- 监听者（Listener）：谁关心下单成功，谁就干活（且可以异步）。
|
||||
|
||||
## 4.1 定义事件
|
||||
```java
|
||||
public class OrderCreatedEvent {
|
||||
private final String orderId;
|
||||
|
||||
public OrderCreatedEvent(String orderId) {
|
||||
this.orderId = orderId;
|
||||
}
|
||||
|
||||
public String getOrderId() {
|
||||
return orderId;
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## 4.2 发布事件
|
||||
```java
|
||||
@Service
|
||||
public class OrderService {
|
||||
|
||||
@Autowired
|
||||
private StockService stockService;
|
||||
|
||||
@Autowired
|
||||
private ApplicationEventPublisher publisher;
|
||||
|
||||
public void createOrder() {
|
||||
// 1. 扣库存
|
||||
boolean success = stockService.decreaseStock();
|
||||
if (success) {
|
||||
// 2. 发布事件（我不关心谁处理）
|
||||
publisher.publishEvent(new OrderCreatedEvent("ORDER_123"));
|
||||
}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
## 4.3 监听事件
|
||||
```java
|
||||
@Component
|
||||
public class OrderListener {
|
||||
|
||||
// 监听下单事件，并异步执行
|
||||
@EventListener
|
||||
@Async("orderExecutor")
|
||||
public void handleSendSms(OrderCreatedEvent event) {
|
||||
System.out.println(Thread.currentThread().getName() + " 监听到事件，发送短信");
|
||||
}
|
||||
|
||||
@EventListener
|
||||
@Async("orderExecutor")
|
||||
public void handleSendCoupon(OrderCreatedEvent event) {
|
||||
System.out.println(Thread.currentThread().getName() + " 监听到事件，发放优惠券");
|
||||
}
|
||||
}
|
||||
```
|
||||
Reference in New Issue
Block a user