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

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `<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

5.6.4 - Copyright © 2003-2021 The Apache Software Foundation.