Package org.eclipse.persistence.descriptors

Class MethodClassExtractor

java.lang.Object
org.eclipse.persistence.descriptors.ClassExtractor
org.eclipse.persistence.descriptors.MethodClassExtractor
public class MethodClassExtractor extends ClassExtractor

Purpose: Used to allow complex inheritance support. Typically class indicators are used to define inheritance in the database, however in complex cases the class type may be determined through another mechanism. The method calls a static method on the descriptor class to determine the class to use for the database row.

See Also:

  • Field Details

    • descriptor

      protected transient ClassDescriptor descriptor

    • classExtractionMethodName

      protected String classExtractionMethodName

    • classExtractionMethod

      protected transient Method classExtractionMethod

  • Constructor Details

    • MethodClassExtractor

      public MethodClassExtractor()

  • Method Details

    • getClassExtractionMethod

      public Method getClassExtractionMethod()
      INTERNAL: Return all the classExtractionMethod

    • getClassExtractionMethodName

      public String getClassExtractionMethodName()
      PUBLIC: A class extraction method can be registered with the descriptor to override the default inheritance mechanism. This allows for the class indicator field to not be used, and a user defined one instead. The method registered must be a static method on the class that the descriptor is for, the method must take DatabaseRow as argument, and must return the class to use for that row. This method will be used to decide which class to instantiate when reading from the database. It is the application's responsibility to populate any typing information in the database required to determine the class from the row. If this method is used then the class indicator field and mapping cannot be used, also the descriptor's withAllSubclasses and onlyInstances expressions must also be setup correctly.

    • setClassExtractionMethod

      protected void setClassExtractionMethod(Method classExtractionMethod)
      INTERNAL:

    • setClassExtractionMethodName

      public void setClassExtractionMethodName(String staticClassClassExtractionMethod)
      PUBLIC: A class extraction method can be registered with the descriptor to override the default inheritance mechanism. This allows for the class indicator field to not be used, and a user defined one instead. The method registered must be a static method on the class that the descriptor is for, the method must take DatabaseRow as argument, and must return the class to use for that row. This method will be used to decide which class to instantiate when reading from the database. It is the application's responsibility to populate any typing information in the database required to determine the class from the row. If this method is used then the class indicator field and mapping cannot be used, also the descriptor's withAllSubclasses and onlyInstances expressions must also be setup correctly.

    • initialize

      public void initialize(ClassDescriptor descriptor, Session session) throws DescriptorException
      INTERNAL: Setup the default classExtractionMethod, or if one was specified by the user make sure it is valid.
      Overrides:
      initialize in class ClassExtractor
      Throws:
      DescriptorException

    • extractClassFromRow

      public Class extractClassFromRow(Record row, Session session)
      INTERNAL Extract/compute the class from the database row and return the class. Map is used as the public interface to database row, the key is the field name, the value is the database value.
      Specified by:
      extractClassFromRow in class ClassExtractor

    • getDescriptor

      protected ClassDescriptor getDescriptor()
      INTERNAL: Return the descriptor.

    • setDescriptor

      protected void setDescriptor(ClassDescriptor descriptor)
      INTERNAL: Set the descriptor.