Spring MVC 监听文件上传进度，实现上传进度条

首先Spring是一个非常成熟的J2EE框架，其非入侵式的架构为系统的集成和扩展提供了最大的可能。所以Spring MVC下实现进度监听非常容易，甚至不需要改以前的上传业务代码，具体实现分三个步骤：
1、接管CommonsMultipartResolver，重写针对文件上传的请求。
2、在第一步中写入监听，以获取上传进度。
3、修改上传部分的配置文件。
具体见代码


1、CommonsMultipartResolver代码

package com.van.utils.upload.handle;
import java.util.List;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileUpload;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;

import com.van.utils.upload.listener.PJProgressListener;
/**
 * 重写CommonsMultipartResolver以监听文件上传进度
 * @author Van
 * @date 2012-12-12
 */
public class PJCommonsMultipartResolver extends CommonsMultipartResolver {
	
	private HttpServletRequest request;
	protected FileUpload newFileUpload(FileItemFactory fileItemFactory) {
		ServletFileUpload upload = new ServletFileUpload(fileItemFactory);
		upload.setSizeMax(-1);
		if (request != null) {
			HttpSession session = request.getSession();
			PJProgressListener uploadProgressListener = new PJProgressListener(session);
			upload.setProgressListener(uploadProgressListener);
		}
		return upload;
	}
	public MultipartHttpServletRequest resolveMultipart(
			HttpServletRequest request) throws MultipartException {
		this.request = request;// 获取到request,要用到session
		return super.resolveMultipart(request);
	}
	
	
 	@SuppressWarnings("unchecked")
	@Override
    public MultipartParsingResult parseRequest(HttpServletRequest request) throws MultipartException {
 		
 		HttpSession session = request.getSession();
 		
        String encoding = "utf-8";
        FileUpload fileUpload = prepareFileUpload(encoding);
       
        PJProgressListener uploadProgressListener = new PJProgressListener(session);
        fileUpload.setProgressListener(uploadProgressListener);
        try {
            List<FileItem> fileItems = ((ServletFileUpload) fileUpload).parseRequest(request);
            return parseFileItems(fileItems, encoding);
        }
        catch (FileUploadBase.SizeLimitExceededException ex) {
            throw new MaxUploadSizeExceededException(fileUpload.getSizeMax(), ex);
        }
        catch (FileUploadException ex) {
            throw new MultipartException("Could not parse multipart servlet request", ex);
        }
    }

}

PJProgressListener 代码：

package com.van.utils.upload.listener;
import javax.servlet.http.HttpSession;
import org.apache.commons.fileupload.ProgressListener;
import com.van.utils.upload.entity.ProgressEntity;

public class PJProgressListener implements ProgressListener{
	private HttpSession session;
	public PJProgressListener() {
	}
	public PJProgressListener(HttpSession _session) {
		session=_session;
		ProgressEntity ps = new ProgressEntity();
		session.setAttribute("upload_ps", ps);
	}
	public void update(long pBytesRead, long pContentLength, int pItems) {
		ProgressEntity ps = (ProgressEntity) session.getAttribute("upload_ps");
		ps.setpBytesRead(pBytesRead);
		ps.setpContentLength(pContentLength);
		ps.setpItems(pItems);
		//更新
		session.setAttribute("upload_ps", ps);
	}

}

上传进度信息记录实体类：

package com.van.utils.upload.entity;

/**
 * 文件上传进度信息
 * @author Van
 *
 */
public class ProgressEntity {
	
	
	private long pBytesRead = 0L;
	private long pContentLength = 0L;
	private int pItems;
	public long getpBytesRead() {
		return pBytesRead;
	}
	public void setpBytesRead(long pBytesRead) {
		this.pBytesRead = pBytesRead;
	}
	public long getpContentLength() {
		return pContentLength;
	}
	public void setpContentLength(long pContentLength) {
		this.pContentLength = pContentLength;
	}
	public int getpItems() {
		return pItems;
	}
	public void setpItems(int pItems) {
		this.pItems = pItems;
	}
	@Override
	public String toString() {
		return "ProgressEntity [pBytesRead=" + pBytesRead + ", pContentLength="
				+ pContentLength + ", pItems=" + pItems + "]";
	}
	
	
	

}

配置文件部分修改：

<!-- 文件上传支持  -->
	<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
		<property name="defaultEncoding" value="UTF-8" />
		<!-- 内存缓存1M -->
		<property name="maxInMemorySize" value="1000000"></property>
		<!-- 最大2GB -->
		<property name="maxUploadSize" value="2000000000" ></property>
	</bean>

将org.springframework.web.multipart.commons.CommonsMultipartResolver替换成：com.van.utils.upload.handle.PJCommonsMultipartResolver