每次操纵数据库都需要进行数据库的注册、连接等大量重复的操作，使得代码变得十分的臃肿，所以此时应该考虑如何把重复代码提取出来，随时需要随时拿来用。这就是工具类的封装。

目录

1.重用性

工具类 DoubleUse.java 内容。

package com.tothefor.Utils;

import java.sql.*;
import java.util.Collection;

/**
 * @Author DragonOne
 * @Date 2021/8/11 14:53
 */
public class DoubleUse {
    static {
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

  //获取连接数据库对象
    public static Connection getConnection(){
        Connection conn = null;
        try {
            String url = "jdbc:mysql://localhost:3306/WeekDay?serverTimezone=GMT%2B8";
            String user = "root";
            String password = "loong461";
            conn = DriverManager.getConnection(url,user,password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

  //关闭函数
    public static void closeAll(Connection connection, Statement st, ResultSet rs){
        try {
            if(rs != null){
                rs.close();
            }
            if(st != null){
                st.close();
            }
            if(connection != null){
                connection.close();
            }

        }catch (SQLException e){
            e.printStackTrace();
        }
    }
}

主函数 内容。

package com.tothefor.Utils;

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

/**
 * @Author DragonOne
 * @Date 2021/8/11 14:53
 */
public class TestMain {
    public static void main(String[] args) throws Exception {
        Connection con = DoubleUse.getConnection();
        PreparedStatement ps = con.prepareStatement("select * from Te");
        ResultSet rs = ps.executeQuery();

        while(rs.next()){
            String s1 = rs.getString(1);
            String s2 = rs.getString(2);
            String s3 = rs.getString(3);
            System.out.println(s1+" | "+s2+" | "+s3);
        }

        DoubleUse.closeAll(con,ps,rs);
    }
}

2.跨平台性

使用配置文件。

src目录下的db.properties内容。

//src目录下的db.properties
driver = com.mysql.cj.jdbc.Driver
url = jdbc:mysql://localhost:3306/WeekDay?serverTimezone=GMT%2B8
user = root
password = loong461

工具类 MoreMove.java 内容。

package com.tothefor.Utils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

/**
 * @Author DragonOne
 * @Date 2021/8/11 14:52
 */
public class MoreMove {
    private static final Properties pr = new Properties();
    static {
        InputStream is = MoreMove.class.getResourceAsStream("/db.properties");
        try {
            pr.load(is);
            Class.forName(pr.getProperty("driver"));
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(pr.getProperty("url"),pr.getProperty("user"),pr.getProperty("password"));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

  //关闭函数
    public static void closeAll(Connection connection, Statement statement, ResultSet resultSet){
        try {
            if(resultSet != null){
                resultSet.close();
            }
            if(statement != null){
                statement.close();
            }
            if(connection != null){
                connection.close();
            }
        }catch (SQLException e){
            e.printStackTrace();
        }
    }

}

主函数 内容。

package com.tothefor.Utils;

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

/**
 * @Author DragonOne
 * @Date 2021/8/11 14:53
 */
public class TestMain {
    public static void main(String[] args) throws Exception {
        Connection con = MoreMove.getConnection();
        PreparedStatement ps = con.prepareStatement("select * from Te");
        ResultSet rs = ps.executeQuery();

        while(rs.next()){
            String s1 = rs.getString(1);
            String s2 = rs.getString(2);
            String s3 = rs.getString(3);
            System.out.println(s1 + " | " + s2 + " | " + s3 + " | ");
        }
        MoreMove.closeAll(con,ps,rs);
    }
}