jdbcutil.java

网上购物系统的简易代码

package com.tarena.develop.common;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCUtil {
	static{
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	public static Connection getConnection(){
		Connection conn = null;
		try {
			conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/css","root","123");
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return conn;
	}
	public static void relese(ResultSet rs,Statement stmt,Connection conn){
		if(rs!=null){
			try {
				rs.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		if(stmt!=null){
			try {
				stmt.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		if(conn!=null){
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
	public static int getToken(){
		
		int token = (int) (Math.random()*9000+1000);
		return token;
	}
	public static int getPrimaryKey(Connection conn){
		int res = 0;
		String sql1 = "select max(nextid) from pkey for update";
		String sql2 = "update pkey set nextid=? where nextid=?";
		PreparedStatement pstm = null;
		ResultSet rs = null;
		try {
			conn.setAutoCommit(false);
			pstm = conn.prepareStatement(sql1);
			rs = pstm.executeQuery();
			if(rs.next()){
				res = rs.getInt(1);
			}
			pstm.close();
			pstm = conn.prepareStatement(sql2);
			pstm.setInt(1,res+1);
			pstm.setInt(2, res);
			pstm.executeUpdate();
			conn.commit();
			
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			try {
				conn.rollback();
			} catch (SQLException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
		} finally {
			JDBCUtil.relese(rs, pstm, null);
		}
		
		return res;
	}
	
}