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We'll go into more detail about the relevant portions of this POM in the later sections.

Step 1: Choose a base package name

Just as with Tapestry applications, Tapestry component libraries should have a unique base package name. In this example, we'll use org.examples.happylib.

As with an application, we'll follow the conventions: we'll place the module for this library inside the services package, and place pages and components under their respective packages.

Step 3: Create your pages and/or components

Our component is very simple:

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Typically, a component library will have many different components and/or mixins, and may even provide pages.

Step 2: Choose a virtual folder name

In Tapestry, components that have been packaged in a library are referenced using a virtual folder name. It's effectively as if the application had a new root-level folder containing the components.

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The special namespace mapping for sets up namespace prefix "h:" to mean the same as "happy/". It then becomes possible to reference components within the happy virtual folder directly.

Step 3: Configure the library

Tapestry needs to know where to search for your component class. This is accomplished in your library's IoC module class, by making a contribution to the ComponentClassResolver service configuration.

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Note: it is possible to add a mapping for "core". "core" is the core library for Tapestry components; all the built-in Tapestry components (TextField, BeanEditForm, Grid, etc.) are actually in the core library. All Tapestry does is search inside the "core" library when it does find a component in the application. Contributing an additional package as "core" simply extends the number of packages searched for core components (it doesn't replace Tapestry's default package, org.apache.tapestry5.corelib). Adding to "core" is sometimes reasonable, if there is virtually no chance of a naming conflict (via different modules contributing packages to core with conflicting class names).

Step 4: Configure the module to autoload

For Tapestry to autoload your module, it is necessary to put an entry in the JAR manifest. This is taken care of in the pom.xml above:

      <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-jar-plugin</artifactId>
           <configuration>
           <archive>
             <manifestEntries>
             <Tapestry-Module-Classes>org.example.happylib.services.HappyModule</Tapestry-Module-Classes>
             </manifestEntries>
           </archive>
           </configuration>
       </plugin>

Conclusion

That's it! Autoloading plus the virtual folders for components and for assets takes care of all the issues related to components. Just build your JARs, setup the JAR Manifest, and drop them into your applications.

A note about Assets

Tapestry automatically creates a mapping for assets inside your JAR. In the above example, the icon image will be exposed as /assets/application version/happy/components/happy.jpg (the application version number is incorporated into the URL). The "happy" portion is a virtual folder that maps to the librarie's root package (as folder "org/example/happylib" on the Java classpath).

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