Operation not allowed after ResultSet closed (mysql, java)

Question

I was stuck with the error , here my line number 42 is while(rs.next()){, please help me with this i am stuck at this for few hrs.

> Exception in thread "main" java.sql.SQLException: Operation not allowed after ResultSet closed
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:998)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:937)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:872)
    at com.mysql.jdbc.ResultSetImpl.checkClosed(ResultSetImpl.java:740)
    at com.mysql.jdbc.ResultSetImpl.next(ResultSetImpl.java:6326)
    at removeStopwords.RemoveStopwords.main(RemoveStopwords.java:42)

This is my code:

package removeStopwords;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.StringTokenizer;

import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;

public class RemoveStopwords {

    // JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost/mydbv2";

    // Database credentials
    static final String USER = "root";
    static final String PASS = "***";

    public static void main(String[] args) throws ClassNotFoundException, SQLException {

        Connection conn = null;
        Statement stmt = null;

        Class.forName("com.mysql.jdbc.Driver");

        conn = (Connection) DriverManager.getConnection(DB_URL, USER, PASS);

        stmt = (Statement) conn.createStatement();
        String sql;
        ResultSet rs = null;
        ResultSet rs2 = null;
        ResultSet rs3 = null;
        java.sql.PreparedStatement ps = null;
        int event_id = 10;
        sql = "SELECT id,text from tweet where event_id = " + event_id;
        rs = stmt.executeQuery(sql);

        String text = "";
        Long id;
        while (rs.next()) {
            id = rs.getLong("id");
            text = rs.getString("text");
            System.out.println("tweet = " + text);
            text = text.replaceAll("http[^\\s]+", "");
            text = text.replaceAll("www[^\\s]+", "");
            System.out.println("tweet after removal of links= " + text);

            StringTokenizer st = new StringTokenizer(text);
            while (st.hasMoreTokens()) {
                String stopword = st.nextToken();
                System.out.println("stopword : " + stopword);

                sql = "SELECT * from stopwords WHERE word =" + '"'+stopword+'"';
                rs2 = stmt.executeQuery(sql);
                if (rs2.next()) {
                    text = text.replaceAll(stopword, "");
                    System.out.println("tweet after removing stopword = " + text);
                }
                sql = "SELECT * from filtertweet where tweet_id = " + id + "";
                rs3 = stmt.executeQuery(sql);
                if (!rs3.next()) {
                    sql = "INSERT INTO filtertweet VALUES(?,?)";
                    ps = conn.prepareStatement(sql);
                    ps.setLong(1, id);
                    ps.setString(2, text);
                    ps.executeUpdate();
                }

            }
        }
        stmt.close();
        conn.close();
    }

}

Answer 1

JDBC does not allow you to close the Statement that created the ResultSet or to execute another query that creates a ResultSet using the same Statement. Create different Statement objects and Resultset objects, make sure to not use the same Statement objects to execute two different Resultset statements.

Answer 2

One ResultSet for one Statement is valid. When you are executing multiple queries use various Statements.

public static void main(String[] args) throws ClassNotFoundException, SQLException {

    Connection conn = null;
    Statement stmt = null;

    Class.forName("com.mysql.jdbc.Driver");

    conn = (Connection) DriverManager.getConnection(DB_URL, USER, PASS);

    stmt = (Statement) conn.createStatement();
    String sql;
    ResultSet rs = null;
    ResultSet rs2 = null;
    ResultSet rs3 = null;
    java.sql.PreparedStatement ps = null;
    int event_id = 10;
    sql = "SELECT id,text from tweet where event_id = " + event_id;
    rs = stmt.executeQuery(sql);

    String text = "";
    Long id;
    while (rs.next()) {
        id = rs.getLong("id");
        text = rs.getString("text");
        System.out.println("tweet = " + text);
        text = text.replaceAll("http[^\\s]+", "");
        text = text.replaceAll("www[^\\s]+", "");
        System.out.println("tweet after removal of links= " + text);

        StringTokenizer st = new StringTokenizer(text);
        while (st.hasMoreTokens()) {
            String stopword = st.nextToken();
            System.out.println("stopword : " + stopword);

            sql = "SELECT * from stopwords WHERE word =" + '"'+stopword+'"';

            Statement stmt2 = conn.createStatement();
            rs2 = stmt2.executeQuery(sql);
            if (rs2.next()) {
                text = text.replaceAll(stopword, "");
                System.out.println("tweet after removing stopword = " + text);
            }
            sql = "SELECT * from filtertweet where tweet_id = " + id + "";

            Statement stmt3 = conn.createStatement();
            rs3 = stmt3.executeQuery(sql);
            if (!rs3.next()) {
                sql = "INSERT INTO filtertweet VALUES(?,?)";
                ps = conn.prepareStatement(sql);
                ps.setLong(1, id);
                ps.setString(2, text);
                ps.executeUpdate();
            }

        }
    }
    stmt.close();
    conn.close();
}

Answer 3

A Statement object can have only one active ResultSet, so when you execute rs2 = stmt.executeQuery(sql), the first ResultSet (rs) gets closed.

Create two Statement objects, one for rs and another for rs2.

Quoting the javadoc of Statement:

By default, only one ResultSet object per Statement object can be open at the same time. Therefore, if the reading of one ResultSet object is interleaved with the reading of another, each must have been generated by different Statement objects. All execution methods in the Statement interface implicitly close a statment's current ResultSet object if an open one exists.