將頁面提交檔案上傳到伺服器目錄下面(只能是POST提交方式)
需要引入commons-fileupload.jar

form表單例子如下

<form action="user.do?op=updateUserImage" id="upfile"  method="post" enctype="multipart/form-data">
     <input id="fuserid" type="hidden" name="id" value="12334" />
     <input id="newuserimage" name="newuserimage"
 
 value="瀏覽圖片" type="file" />
     <input type="submit" value="tijiao"/>
</form>

檔案上傳

package com.xu.utils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import
 
 java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.UUID;

import javax.servlet.ServletException;
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;

@SuppressWarnings(value="all")
public class UploadFile {


    private static String fileNmae="";

    /**
     * 隨機資料夾名
     * @return
     */
    private String randomFilePath(){
        SimpleDateFormat format=new SimpleDateFormat("yyyy/MM/dd/HH");
        return format.format(new Date()).replace("/", File.separator)+File.separator;
    }

    /**
     * 隨機檔名
     * @return
     */
    private String randomFileName(){
        fileNmae= UUID.randomUUID().toString().substring(0,10);
        return fileNmae;
    }

    private String getFileName(String name){
        return name.substring(name.lastIndexOf("."));
    }

    /**
     * 單檔案上傳
     * @param request HttpServletRequest
     * @param directories 在 Tomcat webapps 下面的存放檔案的資料夾的資料夾名
     * @return
     * @throws FileUploadException
     * @throws IOException
     * @throws ServletException
     */
    public FileBean singleFileUpload(HttpServletRequest request,String directories) throws FileUploadException, IOException, ServletException{
        request.setCharacterEncoding("UTf-8");
        String realPath=new File(request.getRealPath("/")).getParent()+File.separator+directories+File.separator+randomFilePath();
        randomFileName();//獲取隨機檔名
        String webPath=directories+File.separator+randomFilePath()+fileNmae;
        DiskFileItemFactory factory=new DiskFileItemFactory(1024*30,new File(realPath));//建立檔案目錄
        ServletFileUpload fileUpload=new ServletFileUpload(factory);
        List<FileItem> list = fileUpload.parseRequest(request); 
        FileBean bean=new FileBean();
        for(FileItem item:list){
            if(!item.isFormField()){//說明是檔案型別
                realPath+=fileNmae+getFileName(item.getName());
                webPath+=getFileName(item.getName());               
                bean.setFileType(item.getContentType());
                bean.setFileSize(item.getSize());
                bean.setRealPath(realPath);
                bean.setWebPath(webPath);
                bean.setOriginName(item.getName());
                bean.setNewName(fileNmae+getFileName(item.getName()));              
                InputStream read=item.getInputStream();
                OutputStream write=new FileOutputStream(realPath);
                byte[] bt = new byte[1024];
                int len=0;
                while((len=read.read(bt))!=-1){
                    write.write(bt, 0, len);
                }
                write.flush();
                write.close();
                read.close();
                item.delete();
                break;
            }
        }
        return bean;
    }

    /**
     * 多檔案上傳
     * @param request HttpServletRequest
     * @param directories directories 在 Tomcat webapps 下面的存放檔案的資料夾的資料夾名
     * @return
     * @throws FileUploadException
     * @throws IOException
     */
    public List<FileBean> multiFileUpload(HttpServletRequest request,String directories) throws FileUploadException, IOException{
        request.setCharacterEncoding("UTf-8");
        String realPath=new File(request.getRealPath("/")).getParent()+File.separator+directories+File.separator+randomFilePath();
        String webPath=directories+File.separator+randomFilePath();
        DiskFileItemFactory factory=new DiskFileItemFactory(1024*30,new File(realPath));//建立檔案目錄
        ServletFileUpload fileUpload=new ServletFileUpload(factory);
        List<FileItem> list = fileUpload.parseRequest(request); 
        List<FileBean> filelist=new ArrayList<FileBean>();
        FileBean bean=null;
        for(FileItem item:list){
            if(!item.isFormField()){//說明是檔案型別
                randomFileName();//獲取隨機檔名
                bean=new FileBean();
                realPath+=fileNmae+getFileName(item.getName());
                webPath+=fileNmae+getFileName(item.getName());              
                bean.setFileType(item.getContentType());
                bean.setFileSize(item.getSize());
                bean.setRealPath(realPath);
                bean.setWebPath(webPath);
                bean.setOriginName(item.getName());
                bean.setNewName(fileNmae+getFileName(item.getName()));              
                InputStream read=item.getInputStream();
                OutputStream write=new FileOutputStream(realPath);
                byte[] bt = new byte[1024];
                int len=0;
                while((len=read.read(bt))!=-1){
                    write.write(bt, 0, len);
                }
                write.flush();
                write.close();
                read.close();
                item.delete();
                filelist.add(bean);
            }
        }       
        return filelist;
    }




}

檔案上傳Bean

package com.xu.utils;

import java.io.Serializable;

public class FileBean implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 8999004458855350561L;


    private String fileType;
    private String originName;
    private String realPath;
    private String webPath;
    private String newName;
    private Long fileSize;
    public String getFileType() {
        return fileType;
    }
    public void setFileType(String fileType) {
        this.fileType = fileType;
    }
    public String getOriginName() {
        return originName;
    }
    public void setOriginName(String originName) {
        this.originName = originName;
    }
    public String getRealPath() {
        return realPath;
    }
    public void setRealPath(String realPath) {
        this.realPath = realPath;
    }
    public String getWebPath() {
        return webPath;
    }
    public void setWebPath(String webPath) {
        this.webPath = webPath;
    }
    public String getNewName() {
        return newName;
    }
    public void setNewName(String newName) {
        this.newName = newName;
    }
    public Long getFileSize() {
        return fileSize;
    }
    public void setFileSize(Long fileSize) {
        this.fileSize = fileSize;
    }
    @Override
    public String toString() {
        return "FileBean [fileType=" + fileType + ", originName=" + originName + ", realPath=" + realPath
                + ", webPath=" + webPath + ", newName=" + newName + ", fileSize=" + fileSize + "]";
    }   
}