generate-features.md

generate-features

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This goal modifies the source configuration directory of your application. This goal has a runtime dependency on IBM WebSphere Application Server Migration Toolkit for Application Binaries, which is separately licensed under IBM License Agreement for Non-Warranted Programs. See license here.

Scan the class files of an application and create a new generated-features.xml Liberty configuration file in the source configuration directory that contains the Liberty features the application requires.

This feature is best accessed through dev mode during development. When you start liberty:dev your application will be compiled and the class files will be scanned to verify that all the required Liberty features are included in your server configuration. Then as you work, dev mode will continue to monitor the project to confirm the Liberty features configured are up to date. If you implement a new interface in Java, the scanner will determine if that API is connected to a Liberty feature, then update the server configuration and install the feature. If you remove a feature from server.xml, dev mode will determine if that feature is actually necessary, and if so, add it to the generated configuration file as described below.

Feature generation is disabled through dev mode by default. If you need to enable feature generation, you can start dev mode with the parameter -DgenerateFeatures=true. When running dev mode, you can toggle the generation of features off and on by typing 'g' and pressing Enter. Normally dev mode only scans a class file that has just been updated, but you can tell dev mode to rescan all class files by typing 'o' and pressing Enter. This will optimize the feature list in the generated configuration file.

Lifecycle

This goal is not part of the Maven lifecycle, so to use it in your build you will need to understand its dependencies. Since it will scan the class files of your application, it must be run after the compile goal. The list of features that it generates will be used by the liberty:create and the liberty:install-feature goals, so run this goal first.

If this goal detects Liberty features used in your project but not present in your Liberty configuration, it will create a new file configDropins/overrides/generated-features.xml in the src/main/liberty/config directory of your project. The generated-features.xml file will contain a list of features required for your project. If the generated-features.xml file has been created in the past and no additional features have been detected, this file will be retained.

If you are using devc, ensure that the generated-features.xml configuration file is copied to your Docker image via your Dockerfile.

COPY --chown=1001:0  target/liberty/wlp/usr/servers/defaultServer/configDropins/overrides/generated-features.xml /config/configDropins/overrides/

If on Linux, it is recommended that you copy the entire configDropins/overrides directory to your Docker image via your Dockerfile.

COPY --chown=1001:0  target/liberty/wlp/usr/servers/defaultServer/configDropins/overrides /config/configDropins/overrides

This goal examines the pom.xml dependencies to determine which version of Jakarta EE, MicroProfile or Java EE API you may be using. Compatible features will then be generated.

For Jakarta EE API, this goal looks for a jakarta.platform:jakarta.jakartaee-api dependency and generates features according to the version number.

For MicroProfile API, this goal looks for a org.eclipse.microprofile:microprofile dependency and generates features according to the version number.

For Java EE API, this goal looks for a javax:javaee-api dependency with versions 6.0, 7.0 or 8.0.

For example, if you have the following Jakarta EE and MicroProfile dependencies in your pom.xml file, features compatible with Jakarta EE 9.1.0 and MicroProfile 5.0 will be generated.

<dependency>
    <groupId>jakarta.platform</groupId>
    <artifactId>jakarta.jakartaee-api</artifactId>
    <version>9.1.0</version>
    <scope>provided</scope>
</dependency>
<dependency>
    <groupId>org.eclipse.microprofile</groupId>
    <artifactId>microprofile</artifactId>
    <version>5.0</version>
    <type>pom</type>
    <scope>provided</scope>
</dependency>

This goal also considers the features you have already specified in server.xml or other Liberty server configuration files (e.g. include elements and configDropins files). This goal will attempt to find a working set of features that are compatible with each other.

If there are conflicts with features specified in Liberty configuration files or features used in the application code, this goal will print an error message. If available, this goal will also print a list of suggested features with no conflicts.

Example (outside of dev mode)

Compile the application code and generate Liberty features.

• mvn compile liberty:generate-features

Limitations

• When using the serverXmlFile parameter in the POM, if you specify a file not in the directory src/main/liberty/config and that file uses relative paths to include other files, any features in those files will not be considered for feature generation
• Any features accessed using property variables (e.g. ${custom.key}/configFile.xml) are not considered for feature generation

See issues tagged with generateFeatures for futher information.