檔案上傳程式碼

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.List;
import java.util.UUID;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import
 
 javax.servlet.http.HttpServletResponse;

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

public class UploadServlet2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    // request.setCharacterEncoding("UTF-8");
    // 要執行檔案上傳的操作
    // 判斷表單是否支援檔案上傳。即：enctype="multipart/form-data"
 

    boolean isMultipartContent = ServletFileUpload
            .isMultipartContent(request);
    if (!isMultipartContent) {
        throw new RuntimeException("your form is not multipart/form-data");
    }

    // 建立一個DiskFileItemfactory工廠類
    DiskFileItemFactory factory = new DiskFileItemFactory();
    factory.setRepository(new File("f:\\"));// 指定臨時檔案的儲存目錄
    // 建立一個ServletFileUpload核心物件
    ServletFileUpload sfu = new ServletFileUpload(factory);
    // 解決上傳表單項亂碼問題
    sfu.setHeaderEncoding("UTF-8");
    // 限制上傳檔案的大小

    // 解析request物件，並得到一個表單項的集合
    try {
        // sfu.setFileSizeMax(1024*1024*3);//表示3M大小
        List<FileItem> fileItems = sfu.parseRequest(request);

        // 遍歷表單項資料
        for (FileItem fileitem : fileItems) {
            if (fileitem.isFormField()) {
                // 普通表單項
                processFormField(fileitem);
            } else {
                // 上傳表單項
                processUploadField(fileitem);
            }
        }

    } catch (FileUploadBase.FileSizeLimitExceededException e) {
        // throw new RuntimeException("檔案過在，不能超過3M");

        System.out.println("檔案過在，不能超過3M");
    } catch (FileUploadBase.SizeLimitExceededException e) {
        System.out.println("總檔案大小不能超過6M");
    } catch (FileUploadException e) {
        e.printStackTrace();
    }
}

private void processUploadField(FileItem fileitem) {
    try {
        // 得到檔案輸入流
        InputStream is = fileitem.getInputStream();

        // 建立一個檔案存檔的目錄
        String directoryRealPath = this.getServletContext().getRealPath(
                "/WEB-INF/upload");
        File storeDirectory = new File(directoryRealPath);// 即代表檔案又代表目錄
        if (!storeDirectory.exists()) {
            storeDirectory.mkdirs();// 建立一個指定的目錄
        }
        // 得到上傳的名子
        String filename = fileitem.getName();// 檔案項中的值 F:\**\**\
        if (filename != null) {
            // filename =
            // filename.substring(filename.lastIndexOf(File.separator)+1);
            filename = FilenameUtils.getName(filename);// 效果同上
        }

        // 解決檔案同名的問題
        filename = UUID.randomUUID() + "_" + filename;
        // 目錄打散
        // String childDirectory = makeChildDirectory(storeDirectory); //
        // 2015-10-19
        String childDirectory = makeChildDirectory(storeDirectory, filename); // a/b

        // 上傳檔案，自動刪除臨時檔案
        fileitem.write(new File(storeDirectory, childDirectory
                + File.separator + filename));
        fileitem.delete();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

// 上傳表單項
private void processUploadField1(FileItem fileitem) {

    try {
        // 得到檔案輸入流
        InputStream is = fileitem.getInputStream();

        // 建立一個檔案存檔的目錄
        String directoryRealPath = this.getServletContext().getRealPath(
                "/WEB-INF/upload");
        File storeDirectory = new File(directoryRealPath);// 即代表檔案又代表目錄
        if (!storeDirectory.exists()) {
            storeDirectory.mkdirs();// 建立一個指定的目錄
        }
        // 得到上傳的名子
        String filename = fileitem.getName();// 
        // 處理檔名
        /*
         * 解決此問題： F:\\apache-tomcat-7.0.52\\webapps\\**\\upload\\F:\\**
         */
        if (filename != null) {
            // filename =
            // filename.substring(filename.lastIndexOf(File.separator)+1);
            filename = FilenameUtils.getName(filename);// 效果同上
        }

        // 解決檔案同名的問題
        filename = UUID.randomUUID() + "_" + filename;

        // 目錄打散
        // String childDirectory = makeChildDirectory(storeDirectory); //
        // 2015-10-19
        String childDirectory = makeChildDirectory(storeDirectory, filename); // 2015-10-19

        // 在storeDirectory下，建立完整目錄下的檔案
        File file = new File(storeDirectory, childDirectory
                + File.separator + filename); // 絕對目錄/日期目錄/檔名
        // 通過檔案輸出流將上傳的檔案儲存到磁碟
        FileOutputStream fos = new FileOutputStream(file);

        int len = 0;
        byte[] b = new byte[1024];
        while ((len = is.read(b)) != -1) {
            fos.write(b, 0, len);
        }
        //關閉流
        fos.close();
        is.close();

        fileitem.delete();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

// 目錄打散
private String makeChildDirectory(File storeDirectory, String filename) {
    int hashcode = filename.hashCode();// 返回字元轉換的32位hashcode碼
    System.out.println(hashcode);
    String code = Integer.toHexString(hashcode); // 把hashcode轉換為16進位制的字元
                                                    // abdsaf2131safsd
    System.out.println(code);
    String childDirectory = code.charAt(0) + File.separator
            + code.charAt(1); // a/b
    // 建立指定目錄
    File file = new File(storeDirectory, childDirectory);
    if (!file.exists()) {
        file.mkdirs();
    }
    return childDirectory;
}

// 按日期打散
/*
 * private String makeChildDirectory(File storeDirectory) {
 * 
 * SimpleDateFormat sdf =new SimpleDateFormat("yyyy-MM-dd"); String
 * dateDirectory = sdf.format(new Date()); //只管建立目錄 File file = new
 * File(storeDirectory,dateDirectory); if(!file.exists()){ file.mkdirs(); }
 * 
 * return dateDirectory; }
 */
// 普通表單項
private void processFormField(FileItem fileitem) {
    try {
        String fieldname = fileitem.getFieldName();// 欄位名
        String fieldvalue = fileitem.getString("UTF-8");// 欄位值
        //fieldvalue = new String(fieldvalue.getBytes("iso-8859-1"),"utf-8");
        System.out.println(fieldname + "=" + fieldvalue);
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
}

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

}

檔案上傳注意問題

1. 設定上傳檔案的大小問題；
2. 判斷上傳檔案型別，如果是可執行檔案等是非常危險的；
3. 如果系統較大，上傳的檔案比較多，注意要多分一下目錄(按時間等)，解決可能上傳檔案同名情況，以及上傳檔案的儲存路徑
4. 注意設定編碼問題，form表單中要有上傳的屬性，才能上傳。

檔案下載程式碼

import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //設定一個要下載的檔案
        String filename = "電器";

        //設定檔名的編碼
        if(request.getHeader("user-agent").toLowerCase().contains("msie")){
            filename = URLEncoder.encode(filename, "UTF-8");//將不安全的檔名改為UTF-8格式
        }else{
            filename = new String(filename.getBytes("UTF-8"),"iso-8859-1");//火狐瀏覽器
        }
        //告知瀏覽器要下載檔案
        response.setHeader("content-disposition", "attachment;filename="+filename);
        //response.setHeader("content-type", "image/jpeg");
        response.setContentType(this.getServletContext().getMimeType(filename));//根據檔名自動獲得檔案型別

        response.setCharacterEncoding("UTF-8");//告知伺服器使用什麼編碼
        //建立一個檔案輸出流
        PrintWriter out = response.getWriter();
        out.write("電視機,20\n");
        out.write("洗衣機,10\n");
        out.write("冰箱,8\n");
    }

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

}