Java ThreadLocal线程封闭
共饮一杯无 人气:0线程封闭
线程封闭一般通过以下三个方法:
- Ad-hoc线程封闭:程序控制实现,最糟糕,忽略
- 堆栈封闭:局部变量,无并发问题
- ThreadLocal线程封闭:特别好的封闭方法
方法2是最常用的,变量定义在接口内,本文主要讲解方法三,SpringBoot项目通过自定义过滤器和拦截器实现ThreadLocal线程封闭。实现Filter接口自定义过滤器和继承HandlerInterceptorAdapter自定义拦截器。
ThreadLocal线程封闭实现步骤
封装ThredLocal的方法
/** * <p>自定义RequestHolder</p></p> * * @Author zjq * @Date 2021/12 */ public class RequestHolder { private final static ThreadLocal<Long> requestHolder = new ThreadLocal<>(); public static void set(Long id) { requestHolder.set(id); } public static Long get() { return requestHolder.get(); } public static void remove() { requestHolder.remove(); } }
自定义过滤器
自定义定义拦截器继承Filter接口,实现ThredLocal.add()方法
/** * <p>自定义过滤器</p> * * @Author zjq * @Date 2021/12/7 */ @Slf4j public class HttpFilter implements Filter { /** * 为Filter初始化 提供支持 * * @param filterConfig * @throws ServletException */ @Override public void init(FilterConfig filterConfig) throws ServletException { } /** * 拦截到要执行的请求时,doFilter就会执行。这里我们可以写对请求和响应的预处理。 * FilterChain把请求和响应传递给下一个 Filter处理 * * @param servletRequest * @param servletResponse * @param filterChain * @throws IOException * @throws ServletException */ @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { //把普通servlet强转成httpServlet HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest; Long threadId = Thread.currentThread().getId(); log.info("do filter,threadId:{} servletPath:{}", threadId, httpServletRequest.getServletPath()); //把当前线程id放入requestHolder RequestHolder.set(threadId); //放行 filterChain.doFilter(httpServletRequest, servletResponse); } /** * Filter 实例销毁前的准备工作 */ @Override public void destroy() { } }
自定义拦截器
自定义拦截器在线程使用完毕后移除ThredLocal中内容,避免内存溢出
/** * <p>自定义拦截器</p> * * @Author zjq * @Date 2021/12/7 */ @Slf4j public class HttpInterceptor extends HandlerInterceptorAdapter { /** * 拦截处理程序的执行。在 HandlerMapping 确定合适的处理程序对象之后,在 HandlerAdapter 调用处理程序之前调用。 * @param request * @param response * @param handler * @return * @throws Exception */ @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { log.info("preHandle执行。。。"); return true; } /** * 请求处理完成后(渲染视图后)的回调。将在处理程序执行的任何结果上调用,从而允许进行适当的资源清理。 * @param request * @param response * @param handler * @param ex * @throws Exception */ @Override public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { RequestHolder.remove(); log.info("afterCompletion执行。。。"); return; } }
Application类启动类中配置自定义过滤器和拦截器
/** * * @author zjq */ @SpringBootApplication public class Application extends WebMvcConfigurationSupport { public static void main(String[] args) { SpringApplication.run(ConcurrencyApplication.class, args); } /** * 自定义过滤器 * @return */ @Bean public FilterRegistrationBean filterRegistrationBean(){ FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(); filterRegistrationBean.setFilter(new HttpFilter()); //设置自定义过滤器拦截的url filterRegistrationBean.addUrlPatterns("/threadLocal/*"); return filterRegistrationBean; } /** * 定义自定义拦截器原先需要继承WebMvcConfigurerAdapter * SpringBoot2.0后WebMvcConfigurerAdapter被定义成过时了,推荐使用继承WebMvcConfigurationSupport * @param registry */ @Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(new HttpInterceptor()).addPathPatterns("/**"); } }
定义调用接口
/** * ThreadLocal测试controller * @author zjq */ @Controller @RequestMapping("/threadLocal") public class ThreadLocalController { @RequestMapping("/test") @ResponseBody public Long test() { return RequestHolder.get(); } }
请求访问验证
访问调用接口http://localhost:8080/threadLocal/test,控制台输出如下:
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