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java.lang.Object org.apache.commons.configuration.event.EventSource org.apache.commons.configuration.AbstractConfiguration org.apache.commons.configuration.HierarchicalConfiguration org.apache.commons.configuration.CombinedConfiguration
public class CombinedConfiguration
A hierarchical composite configuration class.
This class maintains a list of configuration objects, which can be added
using the divers addConfiguration()
methods. After that the
configurations can be accessed either by name (if one was provided when the
configuration was added) or by index. For the whole set of managed
configurations a logical node structure is constructed. For this purpose a
object can be set. This makes it possible to specify different algorithms for
the combination process.
NodeCombiner
The big advantage of this class is that it creates a truely hierarchical structure of all the properties stored in the contained configurations - even if some of them are no hierarchical configurations per se. So all enhanced features provided by a hierarchical configuration (e.g. choosing an expression engine) are applicable.
The class works by registering itself as an event listener add all added
configurations. So it gets notified whenever one of these configurations is
changed and can invalidate its internal node structure. The next time a
property is accessed the node structure will be re-constructed using the
current state of the managed configurations. Node that, depending on the used
NodeCombiner
, this may be a complex operation.
It is not strictly forbidden to manipulate a
CombinedConfiguration
directly, but the results may be
unpredictable. For instance some node combiners use special view nodes for
linking parts of the original configurations' data together. If new
properties are added to such a special node, they do not belong to any of the
managed configurations and thus hang in the air. It is also possible that
direct updates on a CombinedConfiguration
are incompatible
with the used node combiner (e.g. if the
is used and properties are removed the resulting node structure may be
incorrect because some properties that were hidden by the removed properties
are not visible). So it is recommended to perform updates only on the managed
configurations.
OverrideCombiner
Whenever the node structure of a CombinedConfiguration
becomes
invalid (either because one of the contained configurations was modified or
because the invalidate()
method was directly called) an event
is generated. So this can be detected by interested event listeners. This
also makes it possible to add a combined configuration into another one.
Implementation note: Adding and removing configurations to and from a combined configuration is not thread-safe. If a combined configuration is manipulated by multiple threads, the developer has to take care about properly synchronization.
Nested Class Summary | |
---|---|
(package private) static class |
CombinedConfiguration.ConfigData
An internal helper class for storing information about contained configurations. |
Nested classes/interfaces inherited from class org.apache.commons.configuration.HierarchicalConfiguration |
---|
HierarchicalConfiguration.BuilderVisitor, HierarchicalConfiguration.CloneVisitor, HierarchicalConfiguration.DefinedKeysVisitor, HierarchicalConfiguration.DefinedVisitor, HierarchicalConfiguration.Node, HierarchicalConfiguration.NodeVisitor |
Field Summary | |
---|---|
static int |
EVENT_COMBINED_INVALIDATE
Constant for the invalidate event that is fired when the internal node structure becomes invalid. |
Fields inherited from class org.apache.commons.configuration.HierarchicalConfiguration |
---|
EVENT_ADD_NODES, EVENT_CLEAR_TREE |
Fields inherited from class org.apache.commons.configuration.AbstractConfiguration |
---|
END_TOKEN, EVENT_ADD_PROPERTY, EVENT_CLEAR, EVENT_CLEAR_PROPERTY, EVENT_READ_PROPERTY, EVENT_SET_PROPERTY, START_TOKEN |
Constructor Summary | |
---|---|
CombinedConfiguration()
Creates a new instance of CombinedConfiguration that uses
a union combiner. |
|
CombinedConfiguration(NodeCombiner comb)
Creates a new instance of CombinedConfiguration and
initializes the combiner to be used. |
Method Summary | |
---|---|
void |
addConfiguration(AbstractConfiguration config)
Adds a new configuration to this combined configuration. |
void |
addConfiguration(AbstractConfiguration config,
String name)
Adds a new configuration to this combined configuration with an optional name. |
void |
addConfiguration(AbstractConfiguration config,
String name,
String at)
Adds a new configuration to this combined configuration. |
void |
clear()
Clears this configuration. |
Object |
clone()
Returns a copy of this object. |
void |
configurationChanged(ConfigurationEvent event)
Event listener call back for configuration update events. |
Configuration |
getConfiguration(int index)
Returns the configuration at the specified index. |
Configuration |
getConfiguration(String name)
Returns the configuration with the given name. |
Set |
getConfigurationNames()
Returns a set with the names of all configurations contained in this combined configuration. |
NodeCombiner |
getNodeCombiner()
Returns the node combiner that is used for creating the combined node structure. |
int |
getNumberOfConfigurations()
Returns the number of configurations that are contained in this combined configuration. |
Object |
getProperty(String key)
Returns the value of the specified property. |
ConfigurationNode |
getRootNode()
Returns the configuration root node of this combined configuration. |
void |
invalidate()
Invalidates this combined configuration. |
boolean |
isForceReloadCheck()
Returns a flag whether an enhanced reload check must be performed. |
boolean |
removeConfiguration(Configuration config)
Removes the specified configuration from this combined configuration. |
Configuration |
removeConfiguration(String name)
Removes the configuration with the specified name. |
Configuration |
removeConfigurationAt(int index)
Removes the configuration at the specified index. |
void |
setForceReloadCheck(boolean forceReloadCheck)
Sets the force reload check flag. |
void |
setNodeCombiner(NodeCombiner nodeCombiner)
Sets the node combiner. |
Methods inherited from class org.apache.commons.configuration.HierarchicalConfiguration |
---|
addNodes, addPropertyDirect, clearNode, clearNode, clearProperty, clearReferences, clearTree, configurationAt, configurationsAt, containsKey, createAddPath, createNode, createSubnodeConfiguration, fetchAddNode, fetchNodeList, findLastPathNode, findPropertyNodes, getDefaultExpressionEngine, getExpressionEngine, getKeys, getKeys, getMaxIndex, getRoot, isEmpty, nodeDefined, nodeDefined, removeNode, removeNode, setDefaultExpressionEngine, setExpressionEngine, setProperty, setRoot, setRootNode, subset |
Methods inherited from class org.apache.commons.configuration.event.EventSource |
---|
addConfigurationListener, addErrorListener, clearConfigurationListeners, clearErrorListeners, createErrorEvent, createEvent, fireError, fireEvent, getConfigurationListeners, getErrorListeners, isDetailEvents, removeConfigurationListener, removeErrorListener, setDetailEvents |
Methods inherited from class java.lang.Object |
---|
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
public static final int EVENT_COMBINED_INVALIDATE
Constructor Detail |
---|
public CombinedConfiguration(NodeCombiner comb)
CombinedConfiguration
and
initializes the combiner to be used.
comb
- the node combiner (can be null, then a union combiner
is used as default)public CombinedConfiguration()
CombinedConfiguration
that uses
a union combiner.
UnionCombiner
Method Detail |
---|
public NodeCombiner getNodeCombiner()
public void setNodeCombiner(NodeCombiner nodeCombiner)
IllegalArgumentException
exception is thrown. Changing the
node combiner causes an invalidation of this combined configuration, so
that the new combiner immediately takes effect.
nodeCombiner
- the node combinerpublic boolean isForceReloadCheck()
public void setForceReloadCheck(boolean forceReloadCheck)
forceReloadCheck
- the value of the flagpublic void addConfiguration(AbstractConfiguration config, String name, String at)
ConfigurationRuntimeException
will
be thrown. With the optional at
argument you can specify
where in the resulting node structure the content of the added
configuration should appear. This is a string that uses dots as property
delimiters (independent on the current expression engine). For instance
if you pass in the string "database.tables"
,
all properties of the added configuration will occur in this branch.
config
- the configuration to add (must not be null)name
- the name of this configuration (can be null)at
- the position of this configuration in the combined tree (can be
null)public void addConfiguration(AbstractConfiguration config, String name)
config
- the configuration to add (must not be null)name
- the name of this configuration (can be null)public void addConfiguration(AbstractConfiguration config)
config
- the configuration to add (must not be null)public int getNumberOfConfigurations()
public Configuration getConfiguration(int index)
index
- the index
public Configuration getConfiguration(String name)
name
- the name of the configuration
public boolean removeConfiguration(Configuration config)
config
- the configuration to be removed
public Configuration removeConfigurationAt(int index)
index
- the index
public Configuration removeConfiguration(String name)
name
- the name of the configuration to be removed
public Set getConfigurationNames()
public void invalidate()
EVENT_COMBINED_INVALIDATE
is fired. Note that while other
events most times appear twice (once before and once after an update),
this event is only fired once (after update).
public void configurationChanged(ConfigurationEvent event)
configurationChanged
in interface ConfigurationListener
event
- the update eventpublic ConfigurationNode getRootNode()
getRootNode
in class HierarchicalConfiguration
public void clear()
clear
in interface Configuration
clear
in class AbstractConfiguration
public Object clone()
clone
in class HierarchicalConfiguration
public Object getProperty(String key)
getProperty
in interface Configuration
getProperty
in class HierarchicalConfiguration
key
- the key of the desired property
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