Monday, April 22, 2019

Load Testing Web Apps Using Apache JMeter

Apache JMeter is an excellent tool for simulating user load on a web application in order to test performance. You can easily build a test plan by specifying the number of users and the interval between requests, and JMeter will then spawn a thread per user and hit your webapp. At the end of the test, you will get a performance summary report showing the min, max and average response times.

Here is a quick walkthrough of using JMeter:

  • Download JMeter from here
  • Run the jmeter.bat (for Windows) or jmeter (for Unix) file to start the JMeter GUI
  • Add a "Thread Group" to the Test Plan and configure the number of users, ramp-up period and duration of the test
  • Add a "HTTP Request" to the Thread Group and set the server URL and any request parameters
  • Add a "Constant Timer" (or any other Timer) to the HTTP Request and specify the time interval between requests
  • Add a "Summary Report" to the Thread Group
  • Add a "View Results in Table" to the Thread Group
  • Run the test and view the Summary Report

There are a number of other components that can be added to the test plan as well. For example, you can add a "HTTP Header Manager" to the Thread Group if you want to add any fields to the request's header. The "Response Assertion" component is useful for checking if you have received the desired response from the server.

Once you are happy with your test plan, you can save it to a file and then run it on the command line whenever you need to load test your application or as part of your continuous build process.

Tuesday, January 01, 2019 in 2018

Happy 2019, everyone!

I'd like to wish everyone a great start to an even greater new year!

In keeping with tradition, here's one last look back at in 2018.

During 2018, I posted 14 new entries on I am also thrilled that I have more readers from all over the world! Thanks for reading and especially for giving feedback.

Top 5 posts of 2018:

I'm going to be writing a lot more this year, so stay tuned for more great techie tips, tricks and hacks! :)

Related posts:

Saturday, December 29, 2018

Java 11: Running single-file programs and "shebang" scripts

In Java 11, the java launcher has been enhanced to run single-file source code programs directly, without having to compile them first.

For example, consider the following class that simply adds its arguments:

import java.util.*;
public class Add {
  public static void main(String[] args) {

In previous versions of Java, you would first have to compile the source file and then run it as follows:

$ javac
$ java Add 1 2 3

In Java 11, there is no need to compile the file! You can run it directly as follows:

$ java 1 2 3

It's not even necessary to have the ".java" extension on your file. You can call the file whatever you like but, if the file does not have the ".java" extension, you need to specify the --source option in order to tell the java launcher to use source-file mode. In the example below, I have renamed my file to MyJava.code and run it with --source 11:

$ java --source 11 MyJava.code 1 2 3

It gets even better! It is also possible to run a Java program directly on Unix-based systems using the shebang (#!) mechanism.

For example, you can take the code from and put it in a file called add, with the shebang at the start of the file, as shown below:

#!/path/to/java --source 11
import java.util.*;
public class Add {
  public static void main(String[] args) {

Mark the file as executable using chmod and run it as follows:

$ chmod +x add
$ ./add 1 2 3

Tuesday, December 25, 2018

Java 11: Converting a Collection to an Array

In Java 11, a new default method, toArray(IntFunction), has been added to the java.util.Collection interface, which allows the collection's elements to be transferred to a newly created array of a desired runtime type.

For example:

// Java 11
List<String> list = Arrays.asList("foo","bar","baz");
String[] array = list.toArray(String[]::new);

// The above is equivalent to:
String[] array2 = list.toArray(new String[0]);

Sunday, December 23, 2018

Java 11: New HTTP Client API

In Java 11, the incubated HTTP Client API first introduced in Java 9, has been standardised. It makes it easier to connect to a URL, manage request parameters, cookies and sessions, and even supports asynchronous requests and websockets.

To recap, this is how you would read from a URL using the traditional URLConnection approach:

var url = new URL("");
var conn = url.openConnection();
try (var in = new BufferedReader(new InputStreamReader(conn.getInputStream()))) {

Here is how you can use HttpClient instead:

var httpClient = HttpClient.newHttpClient();
var request = HttpRequest.newBuilder(URI.create("")).build();
var response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

The HTTP Client API also supports asynchonous requests via the sendAsync method which returns a CompletableFuture, as shown below. This means that the thread executing the request doesn't have to wait for the I/O to complete and can be used to run other tasks.

var httpClient = HttpClient.newHttpClient();
var request = HttpRequest.newBuilder(URI.create("")).build();
httpClient.sendAsync(request, HttpResponse.BodyHandlers.ofString())

It's also very easy to make a POST request containing JSON from a file:

var httpClient = HttpClient.newHttpClient();
var request = HttpRequest.newBuilder(URI.create(""))
 .header("Content-Type", "application/json")