JDBC 04： 创建JDBCUtils并重构之前的代码

1. 创建JDBCUtils

package com.Jasper2003.jdbc01;

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

public class JDBCUtils {

    private static final String connectionURL = "jdbc:mysql://localhost:3306/web01?useUnicode=true&characterEncoding=UTF8&useSSL=false";
    private static final String username = "root";
    private static final String password = "root";
    
    public static Connection getConnection() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            return DriverManager.getConnection(connectionURL,username,password);
        }catch(Exception e) {
            e.printStackTrace();
        }
        
        return null;
    }
    
    public static void close(ResultSet rs, Statement stmt, Connection con) {
        try {
            if(rs!=null)
                rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    
        try {
            if(stmt!=null)
                stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    
        try {
            if(con!=null)
                con.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

2. 重构selectAll()

public static void selectAll() {

        
        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;
        
        try {
            con = JDBCUtils.getConnection();
            stmt = con.createStatement();
            rs = stmt.executeQuery("select * from user");
            
            while(rs.next()) {

　　　　　　　　　　System.out.println(rs.getInt("id")+","+rs.getString("username")+","+rs.getString("password"));
            }    
            
        } catch (Exception e) {
            
            e.printStackTrace();
        } finally {
            JDBCUtils.close(rs, stmt, con);
        }
    }