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教育网站都有哪些,工程竣工验收公示网,外贸企业有哪些公司,头像设计logo今天我们来聊聊一个即将改变我们编程习惯的新特性——ScopedValue。有些小伙伴在工作中#xff0c;一提到线程内数据传递就想到ThreadLocal#xff0c;但真正用起来却遇到各种坑#xff1a;内存泄漏、数据污染、性能问题等等。其实#xff0c;ScopedValue就像ThreadLocal的…今天我们来聊聊一个即将改变我们编程习惯的新特性——ScopedValue。有些小伙伴在工作中一提到线程内数据传递就想到ThreadLocal但真正用起来却遇到各种坑内存泄漏、数据污染、性能问题等等。其实ScopedValue就像ThreadLocal的升级版既保留了优点又解决了痛点。我们一起聊聊ScopedValue的优势和用法希望对你会有所帮助。加苏三的工作内推群一、ThreadLocal的痛点在介绍ScopedValue之前我们先回顾一下ThreadLocal的常见问题。有些小伙伴可能会想ThreadLocal用得好好的为什么要换其实ThreadLocal在设计上存在一些固有缺陷。ThreadLocal的内存泄漏问题为了更直观地理解ThreadLocal的内存泄漏问题我画了一个内存泄漏的示意图imageThreadLocal的典型问题代码/*** ThreadLocal典型问题演示*/public class ThreadLocalProblems {private static final ThreadLocalUserContext userContext new ThreadLocal();private static final ThreadLocalConnection connectionHolder new ThreadLocal();/*** 问题1内存泄漏 - 忘记调用remove()*/public void processRequest(HttpServletRequest request) {// 设置用户上下文UserContext context new UserContext(request.getHeader(X-User-Id));userContext.set(context);try {// 业务处理businessService.process();// 问题忘记调用 userContext.remove()// 在线程池中这个线程被重用时还会保留之前的用户信息} catch (Exception e) {// 异常处理}}/*** 问题2数据污染 - 线程复用导致数据混乱*/public void processMultipleRequests() {// 线程池处理多个请求ExecutorService executor Executors.newFixedThreadPool(5);for (int i 0; i 10; i) {final int userId i;executor.submit(() - {// 设置用户上下文userContext.set(new UserContext(user_ userId));try {// 模拟业务处理Thread.sleep(100);// 问题如果线程被复用这里可能读取到错误的用户信息String currentUser userContext.get().getUserId();System.out.println(处理用户: currentUser);} catch (InterruptedException e) {Thread.currentThread().interrupt();} finally {// 即使调用remove也可能因为异常跳过userContext.remove(); // 不保证一定执行}});}executor.shutdown();}/*** 问题3继承性问题 - 子线程无法继承父线程数据*/public void parentChildThreadProblem() {userContext.set(new UserContext(parent_user));Thread childThread new Thread(() - {// 这里获取不到父线程的ThreadLocal值UserContext context userContext.get(); // nullSystem.out.println(子线程用户: context); // 输出null// 需要手动传递数据});childThread.start();}/*** 问题4性能问题 - 大量ThreadLocal影响性能*/public void performanceProblem() {long startTime System.currentTimeMillis();for (int i 0; i 100000; i) {ThreadLocalString tl new ThreadLocal();tl.set(value_ i);String value tl.get();tl.remove();}long endTime System.currentTimeMillis();System.out.println(ThreadLocal操作耗时: (endTime - startTime) ms);}}/*** 用户上下文*/class UserContext {private final String userId;private final long timestamp;public UserContext(String userId) {this.userId userId;this.timestamp System.currentTimeMillis();}public String getUserId() {return userId;}public long getTimestamp() {return timestamp;}Overridepublic String toString() {return UserContext{userId userId , timestamp timestamp };}}ThreadLocal问题的根本原因生命周期管理复杂需要手动调用set/remove容易遗漏内存泄漏风险线程池中线程复用Value无法被GC继承性差子线程无法自动继承父线程数据性能开销ThreadLocalMap的哈希表操作有开销有些小伙伴可能会问我们用InheritableThreadLocal不就能解决继承问题了吗我的经验是InheritableThreadLocal只是缓解了问题但带来了新的复杂度而且性能更差。二、ScopedValue新一代线程局部变量ScopedValue是Java 20中引入的预览特性在Java 21中成为正式特性。它旨在解决ThreadLocal的痛点提供更安全、更高效的线程内数据传递方案。ScopedValue的核心设计理念为了更直观地理解ScopedValue的工作原理我画了一个ScopedValue的架构图imageScopedValue的核心优势imageScopedValue基础用法/*** ScopedValue基础用法演示*/public class ScopedValueBasics {// 1. 定义ScopedValue相当于ThreadLocalprivate static final ScopedValueUserContext USER_CONTEXT ScopedValue.newInstance();private static final ScopedValueConnection DB_CONNECTION ScopedValue.newInstance();private static final ScopedValueString REQUEST_ID ScopedValue.newInstance();/*** 基础用法在作用域内使用ScopedValue*/public void basicUsage() {UserContext user new UserContext(user_123);// 在作用域内绑定值ScopedValue.runWhere(USER_CONTEXT, user, () - {// 在这个作用域内USER_CONTEXT.get()返回user_123System.out.println(当前用户: USER_CONTEXT.get().getUserId());// 可以嵌套使用ScopedValue.runWhere(REQUEST_ID, req_456, () - {System.out.println(请求ID: REQUEST_ID.get());System.out.println(用户: USER_CONTEXT.get().getUserId());});// 这里REQUEST_ID已经超出作用域获取会抛出异常});// 这里USER_CONTEXT已经超出作用域}/*** 带返回值的作用域*/public String scopedValueWithReturn() {UserContext user new UserContext(user_789);// 使用callWhere获取返回值String result ScopedValue.callWhere(USER_CONTEXT, user, () - {// 业务处理String userId USER_CONTEXT.get().getUserId();return 处理用户: userId;});return result;}/*** 多个ScopedValue同时使用*/public void multipleScopedValues() {UserContext user new UserContext(user_multi);Connection conn createConnection();// 同时绑定多个ScopedValueScopedValue.runWhere(ScopedValue.where(USER_CONTEXT, user).where(DB_CONNECTION, conn).where(REQUEST_ID, multi_req),() - {// 在这个作用域内可以访问所有绑定的值processBusinessLogic();});// 作用域结束后自动清理}/*** 异常处理示例*/public void exceptionHandling() {UserContext user new UserContext(user_exception);try {ScopedValue.runWhere(USER_CONTEXT, user, () - {// 业务处理processBusinessLogic();// 如果抛出异常作用域也会正常结束if (someCondition()) {throw new RuntimeException(业务异常);}});} catch (RuntimeException e) {// 异常处理System.out.println(捕获异常: e.getMessage());}// 即使发生异常USER_CONTEXT也会自动清理}private Connection createConnection() {// 创建数据库连接return null;}private void processBusinessLogic() {// 业务逻辑处理UserContext user USER_CONTEXT.get();System.out.println(处理业务逻辑用户: user.getUserId());}private boolean someCondition() {return Math.random() 0.5;}}三、ScopedValue vs ThreadLocal全面对比有些小伙伴可能还想知道ScopedValue到底比ThreadLocal强在哪里。让我们通过详细的对比来看看。3.1 内存管理对比为了更直观地理解两者的内存管理差异我画了几张图做对比。ThreadLocal的内存模型图imageScopedValue的内存模型图image二者的关键差异如下图image3.2 代码对比示例/*** ThreadLocal vs ScopedValue 对比演示*/public class ThreadLocalVsScopedValue {// ThreadLocal方式private static final ThreadLocalUserContext TL_USER_CONTEXT new ThreadLocal();private static final ThreadLocalConnection TL_CONNECTION new ThreadLocal();// ScopedValue方式private static final ScopedValueUserContext SV_USER_CONTEXT ScopedValue.newInstance();private static final ScopedValueConnection SV_CONNECTION ScopedValue.newInstance();/*** ThreadLocal方式 - 传统实现*/public void processRequestThreadLocal(HttpServletRequest request) {// 设置上下文UserContext userContext new UserContext(request.getHeader(X-User-Id));TL_USER_CONTEXT.set(userContext);Connection conn null;try {// 获取数据库连接conn dataSource.getConnection();TL_CONNECTION.set(conn);// 业务处理processBusinessLogic();} catch (SQLException e) {// 异常处理handleException(e);} finally {// 必须手动清理 - 容易忘记TL_USER_CONTEXT.remove();TL_CONNECTION.remove();// 关闭连接if (conn ! null) {try {conn.close();} catch (SQLException e) {// 日志记录}}}}/*** ScopedValue方式 - 现代实现*/public void processRequestScopedValue(HttpServletRequest request) {UserContext userContext new UserContext(request.getHeader(X-User-Id));// 使用try-with-resources管理连接try (Connection conn dataSource.getConnection()) {// 在作用域内执行自动管理生命周期ScopedValue.runWhere(ScopedValue.where(SV_USER_CONTEXT, userContext).where(SV_CONNECTION, conn),() - {// 业务处理processBusinessLogic();});// 作用域结束后自动清理无需手动remove} catch (SQLException e) {handleException(e);}}/*** 业务逻辑处理 - 两种方式对比*/private void processBusinessLogic() {// ThreadLocal方式 - 需要处理null值UserContext tlUser TL_USER_CONTEXT.get();if (tlUser null) {throw new IllegalStateException(用户上下文未设置);}Connection tlConn TL_CONNECTION.get();if (tlConn null) {throw new IllegalStateException(数据库连接未设置);}// ScopedValue方式 - 在作用域内保证不为nullUserContext svUser SV_USER_CONTEXT.get(); // 不会为nullConnection svConn SV_CONNECTION.get(); // 不会为null// 实际业务处理...System.out.println(处理用户: svUser.getUserId());}/*** 线程池场景对比*/public void threadPoolComparison() {ExecutorService executor Executors.newFixedThreadPool(5);// ThreadLocal方式 - 容易出问题for (int i 0; i 10; i) {final int userId i;executor.submit(() - {TL_USER_CONTEXT.set(new UserContext(user_ userId));try {processBusinessLogic();} finally {TL_USER_CONTEXT.remove(); // 容易忘记或异常跳过}});}// ScopedValue方式 - 更安全for (int i 0; i 10; i) {final int userId i;executor.submit(() - {UserContext user new UserContext(user_ userId);ScopedValue.runWhere(SV_USER_CONTEXT, user, () - {processBusinessLogic(); // 自动管理生命周期});});}executor.shutdown();}private Connection getConnectionFromTL() {return TL_CONNECTION.get();}private DataSource dataSource null; // 模拟数据源private void handleException(SQLException e) {} // 异常处理}3.3 性能对比测试/*** 性能对比测试*/BenchmarkMode(Mode.AverageTime)OutputTimeUnit(TimeUnit.MICROSECONDS)State(Scope.Thread)public class PerformanceComparison {private static final ThreadLocalString THREAD_LOCAL new ThreadLocal();private static final ScopedValueString SCOPED_VALUE ScopedValue.newInstance();private static final int ITERATIONS 100000;/*** ThreadLocal性能测试*/Benchmarkpublic void threadLocalPerformance() {for (int i 0; i ITERATIONS; i) {THREAD_LOCAL.set(value_ i);String value THREAD_LOCAL.get();THREAD_LOCAL.remove();}}/*** ScopedValue性能测试*/Benchmarkpublic void scopedValuePerformance() {for (int i 0; i ITERATIONS; i) {ScopedValue.runWhere(SCOPED_VALUE, value_ i, () - {String value SCOPED_VALUE.get();// 自动清理无需remove});}}/*** 实际场景性能测试*/public void realScenarioTest() {long tlStart System.nanoTime();// ThreadLocal场景THREAD_LOCAL.set(initial_value);for (int i 0; i ITERATIONS; i) {String current THREAD_LOCAL.get();THREAD_LOCAL.set(current _ i);}THREAD_LOCAL.remove();long tlEnd System.nanoTime();// ScopedValue场景long svStart System.nanoTime();ScopedValue.runWhere(SCOPED_VALUE, initial_value, () - {String current SCOPED_VALUE.get();for (int i 0; i ITERATIONS; i) {// ScopedValue是不可变的需要重新绑定String newValue current _ i;ScopedValue.runWhere(SCOPED_VALUE, newValue, () - {// 嵌套作用域String nestedValue SCOPED_VALUE.get();});}});long svEnd System.nanoTime();System.out.printf(ThreadLocal耗时: %d ns%n, tlEnd - tlStart);System.out.printf(ScopedValue耗时: %d ns%n, svEnd - svStart);}}四、ScopedValue高级特性有些小伙伴掌握了基础用法后还想了解更高级的特性。ScopedValue确实提供了很多强大的功能。4.1 结构化并发支持ScopedValue与虚拟线程和结构化并发完美配合/*** ScopedValue与结构化并发*/public class StructuredConcurrencyExample {private static final ScopedValueUserContext USER_CONTEXT ScopedValue.newInstance();private static final ScopedValueRequestInfo REQUEST_INFO ScopedValue.newInstance();/*** 结构化并发中的ScopedValue使用*/public void structuredConcurrencyWithScopedValue() throws Exception {UserContext user new UserContext(structured_user);RequestInfo request new RequestInfo(req_123, System.currentTimeMillis());try (var scope new StructuredTaskScope.ShutdownOnFailure()) {ScopedValue.runWhere(ScopedValue.where(USER_CONTEXT, user).where(REQUEST_INFO, request),() - {// 在作用域内提交子任务FutureString userTask scope.fork(this::fetchUserData);FutureString orderTask scope.fork(this::fetchOrderData);FutureString paymentTask scope.fork(this::fetchPaymentData);try {// 等待所有任务完成scope.join();scope.throwIfFailed();// 处理结果String userData userTask.resultNow();String orderData orderTask.resultNow();String paymentData paymentTask.resultNow();System.out.println(聚合结果: userData , orderData , paymentData);} catch (InterruptedException | ExecutionException e) {Thread.currentThread().interrupt();throw new RuntimeException(任务执行失败, e);}});}}private String fetchUserData() {// 可以访问ScopedValue无需参数传递UserContext user USER_CONTEXT.get();RequestInfo request REQUEST_INFO.get();return 用户数据: user.getUserId() , 请求: request.getRequestId();}private String fetchOrderData() {UserContext user USER_CONTEXT.get();return 订单数据: user.getUserId();}private String fetchPaymentData() {UserContext user USER_CONTEXT.get();return 支付数据: user.getUserId();}}class RequestInfo {private final String requestId;private final long timestamp;public RequestInfo(String requestId, long timestamp) {this.requestId requestId;this.timestamp timestamp;}public String getRequestId() { return requestId; }public long getTimestamp() { return timestamp; }}4.2 继承和嵌套作用域/*** ScopedValue继承和嵌套*/public class ScopedValueInheritance {private static final ScopedValueString PARENT_VALUE ScopedValue.newInstance();private static final ScopedValueString CHILD_VALUE ScopedValue.newInstance();/*** 作用域嵌套*/public void nestedScopes() {ScopedValue.runWhere(PARENT_VALUE, parent_value, () - {System.out.println(外层作用域: PARENT_VALUE.get());// 内层作用域可以访问外层值ScopedValue.runWhere(CHILD_VALUE, child_value, () - {System.out.println(内层作用域 - 父值: PARENT_VALUE.get());System.out.println(内层作用域 - 子值: CHILD_VALUE.get());// 可以重新绑定父值遮蔽ScopedValue.runWhere(PARENT_VALUE, shadowed_parent, () - {System.out.println(遮蔽作用域 - 父值: PARENT_VALUE.get());System.out.println(遮蔽作用域 - 子值: CHILD_VALUE.get());});// 恢复原来的父值System.out.println(恢复作用域 - 父值: PARENT_VALUE.get());});// 子值已超出作用域try {System.out.println(CHILD_VALUE.get()); // 抛出异常} catch (Exception e) {System.out.println(子值已超出作用域: e.getMessage());}});}/*** 虚拟线程中的继承*/public void virtualThreadInheritance() throws Exception {ScopedValue.runWhere(PARENT_VALUE, virtual_parent, () - {try (var scope new StructuredTaskScope.ShutdownOnFailure()) {// 虚拟线程自动继承ScopedValuefor (int i 0; i 3; i) {final int taskId i;scope.fork(() - {// 可以访问父线程的ScopedValueString parentVal PARENT_VALUE.get();return 任务 taskId - 父值: parentVal;});}scope.join();scope.throwIfFailed();}});}/*** 条件绑定*/public void conditionalBinding() {String condition Math.random() 0.5 ? case_a : case_b;ScopedValue.runWhere(PARENT_VALUE, condition, () - {String value PARENT_VALUE.get();if (case_a.equals(value)) {System.out.println(处理情况A);} else {System.out.println(处理情况B);}});}}4.3 错误处理和调试/*** ScopedValue错误处理和调试*/public class ScopedValueErrorHandling {private static final ScopedValueString MAIN_VALUE ScopedValue.newInstance();private static final ScopedValueInteger COUNT_VALUE ScopedValue.newInstance();/*** 异常处理*/public void exceptionHandling() {try {ScopedValue.runWhere(MAIN_VALUE, test_value, () - {// 业务逻辑processWithError();});} catch (RuntimeException e) {System.out.println(捕获异常: e.getMessage());// ScopedValue已自动清理无需额外处理}// 验证值已清理try {String value MAIN_VALUE.get();System.out.println(不应该执行到这里: value);} catch (Exception e) {System.out.println(值已正确清理: e.getMessage());}}/*** 调试信息*/public void debugInformation() {ScopedValue.runWhere(ScopedValue.where(MAIN_VALUE, debug_value).where(COUNT_VALUE, 42),() - {// 获取当前绑定的所有ScopedValueSystem.out.println(当前作用域绑定:);System.out.println(MAIN_VALUE: MAIN_VALUE.get());System.out.println(COUNT_VALUE: COUNT_VALUE.get());// 模拟复杂调试debugComplexScenario();});}/*** 资源清理保证*/public void resourceCleanupGuarantee() {ListString cleanupLog new ArrayList();ScopedValue.runWhere(MAIN_VALUE, resource_value, () - {// 注册清理钩子Runtime.getRuntime().addShutdownHook(new Thread(() - {cleanupLog.add(资源清理完成);}));// 即使这里发生异常ScopedValue也会清理if (Math.random() 0.5) {throw new RuntimeException(模拟异常);}});// 检查清理情况System.out.println(清理日志: cleanupLog);}private void processWithError() {throw new RuntimeException(业务处理异常);}private void debugComplexScenario() {// 复杂的调试场景ScopedValue.runWhere(COUNT_VALUE, COUNT_VALUE.get() 1, () - {System.out.println(嵌套调试 - COUNT_VALUE: COUNT_VALUE.get());});}}五、实战案例有些小伙伴可能还想看更复杂的实战案例。让我们用一个Web应用中的用户上下文管理来展示ScopedValue在真实项目中的应用。为了更直观地理解Web应用中ScopedValue的应用我画了一个请求处理流程的架构图imageScopedValue的生命周期如下图所示image优势如下图所示image5.1 定义Web应用中的ScopedValue/*** Web应用ScopedValue定义*/public class WebScopedValues {// 用户上下文public static final ScopedValueUserContext USER_CONTEXT ScopedValue.newInstance();// 请求信息public static final ScopedValueRequestInfo REQUEST_INFO ScopedValue.newInstance();// 数据库连接可选public static final ScopedValueConnection DB_CONNECTION ScopedValue.newInstance();// 追踪IDpublic static final ScopedValueString TRACE_ID ScopedValue.newInstance();}/*** 用户上下文详细信息*/class UserContext {private final String userId;private final String username;private final ListString roles;private final MapString, Object attributes;private final Locale locale;public UserContext(String userId, String username, ListString roles,MapString, Object attributes, Locale locale) {this.userId userId;this.username username;this.roles Collections.unmodifiableList(new ArrayList(roles));this.attributes Collections.unmodifiableMap(new HashMap(attributes));this.locale locale;}// Getter方法public String getUserId() { return userId; }public String getUsername() { return username; }public ListString getRoles() { return roles; }public MapString, Object getAttributes() { return attributes; }public Locale getLocale() { return locale; }public boolean hasRole(String role) {return roles.contains(role);}public Object getAttribute(String key) {return attributes.get(key);}}/*** 请求信息*/class RequestInfo {private final String requestId;private final String method;private final String path;private final String clientIp;private final MapString, String headers;public RequestInfo(String requestId, String method, String path,String clientIp, MapString, String headers) {this.requestId requestId;this.method method;this.path path;this.clientIp clientIp;this.headers Collections.unmodifiableMap(new HashMap(headers));}// Getter方法public String getRequestId() { return requestId; }public String getMethod() { return method; }public String getPath() { return path; }public String getClientIp() { return clientIp; }public MapString, String getHeaders() { return headers; }}5.2 过滤器实现/*** 认证过滤器 - 使用ScopedValue*/ComponentSlf4jpublic class AuthenticationFilter implements Filter {Autowiredprivate UserService userService;Autowiredprivate JwtTokenProvider tokenProvider;Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {HttpServletRequest httpRequest (HttpServletRequest) request;HttpServletResponse httpResponse (HttpServletResponse) response;// 生成请求IDString requestId generateRequestId();// 提取请求信息RequestInfo requestInfo extractRequestInfo(httpRequest, requestId);// 认证用户UserContext userContext authenticateUser(httpRequest);// 在作用域内执行请求处理ScopedValue.runWhere(ScopedValue.where(WebScopedValues.REQUEST_INFO, requestInfo).where(WebScopedValues.USER_CONTEXT, userContext).where(WebScopedValues.TRACE_ID, requestId),() - {try {chain.doFilter(request, response);} catch (Exception e) {log.error(请求处理异常, e);throw new RuntimeException(过滤器异常, e);}});// 作用域结束后自动清理所有ScopedValuelog.info(请求处理完成: {}, requestId);}private String generateRequestId() {return req_ System.currentTimeMillis() _ ThreadLocalRandom.current().nextInt(1000, 9999);}private RequestInfo extractRequestInfo(HttpServletRequest request, String requestId) {MapString, String headers new HashMap();EnumerationString headerNames request.getHeaderNames();while (headerNames.hasMoreElements()) {String headerName headerNames.nextElement();headers.put(headerName, request.getHeader(headerName));}return new RequestInfo(requestId,request.getMethod(),request.getRequestURI(),request.getRemoteAddr(),headers);}private UserContext authenticateUser(HttpServletRequest request) {String authHeader request.getHeader(Authorization);if (authHeader ! null authHeader.startsWith(Bearer )) {String token authHeader.substring(7);return tokenProvider.validateToken(token);}// 返回匿名用户return new UserContext(anonymous,Anonymous User,List.of(GUEST),Map.of(source, web),request.getLocale());}}5.3 业务层使用/*** 用户服务 - 使用ScopedValue*/ServiceSlf4jTransactionalpublic class UserService {Autowiredprivate UserRepository userRepository;Autowiredprivate OrderService orderService;/*** 获取当前用户信息*/public UserProfile getCurrentUserProfile() {UserContext userContext WebScopedValues.USER_CONTEXT.get();RequestInfo requestInfo WebScopedValues.REQUEST_INFO.get();String traceId WebScopedValues.TRACE_ID.get();log.info([{}] 获取用户资料: {}, traceId, userContext.getUserId());// 根据用户ID查询用户信息User user userRepository.findById(userContext.getUserId()).orElseThrow(() - new UserNotFoundException(用户不存在: userContext.getUserId()));// 构建用户资料return UserProfile.builder().userId(user.getId()).username(user.getUsername()).email(user.getEmail()).roles(userContext.getRoles()).locale(userContext.getLocale()).lastLogin(user.getLastLoginTime()).build();}/*** 更新用户信息*/public void updateUserProfile(UpdateProfileRequest request) {UserContext userContext WebScopedValues.USER_CONTEXT.get();String traceId WebScopedValues.TRACE_ID.get();log.info([{}] 更新用户资料: {}, traceId, userContext.getUserId());// 验证权限if (!userContext.getUserId().equals(request.getUserId())) {throw new PermissionDeniedException(无权更新其他用户资料);}// 更新用户信息User user userRepository.findById(request.getUserId()).orElseThrow(() - new UserNotFoundException(用户不存在: request.getUserId()));user.setEmail(request.getEmail());user.setUpdateTime(LocalDateTime.now());userRepository.save(user);log.info([{}] 用户资料更新成功: {}, traceId, userContext.getUserId());}/*** 获取用户订单列表*/public ListOrder getUserOrders() {UserContext userContext WebScopedValues.USER_CONTEXT.get();// 调用订单服务无需传递用户IDreturn orderService.getUserOrders();}}/*** 订单服务*/ServiceSlf4jTransactionalpublic class OrderService {Autowiredprivate OrderRepository orderRepository;public ListOrder getUserOrders() {UserContext userContext WebScopedValues.USER_CONTEXT.get();String traceId WebScopedValues.TRACE_ID.get();log.info([{}] 查询用户订单: {}, traceId, userContext.getUserId());// 直接从ScopedValue获取用户ID无需参数传递return orderRepository.findByUserId(userContext.getUserId());}/*** 创建订单*/public Order createOrder(CreateOrderRequest request) {UserContext userContext WebScopedValues.USER_CONTEXT.get();String traceId WebScopedValues.TRACE_ID.get();log.info([{}] 创建订单: 用户{}, traceId, userContext.getUserId());// 创建订单Order order new Order();order.setOrderId(generateOrderId());order.setUserId(userContext.getUserId());order.setAmount(request.getTotalAmount());order.setStatus(OrderStatus.CREATED);order.setCreateTime(LocalDateTime.now());Order savedOrder orderRepository.save(order);log.info([{}] 订单创建成功: {}, traceId, savedOrder.getOrderId());return savedOrder;}private String generateOrderId() {return ORD System.currentTimeMillis() ThreadLocalRandom.current().nextInt(1000, 9999);}}5.4 Controller层/*** 用户控制器 - 使用ScopedValue*/RestControllerRequestMapping(/api/users)Slf4jpublic class UserController {Autowiredprivate UserService userService;/*** 获取当前用户资料*/GetMapping(/profile)public ResponseEntityUserProfile getCurrentUserProfile() {// 无需传递用户ID直接从ScopedValue获取UserProfile profile userService.getCurrentUserProfile();return ResponseEntity.ok(profile);}/*** 更新用户资料*/PutMapping(/profile)public ResponseEntityVoid updateUserProfile(RequestBody Valid UpdateProfileRequest request) {userService.updateUserProfile(request);return ResponseEntity.ok().build();}/*** 获取用户订单*/GetMapping(/orders)public ResponseEntityListOrder getUserOrders() {ListOrder orders userService.getUserOrders();return ResponseEntity.ok(orders);}/*** 异常处理*/ExceptionHandler({UserNotFoundException.class, PermissionDeniedException.class})public ResponseEntityErrorResponse handleUserExceptions(RuntimeException e) {// 可以从ScopedValue获取请求信息用于日志String traceId WebScopedValues.TRACE_ID.get();log.error([{}] 用户操作异常: {}, traceId, e.getMessage());ErrorResponse error new ErrorResponse(e.getClass().getSimpleName(),e.getMessage(),traceId);return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(error);}}/*** 错误响应*/DataAllArgsConstructorclass ErrorResponse {private String error;private String message;private String traceId;private long timestamp System.currentTimeMillis();}六、迁移指南从ThreadLocal到ScopedValue有些小伙伴可能担心迁移成本其实从ThreadLocal迁移到ScopedValue并不复杂。6.1 迁移步骤/*** ThreadLocal到ScopedValue迁移指南*/public class MigrationGuide {// ThreadLocal定义旧方式private static final ThreadLocalUserContext TL_USER new ThreadLocal();private static final ThreadLocalConnection TL_CONN new ThreadLocal();private static final ThreadLocalString TL_TRACE new ThreadLocal();// ScopedValue定义新方式private static final ScopedValueUserContext SV_USER ScopedValue.newInstance();private static final ScopedValueConnection SV_CONN ScopedValue.newInstance();private static final ScopedValueString SV_TRACE ScopedValue.newInstance();/*** 迁移前ThreadLocal方式*/public void beforeMigration() {// 设置值TL_USER.set(new UserContext(user_old));TL_TRACE.set(trace_old);