原理：
利用Ajax在客户端一直查询服务器端的上传进度，取得进度的状态文本信息(xml,json格式的文本等),然后利用JS解析，显示在前台。
在Struts2. 0中，框架事先已经定义一种监听器：ProgressListener（进度监听器），里面有一个update(long readedBytes, long totalBytes, int currentItem)方法,其中，readedBytes是已经上传到服务器的位数，而totalBytes是上传文件总位数.当文件已二进制的方式上传时，每上传一部分数据，就会调用这个方法一次。故要实现监听进度，必须实现这个接口，并实现update方法，在update方法中保存这个进度到session。当客服端需要进度的信息时，只需要访问某个action，在这个action中读取session中保存的进度状态就可以了.
上传文件可大致分为两个阶段:1. 上传到服务器上，在临时目录中 2.从临时目录中把文件移到指定目录(由自己写的action处理),而struts2.的监听器只监听第一阶段。
实现：
(源代码下载： http://download.csdn.net/source/3568014)
第一步：
实现ProgressListener接口，实现update( )方法，详情见action包中的FileUploadListener.java 文件，里面有一个自定义的类：State ，它描述的是进度的状态，详情请看State注释。Update方法要做的就是不断地更新session中的state对象 代码如下：
package action;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.commons.fileupload.ProgressListener;
public class FileUploadListener implements ProgressListener{
private HttpSession session;
public FileUploadListener(HttpServletRequest request) {
session = request.getSession();
State state = new State();
session.setAttribute("state", state);
}
@Override
public void update(long readedBytes, long totalBytes, int currentItem) {
// TODO Auto-generated method stub
System.out.println("update:"+readedBytes+";"+totalBytes+";"+currentItem);
State state = (State) session.getAttribute("state");
state.setReadedBytes(readedBytes);
state.setTotalBytes(totalBytes);
state.setCurrentItem(currentItem);
}
}
State类:
package action;
public class State {
private long readedBytes = 0L;/*已经上传的位数*/
private long totalBytes = 0L;/*文件所占位数*/
private int currentItem = 0;
private int rate=0; /*上传百分比*/
public long getReadedBytes() {
return readedBytes;
}
public void setReadedBytes(long readedBytes) {
this.readedBytes = readedBytes;
}
public long getTotalBytes() {
return totalBytes;
}
public void setTotalBytes(long totalBytes) {
this.totalBytes = totalBytes;
}
public int getCurrentItem() {
return currentItem;
}
public void setCurrentItem(int currentItem) {
this.currentItem = currentItem;
}
public int getRate() {
return rate;
}
public void setRate(int rate) {
this.rate = rate;
}
}
第二步:
将监听器注入到struts2.0的MultiPartRequest封装类中，客户端发送request到服务器，struts2.0会将request封装成MultiPartRequest。因此必须将监听器注入到MultiPartRequest中。只需要在MultiPartRequest中加入以下两句：
FileUploadListener progressListener = new FileUploadListener(servletRequest);
upload.setProgressListener(progressListener);//添加自己的监听器
所以重新写一个新类MyMultiPartRequest代替MultiPartRequest ，代码与org.apache.struts2.dispatcher.multipart.MultiPartRequest 一样，在方法
private List<FileItem> parseRequest(HttpServletRequest servletRequest, String saveDir) 中加入监听器.
如下:
package action;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.RequestContext;
import org.apache.commons.fileupload.disk.DiskFileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.struts2.StrutsConstants;
import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.struts2.dispatcher.multipart.MultiPartRequest;
public class MyMultiPartRequest implements MultiPartRequest{
static final Logger LOG = LoggerFactory.getLogger(MultiPartRequest.class);
// maps parameter name -> List of FileItem objects
protected Map<String,List<FileItem>> files = new HashMap<String,List<FileItem>>();
// maps parameter name -> List of param values
protected Map<String,List<String>> params = new HashMap<String,List<String>>();
// any errors while processing this request
protected List<String> errors = new ArrayList<String>();
protected long maxSize;
@Inject(StrutsConstants.STRUTS_MULTIPART_MAXSIZE)
public void setMaxSize(String maxSize) {
this.maxSize = Long.parseLong(maxSize);
}
/**
* Creates a new request wrapper to handle multi-part data using methods adapted from Jason Pell's
* multipart classes (see class description).
*
* @param saveDir the directory to save off the file
* @param request the request containing the multipart
* @throws java.io.IOException is thrown if encoding fails.
*/
public void parse(HttpServletRequest request, String saveDir) throws IOException {
try {
processUpload(request, saveDir);
} catch (FileUploadException e) {
LOG.warn("Unable to parse request", e);
errors.add(e.getMessage());
}
}
private void processUpload(HttpServletRequest request, String saveDir) throws FileUploadException, UnsupportedEncodingException {
for (FileItem item : parseRequest(request, saveDir)) {
if (LOG.isDebugEnabled()) {
LOG.debug("Found item " + item.getFieldName());
}
if (item.isFormField()) {
processNormalFormField(item, request.getCharacterEncoding());
} else {
processFileField(item);
}
}
}
private void processFileField(FileItem item) {
LOG.debug("Item is a file upload");
// Skip file uploads that don't have a file name - meaning that no file was selected.
if (item.getName() == null || item.getName().trim().length() < 1) {
LOG.debug("No file has been uploaded for the field: " + item.getFieldName());
return;
}
List<FileItem> values;
if (files.get(item.getFieldName()) != null) {
values = files.get(item.getFieldName());
} else {
values = new ArrayList<FileItem>();
}
values.add(item);
files.put(item.getFieldName(), values);
}
private void processNormalFormField(FileItem item, String charset) throws UnsupportedEncodingException {
LOG.debug("Item is a normal form field");
List<String> values;
if (params.get(item.getFieldName()) != null) {
values = params.get(item.getFieldName());
} else {
values = new ArrayList<String>();
}
// note: see http://jira.opensymphony.com/browse/WW-633
// basically, in some cases the charset may be null, so
// we're just going to try to "other" method (no idea if this
// will work)
if (charset != null) {
values.add(item.getString(charset));
} else {
values.add(item.getString());
}
params.put(item.getFieldName(), values);
}
private List<FileItem> parseRequest(HttpServletRequest servletRequest, String saveDir) throws FileUploadException {
DiskFileItemFactory fac = createDiskFileItemFactory(saveDir);
ServletFileUpload upload = new ServletFileUpload(fac);
upload.setSizeMax(maxSize);
/*自己新建监听器*/
FileUploadListener progressListener = new FileUploadListener(servletRequest);
upload.setProgressListener(progressListener);//添加自己的监听器
return upload.parseRequest(createRequestContext(servletRequest));
}
private DiskFileItemFactory createDiskFileItemFactory(String saveDir) {
DiskFileItemFactory fac = new DiskFileItemFactory();
// Make sure that the data is written to file
fac.setSizeThreshold(0);
if (saveDir != null) {
fac.setRepository(new File(saveDir));
}
return fac;
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getFileParameterNames()
*/
public Enumeration<String> getFileParameterNames() {
return Collections.enumeration(files.keySet());
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getContentType(java.lang.String)
*/
public String[] getContentType(String fieldName) {
List<FileItem> items = files.get(fieldName);
if (items == null) {
return null;
}
List<String> contentTypes = new ArrayList<String>(items.size());
for (FileItem fileItem : items) {
contentTypes.add(fileItem.getContentType());
}
return contentTypes.toArray(new String[contentTypes.size()]);
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getFile(java.lang.String)
*/
public File[] getFile(String fieldName) {
List<FileItem> items = files.get(fieldName);
if (items == null) {
return null;
}
List<File> fileList = new ArrayList<File>(items.size());
for (FileItem fileItem : items) {
File storeLocation = ((DiskFileItem) fileItem).getStoreLocation();
if(fileItem.isInMemory() && storeLocation!=null && !storeLocation.exists()) {
try {
storeLocation.createNewFile();
} catch (IOException e) {
if(LOG.isErrorEnabled()){
LOG.error("Cannot write uploaded empty file to disk: " + storeLocation.getAbsolutePath(),e);
}
}
}
fileList.add(storeLocation);
}
return fileList.toArray(new File[fileList.size()]);
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getFileNames(java.lang.String)
*/
public String[] getFileNames(String fieldName) {
List<FileItem> items = files.get(fieldName);
if (items == null) {
return null;
}
List<String> fileNames = new ArrayList<String>(items.size());
for (FileItem fileItem : items) {
fileNames.add(getCanonicalName(fileItem.getName()));
}
return fileNames.toArray(new String[fileNames.size()]);
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getFilesystemName(java.lang.String)
*/
public String[] getFilesystemName(String fieldName) {
List<FileItem> items = files.get(fieldName);
if (items == null) {
return null;
}
List<String> fileNames = new ArrayList<String>(items.size());
for (FileItem fileItem : items) {
fileNames.add(((DiskFileItem) fileItem).getStoreLocation().getName());
}
return fileNames.toArray(new String[fileNames.size()]);
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getParameter(java.lang.String)
*/
public String getParameter(String name) {
List<String> v = params.get(name);
if (v != null && v.size() > 0) {
return v.get(0);
}
return null;
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getParameterNames()
*/
public Enumeration<String> getParameterNames() {
return Collections.enumeration(params.keySet());
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getParameterValues(java.lang.String)
*/
public String[] getParameterValues(String name) {
List<String> v = params.get(name);
if (v != null && v.size() > 0) {
return v.toArray(new String[v.size()]);
}
return null;
}
/* (non-Javadoc)
* @see org.apache.struts2.dispatcher.multipart.MultiPartRequest#getErrors()
*/
public List getErrors() {
return errors;
}
/**
* Returns the canonical name of the given file.
*
* @param filename the given file
* @return the canonical name of the given file
*/
private String getCanonicalName(String filename) {
int forwardSlash = filename.lastIndexOf("/");
int backwardSlash = filename.lastIndexOf("\\");
if (forwardSlash != -1 && forwardSlash > backwardSlash) {
filename = filename.substring(forwardSlash + 1, filename.length());
} else if (backwardSlash != -1 && backwardSlash >= forwardSlash) {
filename = filename.substring(backwardSlash + 1, filename.length());
}
return filename;
}
/**
* Creates a RequestContext needed by Jakarta Commons Upload.
*
* @param req the request.
* @return a new request context.
*/
private RequestContext createRequestContext(final HttpServletRequest req) {
return new RequestContext() {
public String getCharacterEncoding() {
return req.getCharacterEncoding();
}
public String getContentType() {
return req.getContentType();
}
public int getContentLength() {
return req.getContentLength();
}
public InputStream getInputStream() throws IOException {
InputStream in = req.getInputStream();
if (in == null) {
throw new IOException("Missing content in the request");
}
return req.getInputStream();
}
};
}
}
在struts.xml中重新指定MultiPartRequest:
<bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest" name="requestParser"
class="action.MyMultiPartRequest" scope="default" optional="true" />
<constant name="struts.multipart.handler" value="requestParser" />
到这里，基本完成大部分工作.
接下来是业务，写两个Action ，一个是查询进度的FileProgressAction ,一个是处理上传文件FileProgressUploadAction . FileProgressAction从Session中读入state对象，返回客户端。
在客户端方面，点击”提交”的时候,需要完成两步工作，1.不断到服务器查询进度2.上传文件，因为本人JS不是很好，就潦草写了一些，主要用的是Jquery框架。然后查询进度时,state对象以json数据方式传递到客户端的。
struts.xml文件:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
<!-- 限定文件大小 -->
<constant name="struts.multipart.maxSize" value="500000000000000" />
<package name="upload" namespace="/upload" extends="json-default">
<!-- 查询上传进度 -->
<action name="progress" class="action.FileProgressAction">
<result name="success" type="json"></result>
</action>
<!-- 上传文件 -->
<action name="upload" class="action.FileProgressUploadAction">
<result name="success">/index.jsp</result>
<result name="input">/error.jsp</result>
</action>
</package>
<!-- 重新指定request封装类 -->
<bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest" name="requestParser"
class="action.MyMultiPartRequest" scope="default" optional="true" />
<constant name="struts.multipart.handler" value="requestParser" />
</struts>
前台页面:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript" src="./js/jquery-1.4.min.js"></script>
<script>
var id=0;
function addressAction(){
$.post(
'./upload/progress.action',
function(data){
if(data.currentItem==0){
$("#m").text('0%');
}else if(data.state.rate!=100){
$("#m").text(data.state.readedBytes+'/'+data.state.totalBytes+':'+data.state.rate+'%');
}else{
$("#m").text(data.state.readedBytes+'/'+data.state.totalBytes+':'+'100% 上传完成!');
window.clearInterval(id);
}
$("#img").html("");
var num=data.state.rate/10;
for(var i=1;i<=num;i++){
$("#img").append("<img src='./images/grid.gif' />");
}
for(var j=1;j<=10-num;j++){
$("#img").append("<img src='./images/gray.gif' />");
}
},
'json'
);
}
function submitForm(){
if($("#f1").val()==""){
alert('上传文件为空!!!');
return ;
}
id=window.setInterval(addressAction,1000);
$("form:first").submit();/*提交第一个表单*/
}
</script>
</head>
<body>
<form action="./upload/upload.action" method="post" enctype="multipart/form-data">
File:<input type="file" name="file" id="f1" />
<br/>
<span id="m"></span><br/>
<span id="img"></span>
<br/>
<input type="button" onclick="submitForm()" value="上传" />
</form>
<br/>
</body>
</html>
注意事项:
struts-json包要引进来
使用Jquery框架