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=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 newer versions of JDK and JDBC Driver, you will get correct result:

herong> java -cp .:mssql-jdbc-7.4.1.jre12.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> javac CloseResultSet.java

herong> 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 supporte by Microsoft JDBC Driver 1.0.

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

 MySQL JDBC Driver (MySQL Connector/J)

 MySQL - PreparedStatement

 MySQL - Reference Implementation of JdbcRowSet

 MySQL - JBDC CallableStatement

 MySQL CLOB (Character Large Object) - TEXT

 MySQL BLOB (Binary Large Object) - BLOB

 Oracle Express Edition Installation on Windows

 Oracle JDBC Drivers

 Oracle - Reference Implementation of JdbcRowSet

 Oracle - PreparedStatement

 Oracle - JBDC CallableStatement

 Oracle CLOB (Character Large Object) - TEXT

 Oracle BLOB (Binary Large Object) - BLOB

 Microsoft SQL Server Express Edition

 Microsoft JDBC Driver for SQL Server

Microsoft JDBC Driver - Query Statements and Result Sets

 Commonly Used JDBC Class Methods

 Calling createStatement() and executeQuery

 Receiving ResultSet Objects from executeQuery

Closing ResultSet Objects - res.close()

 Looping through ResultSet with res.next()

 Retrieving Field Values using res.get*() Methods

 Using ResultSetMetaData Objects to List All Fields

 Microsoft JDBC Driver - DatabaseMetaData Object

 Microsoft JDBC Driver - DDL Statements

 Microsoft JDBC Driver - DML Statements

 SQL Server - PreparedStatement

 SQL Server CLOB (Character Large Object) - TEXT

 SQL Server BLOB (Binary Large Object) - BLOB

 JDBC-ODBC Bridge Driver - sun.jdbc.odbc.JdbcOdbcDriver

 JDBC-ODBC Bridge Driver - Flat Text Files

 JDBC-ODBC Bridge Driver - MS Access

 JDBC-ODBC Bridge Driver - MS SQL Server

 Summary of JDBC Drivers and Database Servers

 Additional Tutorial Notes to Be Added

 Outdated Tutorials

 References

 Full Version in PDF/EPUB