JDBC 封裝

  使用 JDBC 連線 MySQL 資料庫，我們每次操作都要寫一堆連線資料庫的資訊，操作完還要釋放一堆資源，做了很多重複的工作，於是我們通常把資料庫連線封裝成工具類。

JdbcUtils 類

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

/**
 * @author Acx7
 */
public class JdbcUtils {
    private static String username = null;
    private static String password = null;
    private static String url = null;

    static {
        try {
            // 載入配置檔案
            Properties properties = new Properties();
            properties.load(new FileInputStream("resources/db.properties"));
            // 獲取配置檔案資訊
            String driver = properties.getProperty("driver");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
            url = properties.getProperty("url");
            // 載入驅動
            Class.forName(driver);
        } catch (ClassNotFoundException | IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 獲取連線物件
     */
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, username, password);
    }
    
    /**
     * 釋放資源
     */
    public static void close(Statement ps, Connection conn) {
        close(null, ps, conn);
    }

    /**
     * 釋放資源
     */
    public static void close(ResultSet rs, Statement ps, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (ps != null) {
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}
 

配置檔案

driver=com.mysql.jdbc.Driver
username=root
password=123456
url=jdbc:mysql://127.0.0.1:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8

使用方法

import java.sql.*;
//import JdbcUtils;

/**
 * @author Acx7
 */
public class JdbcTest {
    public static void main(String[] args) {
        Statement st = null;
        ResultSet rs = null;
        Connection conn = null;
        try {
            conn = JdbcUtils.getConnection();
            st = conn.createStatement();
            String sql = "SELECT * FROM users";
            rs = st.executeQuery(sql);
            while (rs.next()) {
                System.out.println(rs.getObject("id"));
            }
//          String sql = "INSERT INTO users(id,`name`) VALUES (4,'Acx7')";
//          int result = st.executeUpdate(sql); // 返回受影響的行數
//          String sql = "UPDATE users SET `name`='acx' WHERE id=4";
//          int result = st.executeUpdate(sql); // 返回受影響的行數
//          String sql = "DELETE FROM users WHERE id=3";
//          int result = st.executeUpdate(sql); // 返回受影響的行數
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.close(rs, st, conn);
        }
    }
}