Vaadin 7 OSGi Web Application
Vaadin 7 is a Servlet based Java web framework. And as most OSGi container support Servlet based web applications very well this should be a match made in heaven. But their are some minor things one will stumble upon when trying to run a Vaadin application inside an OSGi container. One of those things is always the classpath.
From Vaadin 6 to Vaadin 7
Some major changes have been made to the Vaadin API from version 6 to 7 but also some structural changes to the deployment. When Vaadin 6 was comfortably packaged into one jar Vaadin 7 comes with multiple jars. The Vaadin 6 jar didn't depend on any other jar which was very convenient. In contrast Vaadin 7 depends on dozens of other jars (some of them not OSGi ready out of the box).
OSGi Web Application Packaging
OSGi Web Applications are called WAB ⇒ Web Application Bundle. Same as a bundle is just a jar file with an extended manifest file the same goes for the WAB. A web application bundle is just a WAR file with an extended manifest.
Demo Vaadin 7 OSGi Web Applicaton
The demo application is a stripped barebone Vaadin application. It uses the default widgetset and the default Vaadin Reindeer theme.
It is derived from the Vaadin application maven archetype and just shows a button which will display a message on click.
Development
Maven and the Maven Bundle Plugin (and some other plugins) are used for development.
Application Code
To get the application code from the source code repository just clone it with hg (Mercurial):
hg clone http://hg.code.sf.net/u/fist/test.vaadin7 test.vaadin7
VaadinServlet
The VaadinServlet class is used to register the web application at the servlet container. Due to a classpath problem a class extending VaadinServlet must be created so that the bundle can resolve all needed classes.
public class OsgiVaadinServlet extends VaadinServlet { private static final long serialVersionUID = -4733496883901044844L; @Override protected VaadinServletService createServletService(DeploymentConfiguration deploymentConfiguration) throws ServiceException { VaadinServletService service = new VaadinServletService(this, deploymentConfiguration) { private static final long serialVersionUID = 1L; @Override public ClassLoader getClassLoader() { return OsgiVaadinServlet.class.getClassLoader(); } @Override protected List<RequestHandler> createRequestHandlers() throws ServiceException { ClassLoader actual = Thread.currentThread().getContextClassLoader(); try { Thread.currentThread().setContextClassLoader(DefaultBroadcaster.class.getClassLoader()); return super.createRequestHandlers(); } finally { Thread.currentThread().setContextClassLoader(actual); } } }; service.init(); return service; } }
web.xml
The registration of the servlet is done via the web.xml file (annotations didn't work).
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <servlet> <servlet-name>vaadin_servlet</servlet-name> <servlet-class>test.vaadin7.OsgiVaadinServlet</servlet-class> <init-param> <param-name>UI</param-name> <param-value>test.vaadin7.MyVaadinUI</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>vaadin_servlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> </web-app>
Maven Bundle Plugin
The Maven Bundle Plugin takes care of all things related to the building of a bundle with the needed entries in the manifest file. Just add it to the pom.xml.
<plugin> <groupId>org.apache.felix</groupId> <artifactId>maven-bundle-plugin</artifactId> <version>2.3.6</version> <extensions>true</extensions> <executions> <execution> <id>bundle-manifest</id> <phase>process-classes</phase> <goals> <goal>manifest</goal> </goals> </execution> <execution> <id>bundle-install</id> <phase>install</phase> <goals> <goal>install</goal> </goals> </execution> </executions> <configuration> <supportedProjectTypes> <supportedProjectType>ejb</supportedProjectType> <supportedProjectType>war</supportedProjectType> <supportedProjectType>bundle</supportedProjectType> <supportedProjectType>jar</supportedProjectType> </supportedProjectTypes> <instructions> <!-- Read all OSGi configuration info from this optional file --> <_include>-osgi.properties</_include> <Bundle-PresentationName>${project.artifactId}</Bundle-PresentationName> <Embed-Directory>WEB-INF/lib</Embed-Directory> <Embed-Dependency>*;scope=compile</Embed-Dependency> <Embed-Transitive>true</Embed-Transitive> </instructions> </configuration> </plugin>
vaadinbootstrap.js
The file vaadinbootstrap.js is located in the vaadin-server jar in the folder VAADIN. The file should be copied from the vaadin-server jar to the folder src/main/webapp/VAADIN/
.
Classpath
Vaadin expects some things to be on the classpath of the application, like themes and compiled resources. To get this working in a simple way is to include these in the war (see Embed-Dependency in pom.xml) and add them to the Bundle-ClassPath entry in the manifest file.
Bundle-ClassPath: .,WEB-INF/classes/,WEB-INF/lib/vaadin-themes-7.3.3.jar,WEB-INF/lib/vaadin-client-compiled-7.3.3.jar
Building
Building the web application bundle with maven is no more than doing a
mvn clean package
The “target” folder contains the bundle (war) file.
Deployment
Apache Karaf
For the testing purpose I am using Apache Karaf 3.0.0 which is the latest stable version of Apache Karaf and can be downloaded from the Apache Karaf website.
Karaf is a very easy to manage OSGi container. Just unpack the archive and start it with
bin/karaf
The bundles can be dumped into the deploy folder which will automatically start the bundles.
Installing Prerequisites
The war feature need to be installed with the command
feature:install war
Now drop all the dependencies into the deploy folder and you are ready to proceed.
Installing Vaadin
Sadly not all libraries delivered with the Vaadin All-In-One archive are provided with a valid OSGi manifest header. But for most use cases a subset of libraries is sufficient enough. For this demo only the following libraries are needed:
- json-0.0.20080701.jar
- flute-1.3.0.gg2.jar
- atmosphere-runtime-2.1.2.vaadin6.jar
- org.apache.commons.beanutils-1.8.3.jar
- org.apache.commons.codec-1.7.0.jar
- org.apache.commons-collections-3.2.1.jar
- org.apache.commons.io-2.4.0.jar
- org.apache.commons.lang3-3.1.0.jar
- vaadin-slf4j-jdk14-1.6.1.jar
- jsoup-1.6.3.jar
- guava-16.0.1.vaadin1.jar
- streamhtmlparser-jsilver-0.0.10.vaadin1.jar
- vaadin-shared-7.3.3.jar
- vaadin-server-7.3.3.jar
- vaadin-client-7.3.3.jar
Export-Package: org.json;version="0.0.20141029" Bundle-Version: 0.0.20141029
Installing Demo
Just copy the test.vaadin-x.x.x.war to the deploy folder and you are done. The web application is available under the path which is specified in the manifest with the Web-ContextPath, in this example /test.vaadin7
.
So point the browser to http://localhost:8181/test.vaadin7
.
Checking the web application
Apache Karaf uses Jetty as its HTTP server. By default it uses the port 8181. You can check this by either pointing your browser to http://localhost:8181 or by using netstat.
netstat -an | grep 8181
A good place to start looking for your application is always the log, see karaf/data/logs/karaf.log.
Another nice method is by using the Apache Felix Webconsole. You can install it with feature:install webconsole
. Then go to http://localhost:8181/system/console/http . There you will see the installed WABs.
Stylesheet Compiling
If a CSS style is used or one of the predefined styles then everything is alright and should work. But if you are using your own style (or extending an existing one) than normally Vaadin would compile it on the fly during the first call of the servlet. But that ends in a nice error message.
java.lang.NoClassDefFoundError: com/vaadin/sass/internal/ScssStylesheet
But the Book of Vaadin explains nicely how to compile the stylesheet before the deployment.
For myself the easiest way was to manually compile it with the following command
java -cp "/my/path/to/vaadin-all-7.3.3/lib/*":"/my/path/to/vaadin-all-7.3.3/*" com.vaadin.sass.SassCompiler styles.scss styles.css
Open Questions
The Vaadin Push support has been tested in this setup. It may need some additional classes which has to be available on the bundle classpath.