最近在做一个资源共享的项目中，采用了Struts2.1.8+Spring2.5.6+hibernate3.32的框架整合方式进行开发。在文件上传这块，因为需要实现文件上传时显示进度条的功能，所以尝试了一下。怕以后忘记，先贴出来分享下。
   要在上传文件时能显示进度条，首先需要实时的获知web服务端接收了多少字节，以及文件总大小，这里我们在页面上使用AJAX技术每一秒向服务器发送一次请求来获得需要的实时上传信息。但是当我们使用struts2后怎么在服务端获得实时的上传大小呢？这里需要用到commons-fileupload中的progressListener接口,实现这个接口，然后再实现一个自己的解析器，并在解析器中添加自己实现的那个progressListener;然后再替换struts2自带的解析器（struts2自带的解析器类没有添加progressListener），然后就可以了。下面看看主要的代码(技术有限，如有不对之处，望不吝点解):
 
监听器：
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.commons.fileupload.ProgressListener;
 
public class ResourceProgressListener implements ProgressListener {
    private HttpSession session;
 
    public ResourceProgressListener(HttpServletRequest request) {
       session = request.getSession();
       ResourceFileUploadStatus newUploadStatus = new ResourceFileUploadStatus();
       session.setAttribute("currentUploadStatus", newUploadStatus);
    }
 
    public void update(long readedBytes, long totalBytes, int currentItem) {
       ResourceFileUploadStatus status = (ResourceFileUploadStatus) session.getAttribute("currentUploadStatus");
       status.setReadedBytes(readedBytes);
       status.setTotalBytes(totalBytes);
       status.setCurrentItem(currentItem);
    }
}
上传状态类：
public class ResourceFileUploadStatus {
    private long readedBytes = 0L;
    private long totalBytes = 0L;
    private int currentItem = 0;
  
    public long getReadedBytes() {
       return readedBytes;
    }
    public void setReadedBytes(long bytes) {
       readedBytes = bytes;
    }
    public long getTotalBytes() {
       return totalBytes;
    }
    public void setTotalBytes(long bytes) {
       totalBytes = bytes;
    }
    public int getCurrentItem() {
       return currentItem;
    }
    public void setCurrentItem(int item) {
       currentItem = item;
    }
}
实现自己的解析器类：方法比较简单，找到struts2实现的解析器类，把代码拷贝过来然后添加上监听器即可。这个类代码较多就不整个文件拷了，主要是在parse方法里添加。Parse方法代码如下：红色标注部分即是需要自己添加的progressListener.
public void parse(HttpServletRequest servletRequest, String saveDir)
            throws IOException {
    System.out.println("执行自定义MultiPartRequest");
        DiskFileItemFactory fac = new DiskFileItemFactory();
        // Make sure that the data is written to file
        fac.setSizeThreshold(0);
        if (saveDir != null) {
            fac.setRepository(new File(saveDir));
        }
 
        // Parse the request
        try {
            ServletFileUpload upload = new ServletFileUpload(fac);
            upload.setSizeMax(maxSize);
         
            ResourceProgressListener progressListener = new ResourceProgressListener(servletRequest);//新建一个监听器
            upload.setProgressListener(progressListener);//添加自己的监听器
          
            List items = upload.parseRequest(createRequestContext(servletRequest));
 
            for (Object item1 : items) {
                FileItem item = (FileItem) item1;
                if (LOG.isDebugEnabled()) LOG.debug("Found item " + item.getFieldName());
                if (item.isFormField()) {
                    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>();
                    }
                    String charset = servletRequest.getCharacterEncoding();
                    if (charset != null) {
                        values.add(item.getString(charset));
                    } else {
                        values.add(item.getString());
                    }
                    params.put(item.getFieldName(), values);
                } else {
                    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());
                        continue;
                    }
 
                    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);
                }
            }
        } catch (FileUploadException e) {
            LOG.warn("Unable to parse request", e);
            errors.add(e.getMessage());
        }
}
 
上面的类建立完成后，还需要做一项工作：在struts.xml中添加如下内容：
<bean type="org.apache.struts2.dispatcher.multipart.MultiPartRequest" name="requestParser"
    class="com.zeige.ResourceMultiPartRequest" scope="default" optional="true" />
<constant name="struts.multipart.handler" value="http://www.mamicode.com/requestParser" />
 
下面就可以正常使用了，建立两个action，一个用来接收上传文件，以及对接收的文件作相应处理，处理完成后，在return SUCCESS之前去除session中currentUploadStatus属性，一个用来为页面读取实时上传进度服务，这个类中只要将session中的currentUploadStatus对象拿出来按照相应格式返回给客户端即可。