Assets are any kind of file that may be downloaded to a client web browser in addition to the dynamically generated HTML.
Assets are most often images, stylesheets, and JavaScript libraries.
Normal assets are stored in the web application's context folder ... stored inside the web application WAR file in the ordinary way.
Tapestry will also make files stored on the classpath, with your Java class files, visible to the web browser.
Assets are exposed to your code as instances of the Asset interface.
Components learn about assets via injection. The Inject annotation allows Assets to be injected into components as read-only properties. The path to the resource is specified using the Path annotation.
@Inject
@Path("context:images/tapestry_banner.gif")
private Asset _banner;Assets are located within domains; these domains are identified by the prefix on the Inject annotation's value.
If the prefix is omitted, the value will be interpreted as a path relative to the Java class file itself, within the "classpath:" domain. This is often used when creating component libraries, where the assets used by the components are packaged in the JAR with the components themselves.
Unlike elsewhere in Tapestry, case matters. This is because Tapestry is dependenent on the Servlet API and the Java runtime to access the underlying files, and those APIs, unlike Tapestry, are case sensitive. Be aware that some operating systems (such as Windows) are case insenitive, which may mask errors that will be revealed at deployment (if the deployment operating system is case sensitive, such as Linux).
You can use relative paths with domains (if you omit the prefix):
@Inject
@Path("../edit.png")
private Asset _icon;Since you must omit the prefix, this only makes sense for components packaged in a library for reuse.
Symbols inside the annotation value are expanded. This allows you to define a symbol and reference it as part of the path. For example, you could contribute a symbol named "skin.root" as "context:/skins/basic" and then reference an asset from within it:
@Inject
@Path("${skin.root}/style.css")
private Asset _style;An override of the skin.root symbol would affect all references to the named asset.
Assets are localized; Tapestry will search for a variation of the file appropriate to the effective locale for the request. In the previous example, a German user of the application may see a file named edit_de.png (if such a file exists).
If you wish to create new domains for assets, for example to allow assets to be stored on the file system or in a database, you may define a new AssetFactory and contribute it to the AssetSource service configuration.
Private assets (assets on the classpath) normally have the form: /assets/foo/bar/Baz.css where Baz.css is a file inside the foo.bar Java package. In other words, the package name is converted into a path underneath the virtual folder, /assets/.
You are given some control over this, allowing for shorter paths. The ClasspathAssetAliasManager service has a mapped configuration. The map keys are logical folder names, and the map values are the complete classpath. For example, Tapestry itself makes this contribution:
public static void contributeClasspathAssetAliasManager(
MappedConfiguration<String, String> configuration)
{
configuration.add("tapestry", "org/apache/tapestry");
}Thus, the generated URLs may say /assets/tapestry/Foo.gif but the underlying file will be /org/apache/tapestry/Foo.gif (within the classpath).
Care should be taken to not create overlapping mappings, as the results would not be predictable.