AccessDatabase.java

package ProjectRF;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;

public class AccessDatabase {
	
  private Connection connect = null;
  private Statement statement = null;
  private PreparedStatement preparedStatement = null;
  private ResultSet resultSet = null;

  final private String host = "localhost";
  final private String user = "root";
  final private String passwd = "root";
  
  public void readDataBase() throws Exception {
    try {
      // This will load the MySQL driver, each DB has its own driver
      Class.forName("com.mysql.cj.jdbc.Driver");
      
      // Setup the connection with the DB
      connect = DriverManager
          .getConnection("jdbc:mysql://" + host + "/feedback?"
              + "user=" + user + "&password=" + passwd );

      // Statements allow to issue SQL queries to the database
      statement = connect.createStatement();
      // Result set get the result of the SQL query
      resultSet = statement
          .executeQuery("select * from feedback.comments");
      writeResultSet(resultSet);

      // PreparedStatements can use variables and are more efficient
      preparedStatement = connect
          .prepareStatement("insert into  feedback.comments values (default, ?, ?, ?, ? , ?, ?)");
      // "myuser, webpage, datum, summary, COMMENTS from feedback.comments");
      // Parameters start with 1
      int i = 1;
	preparedStatement.setString(i, "Test");
      preparedStatement.setString(2, "TestEmail");
      preparedStatement.setString(3, "TestWebpage");
      preparedStatement.setDate(4, new java.sql.Date(2019, 10, 1));
      preparedStatement.setString(5, "TestSummary");
      preparedStatement.setString(6, "TestComment");
      preparedStatement.executeUpdate();

      preparedStatement = connect
          .prepareStatement("SELECT myuser, webpage, datum, summary, COMMENTS from feedback.comments");
      resultSet = preparedStatement.executeQuery();
      writeResultSet(resultSet);

      // Remove again the insert comment
      preparedStatement = connect
      .prepareStatement("delete from feedback.comments where myuser= ? ; ");
      preparedStatement.setString(i, "Test");
      preparedStatement.executeUpdate();
      
      resultSet = statement
      .executeQuery("select * from feedback.comments");
      writeMetaData(resultSet);
      
    } catch (Exception e) {
      throw e;
    } finally {
      close();
    }

  }

  private void writeMetaData(ResultSet resultSet) throws SQLException {
    //   Now get some metadata from the database
    // Result set get the result of the SQL query
    
    System.out.println("The columns in the table are: ");
    
    System.out.println("Table: " + resultSet.getMetaData().getTableName(1));
    for  (int i = 1; i<= resultSet.getMetaData().getColumnCount(); i++){
      System.out.println("Column " +i  + " "+ resultSet.getMetaData().getColumnName(i));
    }
  }

  private void writeResultSet(ResultSet resultSet) throws SQLException {
    // ResultSet is initially before the first data set
    while (resultSet.next()) {
      // It is possible to get the columns via name
      // also possible to get the columns via the column number
      // which starts at 1
      // e.g. resultSet.getSTring(2);
      String user = resultSet.getString("myuser");
      String website = resultSet.getString("webpage");
      String summary = resultSet.getString("summary");
      Date date = resultSet.getDate("datum");
      String comment = resultSet.getString("comments");
      System.out.println("User: " + user);
      System.out.println("Website: " + website);
      System.out.println("Summary: " + summary);
      System.out.println("Date: " + date);
      System.out.println("Comment: " + comment);
    }
  }

  // You need to close the resultSet
  private void close() {
    try {
      if (resultSet != null) {
        resultSet.close();
      }

      if (statement != null) {
        statement.close();
      }

      if (connect != null) {
        connect.close();
      }
    } catch (Exception e) {

    }
  }

}