线程封闭示例将Request中的信息封闭在ThreadLocal中

最新推荐文章于 2024-02-23 14:10:45 发布

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本文介绍了一个使用ThreadLocal存储线程私有数据的例子。通过过滤器在请求开始时将线程ID存入ThreadLocal，并在请求结束时通过拦截器清除，确保每个请求间的数据隔离，防止内存泄漏。

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ThreadLocal工具类

线程通过该工具类，将线程私有的数据存入ThreadLocal中；

public class RequestHolder {

    private final static ThreadLocal<Long> requestHolder = new ThreadLocal<>();

    /**
     * 将当前线程的ID存储到ThreadLocal中
     * @param id
     */
    public static void add(Long id) {
        requestHolder.set(id);
    }

    public static Long getId() {
        return requestHolder.get();
    }

    /**
     * 在请求处理完成后，从ThreadLocal中将本次请求的相关信息清除，
     * 以免造成内存泄漏；
     */
    public static void remove() {
        requestHolder.remove();
    }

}

过滤器

在请求到达Controller前，将线程id存入ThreadLocal中；

import com.example.concurrency.example.threadlocal.RequestHolder;
import lombok.extern.slf4j.Slf4j;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

@Slf4j
public class HttpFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {}

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        log.info("do filter, {}, {}", Thread.currentThread().getId(), request.getServletPath());
        RequestHolder.add(Thread.currentThread().getId());
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {}
    
}

拦截器

在请求处理完成后，将当前线程的线程id从ThreadLocal中删除，避免内存泄漏；

import com.example.concurrency.example.threadlocal.RequestHolder;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

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

@Slf4j
public class HttpInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        log.info("preHandle");
        return true;
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        RequestHolder.remove();
        log.info("afterCompletion");
        return;
    }
    
}

Controller

处理请求，在处理的时候可以从ThreadLocal中把线程id取出来；

@Controller
@RequestMapping("/threadLocal")
public class ThreadLocalController {

    @RequestMapping("/test")
    @ResponseBody
    public Long test() {
        return RequestHolder.getId();
    }

}

Springboot启动类

在启动类中注册过滤器和拦截器；

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@SpringBootApplication
public class ConcurrencyApplication extends WebMvcConfigurerAdapter {

    public static void main(String[] args) {
        SpringApplication.run(ConcurrencyApplication.class, args);
    }

    @Bean
    public FilterRegistrationBean httpFilter() {
        FilterRegistrationBean registrationBean = new FilterRegistrationBean();
        registrationBean.setFilter(new HttpFilter());
        registrationBean.addUrlPatterns("/threadLocal/*");
        return registrationBean;
    }

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

}

发送请求

{{host}}/threadLocal/test

响应：

2019-03-28 16:49:32.659 INFO 2432 --- [nio-8080-exec-1] com.example.concurrency.HttpFilter : do filter, 31, /threadLocal/test
2019-03-28 16:49:32.670 INFO 2432 --- [nio-8080-exec-1] com.example.concurrency.HttpInterceptor : preHandle
2019-03-28 16:49:32.742 INFO 2432 --- [nio-8080-exec-1] com.example.concurrency.HttpInterceptor : afterCompletion