Spring4MVC之使用 Servlet API 作为进参_VC/MFC

Spring4MVC之使用 Servlet API 作为入参

使用 Servlet API 作为入参

MVC 的 Handler 方法可以接受哪些 ServletAPI 类型的参数：

HttpServletRequest

HttpServletResponse

HttpSession

java.security.Principal

Locale

InputStream

OutputStream

Reader

Writer

示例

1. 添加JSP页面

        <li>使用 Servlet API作为入参            <ul>                <li><a href="user/testServletAPI">使用 Servlet API作为入参</a></li>                <li><a href="user/testServletAPI2">使用 Servlet API作为入参</a></li>            </ul>        </li>

2. 添加处理器类

/**	 * 可以使用Servlet原生的API作为目标方法的参数 具体支持以下类型	 * 	 * HttpServletRequest	 * HttpServletResponse	 * HttpSession	 * java.security.Principal	 * Locale	 * InputStream	 * OutputStream	 * Reader	 * Writer	 * 	 */	@RequestMapping("testServletAPI")	public String testServletAPI(HttpServletRequest request,HttpServletResponse response)	{		System.out.println("------testServletAPI HttpServletRequest: " + request +  "------");		System.out.println("------testServletAPI HttpServletResponse: " + response +  "------");		return LOGIN;	}		@RequestMapping("testServletAPI2")	public void testServletAPI2(Writer writer) throws IOException	{		System.out.println("------testServletAPI2 Writer: " + writer +  "------");		StringBuffer sb = new StringBuffer();		sb.append("<html><body>");		sb.append("<br/><a href='/org.rabbitx.web.spring4mvc/index.jsp'>Back TO Home Page</a>");		sb.append("</body></html>");		writer.write(sb.toString());	}

原理分析

1. 在?testServletAPI方法中打断点并使用debug模式启动服务器；

2. 在浏览器端点击对应连接启动调试；

3. 在调试窗口选中AnnotationMethodHandlerAdapter$ServletHandlerMethodInvoker(HandlerMethodInvoker).invokeHandlerMethod(Method, Object, NativeWebRequest, ExtendedModelMap) line: 175

?其中，resolveHandlerArguments为解析处理参数方法。

4. 进入resolveHandlerArguments方法；

5. 找到resolveHandlerArguments方法中resolveCommonArgument方法并进入；

6. 找到resolveCommonArgument方法中resolveStandardArgument方法并进入；

7. 在方法resolveStandardArgument上使用Ctrl+T快捷键并选择"ServletHandlerMethodInvoker"进入；

8. 查看方法resolveStandardArgument可以知道SpringMVC本质上还是从原生ServletAPI中获取相应的对象；

@Override		protected Object resolveStandardArgument(Class<?> parameterType, NativeWebRequest webRequest) throws Exception {			HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);			HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);			if (ServletRequest.class.isAssignableFrom(parameterType) ||					MultipartRequest.class.isAssignableFrom(parameterType)) {				Object nativeRequest = webRequest.getNativeRequest(parameterType);				if (nativeRequest == null) {					throw new IllegalStateException(							"Current request is not of type [" + parameterType.getName() + "]: " + request);				}				return nativeRequest;			}			else if (ServletResponse.class.isAssignableFrom(parameterType)) {				this.responseArgumentUsed = true;				Object nativeResponse = webRequest.getNativeResponse(parameterType);				if (nativeResponse == null) {					throw new IllegalStateException(							"Current response is not of type [" + parameterType.getName() + "]: " + response);				}				return nativeResponse;			}			else if (HttpSession.class.isAssignableFrom(parameterType)) {				return request.getSession();			}			else if (Principal.class.isAssignableFrom(parameterType)) {				return request.getUserPrincipal();			}			else if (Locale.class.equals(parameterType)) {				return RequestContextUtils.getLocale(request);			}			else if (InputStream.class.isAssignableFrom(parameterType)) {				return request.getInputStream();			}			else if (Reader.class.isAssignableFrom(parameterType)) {				return request.getReader();			}			else if (OutputStream.class.isAssignableFrom(parameterType)) {				this.responseArgumentUsed = true;				return response.getOutputStream();			}			else if (Writer.class.isAssignableFrom(parameterType)) {				this.responseArgumentUsed = true;				return response.getWriter();			}			return super.resolveStandardArgument(parameterType, webRequest);		}