ojb.broker.accesslayer
Class RsIterator

java.lang.Object
  |
  +--ojb.broker.accesslayer.RsIterator

All Implemented Interfaces:

java.util.Iterator

Direct Known Subclasses:

ReportQueryRsIterator, SqlBasedRsIterator

public class RsIterator

extends java.lang.Object

implements java.util.Iterator

RsIterator can be used to iterate over a jdbc ResultSet to retrieve persistent objects step-by-step and not all at once. In fact the PersistenceBroker::getCollectionByQuery(...) method uses a RsIterator internally to build up a Collection of objects NOTE: this code uses features that only JDBC 2.0 compliant Drivers support. It will NOT work with JDBC 1.0 Drivers (e.g. SUN's JdbcOdbcDriver) If you are forced to use such a driver, you can use code from the 0.1.30 release.

Author:

Thomas Mahler

Field Summary

protected static ObjectCache	cache
protected boolean	hasCalledCheck
protected boolean	hasNext
protected java.lang.Class	itemProxyClass the proxy class to be used or null
protected Logger	logger
protected PersistenceBrokerImpl	m_broker reference to the PersistenceBroker
protected ClassDescriptor	m_mif the classdescriptor providing the mapping information
protected java.lang.Object[]	m_row this container holds the values of the current ro during materialisation
protected java.sql.ResultSet	m_rs the underlying resultset

Constructor Summary

protected	RsIterator()
	RsIterator(Query query, ClassDescriptor mif, PersistenceBrokerImpl broker) RsIterator constructor.

Method Summary

protected java.lang.Class	getExtentClass()
protected Identity	getIdentityFromResultSet() returns an Identity object representing the current resultset row
protected java.lang.Object	getObjectFromResultSet() returns a fully materialized Object from the current row of the underlying resultset.
protected java.lang.Object	getProxyFromResultSet() Reads primary key information from current RS row and generates a corresponding Identity, and returns a proxy from the Identity.
boolean	hasNext() returns true if there are still more rows in the underlying ResultSet.
java.lang.Object	next() moves to the next row of the underlying ResultSet and returns the corresponding Object materialized from this row.
void	releaseDbResources() Release all internally used Database resources of the iterator.
void	remove() removing is not supported

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logger

protected Logger logger

cache

protected static ObjectCache cache

m_broker

protected PersistenceBrokerImpl m_broker

reference to the PersistenceBroker

m_rs

protected java.sql.ResultSet m_rs

the underlying resultset

m_mif

protected ClassDescriptor m_mif

the classdescriptor providing the mapping information

itemProxyClass

protected java.lang.Class itemProxyClass

the proxy class to be used or null

m_row

protected java.lang.Object[] m_row

this container holds the values of the current ro during materialisation

hasCalledCheck

protected boolean hasCalledCheck

hasNext

protected boolean hasNext

Constructor Detail

RsIterator

protected RsIterator()

RsIterator

public RsIterator(Query query,
                  ClassDescriptor mif,
                  PersistenceBrokerImpl broker)

RsIterator constructor.

Parameters:

mif - ojb.broker.metadata.ClassDescriptor

Method Detail

getExtentClass

protected java.lang.Class getExtentClass()

hasNext

public boolean hasNext()

returns true if there are still more rows in the underlying ResultSet. Returns false if ResultSet is exhausted.

Specified by:

hasNext in interface java.util.Iterator

next

public java.lang.Object next()
                      throws java.util.NoSuchElementException

moves to the next row of the underlying ResultSet and returns the corresponding Object materialized from this row.

Specified by:

next in interface java.util.Iterator

java.util.NoSuchElementException

remove

public void remove()

removing is not supported

Specified by:

remove in interface java.util.Iterator

getIdentityFromResultSet

protected Identity getIdentityFromResultSet()
                                     throws PersistenceBrokerException

returns an Identity object representing the current resultset row

PersistenceBrokerException

getObjectFromResultSet

protected java.lang.Object getObjectFromResultSet()
                                           throws PersistenceBrokerException

returns a fully materialized Object from the current row of the underlying resultset. Works as follows: - read Identity from the primary key values of current row - check if Object is in cache - return cached object or read it from current row and put it in cache

PersistenceBrokerException

getProxyFromResultSet

protected java.lang.Object getProxyFromResultSet()
                                          throws PersistenceBrokerException

Reads primary key information from current RS row and generates a corresponding Identity, and returns a proxy from the Identity.

PersistenceBrokerException

releaseDbResources

public void releaseDbResources()

Release all internally used Database resources of the iterator. Clients must call this methods explicitely if the iterator is not exhausted by the client application. If the Iterator is exhauseted this method will be called implicitely.