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在开发过程中，很多时候我们会使用ThreadLocal来临时缓存数据，当一次数据请求执行完成后需要主动执行释放当前ThreadLocal缓存数据资源，防止未能及时释放导致下一次访问时候ThreadLocal依然保持上一次缓存的数据。

spring提供两种方式去监听一次请求完成事件。
1、HandlerInterceptor -> afterCompletion 使用拦截方式，再执行完成后执行afterCompletion
2、ApplicationListener -> ServletRequestHandledEvent ，ApplicationListener 提供的是监听那种事件类型，ServletRequestHandledEvent 就是一次请求结束后的事件。

通过上述两种方式可以很方便的在一次请求完成移除当前线程ThreadLocal。

ThreadLocal 工具

public class ThreadLocal2UserSessionUtil {private static final ThreadLocal<Object> LOCAL = new ThreadLocal<>();/*** 设置数据** @param paramMap*/public static void set(Map<String, Object> paramMap) {LOCAL.set(paramMap);}/*** 获取值** @return*/public static Map<String, Object> get() {if (Objects.isNull(LOCAL.get())) {return new HashMap<>();} else {return (Map<String, Object>) LOCAL.get();}}/*** 获取值** @return*/public static Object get(String key) {Map<String, Object> resMap = (Map<String, Object>) LOCAL.get();if (null == resMap) {return null;}return (null != resMap.get(key)) ? resMap.get(key) : null;}/*** 每次取出数据后必须清空 否则就会出现值重复*/public static void remove() {LOCAL.remove();}/*** 获取app登录token** @return*/public static String getToken4App() {Map<String, Object> map = get();return (null == map) ? "" : (String) map.get(EncryptReqParamNameConstant.PARAM_TOKEN);}/*** 初始化数值** @return*/public static void pushUserToken4App(String appToken) {Map<String, Object> localMap = get();if (StringUtil.isNotBlank(appToken)) {localMap.put(EncryptReqParamNameConstant.PARAM_TOKEN, appToken);set(localMap);}}/*** 初始化数值** @return*/public static void pushUserId4App(Long userId) {Map<String, Object> localMap = get();if (null != userId) {localMap.put(EncryptReqParamNameConstant.USER_ID, userId);set(localMap);}}/*** 初始化数值  注意这里只有加解密才将用户id放入** @return*/public static Long getUserId4App() {Map<String, Object> map = get();return (null == map) ? null : (Long) map.get(EncryptReqParamNameConstant.USER_ID);}
}

HandlerInterceptor 方式

@Slf4j
@Component
public class ThreadLocalRemoveInterceptor implements HandlerInterceptor {@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {HandlerInterceptor.super.afterCompletion(request, response, handler, ex);ThreadLocal2UserSessionUtil.remove();}
}

在web控制器中加入监听器

@Configuration
public class PathPrefixMvcConfigurer implements WebMvcConfigurer {@Autowiredprivate ThreadLocalRemoveInterceptor threadLocalRemoveInterceptor;@Overridepublic void addInterceptors(InterceptorRegistry registry) {registry.addInterceptor(threadLocalRemoveInterceptor).addPathPatterns("/*");}
}

2、通过监听器方式

@Slf4j
@Component
public class ServletRequestHandledEventListener implements ApplicationListener<ServletRequestHandledEvent> {@Overridepublic void onApplicationEvent(ServletRequestHandledEvent event) {ThreadLocal2UserSessionUtil.remove();}
}

完成