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The PropertyAccess service is defined inside TapestryIOCModule's bind() method:
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public static void bind(ServiceBinder binder)
{
. . .
binder.bind(PropertyAccess.class, PropertyAccessImpl.class);
binder.bind(ExceptionAnalyzer.class, ExceptionAnalyzerImpl.class);
. . .
} |
This example includes ExceptionAnalyzer, because it has a dependency on PropertyAccess:
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public class ExceptionAnalyzerImpl implements ExceptionAnalyzer
{
private final PropertyAccess propertyAccess;
public ExceptionAnalyzerImpl(PropertyAccess propertyAccess)
{
this.propertyAccess = propertyAccess;
}
. . .
} |
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Tapestry defines two such services, in the TapestryModule.
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@Marker(ClasspathProvider.class)
public AssetFactory buildClasspathAssetFactory(ResourceCache resourceCache,
ClasspathAssetAliasManager aliasManager)
{
ClasspathAssetFactory factory = new ClasspathAssetFactory(resourceCache, aliasManager);
resourceCache.addInvalidationListener(factory);
return factory;
}
@Marker(ContextProvider.class)
public AssetFactory buildContextAssetFactory(ApplicationGlobals globals)
{
return new ContextAssetFactory(request, globals.getContext());
} |
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Here's an example. Again, we've jumped the gun with this service contributor method (we'll get into the why and how of these later), but you can see how Tapestry is figuring out which service to inject based on the presence of those annotations:
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public void contributeAssetSource(MappedConfiguration<String, AssetFactory> configuration,
@ContextProvider
AssetFactory contextAssetFactory,
@ClasspathProvider
AssetFactory classpathAssetFactory)
{
configuration.add("context", contextAssetFactory);
configuration.add("classpath", classpathAssetFactory);
} |
This is far from the final word on injection and disambiguation; we'll be coming back to this concept repeatedly. And in later chapters of the cookbook, we'll also go into more detail about the many other concepts present in this example. The important part is that Tapestry primarily works off the parameter type (at the point of injection), but when that is insufficient (you'll know ... there will be an error) you can provide additional information, in the form of annotations, to straighten things out.
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