1. 引言
基于浏览器的文件上传,特别是对于通过<input type="file">标签来实现上传的情况, 存在着严重的性能问题,因为用户提交了文件之后,在浏览器把文件上传到服务器的过程中,界面看上去似乎是静止的,如果是小文件还好些,如果不幸需要上传的是几兆、几十兆甚至上百兆的文件,我相信那是一种非常痛苦的体验,我们中间的很多人应该都有过此种不堪的经历。(一笑)
现在我就针对这个问题给出一个解决方案,我们将实现一个具有监控能力的WEB上传的程序——它不仅把文件上传到服务器,而且"实时地"监视文件上传的实际过程。
解决方案的基本思路是这样的:
- 在Form提交上传文件同时,使用AJAX周期性地从Servlet轮询上传状态信息
- 然后,根据此信息更新进度条和相关文字,及时反映文件传输状态
- 如果用户取消上传操作,则进行相应的现场清理工作:删除已经上传的文件,在Form提交页面中显示相关信息
- 如果上传完毕,显示已经上传的文件内容(或链接)
在介绍源代码之前,我们先来看看程序运行界面:
2. 实现代码
实现代码想当然的有服务器端代码和客户端代码(呵呵),我们先从服务器端开始。
2.1. 服务器端代码
2.1.1. 文件上传状态类(FileUploadStatus)
使用FileUploadStatus这个类记录文件上传状态,并将其作为服务器端与web客户端之间通信的媒介,通过对这个类对象提供上传状态作为服务器回应发送给web客户端, web客户端使用JavaScript获得文件上传状态。源代码如下: - /**
- * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。
- * 如果需要转载本例程,请您注明作者。
- *
- * 作者: 刘作晨
- * EMail:liuzuochen@gmail.com
- */
- package liuzuochen.sample.upload;
- import java.util.*;
- public class FileUploadStatus {
- //上传用户地址
- private String uploadAddr;
- //上传总量
- private long uploadTotalSize = 0;
- //读取上传总量
- private long readTotalSize = 0;
- //当前上传文件号
- private int currentUploadFileNum = 0;
- //成功读取上传文件数
- private int successUploadFileCount = 0;
- //状态
- private String status = "";
- //处理起始时间
- private long processStartTime = 0l;
- //处理终止时间
- private long processEndTime = 0l;
- //处理执行时间
- private long processRunningTime = 0l;
- //上传文件URL列表
- private List uploadFileUrlList = new ArrayList();
- //取消上传
- private boolean cancel = false;
- //上传base目录
- private String baseDir = "";
- public FileUploadStatus() {
- }
- public String getBaseDir() {
- return baseDir;
- }
- public void setBaseDir(String baseDir) {
- this.baseDir = baseDir;
- }
- public boolean getCancel() {
- return cancel;
- }
- public void setCancel(boolean cancel) {
- this.cancel = cancel;
- }
- public List getUploadFileUrlList() {
- return uploadFileUrlList;
- }
- public void setUploadFileUrlList(List uploadFileUrlList) {
- this.uploadFileUrlList = uploadFileUrlList;
- }
- public long getProcessRunningTime() {
- return processRunningTime;
- }
- public void setProcessRunningTime(long processRunningTime) {
- this.processRunningTime = processRunningTime;
- }
- public long getProcessEndTime() {
- return processEndTime;
- }
- public void setProcessEndTime(long processEndTime) {
- this.processEndTime = processEndTime;
- }
- public long getProcessStartTime() {
- return processStartTime;
- }
- public void setProcessStartTime(long processStartTime) {
- this.processStartTime = processStartTime;
- }
- public long getReadTotalSize() {
- return readTotalSize;
- }
- public void setReadTotalSize(long readTotalSize) {
- this.readTotalSize = readTotalSize;
- }
- public int getSuccessUploadFileCount() {
- return successUploadFileCount;
- }
- public void setSuccessUploadFileCount(int successUploadFileCount) {
- this.successUploadFileCount = successUploadFileCount;
- }
- public int getCurrentUploadFileNum() {
- return currentUploadFileNum;
- }
- public void setCurrentUploadFileNum(int currentUploadFileNum) {
- this.currentUploadFileNum = currentUploadFileNum;
- }
- public String getStatus() {
- return status;
- }
- public void setStatus(String status) {
- this.status = status;
- }
- public long getUploadTotalSize() {
- return uploadTotalSize;
- }
- public String getUploadAddr() {
- return uploadAddr;
- }
- public void setUploadTotalSize(long uploadTotalSize) {
- this.uploadTotalSize = uploadTotalSize;
- }
- public void setUploadAddr(String uploadAddr) {
- this.uploadAddr = uploadAddr;
- }
- public String toJSon() {
- StringBuffer strJSon = new StringBuffer();
- strJSon.append("{UploadTotalSize:").append(getUploadTotalSize()).append(
- ",")
- .append("ReadTotalSize:").append(getReadTotalSize()).append(",")
- .append("CurrentUploadFileNum:").append(getCurrentUploadFileNum()).
- append(",")
- .append("SuccessUploadFileCount:").append(
- getSuccessUploadFileCount()).append(",")
- .append("Status:'").append(getStatus()).append("',")
- .append("ProcessStartTime:").append(getProcessStartTime()).
- append(",")
- .append("ProcessEndTime:").append(getProcessEndTime()).append(
- ",")
- .append("ProcessRunningTime:").append(getProcessRunningTime()).
- append(",")
- .append("Cancel:").append(getCancel()).append("}");
- return strJSon.toString();
- }
- }
2.1.2. 文件上传状态侦听类(FileUploadListener)
使用Common-FileUpload 1.2版本(20070103)。此版本提供了能够监视文件上传情况的ProcessListener接口,使开发者通过FileUploadBase类对象的setProcessListener方法植入自己的Listener。 FileUploadListener类实现了ProcessListener,在整个文件上传过程中,它对上传进度进行监控,并且根据上传 情况实时的更新上传状态Bean。源代码如下: - /**
- * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。
- * 如果需要转载本例程,请您注明作者。
- *
- * 作者: 刘作晨
- * EMail:liuzuochen@gmail.com
- */
- package liuzuochen.sample.upload;
- import org.apache.commons.fileupload.ProgressListener;
- import javax.servlet.http.HttpServletRequest;
- public class FileUploadListener implements ProgressListener{
- private HttpServletRequest request=null;
- public FileUploadListener(HttpServletRequest request){
- this.request=request;
- }
- /**
- * 更新状态
- */
- public void update(long pBytesRead, long pContentLength, int pItems){
- FileUploadStatus statusBean= BackGroundService.getStatusBean(request);
- statusBean.setUploadTotalSize(pContentLength);
- //读取完成
- if (pContentLength == -1) {
- statusBean.setStatus("完成对" + pItems +"个文件的读取:读取了 " + pBytesRead + " bytes.");
- statusBean.setReadTotalSize(pBytesRead);
- statusBean.setSuccessUploadFileCount(pItems);
- statusBean.setProcessEndTime(System.currentTimeMillis());
- statusBean.setProcessRunningTime(statusBean.getProcessEndTime());
- //读取中
- } else {
- statusBean.setStatus("当前正在处理第" + pItems +"个文件:已经读取了 " + pBytesRead + <br> "/" + pContentLength+ " bytes.");
- statusBean.setReadTotalSize(pBytesRead);
- statusBean.setCurrentUploadFileNum(pItems);
- statusBean.setProcessRunningTime(System.currentTimeMillis());
- }
- BackGroundService.saveStatusBean(request,statusBean);
- }
- }<br>
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