public class ThreadLocalExample {
// 創(chuàng)建一個(gè) ThreadLocal 實(shí)例
private static final ThreadLocal threadLocal = new ThreadLocal<>();
public static void main(String[] args) {
    // 創(chuàng)建多個(gè)線程
    for (int i = 0; i < 5; i++) {
        new Thread(() -> {
            // 為每個(gè)線程設(shè)置不同的值
            threadLocal.set((int) (Math.random() * 100));
            try {
                // 模擬線程執(zhí)行時(shí)間
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            // 獲取并打印當(dāng)前線程的值
            System.out.println("Thread " + Thread.currentThread().getId() + ": " + threadLocal.get());
            // 清除 ThreadLocal 變量，避免內(nèi)存泄漏
            threadLocal.remove();
        }).start();
    }
}
}

/**
 * User
 * @author senfel
 * @version 1.0
 * @date 2025/2/18 17:00
 */
@AllArgsConstructor
@NoArgsConstructor
@Data
public class User {
    private String id;
    private String username;
}

/**
 * UserContext
 * @author senfel
 * @version 1.0
 * @date 2025/2/18 17:01
 */
public class UserContext {
    // 創(chuàng)建一個(gè) ThreadLocal 實(shí)例來存儲(chǔ) User 對(duì)象
    private static final ThreadLocal<User> userThreadLocal = new ThreadLocal<>();
    // 設(shè)置用戶數(shù)據(jù)
    public static void setUser(User user) {
        userThreadLocal.set(user);
    }
    // 獲取用戶數(shù)據(jù)
    public static User getUser() {
        return userThreadLocal.get();
    }
    // 刪除用戶數(shù)據(jù)
    public static void clearUser() {
        userThreadLocal.remove();
    }
}

/**
 * UserInterceptor
 * @author senfel
 * @version 1.0
 * @date 2025/2/18 17:03
 */
@Component
public class UserInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 模擬從請求中獲取用戶數(shù)據(jù)
        String userId = request.getParameter("userId");
        String username = request.getParameter("username");
        if (userId == null || username == null) {
            response.getWriter().write("User ID and Username are required.");
            return false;
        }
        // 創(chuàng)建 User 對(duì)象并存儲(chǔ)在 ThreadLocal 中
        User user = new User(userId, username);
        UserContext.setUser(user);
        return true;
    }
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        // 清除 ThreadLocal 中的用戶數(shù)據(jù)，避免內(nèi)存泄漏
        UserContext.clearUser();
    }
}

/**
 * WebConfig
 * @author senfel
 * @version 1.0
 * @date 2025/2/18 17:10
 */
@Configuration
public class WebConfig implements WebMvcConfigurer {
    @Autowired
    private UserInterceptor userInterceptor;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(userInterceptor).addPathPatterns("/**");
    }