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Custom filters and interceptors implement ThreadLocal thread closure

2022-08-05 09:29:00 【51CTO】

线程封闭
ThreadLocalThread closure implementation steps

封装ThredLocal的方法
自定义过滤器
自定义拦截器
ApplicationConfigure custom filters and interceptors in the class startup class
定义调用接口
Request access verification

线程封闭

Thread closure is generally done in the following three ways：

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,Variables are defined within interfaces,This article mainly explains method three,SpringBootProjects are implemented with custom filters and interceptorsThreadLocal线程封闭.实现FilterInterface custom filters and inheritanceHandlerInterceptorAdapter自定义拦截器.

ThreadLocalThread closure implementation steps

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();
    }

}

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自定义过滤器

Custom definition interceptor inheritanceFilter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.Here we can write preprocessing for requests and responses. * FilterChainPass the request and response to the next one 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 Preparations before the instance is destroyed */
    @Override
    public void destroy() {

    }
}

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自定义拦截器

The custom interceptor is removed after the thread has finished using itThredLocal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 After determining the appropriate handler object,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,This allows for proper resource cleanup. * @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;
    }
}

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ApplicationConfigure custom filters and interceptors in the class startup class

/** * * @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());
        //Set custom filters to blockurl
        filterRegistrationBean.addUrlPatterns("/threadLocal/*");
        return filterRegistrationBean;
    }

    /** * Defining custom interceptors originally required inheritanceWebMvcConfigurerAdapter * SpringBoot2.0后WebMvcConfigurerAdapteris defined as obsolete,推荐使用继承WebMvcConfigurationSupport * @param registry */
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new HttpInterceptor()).addPathPatterns("/**");
    }
}

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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();
    }
}

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