Component Libraries
Page edited by Bob Harner
Comment:
More smoothly integrated the paragraphs on 5.2's automatic asset version mapping
Changes (4)
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The image file here would exposed to the web browser via the URL /happyapp/assets/org/example/happylib/components/happy.jpg (this assumes that the application was deployed as happyapp.war).
Tapestry uses a far-future expiration date for classpath assets; this allows browsers to aggressively cache the file, but in Tapestry 5.1 and earlier this causes a problem should when a later version of the library changes the file. This is discussed in detail in [Yahoos Performance Best Practices|http://developer.yahoo.com/performance/rules.html#expires].
To handle this problem in Tapestry 5.1 and earlier, you should map your library assets to a versioned folder. This can be accomplished using another contribution from the HappyModule, this time to the ClasspathAssetAliasManager service whose configuration maps a virtual folder underneath /assets to a package:
{code}
...
With this in place, and the library and applications rebuilt and redeployed, the URL for happy.jpg becomes /happyapp/assets/happylib/1.0/components/happy.jpg. This is shorter, but also incorporates a version number (1.0) that can be changed in a later release.
{since:since=5.2} In version 5.2 and later, 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 librarys root package (as folder {{org/example/happylib}} on the Java classpath). The application version is a configurable value. {since}
h2. Conclusion Thats 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.
{since:since=5.2}{since} h2. 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 librarys root package (as folder {{org/example/happylib}} on the Java classpath). The application version is a configurable value. In Tapestry 5.1 and earlier, it was necessary to explicitly create a mapping, via a contribution to the ClasspathAssetAliasManager service, to expose library assets. This is no longer necessary in Tapestry 5.2.
Full Content
Supporting Informal ParametersCookbookSwitching Cases
Creating Component Libraries
Nearly every Tapestry application includes a least a couple of custom components, specific to the application. What's exciting about Tapestry is how easy it is to package components for reuse across many applications ... and the fact that applications using a component library need no special configuration.
A Tapestry component library consists of components (and optionally mixins, pages and component base classes). In addition, a component library will have a module that can define new services (needed by the components) or configure other services present in Tapestry. Finally, components can be packaged with assets: resources such as images, stylesheets and _javascript_ libraries that need to be provided to the client web browser.
We're going to create a somewhat insipid component that displays a large happy face icon.
Tapestry doesn't mandate that you use any build system, but we'll assume for the moment that you are using Maven 2. In that case, you'll have a pom.xml file something like the following:
pom.xml
project
modelVersion4.0.0/modelVersion
groupIdorg.example/groupId
artifactIdhappylib/artifactId
version1.0-SNAPSHOT/version
packagingjar/packaging
namehappylib Tapestry 5 Library/name
dependencies
dependency
groupIdorg.apache.tapestry/groupId
artifactIdtapestry-core/artifactId
version${tapestry-release-version}/version
/dependency
dependency
groupIdorg.testng/groupId
artifactIdtestng/artifactId
version5.1/version
classifierjdk15/classifier
scopetest/scope
/dependency
/dependencies
build
plugins
plugin
groupIdorg.apache.maven.plugins/groupId
artifactIdmaven-compiler-plugin/artifactId
configuration
source1.5/source
