@Spring MVC 中几种获取request和response的方式

1.最简单方式：处理方法入参

例如：

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

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

HttpServletRequest req = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest(); HttpServletResponse resp = ((ServletWebRequest)RequestContextHolder.getRequestAttributes()).getResponse();

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.

public class RequestContextListener implements ServletRequestListener { private static final String REQUEST_ATTRIBUTES_ATTRIBUTE = RequestContextListener.class.getName() + ".REQUEST_ATTRIBUTES"; @Override 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
    }