Java Servlet简单实例分享(文件上传下载demo)

项目结构

src
  com
    servletdemo
        DownloadServlet.java
        ShowServlet.java
        UploadServlet.java

WebContent
  jsp
    servlet
        download.html
        fileupload.jsp
        input.jsp

  WEB-INF
    lib
        commons-fileupload-1.3.1.jar
        commons-io-2.4.jar

1.简单实例

ShowServlet.java

package com.servletdemo;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class ShowServlet
 */
@WebServlet("/ShowServlet")
public class ShowServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;
  PrintWriter pw=null;
  /**
   * @see HttpServlet#HttpServlet()
   */
  public ShowServlet() {
    super();
    // TODO Auto-generated constructor stub
  }

  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    this.doPost(request, response);
  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    request.setCharacterEncoding("gb2312");
    response.setContentType("text/html;charset=gb2312");
    pw=response.getWriter();
    String name=request.getParameter("username");
    String password=request.getParameter("password");
    pw.println("user name:" + name);
    pw.println("<br>");
    pw.println("user password:" + password);
  }

}

input.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
  pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>servlet demo</title>
</head>
<body>
<form action="<%=request.getContextPath()%>/ShowServlet">
    <table>
      <tr>
        <td>name</td>
        <td><input type="text" name="username"></td>
      </tr>
      <tr>
        <td>password</td>
        <td><input type="text" name="password"></td>
      </tr>
      <tr>
        <td><input type="submit" value="login"></td>
        <td><input type="reset" value="cancel"></td>
      </tr>
    </table>
  </form>
</body>
</html>

2.文件上传实例

UploadServlet.java

package com.servletdemo;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.text.DateFormat;
import java.util.Date;
import java.util.List;
import java.util.UUID; 

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.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
/**
 * Servlet implementation class UploadServlet
 */
@WebServlet("/servlet/UploadServlet")
public class UploadServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  /**
   * @see HttpServlet#HttpServlet()
   */
  public UploadServlet() {
    super();
    // TODO Auto-generated constructor stub
  }

  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    //设置编码
    request.setCharacterEncoding("UTF-8");
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter pw = response.getWriter();
    try {
      //设置系统环境
      DiskFileItemFactory factory = new DiskFileItemFactory();
      //文件存储的路径
      String storePath = getServletContext().getRealPath("/WEB-INF/files");
      //判断传输方式 form enctype=multipart/form-data
      boolean isMultipart = ServletFileUpload.isMultipartContent(request);
      if(!isMultipart)
      {
        pw.write("传输方式有错误！");
        return;
      }
      ServletFileUpload upload = new ServletFileUpload(factory);
      upload.setFileSizeMax(4*1024*1024);//设置单个文件大小不能超过4M
      upload.setSizeMax(4*1024*1024);//设置总文件上传大小不能超过6M
      //监听上传进度
      upload.setProgressListener(new ProgressListener() { 

        //pBytesRead：当前以读取到的字节数
        //pContentLength：文件的长度
        //pItems:第几项
        public void update(long pBytesRead, long pContentLength,
            int pItems) {
          System.out.println("已读去文件字节 :"+pBytesRead+" 文件总长度："+pContentLength+"  第"+pItems+"项"); 

        }
      });
      //解析
      List<FileItem> items = upload.parseRequest(request);
      for(FileItem item: items)
      {
        if(item.isFormField())//普通字段，表单提交过来的
        {
          String name = item.getFieldName();
          String value = item.getString("UTF-8");
          System.out.println(name+"=="+value);
        }else
        {
//         String mimeType = item.getContentType(); 获取上传文件类型
//         if(mimeType.startsWith("image")){
          InputStream in =item.getInputStream();
          String fileName = item.getName();
          if(fileName==null || "".equals(fileName.trim()))
          {
            continue;
          }
          fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
          fileName = UUID.randomUUID()+"_"+fileName; 

          //按日期来建文件夹
          String newStorePath = makeStorePath(storePath);
          String storeFile = newStorePath+"\\"+fileName;
          OutputStream out = new FileOutputStream(storeFile);
          byte[] b = new byte[1024];
          int len = -1;
          while((len = in.read(b))!=-1)
          {
             out.write(b,0,len);
          }
          in.close();
          out.close();
          item.delete();//删除临时文件
        }
       }
//     }
    }catch(org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException e){
       //单个文件超出异常
      pw.write("单个文件不能超过4M");
    }catch(org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException e){
      //总文件超出异常
      pw.write("总文件不能超过6M"); 

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

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    doGet(request, response);
  }

  private String makeStorePath(String storePath) { 

    Date date = new Date();
    DateFormat df = DateFormat.getDateInstance(DateFormat.MEDIUM);
    String s = df.format(date);
    String path = storePath+"\\"+s;
    File file = new File(path);
    if(!file.exists())
    {
      file.mkdirs();//创建多级目录，mkdir只创建一级目录
    }
    return path; 

  }
  private String makeStorePath2(String storePath, String fileName) {
    int hashCode = fileName.hashCode();
    int dir1 = hashCode & 0xf;// 0000~1111：整数0~15共16个
    int dir2 = (hashCode & 0xf0) >> 4;// 0000~1111：整数0~15共16个 

    String path = storePath + "\\" + dir1 + "\\" + dir2; // WEB-INF/files/1/12
    File file = new File(path);
    if (!file.exists())
      file.mkdirs(); 

    return path;
  } 

}

fileupload.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
  pageEncoding="ISO-8859-1"%>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Upload File Demo</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/servlet/UploadServlet" method="post" enctype="multipart/form-data">
  user name<input type="text" name="username"/> <br/>
  <input type="file" name="f1"/><br/>
  <input type="file" name="f2"/><br/>
  <input type="submit" value="save"/>
 </form>
</body>
</html>

3.文件下载实例

DownloadServlet.java

package com.servletdemo;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter; 

import java.net.URLEncoder;

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 javax.servlet.ServletResponse; 

/**
 * Servlet implementation class DownloadServlet
 */
@WebServlet("/DownloadServlet")
public class DownloadServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  /**
   * @see HttpServlet#HttpServlet()
   */
  public DownloadServlet() {
    super();
    // TODO Auto-generated constructor stub
  }

  /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    download1(response);
  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    doGet(request, response);
  }

  public void download1(HttpServletResponse response) throws IOException{
    //获取所要下载文件的路径
     String path = this.getServletContext().getRealPath("/files/web配置.xml");
     String realPath = path.substring(path.lastIndexOf("\\")+1); 

     //告诉浏览器是以下载的方法获取到资源
     //告诉浏览器以此种编码来解析URLEncoder.encode(realPath, "utf-8"))
    response.setHeader("content-disposition","attachment; filename="+URLEncoder.encode(realPath, "utf-8"));
    //获取到所下载的资源
     FileInputStream fis = new FileInputStream(path);
     int len = 0;
      byte [] buf = new byte[1024];
      while((len=fis.read(buf))!=-1){
        response.getOutputStream().write(buf,0,len);
      }
   }

}

download.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Download Demo</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>
<a href = "/JavabeanDemo/DownloadServlet">download</a>
</body>
</html>

以上这篇Java Servlet简单实例分享(文件上传下载demo)就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持我们。