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);
		}

Spring4MVC之使用 Servlet API 作为入参

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