jdbc connection mysql connection database tool class

        In the past, when writing code, everything involved database connections, especially the DAO layer in the project. Every time I wrote a method, I had to repeat the steps: load the database driver, establish a connection... This made the code very cumbersome and time-consuming, so I thought about it today. After thinking about it, I wrote a tool class to connect to the database for later use. After testing, the function can be realized, and each method can be run.

        code show as below

import java.sql.*;

/**
 * @Description connection database tool class
 * @Author single continuation
 * @Date 2016/10/26 14:50
 */
public class DBConn {
    private String DRIVER = "com.mysql.jdbc.Driver";
    private String USERNAME = "root";
    private String PASSWORD = "root";
    private String URL = "jdbc:mysql://localhost:3306/";
    private Connection conn = null;
    private PreparedStatement ps = null;
    private ResultSet rs = null;

    /**
     * Step 1: Load the database driver
     * Step 2: Establish a database connection
     * @param dbName database name
     */
    public DBConn(String dbName){
        try {
            Class.forName(DRIVER);
            URL = URL + dbName;
            conn = DriverManager.getConnection(URL,USERNAME,PASSWORD);
        } catch (ClassNotFoundException e) {
            e.printStackTrace ();
        } catch (SQLException e) {
            e.printStackTrace ();
        }
    }

    /**
     * Step 3: write sql statement
     * Step 4: Create the sql statement executor preparedStatement
     * @param sql sql statement
     */
    public void preparedStatement(String sql){
        try {
            ps = conn.prepareStatement(sql);
        } catch (SQLException e) {
            e.printStackTrace ();
        }
    }

    /**
     * Step 5: Replace the placeholders with parameters
     * @param index placeholder index (first one is 1)
     * @param value parameter value
     */
    public void setString(int index,String value){
        try {
            ps.setString(index,value);
        } catch (SQLException e) {
            e.printStackTrace ();
        }
    }
    public void setInt(int index,int value){
        try {
            ps.setInt(index,value);
        } catch (SQLException e) {
            e.printStackTrace ();
        }
    }

    /**
     * Step 6: Execute the sql statement and return the number of affected rows
     * @return the number of rows affected by executing the sql statement
     */
    public int executeUpdate(){
        try {
            //System.out.println(ps);
            return ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace ();
        }
        return 0;
    }

    /**
     * Step 6: Execute the sql statement and return the result set
     * @return ResultSet
     */
    public ResultSet executeQuery(){
        try {
            return ps.executeQuery();
        } catch (SQLException e) {
            e.printStackTrace ();
        }
        return null;
    }

    /**
     * close the connection and others
     */
    public void close(){
        try{
            if(rs != null){
                rs.close();
            }
            if(ps != null){
                ps.close();
            }
            if(conn != null){
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace ();
        }
    }
}

         When in use, instantiate this class, and the constructor will pass in the database name as a parameter to form a link.