org.apache.tapestry5.ioc

## Interface ObjectLocator

- All Known Subinterfaces:
    InternalRegistry, Registry, ServiceBuilderResources, ServiceResources
  All Known Implementing Classes:
    ObjectLocatorImpl, RegistryImpl, RegistryWrapper, ServiceResourcesImpl

      public interface ObjectLocator

  Defines an object which can provide access to services defined within a `Registry`, or to objects or object instances available by other means. Services are accessed via service id, or (when appropriate) by just service interface. The Registry itself implements this interface, as does `ServiceResources`.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `<T> T` | `autobuild(Class<T> clazz)` Autobuilds a class by finding the public constructor with the most parameters.
    `<T> T` | `autobuild(String description, Class<T> clazz)` Preferred version of `autobuild(Class)` that tracks the operation using `OperationTracker.invoke(String, org.apache.tapestry5.ioc.Invokable)`.
    `<T> T` | `getObject(Class<T> objectType, AnnotationProvider annotationProvider)` Obtains an object indirectly, using the `MasterObjectProvider` service.
    `<T> T` | `getService(Class<T> serviceInterface)` Locates a service given a service interface and (optionally) some marker annotation types.
    `<T> T` | `getService(Class<T> serviceInterface, Class<? extends Annotation>... markerTypes)` Locates a service given a service interface and (optionally) some marker annotation types.
    `<T> T` | `getService(String serviceId, Class<T> serviceInterface)` Obtains a service via its unique service id.
    `<T> T` | `proxy(Class<T> interfaceClass, Class<? extends T> implementationClass)` Creates a proxy.

- - ### Method Detail

    - #### getService

          <T> T getService(String serviceId,
                           Class<T> serviceInterface)

      Obtains a service via its unique service id. Returns the service's proxy. The service proxy implements the same interface as the actual service, and is used to instantiate the actual service only as needed (this is transparent to the application).
      Type Parameters:
        `T` -
      Parameters:
        `serviceId` - unique Service id used to locate the service object (may contain symbols, which will be expanded), case is ignored
        `serviceInterface` - the interface implemented by the service (or an interface extended by the service interface)
      Returns:
        the service instance
      Throws:
        `RuntimeException` - if the service is not defined, or if an error occurs instantiating it

    - #### getService

          <T> T getService(Class<T> serviceInterface)

      Locates a service given a service interface and (optionally) some marker annotation types. A single service must implement the service interface (which * can be hard to guarantee) and by marked by all the marker types. The search takes into account inheritance of the service interface (not the service implementation), which may result in a failure due to extra matches.
      Parameters:
        `serviceInterface` - the interface the service implements
      Returns:
        the service's proxy
      Throws:
        `RuntimeException` - if the service does not exist (this is considered programmer error), or multiple services directly implement, or extend from, the service interface
      See Also:
        `Marker`

    - #### getService

          <T> T getService(Class<T> serviceInterface,
                           Class<? extends Annotation>... markerTypes)

      Locates a service given a service interface and (optionally) some marker annotation types. A single service must implement the service interface (which * can be hard to guarantee) and by marked by all the marker types. The search takes into account inheritance of the service interface (not the service implementation), which may result in a failure due to extra matches. The ability to specify marker annotation types was added in 5.3
      Parameters:
        `serviceInterface` - the interface the service implements
        `markerTypes` - Markers used to select a specific service that implements the interface
      Returns:
        the service's proxy
      Throws:
        `RuntimeException` - if the service does not exist (this is considered programmer error), or multiple services directly implement, or extend from, the service interface
      Since:
        5.3
      See Also:
        `Marker`

    - #### getObject

          <T> T getObject(Class<T> objectType,
                          AnnotationProvider annotationProvider)

      Obtains an object indirectly, using the `MasterObjectProvider` service.
      Type Parameters:
        `T` -
      Parameters:
        `objectType` - the type of object to be returned
        `annotationProvider` - provides access to annotations on the field or parameter for which a value is to be obtained, which may be utilized in selecting an appropriate object, use null when annotations are not available (in which case, selection will be based only on the object type)
      Returns:
        the requested object
      See Also:
        `ObjectProvider`

    - #### autobuild

          <T> T autobuild(Class<T> clazz)

      Autobuilds a class by finding the public constructor with the most parameters. Services and other resources or dependencies will be injected into the parameters of the constructor and into private fields marked with the `Inject` annotation. There are two cases: constructing a service implementation, and constructing an arbitrary object. In the former case, many service resources are also available for injection, not just dependencies or objects provided via the MasterObjectProvider service.
      Type Parameters:
        `T` -
      Parameters:
        `clazz` - the type of object to instantiate
      Returns:
        the instantiated instance
      Throws:
        `RuntimeException` - if the autobuild fails

    - #### autobuild

          <T> T autobuild(String description,
                          Class<T> clazz)

      Preferred version of `autobuild(Class)` that tracks the operation using `OperationTracker.invoke(String, org.apache.tapestry5.ioc.Invokable)`.
      Type Parameters:
        `T` -
      Parameters:
        `description` - description used with `OperationTracker`
        `clazz` - the type of object to instantiate
      Returns:
        the instantiated instance
      Throws:
        `RuntimeException` - if the autobuild fails
      Since:
        5.2.0

    - #### proxy

          <T> T proxy(Class<T> interfaceClass,
                      Class<? extends T> implementationClass)

      Creates a proxy. The proxy will defer invocation of `autobuild(Class)` until just-in-time (that is, first method invocation). In a limited number of cases, it is necessary to use such a proxy to prevent service construction cycles, particularly when contributing (directly or indirectly) to the `MasterObjectProvider` (which is itself at the heart of autobuilding). If the class file for the class is a file on the file system (not a file packaged in a JAR), then the proxy will autoreload: changing the class file will result in the new class being reloaded and re-instantiated (with dependencies).
      Type Parameters:
        `T` -
      Parameters:
        `interfaceClass` - the interface implemented by the proxy
        `implementationClass` - a concrete class that implements the interface
      Returns:
        a proxy
      See Also:
        `autobuild(Class)`

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