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Web上传和下载应该是很普遍的一个需求，无论是小型网站还是大并发访问的交易网站。WebWork 当然也提供了很友好的拦截器来实现对文件的上传，让我们可以专注与业务逻辑的设计和实现，在实现上传和下载时顺便关注了下框架上传下载的实现，在本篇博文中总结记录如下。
具体过程请参照： http://www.cnblogs.com/java-class/p/5155793.html
public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException { try { if (encoding != null) { try { request.setCharacterEncoding(encoding); } catch (Exception localException) { } } if (locale != null) { response.setLocale(locale); } if (this.paramsWorkaroundEnabled) { request.getParameter("foo"); } request = wrapRequest(request); //封装 request请求 serviceAction(request, response, getNameSpace(request), getActionName(request), getRequestMap(request), getParameterMap(request), getSessionMap(request), getApplicationMap()); } catch (IOException e) { String message = "Could not wrap servlet request with MultipartRequestWrapper!"; log.error(message, e); sendError(request, response, 500, new ServletException(message, e)); } }
先来看看 wrapRequest 方法做了什么：
protected HttpServletRequest wrapRequest(HttpServletRequest request) throws IOException { if ((request instanceof MultiPartRequestWrapper)) { return request; } if (MultiPartRequest.isMultiPart(request)) { request = new MultiPartRequestWrapper(request, getSaveDir(), getMaxSize()); } return request; }
MultiPartRequest.isMultiPart() 方法实现如下：
public static boolean isMultiPart(HttpServletRequest request){ String content_type = request.getHeader("Content-Type"); return content_type != null && content_type.startsWith("multipart/form-data"); }
具体实现如下：
protected String getSaveDir() { String saveDir = Configuration.getString("webwork.multipart.saveDir").trim(); if (saveDir.equals("")) { File tempdir = (File) getServletConfig().getServletContext().getAttribute("javax.servlet.context.tempdir"); log.info("Unable to find ‘webwork.multipart.saveDir‘ property setting. Defaulting to javax.servlet.context.tempdir"); if (tempdir != null) { saveDir = tempdir.toString(); } } else { File multipartSaveDir = new File(saveDir); if (!multipartSaveDir.exists()) { multipartSaveDir.mkdir(); } } if (log.isDebugEnabled()) { log.debug("saveDir=" + saveDir); } return saveDir; }
再来看一下 MultiPartRequestWrapper 的构造函数使如何包装 request 的：
public MultiPartRequestWrapper(HttpServletRequest request, String saveDir, int maxSize) throws IOException { super(request); if ((request instanceof MultiPartRequest)) { this.multi = ((MultiPartRequest) request); } else { String parser = ""; parser = Configuration.getString("webwork.multipart.parser"); if (parser.equals("")) { log.warn("Property webwork.multipart.parser not set. Using com.opensymphony.webwork.dispatcher.multipart.PellMultiPartRequest"); parser = "com.opensymphony.webwork.dispatcher.multipart.PellMultiPartRequest"; } else if (parser.equals("pell")) { parser = "com.opensymphony.webwork.dispatcher.multipart.PellMultiPartRequest"; } else if (parser.equals("cos")) { parser = "com.opensymphony.webwork.dispatcher.multipart.CosMultiPartRequest"; } else if (parser.equals("jakarta")) { parser = "com.opensymphony.webwork.dispatcher.multipart.JakartaMultiPartRequest"; } try { Class baseClazz = MultiPartRequest.class; Class clazz = Class.forName(parser); if (!baseClazz.isAssignableFrom(clazz)) { addError("Class ‘" + parser + "‘ does not extend MultiPartRequest"); return; } Constructor ctor = clazz.getDeclaredConstructor(new Class[] { Class.forName("javax.servlet.http.HttpServletRequest"), String.class, Integer.TYPE }); Object[] parms = { request, saveDir, new Integer(maxSize) }; this.multi = ((MultiPartRequest) ctor.newInstance(parms)); } catch (ClassNotFoundException e) { addError("Class: " + parser + " not found."); } catch (NoSuchMethodException e) { addError("Constructor error for " + parser + ": " + e); } catch (InstantiationException e) { addError("Error instantiating " + parser + ": " + e); } catch (IllegalAccessException e) { addError("Access errror for " + parser + ": " + e); } catch (InvocationTargetException e) { addError(e.getTargetException().toString()); } } }
action 配置： <action name="uploadAttach" class=".....attach.action.uploadAttach" caption="上传附件"> <result name="success" type="dispatcher"> <param name="location">/result.jsp</param> </result> <result name="error" type="dispatcher"> <param name="location">/result.jsp</param> </result> <interceptor-ref name="defaultStack" /> <interceptor-ref name="fileUploadStack" /> //webwok 上传所需要的拦截栈 </action> //拦截栈的定义 <interceptor-stack name="fileUploadStack"> <interceptor-ref name="fileUpload"/> <interceptor-ref name="params"/> </interceptor-stack> //拦截栈对应的拦截器 <interceptor name="fileUpload" class="com.opensymphony.webwork.interceptor.FileUploadInterceptor"/> <interceptor name="params" class="com.opensymphony.xwork.interceptor.ParametersInterceptor"/>
public String intercept(ActionInvocation invocation) throws Exception {if (!(ServletActionContext.getRequest() instanceof MultiPartRequestWrapper)) { if (log.isDebugEnabled()) { log.debug("bypass " + invocation.getProxy().getNamespace() + "/" + invocation.getProxy().getActionName()); } return invocation.invoke(); } Action action = invocation.getAction(); ValidationAware validation = null; if ((action instanceof ValidationAware)) { validation = (ValidationAware) action; } MultiPartRequestWrapper multiWrapper = (MultiPartRequestWrapper) ServletActionContext.getRequest(); if (multiWrapper.hasErrors()) { Collection errors = multiWrapper.getErrors(); Iterator i = errors.iterator(); while (i.hasNext()) { String error = (String) i.next(); if (validation != null) { validation.addActionError(error); } log.error(error); } } Enumeration e = multiWrapper.getFileParameterNames(); while ((e != null) && (e.hasMoreElements())) { String inputName = (String) e.nextElement(); String[] contentType = multiWrapper.getContentTypes(inputName); String[] fileName = multiWrapper.getFileNames(inputName); File[] file = multiWrapper.getFiles(inputName); if (file != null) { for (int i = 0; i < file.length; i++) { log.info("file " + inputName + " " + contentType[i] + " " + fileName[i] + " " + file[i]); } } if (file == null) { if (validation != null) { validation.addFieldError(inputName, "Could not upload file(s). Perhaps it is too large?"); } log.error("Error uploading: " + fileName); } else { invocation.getInvocationContext().getParameters().put(inputName, file); invocation.getInvocationContext().getParameters().put(inputName + "ContentType", contentType); invocation.getInvocationContext().getParameters().put(inputName + "FileName", fileName); } } String result = invocation.invoke(); for (Enumeration e1 = multiWrapper.getFileParameterNames(); e1 != null && e1.hasMoreElements();) { String inputValue = (String) e1.nextElement(); File file[] = multiWrapper.getFiles(inputValue); for (int i = 0; i < file.length; i++) { File f = file[i]; log.info("removing file " + inputValue + " " + f); if (f != null && f.isFile()) f.delete(); } } return result; }
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原文地址：http://www.cnblogs.com/java-class/p/5175619.html
