Package org.eclipse.persistence.queries
Class CursoredStream
- java.lang.Object
-
- org.eclipse.persistence.queries.Cursor
-
- org.eclipse.persistence.queries.CursoredStream
-
- All Implemented Interfaces:
Serializable
,Enumeration
,Iterator
public class CursoredStream extends Cursor
Purpose: Stream class which is used to deal with large collections returned from TOPLink queries more efficiently.
Responsibilities: Wraps a database result set cursor to provide a stream on the resulting selected objects.
- Since:
- TOPLink/Java 1.0
- Author:
- Yvon Lavoie
- See Also:
- Serialized Form
-
-
Constructor Summary
Constructors Constructor Description CursoredStream()
INTERNAL: Initialize the state of the streamCursoredStream(org.eclipse.persistence.internal.databaseaccess.DatabaseCall call, CursoredStreamPolicy policy)
INTERNAL: Initialize the state of the stream
-
Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
atEnd()
PUBLIC: Return whether the cursored stream is at its end.int
available()
PUBLIC: Returns the number of objects that can be read from this input without blocking.Expression
buildCountDistinctExpression(List includeFields, ExpressionBuilder builder)
INTERNAL: Must build the count on the primary key fields, not * as * is not allowed if there was a distinct.void
clear()
PUBLIC: Release all objects read in so far.int
getPageSize()
INTERNAL: Return the page size for the stream.int
getPosition()
INTERNAL: Return the position of the stream inside the object collectionboolean
hasMoreElements()
PUBLIC: Return whether the cursored stream has any more elements.boolean
hasNext()
PUBLIC: Return whether the cursored stream has any more elements.void
mark(int readAheadLimit)
PUBLIC: Mark the present position in the stream.boolean
markSupported()
PUBLIC: Tests if this input stream supports themark
andreset
methods.Object
next()
PUBLIC: Return the next object from the collection, if beyond the read limit read from the cursor.List<Object>
next(int numberOfElements)
PUBLIC: Return a Vector of at most numberOfElements of the next objects from the collection.Object
nextElement()
PUBLIC: Return the next object from the collection, if beyond the read limit read from the cursor.Vector
nextElements(int numberOfElements)
PUBLIC: Return a Vector of at most numberOfElements of the next objects from the collection.Object
peek()
PUBLIC: Return the next object in the stream, without incrementing the stream's position.Object
read()
PUBLIC: This method differs slightly from conventional read() operation on a Java stream.List<Object>
read(int number)
PUBLIC: This method differs slightly from conventional read() operation on a Java stream.void
releasePrevious()
PUBLIC: Release all objects read in so far.void
reset()
PUBLIC: Repositions this stream to the position at the time the mark method was last called on this stream.-
Methods inherited from class org.eclipse.persistence.queries.Cursor
close, getAccessor, getExecutionSession, getFields, getInitiallyConformingIndex, getObjectCollection, getPolicy, getQuery, getResultSet, getSelectionCriteriaClone, getSession, isClosed, remove, setInitiallyConformingIndex, setObjectCollection, setPolicy, setSelectionCriteriaClone, setSession, setSize, setTranslationRow, size
-
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
-
Methods inherited from interface java.util.Enumeration
asIterator
-
Methods inherited from interface java.util.Iterator
forEachRemaining
-
-
-
-
Constructor Detail
-
CursoredStream
public CursoredStream()
INTERNAL: Initialize the state of the stream
-
CursoredStream
public CursoredStream(org.eclipse.persistence.internal.databaseaccess.DatabaseCall call, CursoredStreamPolicy policy)
INTERNAL: Initialize the state of the stream
-
-
Method Detail
-
atEnd
public boolean atEnd() throws DatabaseException
PUBLIC: Return whether the cursored stream is at its end.- Throws:
DatabaseException
-
available
public int available() throws DatabaseException
PUBLIC: Returns the number of objects that can be read from this input without blocking.- Throws:
DatabaseException
-
buildCountDistinctExpression
public Expression buildCountDistinctExpression(List includeFields, ExpressionBuilder builder)
INTERNAL: Must build the count on the primary key fields, not * as * is not allowed if there was a distinct. This require a manually defined operator. added for CR 2900
-
getPageSize
public int getPageSize()
INTERNAL: Return the page size for the stream.- Overrides:
getPageSize
in classCursor
-
getPosition
public int getPosition()
INTERNAL: Return the position of the stream inside the object collection- Specified by:
getPosition
in classCursor
-
hasMoreElements
public boolean hasMoreElements()
PUBLIC: Return whether the cursored stream has any more elements.
-
hasNext
public boolean hasNext()
PUBLIC: Return whether the cursored stream has any more elements.
-
mark
public void mark(int readAheadLimit)
PUBLIC: Mark the present position in the stream. Subsequent calls to reset() will attempt to reposition the stream to this point.- Parameters:
readAheadLimit
- Limit on the number of characters that may be read while still preserving the mark. Because the stream's input comes from the database, there is no actual limit, so this argument is ignored.
-
markSupported
public boolean markSupported()
PUBLIC: Tests if this input stream supports themark
andreset
methods. ThemarkSupported
method ofInputStream
returnsfalse
.
-
nextElement
public Object nextElement()
PUBLIC: Return the next object from the collection, if beyond the read limit read from the cursor.- Returns:
- the next object in stream
-
next
public Object next()
PUBLIC: Return the next object from the collection, if beyond the read limit read from the cursor.- Returns:
- the next object in stream
-
nextElements
public Vector nextElements(int numberOfElements)
PUBLIC: Return a Vector of at most numberOfElements of the next objects from the collection. If there aren't that many objects left to read, just return what is available.- Returns:
- the next objects in stream
-
next
public List<Object> next(int numberOfElements)
PUBLIC: Return a Vector of at most numberOfElements of the next objects from the collection. If there aren't that many objects left to read, just return what is available.- Returns:
- the next objects in stream
-
peek
public Object peek() throws DatabaseException
PUBLIC: Return the next object in the stream, without incrementing the stream's position.- Throws:
DatabaseException
-
read
public Object read() throws DatabaseException, QueryException
PUBLIC: This method differs slightly from conventional read() operation on a Java stream. This method return the next object in the collection rather than specifying the number of bytes to be read in. Return the next object from the collection, if beyond the read limit read from the cursor- Returns:
- - next object in stream
- Throws:
DatabaseException
- if read pass end of streamQueryException
-
read
public List<Object> read(int number) throws DatabaseException
PUBLIC: This method differs slightly from conventional read() operation on a Java stream. This method returns the next number of objects in the collection in a vector. Return the next object from the collection, if beyond the read limit read from the cursor- Parameters:
number
- - number of objects to be returned- Returns:
- - vector containing next number of objects
- Throws:
DatabaseException
- if read pass end of stream
-
clear
public void clear()
PUBLIC: Release all objects read in so far. This should be performed when reading in a large collection of objects in order to preserve memory.
-
releasePrevious
public void releasePrevious()
PUBLIC: Release all objects read in so far. This should be performed when reading in a large collection of objects in order to preserve memory.
-
reset
public void reset()
PUBLIC: Repositions this stream to the position at the time the mark method was last called on this stream.
-
-