DBUtils笔记

1、使用类的加载器来加载database.properties文件流。

2、读取配置文件，获取连接，只执行一次，static{ }

3、JDBCUtils封装类

package cn.itcast.jdbcutils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

public class JDBCUtils {
    
    public static Connection con;
    private static String driverClass;
    private static String url;
    private static String username;
    private static String password;
    public JDBCUtils(){};
    
    //定义静态方法，返回数据库的连接对象
    static{
        try{
            readConfig();
            // 1注册驱动
            Class.forName(driverClass);
            
            con = DriverManager.getConnection(url, username, password);
        }catch(Exception ex){
            throw new RuntimeException(ex+" 数据库连接失败!");
        }
    }
    
    //获取连接
    public static Connection getConnection(){
        return con;
    }
    
    private static void readConfig() throws IOException{
        // 2、获取配置文件流，读取文件信息，获取连接
        //使用类的加载器加载database文件
        InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream("database.properties");
        Properties pro = new Properties();
        pro.load(in);
        //System.out.println(pro);
        //获取集合中的键值对
        String driverClass = pro.getProperty("driverClass");
        String url = pro.getProperty("url");
        String username = pro.getProperty("username");
        String password = pro.getProperty("password");
    }
    
    
    public static void close(Connection con,ResultSet rs,PreparedStatement ps){
        if(rs != null){
            try{
                rs.close();                
            }catch(SQLException ex){}
            
        }
        if(ps != null){
            try{
                ps.close();                
            }catch(SQLException ex){}
            
        }
        if(con != null){
            try{
                con.close();                
            }catch(SQLException ex){}
            
        }
    }
    
    public static void close(Connection con,PreparedStatement ps){
        
        if(ps != null){
            try{
                ps.close();                
            }catch(SQLException ex){}
            
        }
        if(con != null){
            try{
                con.close();                
            }catch(SQLException ex){}
            
        }
    }

}