原本打算使用jquery插件进行异步文件上传，比如uploadfy但是需要额外的支持，也有人用iframe模仿异步上传机制，感觉都比较别扭。因为项目不考虑低版本浏览器，所以决定用html5实现。下面只是一个简单的demo，具体样式需要自己去做。
后台基于strut2进行文件处理，具体因项目而定。只是要注意设置文件大小的限制。 <constant value="52428800"/>这个配置根据具体情况设定，超过此值会报404.
首先是上传页面,比较简单，附带了文件上者这个参数。
upload.jsp
<%@page language="java" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%> <% String path = request.getContextPath(); %> <!DOCTYPE html> <html> <head> <title>使用XMLHttpRequest上传文件</title> <script type="text/javascript"> var xhr = new XMLHttpRequest(); //监听选择文件信息 function fileSelected() { //HTML5文件API操作 var file = document.getElementById('fileName').files[0]; if (file) { var fileSize = 0; if (file.size > 1024 * 1024) fileSize = (Math.round(file.size * 100 / (1024 * 1024)) / 100).toString() + 'MB'; else fileSize = (Math.round(file.size * 100 / 1024) / 100).toString() + 'KB'; document.getElementById('fileName').innerHTML = 'Name: ' + file.name; document.getElementById('fileSize').innerHTML = 'Size: ' + fileSize; document.getElementById('fileType').innerHTML = 'Type: ' + file.type; } } //上传文件 function uploadFile() { var fd = new FormData(); //关联表单数据,可以是自定义参数 fd.append("name", document.getElementById('name').value); fd.append("fileName", document.getElementById('fileName').files[0]); //监听事件 xhr.upload.addEventListener("progress", uploadProgress, false); xhr.addEventListener("load", uploadComplete, false); xhr.addEventListener("error", uploadFailed, false); xhr.addEventListener("abort", uploadCanceled, false); //发送文件和表单自定义参数 xhr.open("POST", "<%=path%>/user/uploadifyTest_doUpload"); xhr.send(fd); } //取消上传 function cancleUploadFile(){ xhr.abort(); } //上传进度 function uploadProgress(evt) { if (evt.lengthComputable) { var percentComplete = Math.round(evt.loaded * 100 / evt.total); document.getElementById('progressNumber').innerHTML = percentComplete.toString() + '%'; } else { document.getElementById('progressNumber').innerHTML = 'unable to compute'; } } //上传成功响应 function uploadComplete(evt) { //服务断接收完文件返回的结果 alert(evt.target.responseText); } //上传失败 function uploadFailed(evt) { alert("上传失败"); } //取消上传 function uploadCanceled(evt) { alert("您取消了本次上传."); } </script> </head> <body> <form enctype="multipart/form-data" method="post" action="upload.php"> <div> <label for="fileToUpload">选择文件</label> <input type="file" onchange="fileSelected();"/> </div> <div></div> <div></div> <div></div> <div> 上传者：<input type="text"/> <input type="button" value="上传" /> <input type="button" value="取消" /> </div> <div></div> </form> </body> </html>
fd.append("name", document.getElementById('name').value);
fd.append("fileName", document.getElementById('fileName').files[0]);
这两句是把数据绑定到表单。因为html5支持多文件上传，所以
document.getElementById('fileName').files
返回的是数组。这里只有一个文件所以取下标0的元素。
xhr.upload.addEventListener("progress", uploadProgress, false);
xhr.addEventListener("load", uploadComplete, false);
xhr.addEventListener("error", uploadFailed, false);
xhr.addEventListener("abort", uploadCanceled, false);
这里绑定进度、上传、错误、中断的事件，提供一些交互。文件进度显示就是在progress回调中进行显示的。
然后贴上后台代码和action配置，UploadifyTestAction.java
package com.bjhit.eranges.actions.test; import java.io.File; import com.opensymphony.xwork2.ActionSupport; public class UploadifyTestAction extends ActionSupport { private static final long serialVersionUID = 837481714629791752L; private File fileName; private String name; private String responseInfo; public String doUpload() throws Exception { System.out.println(name); File myFile = fileName; System.out.println(myFile.getName()); responseInfo = "上传成功!"; return "doUpload"; } public String getName() { return name; } public void setName(String name) { this.name = name; } public File getFileName() { return fileName; } public void setFileName(File fileName) { this.fileName = fileName; } public String getResponseInfo() { return responseInfo; } public void setResponseInfo(String responseInfo) { this.responseInfo = responseInfo; } }
action配置