JAVA POI上传excel文件到数据库并备份（上）

一、电商系统和办公系统时常会用到Excel的导入与导出，在JAVA代码实现时，通常使用POI来处理，今天用一个demo为大家介绍POI上传excel文件并将数据导入数据库的实现过程。demo是一个jsp/servlet+maven的web项目。

二、环境：

数据库：mysql

excel：*.xls

工具：IDEA

三、介绍MAVEN配置文件，引入poi，jstl（因为页面展示用到了el表达式），mysql

<dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency><groupId>org.apache.poi</groupId>
      <artifactId>poi-ooxml</artifactId>
      <version>3.5-FINAL</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.32</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>taglibs</groupId>
      <artifactId>standard</artifactId>
      <version>1.1.2</version>
    </dependency>
  </dependencies>

四、各个页面
前端页面：

前端代码：

<%@ page import="java.io.File" %>
<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %>
<%@page language="java" contentType="text/html;charset=UTF-8" pageEncoding="utf-8" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ page isELIgnored="false" %>
<%--显示文件夹中已上传的文件--%>
<%
    String savePath = getClass().getResource("/").getPath();
    File file = new File(savePath);
    File[] arr = file.listFiles();
    List<String> array = new ArrayList<String>();
    for(int m=0;m<arr.length;m++){
        if(arr[m].getName().endsWith(".xls")) {
            array.add(arr[m].getName());
        }
    }
    System.out.println(array.size());

%>
<html>
<body>
<h2>Hello World!</h2>
<meta charset="utf-8">

<h3>上传</h3>
<form action="UploadServlet" enctype="multipart/form-data" method="post">
<input type="file" id="excel" name="excel" />
<input  type="submit" value="Upload">
</form>

<hr>
<h3>下载目录</h3>
<ul>
    <%--这里是下载操作--%>
<c:forEach var="i" items="<%=array%>">
    <a href="DownloadServlet?filename=${i}"><li>${i}</li></a>
</c:forEach>
</ul>
</body>
</html>

Excel文件：

数据库表结构：

五、代码实现

JDBC连接数据库：

PropertiesUtils.java

public class PropertiesUtils {

    static Properties prop = new Properties();
    /**
     * @param fileName 需要加载的properties文件，文件需要放在src根目录下
     * 是否加载成功
     */
    public static boolean loadFile(String fileName){
        try {
            prop.load(PropertiesUtils.class.getClassLoader().getResourceAsStream(fileName));
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }
        return true;
    }
    /**
     * 根据KEY取回相应的value

     */
    public static String getPropertyValue(String key){
        return prop.getProperty(key);
    }
}

BaseDao.java

public class BaseDao {

    protected Connection conn;

    protected PreparedStatement ps;

    protected Statement stmt;

    protected ResultSet rs;

    //获取数据库连接
    public boolean getConnection(){
        //读取配置信息
        PropertiesUtils.loadFile("config.properties");

        String url = PropertiesUtils.getPropertyValue("url");
        String username = PropertiesUtils.getPropertyValue("username");
        String password = PropertiesUtils.getPropertyValue("password");
        String driver = PropertiesUtils.getPropertyValue("driver");

        //加载jdbc驱动
        try{
            Class.forName(driver);
            //与数据库建立连接
            conn = DriverManager.getConnection(url,username,password);
        }catch(ClassNotFoundException e){
            e.printStackTrace();
            return false;
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return false;
        }
        return true;
    }
    //增删改
    public int executeUpdate(String sql,Object[] params){
        int updateRows = 0;
        getConnection();
        try{
            ps = conn.prepareStatement(sql);
            for(int i= 0;i<params.length;i++){
                ps.setObject(i+1, params[i]);
            }
            updateRows = ps.executeUpdate();
        }catch(SQLException e){
            e.printStackTrace();
        }
        return updateRows;
    }

    //查询
    public ResultSet executeSQL(String sql,Object[] params){
        getConnection();
        try{
            ps = conn.prepareStatement(sql);
            for(int i=0;i<params.length;i++){
                ps.setObject(i+1, params[i]);
            }
            rs = ps.executeQuery();
        }catch(SQLException e){
            e.printStackTrace();
        }
        return rs;
    }
    //关闭资源
    public boolean close(){
        if(rs!=null){
            try{
                rs.close();
            }catch(SQLException E){
                E.printStackTrace();
                return false;
            }
        }
        if(ps !=null){
            try{
                ps.close();
            }catch(SQLException E){
                E.printStackTrace();
                return false;
            }
        }
        if(stmt!=null){
            try{
                stmt.close();
            }catch(SQLException E){
                E.printStackTrace();
                return false;
            }
        }
        if(conn!=null){
            try{
                conn.close();
            }catch(SQLException E){
                E.printStackTrace();
                return false;
            }
        }
        return true;
    }

}

UserDao.java

public class UserDao extends BaseDao{
//用于上传excel时向数据库添加用户的方法
    public int addAllUser(List<User> users){
        int n = 0;
        for(User user:users){
            try{
                String sql = "insert into user_table values(?,?,?,?)";
                Object[] params = {user.getUid(),user.getUsername(),user.getAge(),user.getText()};
                int ex = this.executeUpdate(sql,params);
                n+=ex;
            }catch (Exception e){
                e.printStackTrace();
            }

        }
        return n;
    }
//用于下载导出excel时用的数据库查询方法
    public List<User> getAllUser() throws SQLException {
        List<User> users = new ArrayList<User>();
        User user = null;
        try{
            String sql = "select * from user_table";
            Object[] params = {};
            ResultSet rs = this.executeSQL(sql,params);
            while(rs.next()){
                user = new User();
                user.setUid(rs.getInt(0));
                user.setUsername(rs.getString(1));
                user.setAge(rs.getInt(2));
                user.setText(rs.getString(3));
                users.add(user);
            }
        }catch (SQLException e){
            e.printStackTrace();
        }
        return users;
    }
}

config.properties

##jdbc config

driver = com.mysql.jdbc.Driver
url = jdbc:mysql://localhost:3306/mydb?useUnicode=true&characterEncoding=utf8
username = root
password = 123456

Upload.java（关键servlet）

import Dao.UserDao;
import Entity.User;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;

import java.io.*;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

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

/**
 * Created by qianbei476 on 2017/6/22.
 */
@MultipartConfig
@WebServlet(urlPatterns="/UploadServlet")
public class Upload extends HttpServlet {

    private POIFSFileSystem fs;
    private HSSFWorkbook wb;
    private HSSFSheet sheet;
    private HSSFRow row;

    UserDao userDao = new UserDao();

    public String savePath = getClass().getResource("/").getPath();
    public static String excelname;
    //上传文件保存目录

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        getFile(request, response);  //上传文件

        List<User> users = getUser(excelname);  //读取excel中的users,生成user_table.xls

        int exi = userDao.addAllUser(users);  //将读取的List<User>插入数据库

        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter pw = response.getWriter();
        pw.print("<script>添加成功，一共有:"+exi+"条数据</script>");

    }

//传入文件路径读取excel，得到List<User>
    public List<User> getUser(String fileurl) throws IOException {

        InputStream is = new FileInputStream(fileurl);
        fs = new POIFSFileSystem(is);
        wb = new HSSFWorkbook(fs);
        sheet = wb.getSheetAt(0);
        row = sheet.getRow(0);

        int rowNum = sheet.getLastRowNum();
        System.out.println("excel总行数：" + (rowNum+1));

        System.out.println("标题为：" + row.getCell(0));
        List<User> userList = new ArrayList<User>();
        User user = null;
        int i = 1;  //控制读取数
        while (i<rowNum) {
                user = new User();
                i++;
                user.setUid((int) (sheet.getRow(i).getCell(0).getNumericCellValue()));
                user.setUsername(sheet.getRow(i).getCell(1).getStringCellValue());
                user.setAge((int) (sheet.getRow(i).getCell(2).getNumericCellValue()));
                user.setText(sheet.getRow(i).getCell(3).getStringCellValue());
                userList.add(user);
            }

        return userList;

    }



//将上传的excel文件保存为文件，可选进行备份操作。
    public void getFile(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {

        request.getInputStream();
        Part part = request.getPart("excel");
        String cd = part.getHeader("Content-Disposition");
        String[] cds = cd.split(";");
        String filename = cds[2].split("=")[1].replace("\"","");
        System.out.println("文件名:"+filename);

        InputStream is = part.getInputStream();
        filename = savePath+filename;
        System.out.println("路径:"+filename);
        excelname = filename;
        File file = new File(filename);
        FileOutputStream fos = new FileOutputStream(file); //生成excel文件
        byte[] b = new byte[1024];
        int len = 0;
        while((len = is.read(b)) != -1){
            fos.write(b,0,len);
        }
        is.close();
        fos.close();


    }
}

六、结果演示

七、注意

（1）Excel上传与下载时都容易出现的中文乱码问题，应该注意几点

jsp页面显示乱码问题：

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

<meta charset="utf-8">

servlet获取后乱码问题：

request.setCharacterEncoding("utf-8");

servlet返回后乱码问题：

response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");

response.setContentType("application/vnd.ms-excel;charset=gb2312");

数据库操作乱码问题：

url = jdbc:mysql://localhost:3306/mydb?useUnicode=true&characterEncoding=utf8

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