转载 文件上传下载

web.xml 更新为:

web.xml<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>FileUploadServlet</servlet-name>
    <servlet-class>FileUploadServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>FileUploadServlet</servlet-name>
    <url-pattern>/FileUploadServlet</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>upload.html</welcome-file>
  </welcome-file-list>
</web-app>

 
    其中,我把<welcome-file-list>    <welcome-file>index.jsp</welcome-file>  </welcome-file-list> 的欢迎文件设为了upload.html,
这样等完成后可能直接用http://localhost:8080/FileUpload/ 来访问upload.html. 不改的话, 可以在http://localhost:8080/FileUpload/upload.html
页面上传文件.    在写FileUploadServlet 之前, 先将之前下载的commons-fileupload 和commons-io 组件包压缩文件解压出来, 把里面的
commons-fileupload-1.2.jar (lib文件夹下) 和 commons-io-1.3.2.jar 拷到WebRoot/WEB-INF/lib 文件夹下, 以便使用它们的功能.

    FileUploadServlet.java 的源代码如下, 附有详细注解:
FileUploadServlet.java import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
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.FileUploadException;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class FileUploadServlet extends HttpServlet {
public FileUploadServlet() {
  super();
}
public void destroy() {
  super.destroy(); // Just puts "destroy" string in log
  // Put your code here
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  final long MAX_SIZE = 3 * 1024 * 1024;// 设置上传文件最大为 3M
  // 允许上传的文件格式的列表
  final String[] allowedExt = new String[] { "jpg", "jpeg", "gif", "txt",
    "doc", "docx", "mp3", "wma", "m4a" };
  response.setContentType("text/html");
  // 设置字符编码为UTF-8, 这样支持汉字显示
  response.setCharacterEncoding("UTF-8");
  // 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload
  DiskFileItemFactory dfif = new DiskFileItemFactory();
  dfif.setSizeThreshold(4096);// 设置上传文件时用于临时存放文件的内存大小,这里是4K.多于的部分将临时存在硬盘
  dfif.setRepository(new File(request.getRealPath("/")
    + "ImagesUploadTemp"));// 设置存放临时文件的目录,web根目录下的ImagesUploadTemp目录
  // 用以上工厂实例化上传组件
  ServletFileUpload sfu = new ServletFileUpload(dfif);
  // 设置最大上传尺寸
  sfu.setSizeMax(MAX_SIZE);
  PrintWriter out = response.getWriter();
  // 从request得到 所有 上传域的列表
  List fileList = null;
  try {
   fileList = sfu.parseRequest(request);
  } catch (FileUploadException e) {// 处理文件尺寸过大异常
   if (e instanceof SizeLimitExceededException) {
    out.println("文件尺寸超过规定大小:" + MAX_SIZE + "字节<p />");
    out.println("<a href=/"upload.html/" target=/"_top/">返回</a>");
    return;
   }
   e.printStackTrace();
  }
  // 没有文件上传
  if (fileList == null || fileList.size() == 0) {
   out.println("请选择上传文件<p />");
   out.println("<a href=/"upload.html/" target=/"_top/">返回</a>");
   return;
  }
  // 得到所有上传的文件
  Iterator fileItr = fileList.iterator();
  // 循环处理所有文件
  while (fileItr.hasNext()) {
   FileItem fileItem = null;
   String path = null;
   long size = 0;
   // 得到当前文件
   fileItem = (FileItem) fileItr.next();
   // 忽略简单form字段而不是上传域的文件域(<input type="text" />等)
   if (fileItem == null || fileItem.isFormField()) {
    continue;
   }
   // 得到文件的完整路径
   path = fileItem.getName();
   // 得到文件的大小
   size = fileItem.getSize();
   if ("".equals(path) || size == 0) {
    out.println("请选择上传文件<p />");
    out.println("<a href=/"upload.html/" target=/"_top/">返回</a>");
    return;
   }
   // 得到去除路径的文件名
   String t_name = path.substring(path.lastIndexOf("//") + 1);
   // 得到文件的扩展名(无扩展名时将得到全名)
   String t_ext = t_name.substring(t_name.lastIndexOf(".") + 1);
   // 拒绝接受规定文件格式之外的文件类型
   int allowFlag = 0;
   int allowedExtCount = allowedExt.length;
   for (; allowFlag < allowedExtCount; allowFlag++) {
    if (allowedExt[allowFlag].equals(t_ext))
     break;
   }
   if (allowFlag == allowedExtCount) {
    out.println("请上传以下类型的文件<p />");
    for (allowFlag = 0; allowFlag < allowedExtCount; allowFlag++)
     out.println("*." + allowedExt[allowFlag]
       + "&nbsp;&nbsp;&nbsp;");
    out.println("<p /><a href=/"upload.html/" target=/"_top/">返回</a>");
    return;
   }
   long now = System.currentTimeMillis();
   // 根据系统时间生成上传后保存的文件名
   String prefix = String.valueOf(now);
   // 保存的最终文件完整路径,保存在web根目录下的ImagesUploaded目录下
   String u_name = request.getRealPath("/") + "ImagesUploaded/"
     + prefix + "." + t_ext;
   try {
    // 保存文件
    fileItem.write(new File(u_name));
    out.println("文件上传成功. 已保存为: " + prefix + "." + t_ext
      + " &nbsp;&nbsp;文件大小: " + size + "字节<p />");
    out.println("<a href=/"upload.html/" target=/"_top/">继续上传</a>");
   } catch (Exception e) {
    e.printStackTrace();
   }
}
}
public void init() throws ServletException {
  // Put your code here
}
}



    保存后部署项目(MyEclipse下直接点击Deploy J2EE...按钮, 然后选择Tomcat服务器). 没有MyEclipse的话, 把WebRoot 拷到
Tomcat 主目录下的webapps 目录下, 并重命名为 FileUpload 然后启动Tomcat. (或直接下载我在文章开始提供的工程打包rar文件).
最后打开浏览器, 输入url:





public HttpServletResponse download(String path, HttpServletResponse response) {
        try {
            // path是指欲下载的文件的路径。
            File file = new File(path);
            // 取得文件名。
            String filename = file.getName();
            // 取得文件的后缀名。
            String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();

            // 以流的形式下载文件。
            InputStream fis = new BufferedInputStream(new FileInputStream(path));
            byte[] buffer = new byte[fis.available()];
            fis.read(buffer);
            fis.close();
            // 清空response
            response.reset();
            // 设置response的Header
            response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
            response.addHeader("Content-Length", "" + file.length());
            OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
            response.setContentType("application/octet-stream");
            toClient.write(buffer);
            toClient.flush();
            toClient.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        return response;
    }

    public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {
        // 下载本地文件
        String fileName = "Operator.doc".toString(); // 文件的默认保存名
        // 读到流中
        InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径
        // 设置输出的格式
        response.reset();
        response.setContentType("bin");
        response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
        // 循环取出流中的数据
        byte[] b = new byte[100];
        int len;
        try {
            while ((len = inStream.read(b)) > 0)
                response.getOutputStream().write(b, 0, len);
            inStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void downloadNet(HttpServletResponse response) throws MalformedURLException {
        // 下载网络文件
        int bytesum = 0;
        int byteread = 0;

        URL url = new URL("windine.blogdriver.com/logo.gif");

        try {
            URLConnection conn = url.openConnection();
            InputStream inStream = conn.getInputStream();
            FileOutputStream fs = new FileOutputStream("c:/abc.gif");

            byte[] buffer = new byte[1204];
            int length;
            while ((byteread = inStream.read(buffer)) != -1) {
                bytesum += byteread;
                System.out.println(bytesum);
                fs.write(buffer, 0, byteread);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }