简单的数据库操作练习,实现学生成绩管理系统(纯控制台操作数据库的增删查改)

依赖的jar包

数据库结构:表名student

JDBC类,增删查改操作

package cn.com.lsh;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Scanner;
import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JDBC {

	public static void main(String[] args) {
		ComboPooledDataSource pool = new ComboPooledDataSource();
		while (true) {
			System.out.println("输入指令进行操作:");
			System.out.println("1:查询表记录  2:新增一条记录 3:修改一条记录 4:删除一条记录");
			//控制台输入获取值
			Scanner in = new Scanner(System.in);
			int s = in.nextInt();
			if (s == 1) {
				getAll(pool);
			} else if (s == 2) {
				Scanner in1 = new Scanner(System.in);
				System.out.println("输入学生姓名");
				String name = in1.nextLine();
				System.out.println("输入分数");
				double score = in1.nextDouble();
				add(name, score,pool);
			} else if (s == 3) {
				Scanner in1 = new Scanner(System.in);
				System.out.println("输入要修改学生的姓名");
				String name = in1.nextLine();
				System.out.println("输入新的分数");
				double score = in1.nextDouble();
				update(name, score,pool);
			} else if (s == 4) {
				Scanner in1 = new Scanner(System.in);
				System.out.println("输入要删除学生的姓名");
				String name = in1.nextLine();
				delete(name,pool);
			}
			System.out.println();
			System.out.println();
		}
	}

	/*
	 * 查询所有表记录
	 */
	public static void getAll(ComboPooledDataSource pool) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			// 注册数据库驱动
			conn = pool.getConnection();
			// sql语句
			String sql = "select * from student";
			// 获取传输器
			ps = conn.prepareStatement(sql);
			// 执行sql语句,保存到ResultSet结果集中
			rs = ps.executeQuery();
			while (rs.next()) {// rs中有指针,指针开始时指向数据库的表头,
				// 当指针指向内容时rs.next返回true
				int id = rs.getInt("id");
				String name = rs.getString("name");
				String pswd = rs.getString("score");
				System.out.println(id + " " + name + " " + pswd);
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			//将数据库连接对象放回池中
			closepool.repayClose(conn, ps, rs);
		}

	}

	/*
	 * 新增一条表记录
	 */
	public static void add(String name, Double score,ComboPooledDataSource pool) {
		Connection conn = null;
		//PreparedStatement是Statement的子类,拥有更多的方法,可以防止sql注入攻击
		PreparedStatement ps = null;		
		try {
			// 注册数据库驱动
			conn = pool.getConnection();
			//sql语句的骨架
			String sql = "insert into student value(null,?,?)";
			//获取传输器,将sql语句的骨架发送给mysql服务器
			ps = conn.prepareStatement(sql);
			//设置sql语句的两个??参数,
			//这样做可以将sql语句的参数看为一个整体发给服务器,避免sql注入攻击
			ps.setString(1, name);
			ps.setDouble(2, score);
			//执行sql语句,返回影响行数
			int row = ps.executeUpdate();
			if (row != 0) {
				System.out.println("成功添加1行记录");
			} else {
				System.out.println("添加失败,请重新输入!");
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			//将数据库连接对象放回池中
			closepool.repayClose(conn, ps);
		}
	}

	public static void update(String name, Double score,ComboPooledDataSource pool) {
		Connection conn = null;
		PreparedStatement ps = null;
		
		try {
			//注册数据库驱动,获取数据库连接
			conn = pool.getConnection();
			String sql = "update student set score=? where name=?";
			//获取传输器
			ps = conn.prepareStatement(sql);
			//设置sql语句的参数score=? 和name=?
			ps.setDouble(1, score);
			ps.setString(2, name);
			//执行sql语句,返回执行结果
			int row = ps.executeUpdate();
			if (row != 0) {
				System.out.println("修改记录成功,影响行数" + row);
			} else {
				System.out.println("修改失败,请重新输入!");
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			//对象放回池中
			closepool.repayClose(conn, ps);
		}

	}

	public static void delete(String name,ComboPooledDataSource pool) {
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			//注册数据库驱动,获取数据库连接
			conn = pool.getConnection();
			String sql = "delete from student where name=?";
			//获取传输器
			ps = conn.prepareStatement(sql);
			//设置sql语句的参数name=?
			ps.setString(1, name);
			int row = ps.executeUpdate();
			if (row != 0) {
				System.out.println("删除" + row + "行记录成功");
			} else {
				System.out.println("删除失败,请重新输入!");
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			//对象放回池中
			closepool.repayClose(conn, ps);
		}
	}

}

closepool类,用于对使用后的数据库连接对象放回连接池中

package cn.com.lsh;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class closepool {
	public static void repayClose(Connection conn,PreparedStatement ps,ResultSet rs) {
		if(conn!=null) {
			try {
				//close()方法如果是对单个对象,是释放资源,对对象池,是放回池中
				conn.close();
			} catch (Exception e) {
				e.printStackTrace();
			}finally {
				
				conn=null;
			}
			
		}
		if(ps!=null) {
			try {
				ps.close();
			} catch (Exception e) {
				e.printStackTrace();
			}finally {
				
				ps=null;
			}
			
		}
		if(rs!=null) {
			try {
				rs.close();
			} catch (Exception e) {
				e.printStackTrace();
			}finally {
				
				rs=null;
			}
			
		}
	}
	//方法重载,用于只用到两个参数的方法
	public static void repayClose(Connection conn,PreparedStatement ps) {
		if(conn!=null) {
			try {
				conn.close();
			} catch (Exception e) {
				e.printStackTrace();
			}finally {
				
				conn=null;
			}
			
		}
		if(ps!=null) {
			try {
				ps.close();
			} catch (Exception e) {
				e.printStackTrace();
			}finally {
				
				ps=null;
			}
			
		}
	}
}