org.apache.tapestry5.services
Interface MetaDataLocator

All Known Implementing Classes:

MetaDataLocatorImpl

@UsesMappedConfiguration(value=java.lang.String.class)
public interface MetaDataLocator

Used to lookup meta data concerning a particular component. The primary source of meta data is the meta data defined for the component, accessed via ComponentModel.getMeta(String). This includes meta data defined by base classes. When meta-data for a particular component can not be found, a search works up the containment hierarchy (to the component's container, and the container's container, and so on). If that proves unfruitful, a system of defaults is provided by configuration and matched against the containing page's logical name.

Finally, if no metadata is available, then SymbolSource.valueForSymbol(String) is used to obtain a value. Generally speaking, if you are going to use this service to look up meta data, your should also make a contribution to the FactoryDefaults service; otherwise, you risk a runtime exception if a meta-data key can not be resolved.

Method Summary

<T> T	findMeta(String key, ComponentResources resources, Class<T> expectedType) Searches for the value for the corresponding key.
<T> T	findMeta(String key, String pageName, Class<T> expectedType) Searches for the value for the corresponding key for a particular page name (the page will not be loaded).

Method Detail

findMeta

<T> T findMeta(String key,
               ComponentResources resources,
               Class<T> expectedType)

Searches for the value for the corresponding key. The value, if located, will have symbols expanded, and will be type coerced to the desired type.

Parameters:

key - the key used to locate the meta data (case insensitive)

resources - the resources of the initial component used in the search

Returns:

the value if found (in the component, the component's container, etc. or via a folder default)

Throws:

RuntimeException - if the value for the key is not present as meta data of the component, as an override, or as a symbol

findMeta

<T> T findMeta(String key,
               String pageName,
               Class<T> expectedType)

Searches for the value for the corresponding key for a particular page name (the page will not be loaded). The value, if located, will have symbols expanded, and will be type coerced to the desired type.

Parameters:

key - the key used to locate the meta data (case insensitive)

pageName - the name of the page to search

Returns:

the value if found

Throws:

RuntimeException - if the value for the key is not present as meta data of the page, as an override, or as a symbol