Closing ResultSet Objects

JDBC for SQL Server - Herong's Tutorial Examples

∟Microsoft JDBC Driver - Query Statements and Result Sets

∟Closing ResultSet Objects - res.close()

This section describes how to close ResultSet objects with the res.close() method.

For each ResultSet object you received from a SELECT statement execution, there is large amount of resource allocated to this object. When you no longer need any data from a ResultSet object, you should close it with the res.close() method.

This tutorial Java program shows you how to do this:

/* CloseResultSet.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.sql.*;
public class CloseResultSet {
  public static void main(String [] args) {
    Connection con = null;
    try {

// Obtaining a connection to SQL Server
      con = DriverManager.getConnection(
          "jdbc:sqlserver://localhost\\SQLEXPRESS;"
        + "user=herong;password=T0pSecret;"
        + "database=AdventureWorks2019");

// Run a SELECT statement
      Statement sta = con.createStatement();
      ResultSet res = sta.executeQuery(
        "SELECT * FROM Person.Person");
      res.next();
      String firstName = res.getString("FirstName");
      String lastName = res.getString("LastName");
      System.out.println("First customer: "+firstName+" "+lastName);

// Closing the ResultSet object
      res.close();
      if (res.isClosed())
        System.out.println("ResultSet closed.");

      con.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

If you run this program with newer versions of JDK and JDBC Driver, you will get correct result:

herong> java -cp .;mssql-jdbc-9.4.1.jre16.jar CloseResultSet.java

First customer: Ken Sanchez
ResultSet closed.

Previously, when I ran the same example program with JDK 1.6, JDBC Driver 1.0, and SQL Server 2005 Express Edition, the program failed with an error message:

herong> java -cp .;sqljdbc.jar CloseResultSet

First customer: Orlando Gee

Exception in thread "main" java.lang.AbstractMethodError:
com.microsoft.sqlserver.jdbc.SQLServerResultSet.isClosed()Z
        at CloseResultSet.main(CloseResultSet.java:32)

As you can see, the res.close() method worked ok. But the res.isClosed() method gave an error, because res.isClosed was introduced in JDBC 4.0, and is not supporte by Microsoft JDBC Driver 1.0.