关于ThreadLocal对request和response的用法说明

2023-07-18 15:34:03 294

记得在一篇博文中看到描述threadLocal的一句话：

ThreadLocal除了适用于多线程保证每条线程都有自己的变量副本外，还适用于在线程上下文中共享某些变量值。

这两种说法是有区别的。前者强调的是，使用ThreadLocal对副本做保护，避免同步、加锁，降低效率；后者强调的是，某个变量线程上下文中，A处用到、B处用到、C处用到，先在入口处set一个值，后使用ThreadLocal的get方法直接在需要用到的地方拿这个值。

项目中，最近理由cookie存值，使用到了threadLocal这个字段，自己就想去研究下，原理这里跟后者强调的一样，上代码：

1.web.xml里边配置过滤器，拦截请求，做处理


InterceptorFilter
com.fx.anniversary.core.filter.InterceptorFilter


InterceptorFilter
/*

2.赋值

publicclassInterceptorFilterimplementsFilter{
publicvoiddestroy(){

}
publicvoiddoFilter(ServletRequestrequest,ServletResponseresponse,FilterChainchain)throwsIOException,ServletException{
HttpServletRequesthttpRequest=(HttpServletRequest)request;
HttpServletResponsehttpResponse=(HttpServletResponse)response;
InterceptorContext.setRequest(httpRequest);
InterceptorContext.setResponse(httpResponse);
try{
chain.doFilter(request,
response);
}finally{
//不管有木有出现异常，finally块中代码都会执行;在这里，相当于只服务于当前请求。
InterceptorContext.removeRequest();
InterceptorContext.removeResponse();
}
}
publicvoidinit(FilterConfigfilterConfig)throwsServletException{

}
}

3.InterceptorContext实体

publicclassInterceptorContext{
privatestaticThreadLocal_request=newThreadLocal();
privatestaticThreadLocal_response=newThreadLocal();
publicstaticvoidsetRequest(HttpServletRequestrequest){
_request.set(request);
}
publicstaticHttpServletRequestgetRequest(){
HttpServletRequestrequest=_request.get();returnrequest;
}
publicstaticvoidremoveRequest(){
_request.remove();
}
publicstaticvoidsetResponse(HttpServletResponseresponse){
_response.set(response);
}
publicstaticHttpServletResponsegetResponse(){
HttpServletResponseresponse=_response.get();
returnresponse;
}
publicstaticvoidremoveResponse(){
_response.remove();
}
}

4.项目中的开始调用。（因为这两个方法调用的地方太多，每次都带一个参数也比较繁琐，所以采用这种方式，文章开头总结过）

publicStringgetAttribute(Stringkey){
HttpServletRequestrequest=InterceptorContext.getRequest();
Cookie[]cookies=request.getCookies();
if(cookies!=null){
for(Cookiecookie:cookies){
if(cookie.getName().equals(key)){
returncookie.getValue();
}
}
}
return"";
}
@Override
publicvoidsetAttribute(Stringkey,Stringvalue){
HttpServletResponseresponse=InterceptorContext.getResponse();
Cookiecookie=newCookie(key,value);
response.addCookie(cookie);
}

补充知识：利用ThreadLocal管理request和session以及用户信息，实现Useanywhere

1.我们有时需要获取request或session中的数据的时候，首先需要获取request和session对象，这个通常是在Controller的时候当做入参获取，这样方法的入参会显得很长很臃肿的感觉。这就是的出发点，接下来就展示一下是如何实现的。

2.首先我们写个一个拦截器：WebContextFilter

packagecom.office.common.filter;
importjava.io.IOException;
importjavax.servlet.FilterChain;
importjavax.servlet.ServletException;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importorg.springframework.web.filter.OncePerRequestFilter;
importcom.office.common.context.WebContextHolder;

/**
*webcontent信息加载到TheadLocal中
*@authorNeo
*@date2017年10月20日11:38:45
*/
publicclassWebContextFilterextendsOncePerRequestFilter{

	publicWebContextFilter(){
	}

	protectedvoiddoFilterInternal(HttpServletRequestrequest,HttpServletResponseresponse,FilterChainfilterChain)
			throwsServletException,IOException{
		if(request==null||response==null){
			return;
		}else{
			WebContextHolder.setRequest(request);
			WebContextHolder.setResponse(response);
			filterChain.doFilter(request,response);
			return;
		}
	}
}

3.然后我们将写好的拦截器配置到web.xml中：



	
	ArchetypeCreatedWebApplication

	
		contextConfigLocation
		
	

	
		encodingFilter
		org.springframework.web.filter.CharacterEncodingFilter
		
			encoding
			UTF-8
		
		
			forceEncoding
			true
		
	
	
		encodingFilter
		/*
	
	
	
	
	
	
		webContentFilter
		com.office.common.filter.WebContextFilter
	
	
		webContentFilter
		/*
	
	
		org.springframework.web.context.ContextLoaderListener
	
	

	
		springMVC
		org.springframework.web.servlet.DispatcherServlet
		
			contextConfigLocation
			classpath*:applicationContext.xml
		
		1
	
	
		springMVC
		/

4.编写一个同一个管理操作工具类：WebContextHolder

packagecom.office.common.context;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importjavax.servlet.http.HttpSession;
importcom.office.common.dto.UserDTO;

/**
*上下文
*@authorNeo
*@date2017年10月20日11:42:57
*/
@SuppressWarnings({"rawtypes","unchecked"})
publicclassWebContextHolder{

	publicWebContextHolder(){
	}

	publicstaticStringgetRequestIp(){
		if(getRequest()==null)
			returnnull;
		HttpServletRequestrequest=getRequest();
		Stringip=request.getHeader("X-Forwarded-For");
		if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip)){
			if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip))
				ip=request.getHeader("Proxy-Client-IP");
			if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip))
				ip=request.getHeader("WL-Proxy-Client-IP");
			if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip))
				ip=request.getHeader("HTTP_CLIENT_IP");
			if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip))
				ip=request.getHeader("HTTP_X_FORWARDED_FOR");
			if(ip==null||ip.length()==0||"unknown".equalsIgnoreCase(ip))
				ip=request.getRemoteAddr();
		}elseif(ip.length()>15){
			Stringips[]=ip.split(",");
			intindex=0;
			do{
				if(index>=ips.length)
					break;
				StringstrIp=ips[index];
				if(!"unknown".equalsIgnoreCase(strIp)){
					ip=strIp;
					break;
				}
				index++;
			}while(true);
		}
		returnip;
	}

	publicstaticHttpServletRequestgetRequest(){
		if(requestLocal==null)
			returnnull;
		else
			return(HttpServletRequest)requestLocal.get();
	}

	publicstaticStringgetContextPath(){
		if(getRequest()==null)
			returnnull;
		else
			return(newStringBuilder()).append(getRequest().getContextPath()).append("/").toString();
	}

	publicstaticStringgetCurrRequestURI(){
		if(getRequest()==null)
			returnnull;
		else
			return(newStringBuilder()).append(getRequest().getRequestURI().replace(getRequest().getContextPath(),""))
					.append("/").toString();
	}

	publicstaticHttpServletResponsegetResponse(){
		if(responseLocal==null)
			returnnull;
		else
			return(HttpServletResponse)responseLocal.get();
	}

	publicstaticHttpSessiongetSession(){
		if(requestLocal==null)
			returnnull;
		if(requestLocal.get()==null)
			returnnull;
		else
			return((HttpServletRequest)requestLocal.get()).getSession();
	}

	publicstaticUserDTOgetLoginUserSession(ClassloginUserClass){
		if(getSession()==null)
			returnnull;
		Objectobj=getSession().getAttribute(CURRENT_USER);
		if(obj==null)
			returnnull;
		else
			return(UserDTO)obj;
	}

	publicstaticUserDTOgetLoginUserSession(){
		returngetLoginUserSession(UserDTO.class);
	}

	publicstaticvoidcreateLoginUserSession(UserDTOloginUser){
		if(loginUser!=null)
			getSession().setAttribute(CURRENT_USER,loginUser);
	}

	publicstaticvoiddestroyLoginUserSession(){
		if(getLoginUserSession()!=null){
			getSession().removeAttribute(CURRENT_USER);
			getSession().invalidate();
		}
	}

	publicstaticvoidsetRequest(HttpServletRequestrequest){
		if(requestLocal==null)
			requestLocal=newThreadLocal();
		requestLocal.set(request);
	}

	publicstaticvoidsetResponse(HttpServletResponseresponse){
		if(responseLocal==null)
			responseLocal=newThreadLocal();
		responseLocal.set(response);
	}
	
/**
*获取项目请求的根目录
*
*@returneg:http://localhost:8080/projectName
*/
	publicstaticStringgetProjectRequestRootPath(){
		HttpServletRequestrequest=WebContextHolder.getRequest();
		StringBuffersb=newStringBuffer();
		sb.append(request.getScheme()).
		append("://").
		append(request.getServerName()).
		append(":").
		append(request.getServerPort()).
		append(request.getContextPath()).
		append("/");
		returnsb.toString();
	}

	privatestaticThreadLocalrequestLocal;
	privatestaticThreadLocalresponseLocal;
	publicstaticStringCURRENT_USER="CURRENT_USER";

}

5.使用展示：

//我们可以在任何地方使用这种方法取值

WebContextHolder.getRequest().getParameter("id");

以上这篇关于ThreadLocal对request和response的用法说明就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持毛票票。

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