Closing ResultSet Objects

JDBC Tutorials - Herong's Tutorial Examples - Version 3.03, by Dr. Herong Yang

JDBC Tutorials - 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) 2015, 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=sa;password=HerongY@ng;"
        + "database=AdventureWorks2014");

// 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 JDK 1.8 and JDBC Driver 4.2, you will get:

C:\herong>\Progra~1\java\jdk1.8.0_45\bin\javac CloseResultSet.java

C:\herong>\Progra~1\java\jdk1.8.0_45\bin\java 
   -cp .;\local\lib\sqljdbc42.jar CloseResultSet

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:

C:\herong>\progra~1\java\jdk1.6.0_02\bin\javac CloseResultSet.java

C:\herong>\progra~1\java\jdk1.6.0_02\bin\java 
   -cp .;\local\lib\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 by Microsoft JDBC Driver 1.0.

Last update: 2015.

Table of Contents

About This Book

JDBC (Java Database Connectivity) Introduction

JDK (Java SE) Installation

Installing and Running Java DB - Derby

Derby (Java DB) JDBC Driver

Derby (Java DB) JDBC DataSource Objects

Java DB (Derby) - DML Statements

Java DB (Derby) - ResultSet Objects of Queries

Java DB (Derby) - PreparedStatement

MySQL Installation on Windows