Servlet实现文件的上传与下载

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileUpload;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.util.List;

public class UploadServlet extends HttpServlet {
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 //1.判断上传的数据是否是多段数据（只有事多段的数据才是文件上传的）
 if(FileUpload.isMultipartContent(req)){
  //创建FileItemFactory工厂实现类
  FileItemFactory fileItemFactory=new DiskFileItemFactory();
  //创建用于解析上传数据的工具类FileUpload
 FileUpload fileUpload=new FileUpload(fileItemFactory);
  try {
  List list=fileUpload.parseRequest(req);
  //循环判断每一个表单项是普通类型还是上传的文件
  for(FileItem fileItem:list){
   if(fileItem.isFormField()){
   //普通表单项
   System.out.println("表单项的name属性值："+fileItem.getFieldName());
   //参数UTF-8解决乱码问题
   System.out.println("表单项的value值："+fileItem.getString("UTF-8"));
   }else{
   //上传的文件
   System.out.println("表单项的name属性值："+fileItem.getFieldName());
   System.out.println("上传的文件名："+fileItem.getName());
   fileItem.write(new File("D:\\"+fileItem.getName()));
   }

  }
  } catch (Exception e) {
  e.printStackTrace();
  }
 }
 }
}

import org.apache.commons.io.IOUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URLEncoder;

public class download extends HttpServlet {
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 //1.获取要下载的文件名
 String downloadfilename="1.jpg";
 //2.读取下载的文件内容（通过ServletContext对象可以读取）
 ServletContext servletCOntext=getServletContext();
 //获取要下载的文件类型
 String mimetype=servletContext.getMimeType("/file/"+downloadfilename);
 //4.回传前告诉客户端回传的类型
 resp.setContentType("mimetype");
 //5.告诉客户端收到的数据是用来下载的（响应头）
 //Content-Disposition 响应头表示收到的数据怎么处理
 //attachment表示附件，表示下载
 resp.setHeader("Content-Disposition","attachment;filename="+downloadfilename);
  //url编码解决下载文件名乱码问题(谷歌和IE)
 // resp.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode("中国.jpg","UTF-8"));

 InputStream resourceAsStream= servletContext.getResourceAsStream("/file/"+downloadfilename);
 //获取响应的输出流
 OutputStream outputStream=resp.getOutputStream();
 //3，把下载的文件传回给客户端
 //读取输入流的数据复制给输出流，输出给客户端
 IOUtils.copy(resourceAsStream,outputStream);

 }
}

<%@ page cOntentType="text/html;charset=UTF-8" language="java" %>



 
 



 用户名：

 头像：