org.mmbase.module.core
Class ClusterNode

java.lang.Object
  |
  +--org.mmbase.module.core.MMObjectNode
        |
        +--org.mmbase.module.core.VirtualNode
              |
              +--org.mmbase.module.core.ClusterNode

All Implemented Interfaces:

SizeMeasurable

public class ClusterNode

extends VirtualNode

ClusterNode is a representation of a 'cluster' of objectnodes. It represents a set of related nodes, retrieved using a multilevel query. This class overrides a number of methods, allowing direct access to data in the nodes which form the 'virtual' node.
In future releases, data will NOT be stored directkly in this node anymore. Instead, it will be stored in the underlying MMObjectNodes. For reasons of optiomalization, however, we cannot do this right now. MMObjectNode will need a status field that allows us to recognize whether it is fully loaded, partially loaded, or being edited. This can then be checked in 'retrievevalue'. In addition, to prevent caching conflicts, nodes will need to maintain their references. This allows for a secure caching mechanism.
Among other things, this allows one to change values in a multilevel node, or to access functionality that would otherwise be restricted to 'real' nodes.

Version:

26 Apr 2001

Author:

Pierre van Rooden

Field Summary

boolean	initializing Determines whether the node is being loaded.
protected java.util.Hashtable	nodes Holds the name - value pairs of related nodes in this virtual node.

Fields inherited from class org.mmbase.module.core.MMObjectNode

alias, changed, parent, prefix, properties, values, virtual

Constructor Summary

ClusterNode(MMObjectBuilder parent)
Main contructor.

ClusterNode(MMObjectBuilder parent, int nrofnodes)
Main contructor.

Method Summary

boolean	commit() commit : commits the node to the database or other storage system this can only be done on a existing (inserted) node.
protected java.lang.String	getBuilderName(java.lang.String fieldname) Determines the builder name of a specified fieldname, i.e.
byte[]	getByteValue(java.lang.String fieldname) Get a binary value of a certain field.
MMObjectNode	getRealNode(java.lang.String buildername) Obtain the 'real' nodes, associated with a specified objectbuilder.
java.util.Enumeration	getRelations() Return the relations of this node.
java.lang.String	getStringValue(java.lang.String fieldname) Get a value of a certain field.
java.lang.Object	getValue(java.lang.String fieldname) Get a value of a certain field.
boolean	isChanged() Tests whether one of the values of this node was changed since the last commit/insert.
boolean	setValue(java.lang.String fieldname, java.lang.Object fieldvalue) Sets a key/value pair in the main values of this node.
protected void	storeValue(java.lang.String fieldname, java.lang.Object fieldvalue) Stores a value in the values hashtable.
void	testValidData() Tests whether the data in a node is valid (throws an exception if this is not the case).

Methods inherited from class org.mmbase.module.core.VirtualNode

getAge, getRelationCount, getRelationCount, hasRelations, insert

Methods inherited from class org.mmbase.module.core.MMObjectNode

clearChanged, defaultEquals, delPropertiesCache, delRelationsCache, equals, getAlias, getAllRelations, getBooleanValue, getBuilder, getByteSize, getByteSize, getChanged, getDBState, getDBType, getDoubleValue, getFloatValue, getFunctionValue, getGUIIndicator, getIntegerValue, getIntValue, getLongValue, getName, getNodeValue, getNumber, getOType, getProperties, getProperty, getRelatedNodes, getRelatedNodes, getRelatedNodes, getRelatedNodes, getRelationCacheHits, getRelationCacheMiss, getRelations, getRelations, getTableName, getValues, getXMLValue, hashCode, insertDone, isVirtual, preEdit, putProperty, removeRelations, retrieveValue, sendFieldChangeSignal, setAlias, setValue, setValue, setValue, setValue, setValue, toString, toXML, toXML

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

nodes

protected java.util.Hashtable nodes

Holds the name - value pairs of related nodes in this virtual node.

initializing

public boolean initializing

Determines whether the node is being loaded.

Constructor Detail

ClusterNode

public ClusterNode(MMObjectBuilder parent)

Main contructor.

Parameters:

parent - the node's parent, generally an instance of the ClusterBuilder builder.

ClusterNode

public ClusterNode(MMObjectBuilder parent,
                   int nrofnodes)

Main contructor.

Parameters:

parent - the node's parent, generally an instance of the ClusterBuilder builder.

rnofnodes - Nr of referenced nodes.

Method Detail

testValidData

public void testValidData()
                   throws InvalidDataException

Tests whether the data in a node is valid (throws an exception if this is not the case). The call is performed on all loaded 'real' nodes. If a 'real' node has not previously been forcably loaded, it is assumed to be correct.

Overrides:

testValidData in class MMObjectNode

Throws:

InvalidDataException - If the data was unrecoverably invalid (the references did not point to existing objects)

commit

public boolean commit()

commit : commits the node to the database or other storage system this can only be done on a existing (inserted) node. it will use the changed Vector as its base of what to commit/changed

Overrides:

commit in class VirtualNode

Returns:

true if the commit was succesfull, false is it failed

getRealNode

public MMObjectNode getRealNode(java.lang.String buildername)

Obtain the 'real' nodes, associated with a specified objectbuilder.

Parameters:

buildername - the name of the builder of the requested node, as known within the virtual node

Returns:

the node, or null if it does not exist or is unknown

storeValue

protected void storeValue(java.lang.String fieldname,
                          java.lang.Object fieldvalue)

Stores a value in the values hashtable. If the value is not stored in the virtualnode, the 'real' node is used instead.

Overrides:

storeValue in class MMObjectNode

Parameters:

fieldname - the name of the field to change

fieldValue - the value to assign

setValue

public boolean setValue(java.lang.String fieldname,
                        java.lang.Object fieldvalue)

Sets a key/value pair in the main values of this node. Note that if this node is a node in cache, the changes are immediately visible to everyone, even if the changes are not committed. The fieldname is added to the (public) 'changed' vector to track changes.

Overrides:

setValue in class MMObjectNode

Parameters:

fieldname - the name of the field to change

fieldValue - the value to assign

Returns:

always true

getBuilderName

protected java.lang.String getBuilderName(java.lang.String fieldname)

Determines the builder name of a specified fieldname, i.e. "news" in "news.title",

Parameters:

fieldname - the name of the field

Returns:

the buidler name of the field

getValue

public java.lang.Object getValue(java.lang.String fieldname)

Get a value of a certain field.

Overrides:

getValue in class MMObjectNode

Parameters:

fieldname - the name of the field who's data to return

Returns:

the field's value as an Object

getStringValue

public java.lang.String getStringValue(java.lang.String fieldname)

Get a value of a certain field. The value is returned as a String. Non-string values are automatically converted to String.

Overrides:

getStringValue in class MMObjectNode

Parameters:

fieldname - the name of the field who's data to return

Returns:

the field's value as a String

getByteValue

public byte[] getByteValue(java.lang.String fieldname)

Get a binary value of a certain field.

Overrides:

getByteValue in class MMObjectNode

Parameters:

fieldname - the name of the field who's data to return

Returns:

the field's value as an byte [] (binary/blob field)

isChanged

public boolean isChanged()

Tests whether one of the values of this node was changed since the last commit/insert.

Overrides:

isChanged in class MMObjectNode

Returns:

true if changes have been made, false otherwise

getRelations

public java.util.Enumeration getRelations()

Return the relations of this node. This is not allowed on a cluster node

Overrides:

getRelations in class VirtualNode

Throws:

RuntimeException -