导入导出数据

把jxl.jar    mysql-connector-java-5.1.7-bin.jar 添加到libx下，创建数据库student 创建表stu  。

创建实体类entity

package entity;

/*
 * 实体类
 */
public class Entity {
	private int id;
	private String name;
	private String sex;
	private int num;
                     
	                 
	public Entity() {
	}

	public Entity(int id, String name, String sex, int num) {
		this.id = id;
		this.name = name;
		this.sex = sex;
		this.num = num;
	}

	@Override
	public String toString() {
		return "StuEntity [id=" + id + ", name=" + name + ", sex=" + sex + ", num=" + num + "]";
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public int getNum() {
		return num;
	}

	public void setNum(int num) {
		this.num = num;
	}

}

　创建连接数据库工具类

// 连接数据库的工具类

package jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class JdbcTom{

    
    String driver = "com.mysql.jdbc.Driver";
    String url = "jdbc:mysql://127.0.0.1:3306/student";
    
    
    Connection con = null;
    ResultSet res = null;

    public void DataBase() {
            try {
                Class.forName(driver);
                con = DriverManager.getConnection(url, "root", "root");
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                  System.err.println("装载 JDBC/ODBC 驱动程序失败。" );  
                e.printStackTrace();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                System.err.println("无法连接数据库" ); 
                e.printStackTrace();
            }
    }

    // 查询
    public ResultSet  Search(String sql, String str[]) {
        DataBase();
        try {
            PreparedStatement pst =con.prepareStatement(sql);
            if (str != null) {
                for (int i = 0; i < str.length; i++) {
                    pst.setString(i + 1, str[i]);
                }
            }
            res = pst.executeQuery();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return res;
    }

    // 增删修改
    public int AddU(String sql, String str[]) {
        int a = 0;
        DataBase();
        try {
            PreparedStatement pst = con.prepareStatement(sql);
            if (str != null) {
                for (int i = 0; i < str.length; i++) {
                    pst.setString(i + 1, str[i]);
                }
            }
            a = pst.executeUpdate();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return a;
    }
	
	
	
}

　　创建业务逻辑类

package service;

import java.io.File;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import entity.Entity;
import jdbc.JdbcTom;
import jxl.Sheet;
import jxl.Workbook;

public class Service {
	/**
	 * 查询stu表中所有的数据
	 * 
	 * @return
	 */
	public static List<Entity> getAllByDb() {
		List<Entity> list = new ArrayList<Entity>();
		try {
			JdbcTom db = new JdbcTom();
			String sql = "select * from stu";
			ResultSet rs = db.Search(sql, null);
			while (rs.next()) {
				int id = rs.getInt("id");
				String name = rs.getString("name");
				String sex = rs.getString("sex");
				int num = rs.getInt("num");

				// System.out.println(id+" "+name+" "+sex+ " "+num);
				list.add(new Entity(id, name, sex, num));
			}

		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return list;
	}

	/**
	 * 查询指定目录中电子表格中所有的数据
	 * 
	 * @param file
	 *            文件完整路径
	 * @return
	 */
	public static List<Entity> getAllByExcel(String file) {
		List<Entity> list = new ArrayList<Entity>();
		try {
			Workbook rwb = Workbook.getWorkbook(new File(file));
			Sheet rs = rwb.getSheet("Test Shee 1");// 或者rwb.getSheet(0)
			int clos = rs.getColumns();// 得到所有的列
			int rows = rs.getRows();// 得到所有的行

			System.out.println(clos + " rows:" + rows);
			for (int i = 1; i < rows; i++) {
				for (int j = 0; j < clos; j++) {
					// 第一个是列数，第二个是行数
					String id = rs.getCell(j++, i).getContents();// 默认最左边编号也算一列 所以这里得j++
					String name = rs.getCell(j++, i).getContents();
					String sex = rs.getCell(j++, i).getContents();
					String num = rs.getCell(j++, i).getContents();

					System.out.println("id:" + id + " name:" + name + " sex:" + sex + " num:" + num);
					list.add(new Entity(Integer.parseInt(id), name, sex, Integer.parseInt(num)));
				}
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return list;

	}

	/**
	 * 通过Id判断是否存在
	 * 
	 * @param id
	 * @return
	 */
	public static boolean isExist(int id) {
		try {
			JdbcTom db = new JdbcTom();
			ResultSet rs = db.Search("select * from stu where id=?", new String[] { id + "" });
			if (rs.next()) {
				return true;
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return false;
	}

	public static void main(String[] args) {
		/*
		 * List<StuEntity> all=getAllByDb(); for (StuEntity stuEntity : all) {
		 * System.out.println(stuEntity.toString()); }
		 */

		System.out.println(isExist(1));

	}

}

　　

创建sql-Excel表格测试类

package excel;

import java.io.File;
import java.util.List;

import entity.Entity;
import jxl.Workbook;
import jxl.write.WritableSheet;
import jxl.write.WritableWorkbook;
import service.Service;
import jxl.write.Label;

/*
 * 从数据库到生成Excel表格数据
 */
public class SqlToExcel {
	public static void main(String[] args) {
		try {
			WritableWorkbook wwb = null;

			// 创建可写入的Excel工作簿
			String fileName = "D://book.xls";
			File file = new File(fileName);
			if (!file.exists()) {
				file.createNewFile();
			}
			// 以fileName为文件名来创建一个Workbook
			wwb = Workbook.createWorkbook(file);

			// 创建工作表
			WritableSheet ws = wwb.createSheet("Test Shee 1", 0);

			// 查询数据库中所有的数据
			List<Entity> list = Service.getAllByDb();
			// 要插入到的Excel表格的行号，默认从0开始
			Label labelId = new Label(0, 0, "编号(id)");// 表示第
			Label labelName = new Label(1, 0, "姓名(name)");
			Label labelSex = new Label(2, 0, "性别(sex)");
			Label labelNum = new Label(3, 0, "薪水(num)");

			ws.addCell(labelId);
			ws.addCell(labelName);
			ws.addCell(labelSex);
			ws.addCell(labelNum);
			for (int i = 0; i < list.size(); i++) {

				Label labelId_i = new Label(0, i + 1, list.get(i).getId() + "");
				Label labelName_i = new Label(1, i + 1, list.get(i).getName());
				Label labelSex_i = new Label(2, i + 1, list.get(i).getSex());
				Label labelNum_i = new Label(3, i + 1, list.get(i).getNum() + "");
				ws.addCell(labelId_i);
				ws.addCell(labelName_i);
				ws.addCell(labelSex_i);
				ws.addCell(labelNum_i);
			}

			// 写进文档
			wwb.write();
			// 关闭Excel工作簿对象
			wwb.close();

		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

　　创建Excel—SQL测试类

package excel;

import java.util.List;

import entity.Entity;
import jdbc.JdbcTom;
import service.Service;
/*
 * 从Excel到数据库
 */
public class ExcelToSql {

	public static void main(String[] args) {
        //得到表格中所有的数据
        List<Entity> listExcel=Service.getAllByExcel("D://book.xls");
        /*//得到数据库表中所有的数据
        List<StuEntity> listDb=StuService.getAllByDb();*/
        
        JdbcTom db=new JdbcTom();
        
        for (Entity stuEntity : listExcel) {
            int id=stuEntity.getId();
            if (!Service.isExist(id)) {
                //不存在就添加
                String sql="insert into stu (name,sex,num) values(?,?,?)";
                String[] str=new String[]{stuEntity.getName(),stuEntity.getSex(),stuEntity.getNum()+""};
                db.AddU(sql, str);
            }else {
                //存在就更新
                String sql="update stu set name=?,sex=?,num=? where id=?";
                String[] str=new String[]{stuEntity.getName(),stuEntity.getSex(),stuEntity.getNum()+"",id+""};
                db.AddU(sql, str);
            }
        }
    }
	
}

有的运行会出现：Field 'id' doesn't have a default value 错误

以下解决方法：

Field 'id' doesn't have a default value昨晚做项目的时候遇到一个问题，在测试数据存储的时候老是报Field 'id' doesn't have a default value异常，从网上找了好久，根据各位大虾的说法也测试了好久好久，可就是没发现原因所在，鼓捣了两三个小时的时间，最后总算找到问题所在：原来是我的数据设计的时候，把主键的类型定义为int的，原本想是用自增的方式来的，可是由于自己的粗心，写sql语句的时候没有加上auto_increment,所以在数据存储的时候老是报Field 'id' doesn't have a default value，id根本就没有值啊！！
加上自己从网上找的其他人说的他们遇到这种时候的原因，在这里总结一下：
1、打开my.ini，查找
sql-mode="STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
修改为
sql-mode="NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"
然后重启MYSQL
2、MySQL 5 uses a strict mode which needs to be disabled.
In Windows, Goto Start-->Programs-->MySQL->MySQL Instance Config Wizard. Follow through the Reconfigure Instance option-->Detailed Configuration-->Continue Next a few screens. At the bottom under Enable TCP/IP option there is 'Enable Strict Mode'. Deslect this option (no tick). Save changes and MySQL will restart.
3、看看你的数据库定义的时候是不是把主键生成方式设置为int的，但是没有设置为自增的！！或者数据定义的时候设置一个默认值就可以了。