JavaWeb中上传和下载文件实例代码

一丶先引入上传下载的lib

二丶上传的的servlet

package com.test.action;
import java.io.file;
import java.io.fileoutputstream;
import java.io.ioexception;
import java.io.inputstream;
import java.io.outputstream;
import java.util.list;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
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.disk.diskfileitemfactory;
import org.apache.commons.fileupload.servlet.servletfileupload;
@webservlet("/upload")
public class fileuploadaction extends httpservlet {
  private static final long serialversionuid = 1l;
  protected void dopost(httpservletrequest request,
      httpservletresponse response) throws servletexception, ioexception {
    // 设置编码
    request.setcharacterencoding("utf-8"); 
    //对提交的数据进行处理，保存上传文件 
    boolean success = processupload(request);
    if(success){
      //获取表单text控件的值
      string account = request.getattribute("account").tostring();
      system.out.println(account);
      //获取文件上传的原始名称
      string filename = request.getattribute("upfile").tostring();
      system.out.println(filename);
      //获取文件上传后，服务器上保存的名字
      string filenameserver = request.getattribute("upfileserver").tostring();
      system.out.println(filenameserver);
      request.setattribute("upfile", filenameserver);
      request.setattribute("message", "上传成功");
    }
    request.getrequestdispatcher("/upload.jsp").forward(request, response);
  }
  private boolean processupload(httpservletrequest request) {
    boolean success = true;
    string message = null;
    // 获取文件需要上传到的路径
    string path = request.getservletcontext().getrealpath("/upload");
    system.out.println(path);
    // 如果此文件夹不存在，则构造此文件夹
    file f = new file(path);
    if (!f.exists()) {
      f.mkdir();
    }
    // 构造出文件工厂，用于存放jsp页面中传递过来的文件
    diskfileitemfactory factory = new diskfileitemfactory();
    // 设置上传文件的保存路径
    factory.setrepository(f);
    // 设置缓存大小，如果文件大于缓存大小时，则先把文件放到缓存中
    factory.setsizethreshold(1 * 1024 * 1024);
    servletfileupload upload = new servletfileupload(factory);
    // 设置可以上传文件大小的上界20mb
    upload.setsizemax(20 * 1024 * 1024);
    try {
      // 可以上传多个文件
      list<fileitem> list = (list<fileitem>) upload.parserequest(request);
      for (fileitem item : list) {
        // 获取表单的属性名字
        string name = item.getfieldname();
        if (item.isformfield()) {
          string value = item.getstring();
          //解决乱码问题
          value = new string(value.getbytes("iso-8859-1"),"utf-8"); 
          request.setattribute(name, value);
        } else {
          // 获得文件类型
          string contenttype = item.getcontenttype();
          // 获得文件大小
          long filesize = item.getsize();
          // 获取路径名
          string value = item.getname();
          // 索引到最后一个反斜杠
          int start = value.lastindexof("\\");
          // 截取 上传文件的 字符串名字，加1是 去掉反斜杠，
          string filename = value.substring(start + 1);
          if (filename != null && !filename.trim().equals("")) {
            // 如果上传的文件不是图片，那么不上传
            string allimgext = ".jpg|.jpeg|.gif|.bmp|.png|";
            string extname = filename.substring(filename.indexof("."), filename.length());
            if (allimgext.indexof(extname + "|") == -1) {
              message = "该文件类型不允许上传。请上传 " + allimgext
                  + " 类型的文件，当前文件类型为" + extname;
              success = false;
              break;
            }
            request.setattribute(name, filename);
            // 随机数产生名称
            string newname = system.currenttimemillis() + extname;
            request.setattribute(name + "server", newname);
            // 将文件保存到服务器中
            inputstream in = item.getinputstream();
            // 原文件名
            // outputstream out = new fileoutputstream(new file(path, filename));
            // 随机数文件名
            outputstream out = new fileoutputstream(new file(path,
                newname));
            int length = 0;
            byte[] buf = new byte[1024];
            while ((length = in.read(buf)) != -1) {
              out.write(buf, 0, length);
            }
            in.close();
            out.close();
          }
        }
      }
    } catch (fileuploadexception e) {
      message = "文件的内容过大，请上传小于20mb的文件" ;
      success = false;
      e.printstacktrace();
    } catch (ioexception e) {
      success = false;
      e.printstacktrace();
    }
    request.setattribute("message", message);
    return success;
  }
}

三丶下载的servlet

package com.test.action;
import java.io.file;
import java.io.fileinputstream;
import java.io.ioexception;
import java.io.outputstream;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
@webservlet("/download")
public class filedownloadaction extends httpservlet {
  private static final long serialversionuid = 1l;
  protected void doget(httpservletrequest request,
      httpservletresponse response) throws servletexception, ioexception {
    string id = request.getparameter("id");
    // 根据主键读取文件的真实名字 + 服务器上的名字
    processdownload("1444442288605.png", "腾讯.png", request, response);
  }
  private boolean processdownload(string filename, string savename,
      httpservletrequest request, httpservletresponse response) {
    boolean success = true;
    // 获取文件下载所在的路径
    string path = request.getservletcontext().getrealpath("/upload");
    file fileload = new file(path, filename); // 下载文件
    long filelength = fileload.length(); // 文件大小
    byte[] buffer = new byte[1024]; // 缓冲字节数组
    try {
      response.reset();
      response.setheader("content-disposition", "attachment;filename=\""
          + new string(savename.getbytes("gb2312"), "iso-8859-1") + "\"");
      response.setcontenttype("application/octet-stream");
      response.setheader("content_length", string.valueof(filelength));
      outputstream os = response.getoutputstream();
      fileinputstream in = new fileinputstream(fileload);
      int hasread = 0;
      while ((hasread = in.read(buffer)) != -1) {
        os.write(buffer, 0, hasread);
      }
      os.flush();
      os.close();
      in.close();
    } catch (ioexception e) {
      success = false;
      e.printstacktrace();
    }
    return success;
  }
}

以上所述是小编给大家介绍的javaweb中上传和下载文件实例代码，希望对大家有所帮助