springMVC中获取request和response对象的几种方式（RequestContextHolder）

客官°小女子只卖身不卖艺 2022-10-06 12:47 251阅读 0赞

### springMVC中获取request和response对象的几种方式 ###

*   *  1.最简单方式：参数
     *  2.加入监听器，然后在代码里面获取

原文链接：https://blog.csdn.net/weixin\_43052839/article/details/82426735

--------------------

## 1.最简单方式：参数 ##

@RequestMapping("/test")
    @ResponseBody
    public void saveTest(HttpServletRequest req, HttpServletResponse resp){ 
    　　
    }

## 2.加入监听器，然后在代码里面获取 ##

在Spring API中提供了一个非常便捷的工具类 **RequestContextHolder**，能够在Controller中获取request对象和response对象，使用方法如下：

public class TestRequest { 
        public HttpServletRequest getRequest() { 
            HttpServletRequest request=((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();
            HttpServletResponse response=((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getResponse();
            return request;
        }
    }

**tips**:需要注意的是如果直接使用这个工具类，则会抛出一个空指针异常。原因是需要先在web.xml配置RequestContextListener监听器:

<listener>
       <listener-class>
             org.springframework.web.context.request.RequestContextListener
       </listener-class>
    </listener>

**原理**  
RequestContextListener实现了 ServletRequestListener ,在其覆盖的requestInitialized(ServletRequestEvent requestEvent)方法中,将request最终设置到了RequestContextHolder中

import javax.servlet.ServletRequestEvent;
    import javax.servlet.ServletRequestListener;
    import javax.servlet.http.HttpServletRequest;
    
    import org.springframework.context.i18n.LocaleContextHolder;
    import org.springframework.web.context.request.RequestContextHolder;
    import org.springframework.web.context.request.ServletRequestAttributes;
    
    public class RequestContextListener implements ServletRequestListener { 
        private static final String REQUEST_ATTRIBUTES_ATTRIBUTE =
            RequestContextListener.class.getName() + ".REQUEST_ATTRIBUTES";
        public void requestInitialized(ServletRequestEvent requestEvent) { 
            if (!(requestEvent.getServletRequest() instanceof HttpServletRequest)) { 
                throw new IllegalArgumentException(
               "Request is not an HttpServletRequest: " + requestEvent.getServletRequest());
            }
            HttpServletRequest request = (HttpServletRequest) requestEvent.getServletRequest();//从事件对象中获取request对象
            ServletRequestAttributes attributes = new ServletRequestAttributes(request);//将request设置到servletRequestAttributes中
            request.setAttribute(REQUEST_ATTRIBUTES_ATTRIBUTE, attributes);//反过来将servletRequestAttributes设置到request中
            LocaleContextHolder.setLocale(request.getLocale());
            RequestContextHolder.setRequestAttributes(attributes);//再将servletRequestAttributes设置到requestContextHolder中
        }
        public void requestDestroyed(ServletRequestEvent arg0) { 
            // TODO Auto-generated method stub
        }
    }