文件上传下载：commons-fileupload + Servlet 2.5

数据库：MySQL

开发技术：JSP + Servlet 2.5

第三方的上传组件：
　　commons-fileupload
　　connons-io

上传页面
1、form表单需要增加：enctype="multipart/form-data" 以字节流形式
2、form表单里面增加上传组件：input="file"
3、取消上传：<button onclick="javascript:window.opener == null;window.close();">取消上传</button>

<form id="form1" method="post" action="upload" enctype="multipart/form-data">
　　<table>
　　　　<tr>
<td width="25%" align="right">上传文件：</td>
<td><input id="file1" type="file" NAME="file1" style="width: 300px;"></td>
</tr>
<tr align="center" valign="middle">
<td height="60" colspan="2">
<input type="submit" id="BtnOK" value="确认上传">
<button onclick="javascript:window.opener == null;window.close();">取消上传</button>
</td>
</tr>
<tr align="center" valign="middle">
测试非表单控件的值接收：<td height="60" colspan="2"><input type="text" name="possess" value="非提交控件的值"></td>
</tr>
　　</table>
</form>

代码：
工具类 MutiFileUpload.java 对fileupload组件进行简单封装

import java.io.UnsupportedEncodingException;

import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
* 当读取上传表单的各部分时会用到该encoding，如果没有指定
* encoding * 则使用系统缺省的encoding。建议在这里设置成utf-8，并把jsp
* 的charset也设置成utf-8，否则可能会出现乱码。
*
*/
@SuppressWarnings("unchecked")
public class MutiFileUpload{

　 public Map<String,String> parameters ;　　　　//保存form表单域中非上传控件的值
public Map<String,FileItem> files;　　　　　　//保存上传的文件

　　//将文件保存在内存还是磁盘临时文件夹的默认临界值，值为10240，即10kb
private int sizeThreshold = DiskFileItemFactory.DEFAULT_SIZE_THRESHOLD;

private long sizeMax = 1024 * 1024 * 20  ;    　　//上传文件的大小限制;
private String encoding = "UTF-8";        　　　　//字符编码，当读取上传表单的各部分时会用到该encoding

　　// 以上属性的 get/set 方法
public String getEncoding() {
return encoding;
}

public void setEncoding(String encoding) {
this.encoding = encoding;
}

public long getSizeMax() {
return sizeMax;
}

public void setSizeMax(long sizeMax) {
this.sizeMax = sizeMax;
}

public int getSizeThreshold() {
return sizeThreshold;
}

public void setSizeThreshold(int sizeThreshold) {
this.sizeThreshold = sizeThreshold;
}
　　
　　 // 解析请求，这个方法很重要
public void parse(HttpServletRequest request){

　　　　　//保存数据的2个Map初始化
parameters = new HashMap<String,String>();
files = new HashMap<String,FileItem>();

DiskFileItemFactory factory = new DiskFileItemFactory();

//设置临界值约束
factory.setSizeThreshold(sizeThreshold);

ServletFileUpload upload = new ServletFileUpload(factory);

upload.setSizeMax(sizeMax);
upload.setHeaderEncoding(encoding);

try {

List items = upload.parseRequest(request);
Iterator iterator = items.iterator();
while(iterator.hasNext()){

FileItem item = (FileItem)iterator.next();
if(item.isFormField()){
String fieldName = item.getFieldName();
String value = new String(item.getString(encoding));
parameters.put(fieldName, value);

}else{
String fieldName = item.getFieldName();
files.put(fieldName, item);
}
}

} catch (FileUploadException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}

/** 得到上传文件的文件名
* @param item
* @return
*/
public String getFileName(FileItem item){

String fileName = item.getName();
fileName = replace(fileName,"\\","/");
fileName = fileName.substring(fileName.lastIndexOf("/")+1);
return fileName;

}

/**字符串替换
* @param source
* @param oldString
* @param newString
* @return
*/
public static String replace(String source, String oldString, String newString) {

StringBuffer output = new StringBuffer();
int lengthOfSource = source.length();
int lengthOfOld = oldString.length();
int posStart = 0;
int pos;

while ((pos = source.indexOf(oldString, posStart)) >= 0) {

output.append(source.substring(posStart, pos));
output.append(newString);
posStart = pos + lengthOfOld;
}

if (posStart < lengthOfSource) {
output.append(source.substring(posStart));
}

return output.toString();
}
}

上传Servlet，doGet方法请求doPost。在doPost方法中编写如下代码：

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

DBUtils db = new DBUtils();

MutiFileUpload fileUpload = new MutiFileUpload();
fileUpload.parse(request);

　　　　　//这里是打印非上传组件的值，查看是否能够正常接收
//System.out.println( fileUpload.parameters.get("possess") );

Iterator<FileItem> iterator = fileUpload.files.values().iterator();
while(iterator.hasNext()){

FileItem item = iterator.next();
　　
String fileName = fileUpload.getFileName(item);
if( fileName != null && !fileName.equals("")){
//获取服务器的路径
String serverPath = request.getSession().getServletContext().getRealPath("");
　　　//对上传文件重新命名
String rename = getReName(fileName);
File file = new File( serverPath+"/upload/"+rename);

try {

if( !file.isDirectory()){

//上传成功后做数据库操作
item.write(file);

//数据库操作，这里没有考虑效率，如果是多文件上传，可以考虑SQL的批处理
db.saveOrUpdateOrDel("insert into uploadfile(realname,rename_) values(?,?)",
new Object[]{fileName ,rename });
}
} catch (Exception e) {
e.printStackTrace();
//将上传的文件删除
if( file.exists()) file.delete();
}
}

}

}

/**
* 以服务器当前时间为为上传文件重新命名
* @param fileName
* @return    新文件名
*/
private String getReName(String fileName){
int begin = fileName.lastIndexOf(".");
String extend = fileName.substring(begin, fileName.length());
return System.currentTimeMillis() + extend;
}

显示文件下载列表Servlet ，实体类就不再发了，可以在最下面按照SQL语句写

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

DBUtils db = new DBUtils();
List<UploadFile> ufs = db.queryForObject("select * from uploadfile", null, UploadFile.class);
request.setAttribute("filelist", ufs);
request.getRequestDispatcher("filelist.jsp").forward(request,response);
}

显示文件下载列表页面

╮(╯▽╰)╭ 循环部分发出来就行了，这个filelist.jsp页面本来就这么一点东西

<c:forEach items="${filelist}" var="uf">
${uf.realname }   <a href="down?re=${uf.rename_}&real=${uf.realname}">下载</a><br>
</c:forEach>

文件下载Servlet

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

//获取下载文件的名字
String re = request.getParameter("re");
//获取下载文件的真实名字
String real = request.getParameter("real");

//获取服务器路径
String serverPath = request.getSession().getServletContext().getRealPath("");
File f = new File( serverPath+"/upload/"+re);

if(    f.exists()    ){
FileInputStream  fis = new FileInputStream(f);
//手动转码，示例中是GET请求，要么手动转码，要么在过滤器中进行GET请求处理，当然能在服务器直接配置get请求编码就一劳永逸了
String filename = new String(real.getBytes("ISO8859-1"),"UTF-8");
byte[] b = new byte[fis.available()];
fis.read(b);
response.setCharacterEncoding("UTF-8");
response.setHeader("Content-Disposition","attachment; filename="+filename );
//获取响应报文输出流对象
ServletOutputStream  out =response.getOutputStream();
out.write(b);
out.flush();
out.close();
}

}

MySQL 数据库部分

SET NAMES utf8;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
--  Table structure for `uploadfile`
-- ----------------------------
DROP TABLE IF EXISTS `uploadfile`;
CREATE TABLE `uploadfile` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`realname` varchar(255) NOT NULL COMMENT '上传前的文件名字',
`rename_` varchar(255) NOT NULL COMMENT '重新命名',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8;

SET FOREIGN_KEY_CHECKS = 1;