Package org.apache.cayenne.access

Class IncrementalFaultList<E>

java.lang.Object
org.apache.cayenne.access.IncrementalFaultList<E>
All Implemented Interfaces:
Serializable, Iterable<E>, Collection<E>, List<E>, SequencedCollection<E>
public class IncrementalFaultList<E> extends Object implements List<E>, Serializable
A synchronized list that serves as a container of DataObjects. It is returned when a paged query is performed by DataContext. On creation, only the first "page" is fully resolved, for the rest of the objects only their ObjectIds are read. Pages following the first page are resolved on demand only. On access to an element, the list would ensure that this element as well as all its siblings on the same page are fully resolved.

The list can hold DataRows or DataObjects. Attempts to add any other object types will result in an exception.

Performance note: certain operations like toArray would trigger full list fetch.

See Also:

  • Field Details

    • pageSize

      protected int pageSize

    • elements

      protected final List elements

    • dataContext

      protected DataContext dataContext

    • rootEntity

      protected ObjEntity rootEntity

    • unfetchedObjects

      protected int unfetchedObjects

    • idWidth

      protected int idWidth
      Stores a hint allowing to distinguish data rows from unfetched ids when the query fetches data rows.

    • metadata

      protected QueryMetadata metadata

    • maxFetchSize

      protected int maxFetchSize
      Defines the upper limit on the size of fetches. This is needed to avoid where clause size limitations.

  • Constructor Details

    • IncrementalFaultList

      public IncrementalFaultList(DataContext dataContext, Query query, int maxFetchSize)
      Creates a new IncrementalFaultList using a given DataContext and query.
      Parameters:
      dataContext - DataContext used by IncrementalFaultList to fill itself with objects.
      query - Main query used to retrieve data. Must have "pageSize" property set to a value greater than zero.
      maxFetchSize - maximum number of fetches in one query

  • Method Details

    • fillIn

      protected void fillIn(Query query, List<Object> elementsList)
      Performs initialization of the list of objects. Only the first page is fully resolved. For the rest of the list, only ObjectIds are read.
      Since:
      3.0

    • resolveAll

      public void resolveAll()
      Will resolve all unread objects.

    • resolveInterval

      protected void resolveInterval(int fromIndex, int toIndex)
      Resolves a sublist of objects starting at fromIndex up to but not including toIndex. Internally performs bound checking and trims indexes accordingly.

    • pageIndex

      public int pageIndex(int elementIndex)
      Returns zero-based index of the virtual "page" for a given array element index.

    • getMaxFetchSize

      public int getMaxFetchSize()
      Get the upper bound on the number of records to resolve in one round trip to the database. This setting governs the size/complexity of the where clause generated to retrieve the next page of records. If the fetch size is less than the page size, then multiple fetches will be made to resolve a page.

    • setMaxFetchSize

      public void setMaxFetchSize(int fetchSize)

    • getDataContext

      public DataContext getDataContext()
      Returns the dataContext.
      Returns:
      DataContext

    • getPageSize

      public int getPageSize()
      Returns the pageSize.
      Returns:
      int

    • listIterator

      public ListIterator<E> listIterator()
      Returns a list iterator for this list. DataObjects are resolved a page (according to getPageSize()) at a time as necessary - when retrieved with next() or previous().
      Specified by:
      listIterator in interface List<E>

    • listIterator

      public ListIterator<E> listIterator(int index)
      Returns a list iterator of the elements in this list (in proper sequence), starting at the specified position in this list. The specified index indicates the first element that would be returned by an initial call to the next method. An initial call to the previous method would return the element with the specified index minus one. DataObjects are resolved a page at a time (according to getPageSize()) as necessary - when retrieved with next() or previous().
      Specified by:
      listIterator in interface List<E>

    • iterator

      public Iterator<E> iterator()
      Return an iterator for this list. DataObjects are resolved a page (according to getPageSize()) at a time as necessary - when retrieved with next().
      Specified by:
      iterator in interface Collection<E>
      Specified by:
      iterator in interface Iterable<E>
      Specified by:
      iterator in interface List<E>

    • add

      public void add(int index, Object element)
      Specified by:
      add in interface List<E>
      See Also:

    • add

      public boolean add(Object o)
      Specified by:
      add in interface Collection<E>
      Specified by:
      add in interface List<E>
      See Also:

    • addAll

      public boolean addAll(Collection<? extends E> c)
      Specified by:
      addAll in interface Collection<E>
      Specified by:
      addAll in interface List<E>
      See Also:

    • addAll

      public boolean addAll(int index, Collection<? extends E> c)
      Specified by:
      addAll in interface List<E>
      See Also:

    • clear

      public void clear()
      Specified by:
      clear in interface Collection<E>
      Specified by:
      clear in interface List<E>
      See Also:

    • contains

      public boolean contains(Object o)
      Specified by:
      contains in interface Collection<E>
      Specified by:
      contains in interface List<E>
      See Also:

    • containsAll

      public boolean containsAll(Collection<?> c)
      Specified by:
      containsAll in interface Collection<E>
      Specified by:
      containsAll in interface List<E>
      See Also:

    • get

      public E get(int index)
      Specified by:
      get in interface List<E>

    • indexOf

      public int indexOf(Object o)
      Specified by:
      indexOf in interface List<E>
      See Also:

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Collection<E>
      Specified by:
      isEmpty in interface List<E>
      See Also:

    • lastIndexOf

      public int lastIndexOf(Object o)
      Specified by:
      lastIndexOf in interface List<E>

    • remove

      public E remove(int index)
      Specified by:
      remove in interface List<E>

    • remove

      public boolean remove(Object o)
      Specified by:
      remove in interface Collection<E>
      Specified by:
      remove in interface List<E>

    • removeAll

      public boolean removeAll(Collection<?> c)
      Specified by:
      removeAll in interface Collection<E>
      Specified by:
      removeAll in interface List<E>

    • retainAll

      public boolean retainAll(Collection<?> c)
      Specified by:
      retainAll in interface Collection<E>
      Specified by:
      retainAll in interface List<E>

    • set

      public E set(int index, Object element)
      Specified by:
      set in interface List<E>
      See Also:

    • size

      public int size()
      Specified by:
      size in interface Collection<E>
      Specified by:
      size in interface List<E>
      See Also:

    • subList

      public List<E> subList(int fromIndex, int toIndex)
      Specified by:
      subList in interface List<E>

    • toArray

      public Object[] toArray()
      Specified by:
      toArray in interface Collection<E>
      Specified by:
      toArray in interface List<E>

    • toArray

      public <T> T[] toArray(T[] a)
      Specified by:
      toArray in interface Collection<E>
      Specified by:
      toArray in interface List<E>

    • getUnfetchedObjects

      public int getUnfetchedObjects()
      Returns a total number of objects that are not resolved yet.