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 name="struts.multipart.maxSize" 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 id="form1" enctype="multipart/form-data" method="post" action="upload.php">
<div class="row">
<label for="fileToUpload">选择文件</label>
<input type="file" name="fileName" id="fileName" onchange="fileSelected();"/>
</div>
<div id="fileName"></div>
<div id="fileSize"></div>
<div id="fileType"></div>
<div class="row">
上传者：<input type="text" name="name" id="name"/>
<input type="button" onclick="uploadFile()" value="上传" />
<input type="button" onclick="cancleUploadFile()" value="取消" />
</div>
<div id="progressNumber"></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
<!-- 文件上传例子 -->
<action name="uploadifyTest_*" class="com.bjhit.eranges.actions.test.UploadifyTestAction" method="{1}">
<result name="doUpload" type="json">
<param name="includeProperties">responseInfo</param>
<param name="excludeNullProperties">true</param>
</result>
</action>
这样基本的上传功能就实现了。
感谢大家的阅读，希望本文所述对大家学习Ajax方式文件上传进度条实现方法有所帮助。
