目录

• 1、直接在Controller层方法参数上获取
• 2、通过@Autowired注入
• 3、通过RequestContextHolder获取

  1、直接在Controller层方法参数上获取

  仅仅适用在controller方法上。当Spring接收到HTTP请求时，会寻找一个合适的方法来处理该请求。如果该方法参数上标注了@RequestMapping或@Get、@Post等注解，Spring就会将HttpServletRequest对象注入到该参数中。

  @RestController
  public class Controller {
      @RequestMapping("/test")
      public String test(HttpServletRequest request,HttpServletResponse response) {
          return "success";
      }
  }
  

  2、通过@Autowired注入

  适用于所有的bean

  @Autowired
  private HttpServletRequest request;
  @Autowired
  private HttpServletResponse response;
  @RequestMapping("/test")
  public String test() {
      Enumeration headerNames = request.getHeaderNames();
      response.setHeader("header","header_value");
      return "success";
  }
  

  通过调试可以看到，注入的Reques是一个代理类，而这个被代理的目标由RequestObjectFactory.getObject() 获取

  

  我们再看一下RequestObjectFactory.getObject() 的方法，最终还是走到了RequestContextHolder.getRequestAttributes()方法

  private static class RequestObjectFactory implements ObjectFactory, Serializable {
  	@Override
  	public ServletRequest getObject() {
  		return currentRequestAttributes().getRequest();
  	}
  	
  	@Override
  	public String toString() {
  		return "Current HttpServletRequest";
  	}
  }
  private static ServletRequestAttributes currentRequestAttributes() {
  	RequestAttributes requestAttr = RequestContextHolder.currentRequestAttributes();
  	if (!(requestAttr instanceof ServletRequestAttributes)) {
  		throw new IllegalStateException("Current request is not a servlet request");
  	}
  	return (ServletRequestAttributes) requestAttr;
  }
  

  3、通过RequestContextHolder获取

  适用于所有的方法，spring会通过RequestContextHolder.setRequestAttributes方法将RequestAttributes设置到ThreadLocal中。

  ServletRequestAttributes attr = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
  HttpServletRequest request = attr.getRequest();
  HttpServletResponse response = attr.getResponse();
  

   
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