高效多线程管理！SpringBoot 3.4 中 ThreadLocal 的使用与坑点！

package com.icoderoad.example;


public class ThreadLocalExample {
    // 创建一个 ThreadLocal 实例
    private static final ThreadLocal<Integer> threadLocal = new ThreadLocal<>();


    public static void main(String[] args) {
        // 创建多个线程
        for (int i = 0; i < 5; i++) {
            new Thread(() -> {
                // 为每个线程设置不同的值
                threadLocal.set((int) (Math.random() * 100));
                try {
                    // 模拟线程执行时间
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                // 获取并打印当前线程的值
                System.out.println("Thread " + Thread.currentThread().getId() + ": " + threadLocal.get());
                // 清除 ThreadLocal 变量，避免内存泄漏
                threadLocal.remove();
            }).start();
        }
    }
}
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package com.icoderoad.entity;


import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;


@AllArgsConstructor
@NoArgsConstructor
@Data
public class User {
    private String id;
    private String username;
}
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package com.icoderoad.context;


public class UserContext {
    // 创建一个 ThreadLocal 实例来存储 User 对象
    private static final ThreadLocal<User> userThreadLocal = new ThreadLocal<>();


    // 设置用户数据
    public static void setUser(User user) {
        userThreadLocal.set(user);
    }


    // 获取用户数据
    public static User getUser() {
        return userThreadLocal.get();
    }


    // 删除用户数据
    public static void clearUser() {
        userThreadLocal.remove();
    }
}
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package com.icoderoad.interceptor;


import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;


import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


@Component
public class UserInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // 从请求中获取用户数据
        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;
        }
        // 创建 User 对象并存储在 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 中的用户数据，避免内存泄漏
        UserContext.clearUser();
    }
}
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package com.icoderoad.config;


import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;


@Configuration
public class WebConfig implements WebMvcConfigurer {


    @Autowired
    private UserInterceptor userInterceptor;


    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(userInterceptor).addPathPatterns("/**");
    }
}
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