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Java子線程調(diào)用RequestContextHolder.getRequestAttributes()方法問(wèn)題詳解

更新時(shí)間：2022年09月27日 09:43:51 作者：ypp91zr

這篇文章主要介紹了Java子線程調(diào)用RequestContextHolder.getRequestAttributes()方法問(wèn)題處理，文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

相信很多開發(fā)過(guò)程中都用過(guò)RequestContextHolder.getRequestAttributes()，沒(méi)錯(cuò)，我也經(jīng)常用，但今天出現(xiàn)了問(wèn)題，獲取到的實(shí)例是空的

原因是因?yàn)槲倚麻_了一個(gè)子線程，在子線程調(diào)用了RequestContextHolder.getRequestAttributes()。實(shí)際獲取到的是空的

然后查看了源碼

ThreadLocal獲取。一個(gè)請(qǐng)求到達(dá)容器后，Spring會(huì)把該請(qǐng)求Request實(shí)例通過(guò)setRequestAttributes方法把Request實(shí)例放入該請(qǐng)求線程內(nèi)ThreadLocalMap中，然后就可以通過(guò)靜態(tài)方法取到。原理就是ThreadLocal，但ThreadLocal不能讓子線程繼承ThreadLocalMap信息，可以使用InherbritableThreadLocal實(shí)現(xiàn)子線程信息傳遞。

Spring Boot 默認(rèn)使用ThreadLocal把Request設(shè)置進(jìn)請(qǐng)求線程中，這樣如果在請(qǐng)求方法里面另起一個(gè)子線程然后再通過(guò)getRequestAttributes方法獲取，是獲取不到的

如果想要在子線程獲取,設(shè)置inheritable=true即可，但我一直沒(méi)找到在哪里可以設(shè)置，于是自己就寫了個(gè)工具類來(lái)讓子線程獲取，思路是自定義一個(gè)注解，攔截注解，將父線程的ServletRequestAttributes給InheritableThreadLocal，然后在子線程即可獲取

package com.shinedata.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface RequestInheritableThread {
}

AOP

package com.shinedata.aop;
import com.shinedata.util.context.RequestHolder;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.ServletRequestAttributes;
@Aspect
@Component
public class RequestHolderAspect {
    @Before("@annotation(com.shinedata.annotation.RequestInheritableThread)")
    public void doBefore(JoinPoint joinPoint) {
        ServletRequestAttributes servletRequestAttributes = RequestHolder.getServletRequestAttributes();
        RequestHolder.setServletRequestAttributes(servletRequestAttributes);
    }
    @After("@annotation(com.shinedata.annotation.RequestInheritableThread)")
    public void doAfter(JoinPoint joinPoint) {
        RequestHolder.removeServletRequestAttributes();
    }
}

工具類

package com.shinedata.util.context;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;
/**
 * @ClassName RequestHolder
 * @Author yupanpan
 */
public class RequestHolder {
    private static final Logger logger = LoggerFactory.getLogger(RequestHolder.class);
    public static final String GET = "GET";
    public static final String POST = "POST";
    public static final String UTF8 = "UTF-8";
    public static InheritableThreadLocal<ServletRequestAttributes> servletRequestAttributesInheritableThreadLocal= new InheritableThreadLocal();
    public static HttpServletRequest getRequest() {
        return getServletRequestAttributes().getRequest();
    }
    public static HttpServletResponse getResponse() {
        return getServletRequestAttributes().getResponse();
    }
    public static ServletRequestAttributes setServletRequestAttributes(ServletRequestAttributes servletRequestAttributes) {
        servletRequestAttributesInheritableThreadLocal.set(servletRequestAttributes);
        return servletRequestAttributes;
    }
    public static void removeServletRequestAttributes() {
        servletRequestAttributesInheritableThreadLocal.remove();
    }
    public static ServletRequestAttributes getServletRequestAttributes() {
        ServletRequestAttributes requestAttributes = (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();
        if(requestAttributes==null){
            requestAttributes=servletRequestAttributesInheritableThreadLocal.get();
        }
        return requestAttributes;
    }
}

需要在子線程獲取ServletRequestAttributes使用的時(shí)候在父方法貼個(gè)注解@RequestInheritableThread就行了，父方法里面即使開子線程，子線程里面也能獲取ServletRequestAttributes

補(bǔ)充第二種解決辦法,在開啟新線程之前，將RequestAttributes對(duì)象設(shè)置為子線程共享

//開啟新線程之前，添加代碼：
ServletRequestAttributes sra = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
RequestContextHolder.setRequestAttributes(sra, true);

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