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This repository contains the guide documentation source. To view the guide in published form, view it on the Open Liberty website. |
Learn how to build and test a simple web application using Maven and Open Liberty.
You will learn how to configure a simple web servlet application using Maven and the Liberty Maven plugin. When you compile and build the application code, Maven downloads and installs Open Liberty. If you run the application, Maven creates an Open Liberty instance and runs the application on it. The application displays a simple web page with a link that, when clicked, calls the servlet to return a simple response of Hello! How are you today?.
One benefit of using a build tool like Maven is that you can define the details of the project and any dependencies it has, and Maven automatically downloads and installs the dependencies. Another benefit of using Maven is that it can run repeatable, automated tests on the application. You can, of course, test your application manually by starting a Liberty instance and pointing a web browser at the application URL. However, automated tests are a much better approach because you can easily rerun the same tests each time the application is built. If the tests don’t pass after you change the application, the build fails, and you know that you introduced a regression that requires a fix to your code.
Choosing a build tool often comes down to personal or organizational preference, but you might choose to use Maven for several reasons. Maven defines its builds by using XML, which is probably familiar to you already. As a mature, commonly used build tool, Maven probably integrates with whichever IDE you prefer to use. Maven also has an extensive plug-in library that offers various ways to quickly customize your build. Maven can be a good choice if your team is already familiar with it.
You will create a Maven build definition file that’s called a pom.xml file, which stands for Project Object Model, and use it to build your web application. You will then create a simple, automated test and configure Maven to automatically run the test.
If Maven isn’t already installed, download the binary zip or tar.gz file. Then, follow the installation instructions for your operating system to extract the .zip file and add the bin directory, which contains the mvn command to the PATH on your computer.
Run the following command to test that Maven is installed:
mvn -v
If Maven is installed properly, you see information about the Maven installation similar to the following example:
Apache Maven 3.8.1 (05c21c65bdfed0f71a2f2ada8b84da59348c4c5d)
Maven home: /Applications/Maven/apache-maven-3.8.1
Java version: 11.0.12, vendor: International Business Machines Corporation, runtime: /Library/Java/JavaVirtualMachines/ibm-semeru-open-11.jdk/Contents/Home
Default locale: en_US, platform encoding: UTF-8
OS name: "mac os x", version: "11.6", arch: "x86_64", family: "mac"The finish directory in the root of this guide contains the finished application. Give it a try before you proceed.
To try out the application, first go to the finish directory and run Maven with the liberty:run goal to build the application and deploy it to Open Liberty:
cd finish
mvn liberty:runAfter you see the following message, your Liberty instance is ready.
The guideServer server is ready to run a smarter planet.
Navigate your browser to the http://localhost:9080/ServletSample/servlet URL to access the application. The servlet returns a simple response of Hello! How are you today?.
The simple web application that you will build using Maven and Open Liberty is provided for you in the start directory so that you can focus on learning about Maven. This application uses a standard Maven directory structure, eliminating the need to customize the pom.xml file so that Maven understands your project layout.
All the application source code, including the Open Liberty server.xml configuration file, is in the src/main/liberty/config directory:
└── src
└── main
└── java
└── resources
└── webapp
└── liberty
└── configNavigate to the start directory to begin.
Before you can build the project, define the Maven Project Object Model (POM) file, the pom.xml.
Create the pom.xml file in thestartdirectory.pom.xml
pom.xml
link:finish/pom.xml[role=include]The pom.xml file starts with a root project element and a modelversion element, which is always set to 4.0.0.
A typical POM for a Liberty application contains the following sections:
-
Project coordinates: The identifiers for this application.
-
Properties (
properties): Any properties for the project go here, including compilation details and any values that are referenced during compilation of the Java source code and generating the application. -
Dependencies (
dependencies): Any Java dependencies that are required for compiling, testing, and running the application are listed here. -
Build plugins (
build): Maven is modular and each of its capabilities is provided by a separate plugin. This is where you specify which Maven plugins should be used to build this project and any configuration information needed by those plugins.
The project coordinates describe the name and version of the application. The artifactId gives a name to the web application project, which is used to name the output files that are generated by the build (e.g. the WAR file) and the Open Liberty instance that is created. You’ll notice that other fields in the pom.xml file use variables that are resolved by the artifactId field. This is so that you can update the name of the sample application, including files generated by Maven, in a single place in the pom.xml file. The value of the packaging field is war so that the project output artifact is a WAR file.
The first four properties in the properties section of the project, just define the encoding (UTF-8) and version of Java (Java 11) that Maven uses to compile the application source code.
Open Liberty configuration properties provide you with a single place to specify values that are used in multiple places throughout the application. For example, the http.port value is used in both the Liberty server.xml configuration file and will be used in the test class that you will add (EndpointIT.java) to the application. Because the http.port value is specified in the pom.xml file, you can easily change the port number that the Liberty instance runs on without updating the application code in multiple places.
HelloServlet.java
link:finish/src/main/java/io/openliberty/guides/hello/HelloServlet.java[role=include]The HelloServlet.java class depends on jakarta.jakartaee-api to compile. Maven will download this dependency from the Maven Central repository using the groupId, artifactId, and version details that you provide here. The dependency is set to provided, which means that the API is in the Liberty runtime and doesn’t need to be packaged by the application.
The build section gives details of the two plugins that Maven uses to build this project.
-
The Maven plugin for generating a WAR file as one of the output files.
-
The Liberty Maven plug-in, which allows you to install applications into Open Liberty and manage the associated Liberty instances.
In the liberty-maven-plugin plug-in section, you can add a configuration element to specify Open Liberty configuration details. For example, the serverName field defines the name of the Open Liberty instance that Maven creates. You specified guideServer as the value for serverName. If the serverName field is not included, the default value is defaultServer.
server.xml
link:finish/src/main/liberty/config/server.xml[role=include]Navigate your browser to the http://localhost:9080/ServletSample/servlet URL to access the application. The servlet returns a simple response of Hello! How are you today?.
One of the benefits of building an application with Maven is that Maven can be configured to run a set of tests. You can write tests for the individual units of code outside of a running Liberty instance (unit tests), or you can write them to call the Liberty instance directly (integration tests). In this example you will create a simple integration test that checks that the web page opens and that the correct response is returned when the link is clicked.
Create theEndpointITclass.src/test/java/io/openliberty/guides/hello/it/EndpointIT.java
EndpointIT.java
link:finish/src/test/java/io/openliberty/guides/hello/it/EndpointIT.java[role=include]The test class name ends in IT to indicate that it contains an integration test.
Maven is configured to run the integration test using the maven-failsafe-plugin. The systemPropertyVariables section defines some variables that the test class uses. The test code needs to know where to find the application that it is testing. While the port number and context root information can be hardcoded in the test class, it is better to specify it in a single place like the Maven pom.xml file because this information is also used by other files in the project. The systemPropertyVariables section passes these details to the Java test program as a series of system properties, resolving the http.port and war.name variables.
pom.xml
link:finish/pom.xml[role=include]The following lines in the EndpointIT test class uses these system variables to build up the URL of the application.
In the test class, after defining how to build the application URL, the @Test annotation indicates the start of the test method.
In the try block of the test method, an HTTP GET request to the URL of the application returns a status code. If the response to the request includes the string Hello! How are you today?, the test passes. If that string is not in the response, the test fails. The HTTP client then disconnects from the application.
In the import statements of this test class, you’ll notice that the test has some new dependencies. Before the test can be compiled by Maven, you need to update the pom.xml to include these dependencies.
The Apache httpclient and junit-jupiter-engine dependencies are needed to compile and run the integration test EndpointIT class. The scope for each of the dependencies is set to test because the libraries are needed only during the Maven build and do not needed to be packaged with the application.
Now, the created WAR file contains the web application, and dev mode can run any integration test classes that it finds. Integration test classes are classes with names that end in IT.
The directory structure of the project should now look like this:
└── src
├── main
│ └── java
│ └── resources
│ └── webapp
│ └── liberty
│ └── config
└── test
└── javaYou see the following output:
-------------------------------------------------------
T E S T S
-------------------------------------------------------
Running io.openliberty.guides.hello.it.EndpointIT
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.255 sec - in io.openliberty.guides.hello.it.EndpointIT
Results :
Tests run: 1, Failures: 0, Errors: 0, Skipped: 0To see whether the test detects a failure, change the response string in the servlet src/main/java/io/openliberty/guides/hello/HelloServlet.java so that it doesn’t match the string that the test is looking for. Then re-run the tests and check that the test fails.
HelloServlet.java
link:finish/src/main/java/io/openliberty/guides/hello/HelloServlet.java[role=include]You built and tested a web application project with an Open Liberty instance using Maven.