Simple database connection example

# Simple database tools

public class SimpleDBDemo {
    

    public static void main(String[] args) {
    
    
        try {
    
            //  Load database driver  com.mysql.cj.jdbc.Driver
            String strDriver = "com.mysql.cj.jdbc.Driver";
            //  obtain mysql Connection address 
            String strURL = "jdbc:mysql://localhost:3306/mytest?&useSSL=false&serverTimezone=UTC";
            //  User name 
            String username = "root";
            //  User password 
            String password = "123456";
    
            Class.forName(strDriver);
            System.out.println("SQLServerDriver success");
    
            //  Get a data connection , Connect MySql database 
            Connection con = DriverManager.getConnection(strURL, username, password);
            System.out.println("Connection success");
    
            //  establish statement Class object , Used to perform SQL sentence ！
            Statement stm = con.createStatement();
    
            //  Executes SQL sentence 
            String strSql = "select * from student";
    
            // ResultSet class , Used to store the result set obtained ！
            ResultSet rs = stm.executeQuery(strSql);
    
            while(rs.next()){
    
    
                String s1 = rs.getString(1);
                String s2 = rs.getString(2);
                double d3 = rs.getDouble(3);
                System.out.println(s1+"\t"+s2+"\t\t"+d3);
            }
    
            rs.close();
            stm.close();
            con.close();
    
        } catch (ClassNotFoundException | SQLException e) {
    
            e.printStackTrace();
        }
    }
}

General database tools

public class JDBCUtil {
    
    private static final String driver;
    private static final String url;
    private static final String userName;
    private static final String password;

    static {
    
        InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("db.properties");
        Properties properties = new Properties();
        try {
    

            properties.load(is);
        } catch (IOException e) {
    
            e.printStackTrace();
        }
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        userName = properties.getProperty("username");
        password = properties.getProperty("password");
    }

    //  Get database connection 
    public static Connection getConnection() {
    
        Connection con = null;
        try {
    
            Class.forName(driver);
            con = DriverManager.getConnection(url, userName, password);
        } catch (SQLException | ClassNotFoundException e) {
    
            e.printStackTrace();

        }
        return con;
    }

    //  Database query , Return result set 
    public static ResultSet query(Connection con, PreparedStatement st, ResultSet rs, String sql
            , Object[] params) throws SQLException {
    
        st = con.prepareStatement(sql, ResultSet.TYPE_SCROLL_SENSITIVE,
                ResultSet.CONCUR_READ_ONLY);
        if (params != null) {
    
            for (int i = 0; i < params.length; i++) {
    
                st.setObject(i + 1, params[i]);
            }
        }
        rs = st.executeQuery();
        return rs;
    }

    //  Database addition, deletion and modification 
    public static int update(Connection con, String sql
            , Object[] params, ResultSet rs, PreparedStatement st) throws SQLException {
    
        st = con.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
    
            st.setObject(i + 1, params[i]);
        }
        return st.executeUpdate();
    }

    //  Close database connection 
    public static void release(Connection con, Statement st, ResultSet rs) {
    
        boolean flag = true;

        if (rs != null) {
    
            try {
    
                rs.close();
                rs = null;
            } catch (SQLException e) {
    
                e.printStackTrace();
                flag = false;
            }
        }

        if (st != null) {
    
            try {
    
                st.close();
                st = null;
            } catch (SQLException e) {
    
                e.printStackTrace();
                flag = false;
            }
        }

        if (con != null) {
    
            try {
    
                con.close();
                con = null;
            } catch (SQLException e) {
    
                e.printStackTrace();
                flag = false;
            }
        }
    }
}

db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/XXX?&useSSL=false&serverTimezone=UTC
username=root
password=123456