数据库连接与关闭函数（DBUtil.java）
package com.po; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; public class DBUtil { private static String Driver; private static String url; private static String username; private static String password; static { Driver ="com.mysql.jdbc.Driver"; url="jdbc:mysql://localhost:3306/Geek99DB"; username="root"; password="123456"; } public static Connection open() { try { Class.forName(Driver); return DriverManager.getConnection(url, username, password); } catch (Exception e) { e.printStackTrace(); } return null; } public static void close(Connection conn) { if(conn!=null) { try { conn.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }创建一个mycar类进行数据库查询的时候保存到一个数组 package com.po; public class mycar { private String carName; private String carId; private int carNum; public String getCarName() { return carName; } public void setCarName(String carName) { this.carName = carName; } public String getCarId() { return carId; } public void setCarId(String carId) { this.carId = carId; } public int getCarNum() { return carNum; } public void setCarNum(int carNum) { this.carNum = carNum; } public String toString() { return carName+","+carId+","+carNum; } } 数据库增删改查数据 package com.po; import java.sql.Connection; import java.sql.ResultSet; import java.sql.Statement; import java.util.ArrayList; import java.util.List; public class test { public static void main(String[] args) { // TODO Auto-generated method stub //createTable(); //insert(); //update(); //delete(); //query(); //queryArr(); } public static List<mycar> queryArr() { Connection conn=DBUtil.open(); String sql="select * from mycar"; try { Statement stmt=conn.createStatement(); ResultSet rs=stmt.executeQuery(sql); List<mycar> list=new ArrayList<mycar>(); while(rs.next()) { String carName=rs.getString(1); String carId= rs.getString(2); int carNum =rs.getInt(3); //System.out.println(carName+","+carId+","+carNum); mycar car =new mycar(); car.setCarName(carName); car.setCarId(carId); car.setCarNum(carNum); list.add(car); } System.out.println(list); return list; } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtil.close(conn); } return null; } public static void query() { Connection conn=DBUtil.open(); String sql="select * from mycar"; try { Statement stmt=conn.createStatement(); ResultSet rs=stmt.executeQuery(sql); while(rs.next()) { String carName=rs.getString(1); String carId= rs.getString(2); int carNum =rs.getInt(3); System.out.println(carName+","+carId+","+carNum); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtil.close(conn); } } public static void delete() { Connection conn=DBUtil.open(); String sql="delete from mycar where carnum=5"; try { Statement stmt=conn.createStatement(); stmt.executeUpdate(sql); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtil.close(conn); } } public static void update() { Connection conn=DBUtil.open(); String sql="update mycar set carname='auto' where carid='88888888'"; try { Statement stmt=conn.createStatement(); stmt.executeUpdate(sql); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtil.close(conn); } } public static void insert() { Connection conn=DBUtil.open(); String sql="insert into mycar(carName,carId,carNum) values('BMW','88888888',5);"; try { Statement stmt=conn.createStatement(); stmt.executeUpdate(sql); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtil.close(conn); } } public static void createTable() { Connection conn=DBUtil.open(); String sql="create table mycar(carName varchar(20),carId varchar(20),carNum int);"; try { Statement stmt=conn.createStatement(); stmt.execute(sql); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { DBUtil.close(conn); } } }