Dynamically registering a WAB

Andrew Lienhard

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Feb 12, 2023, 5:29:46 PM2/12/23

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I have a WAB in a karaf container that I need to deploy using a context path based on environment variables (k8s helm). Currently its web-ContextPath is hardcoded in a pom.xml, so it's compile-time only which won't work for our deployments.

I'm wondering if it's possible to register this WAB dynamically as one would a servlet using HttpService and/or pax-web. I've been digging through the documentation and examples but so far I haven't been able to work it out. Is this doable? If so, are there any examples of this? Ultimately, I don't care what form the service takes as long as it can serve static files from a directory.

clip from the pom.xml

<plugin>
<groupId>org.apache.felix</groupId>
<artifactId>maven-bundle-plugin</artifactId>
<extensions>true</extensions>
<configuration>
<instructions>
<_wab>src/main/webapp</_wab>
<Include-Resource>{maven-resources},OSGI-INF/blueprint/blueprint.xml=${project.build.directory}/classes/OSGI-INF/blueprint/blueprint.xml</Include-Resource>
<Embed-Dependency>*;scope=compile|runtime</Embed-Dependency>
<Embed-Directory>WEB-INF/lib</Embed-Directory>
<Web-ContextPath>/</Web-ContextPath>
</instructions>
</configuration>
</plugin>

Andrew Lienhard

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Feb 12, 2023, 10:49:52 PM2/12/23

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This seems to be the most promising approach. Repackage the WAB as a WAR then deploy it at runtime as shown below. The URL parameters will assist the OSGI Web URL Handler in automagically producing a WAB + MANIFEST.MF with the correct web-contextpath header. Only I need to do it using the bundleContext.installBundle(String location) API instead of in the console. I also need to sort out the URL of the built war itself. Does this sound correct?

karaf@root()> bundle:install -s "webbundle:http://tomcat.apache.org/tomcat-7.0-doc/appdev/sample/sample.war?Bundle-SymbolicName=tomcat-sample&Web-ContextPath=/sample"

From <https://karaf.apache.org/manual/latest/webcontainer>

https://docs.osgi.org/specification/osgi.cmpn/7.0.0/service.war.html#i3100445

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Grzegorz Grzybek

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Feb 13, 2023, 1:58:58 AM2/13/23

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Hello

If you need only static resources, maybe you should simply register Whiteboard-based resources? Something like this:

register a context to "get" a context path:

Dictionary<String, Object> properties = new Hashtable<>();
properties.put("osgi.http.whiteboard.context.name", "my-context");
properties.put("osgi.http.whiteboard.context.path", "/sample");

ServiceRegistration<ServletContextHelper> reg = context.registerService(ServletContextHelper.class, new ServletContextHelper() {}, properties);

register resources into this context path:

Dictionary<String, Object> properties = new Hashtable<>();
properties.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_RESOURCE_PATTERN, new String[] { "/static/*" });
properties.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_RESOURCE_PREFIX, "/resources");
properties.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_CONTEXT_SELECT, String.format("(%s=my-context)",
HttpWhiteboardConstants.HTTP_WHITEBOARD_CONTEXT_NAME));

ServiceRegistration<Object> resReg = context.registerService(Object.class, new Object(), properties);

Then you'll be able to get resources from bundle's "/resources" directory using URI's like "/sample/static/*"

But sure - your WAR approach should work too.

regards

Grzegorz Grzybek

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Andrew Lienhard

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Feb 13, 2023, 8:54:08 PM2/13/23

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Hi. Thanks for taking the time to respond. I managed to get it working using the API example you provided. I had a problem with the context aspect though so I just mapped the path of the resources to include what would have been the new context path. It looks like it always runs under the default "/" context setup in the unomi wab. In the end, I just needed the path, not anything specific to a servlet context since it's just a static website.

I'm including some logs/code to show the issue with attaching the context, if you have any ideas. But the good news is that I was able to get the path stuff sorted out for the static files by simply not using it.

Code:

private static final String MY_CONTEXT_NAME = "my-context";

/**
* Registers a custom web context for use with this endpoint.
*
* @param context
*/
private void registerCustomContext(BundleContext context) {
Dictionary<String, String> contextProps = new Hashtable<>();
contextProps.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_CONTEXT_NAME, MY_CONTEXT_NAME);
contextProps.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_CONTEXT_PATH, "/test" );
context.registerService(ServletContextHelper.class, new ServletContextHelper () {}, contextProps);
log.info("ContextInitializer registered a new context {}", contextProps);
}

/**
* Registers a static resource service.
*
* @param context
*/
private void registerCustomResource(BundleContext context) {
Dictionary<String, Object> resourceProps = new Hashtable<>();
resourceProps.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_RESOURCE_PATTERN, new String[] {"/static/*"});
resourceProps.put(HttpWhiteboardConstants.HTTP_WHITEBOARD_RESOURCE_PREFIX, "/webapp/files");
resourceProps.put(
HttpWhiteboardConstants.HTTP_WHITEBOARD_CONTEXT_SELECT,
String.format("(%s=%s)", HttpWhiteboardConstants.HTTP_WHITEBOARD_CONTEXT_NAME, MY_CONTEXT_NAME ));

context.registerService(Object.class, new Object(), resourceProps);
log.info("ContextInitializer registered a new resource {}", resourceProps);
}

// blueprint.xml init-method="initConfig"
public void initConfig() {
BundleContext bundleContext = FrameworkUtil.getBundle(ContextInitializer.class).getBundleContext();
this.registerCustomContext(bundleContext);
this.registerCustomResource(bundleContext);
}

Custom context: /test

Resource mapping: /static/* -> /webapp/files

Request: /test/static/hello.txt

Logs:

In the system console (Felix) I see the ServletContextHelper and the resource registered accordingly

[org.osgi.service.http.context.ServletContextHelper]

osgi.http.whiteboard.context.name	my-context
osgi.http.whiteboard.context.path	/test
service.bundleid	56
service.scope	singleton

[Object]

osgi.http.whiteboard.context.select

(osgi.http.whiteboard.context.name=my-context)

osgi.http.whiteboard.resource.pattern	/static/*
osgi.http.whiteboard.resource.prefix	/webapp/files
service.bundleid	56
service.scope	singleton
Using Bundles	org.ops4j.pax.web.pax-web-extender-whiteboard (247)

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Grzegorz Grzybek

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Feb 14, 2023, 1:40:37 AM2/14/23

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Hello

Somehow I thought you're using Pax Web 8 which actually has working context selection. Problems with context registration/selection were the MAIN reason I started refactoring of Pax Web 7 into Pax Web 8.

Your example is _canonical_ example of Whiteboard usage and should work perfectly fine with Pax Web 8 (included in Karaf 4.4.3).

regards

Grzegorz Grzybek

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