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Using JMeter
Pages: 1, 2

Now you should be able to figure out the values for the properties in the HTTP Request page. The last element that we need to add to our test plan is a listener, which in JMeter is the same as a report. JMeter comes with various reports to choose from. A report can be a table or a graph. For this testing, use the easiest report available: a table.



To add a listener, right-click the Thread Group element, select Add, and then Listener and View Results in Table. Now you are ready to run the test plan. Before you run your test plan, however, you are advised to save the test plan just in case JMeter crashes the system (an occasional occurrence with higher numbers of threads and loop counts). Afterwards, select Start from the Run menu to execute the test plan.

While the test plan executes, the small box on the bar right below the menu bar will turn green. For a test that does not run indefinitely, JMeter will automatically stop the test plan after it's finished. For a test that goes on indefinitely, you must intervene to stop the test. Do this by selecting Stop from the Run menu.

When I ran my test plan, I got the results like those shown in Figure 4.


Figure 4: A table report.

It is very easy to understand the figures in the table. There are six samples taken (two threads and three loop counts, thus 2 x 3 = 6). The response time from each sample is given in the third column. They are 100, 60, 260, 50, 120, and 80 ms. All samples are taken successfully, as described by the fourth column. On average, each sample has a response time of 111 ms ((100 + 60 + 260 + 50 + 120 + 80)/6).

Another important figure is the standard deviation, defined as the square root of the total of the deviation of each sample from the average. This figure indicates how stable your Web application is. If the standard deviation is high, some users will experience very good responses while some other users will wait for a longer time. The smaller this value, the better.

After conducting a simple test, it is very easy to do more complex tests. For load testing Web applications, increase the number of threads and the loop counts gradually and see how your applications cope with the loads. The following sections of this article tackle some other important aspects of load-testing Web applications with JMeter.

Listeners

JMeter comes with a number of listeners or reports. In the previous test, we used a table to display the test results. If this is not suitable for you, you can choose one or more of the other listeners for a thread group. A popular listener is the Graph Results, as shown in Figure 5.


Figure 5: Graph results.

Multiple HTTP Requests

A real application has multiple resources, both static and dynamic. Chances are, you want to see the performance of these resources. JMeter makes it easy to employ multiple HTTP requests. Just add any number of HTTP Request elements and configure them, as in the previous test. If you have multiple HTTP Request elements, you might want to use a HTTP Request Defaults element, described in the following section.

HTTP Request Defaults

The HTTP Request Defaults element specifies the default values of existing HTTP Request elements within the same thread group. The HTTP Request Defaults element is especially useful because most, if not all, HTTP Request elements normally have the same server and port. Figure 6 shows the detail page of a HTTP Request Defaults element.


Figure 6: HTTP request defaults.

Add an HTTP Request Default element by right-clicking a Thread Group element and then selecting Add, Config Element, and HTTP Request Default.

Cookie Manager

Many Web applications use cookies. JMeter provides cookie capabilities through a Cookie Manager. Adding this element to a thread group allows you to send cookies to the application being tested, just as Web browsers do. Figure 7 displays the details page of a Cookie Manager. Here you can add and delete a cookie.


Figure 7; Cookie Manager.

You can add a Cookie Manager element by right-clicking a Thread Group element and then selecting Add, Config Element, and Cookie Manager.

Summary

JMeter is capable of much more than our simple tests demonstrate. From these building blocks, it's possible to create extensive tests with highly detailed reports. Getting useful results is very easy, though.

For more information, see the JMeter User Manual.

Budi Kurniawan is a senior J2EE architect and author.


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