T
- the type of the nodes managed by this hierarchical configurationpublic abstract class AbstractHierarchicalConfiguration<T> extends AbstractConfiguration implements Cloneable, NodeKeyResolver<T>, HierarchicalConfiguration<T>
A specialized configuration class that extends its base class by the ability of keeping more structure in the stored properties.
There are some sources of configuration data that cannot be stored very well
in a BaseConfiguration
object because then their structure is lost.
This is for instance true for XML documents. This class can deal with such
structured configuration sources by storing the properties in a tree-like
organization. The exact storage structure of the underlying data does not
matter for the configuration instance; it uses a NodeModel
object for
accessing it.
The hierarchical organization allows for a more sophisticated access to single properties. As an example consider the following XML document:
<database> <tables> <table> <name>users</name> <fields> <field> <name>lid</name> <type>long</name> </field> <field> <name>usrName</name> <type>java.lang.String</type> </field> ... </fields> </table> <table> <name>documents</name> <fields> <field> <name>docid</name> <type>long</type> </field> ... </fields> </table> ... </tables> </database>
If this document is parsed and stored in a hierarchical configuration object (which can be done by one of the sub classes), there are enhanced possibilities of accessing properties. Per default, the keys for querying information can contain indices that select a specific element if there are multiple hits.
For instance the key tables.table(0).name
can be used to find out the
name of the first table. In opposite tables.table.name
would return a
collection with the names of all available tables. Similarly the key
tables.table(1).fields.field.name
returns a collection with the names
of all fields of the second table. If another index is added after the
field
element, a single field can be accessed:
tables.table(1).fields.field(0).name
.
There is a getMaxIndex()
method that returns the maximum allowed
index that can be added to a given property key. This method can be used to
iterate over all values defined for a certain property.
Since the 1.3 release of Commons Configuration hierarchical
configurations support an expression engine. This expression engine
is responsible for evaluating the passed in configuration keys and map them
to the stored properties. The examples above are valid for the default
expression engine, which is used when a new
AbstractHierarchicalConfiguration
instance is created. With the
setExpressionEngine()
method a different expression engine can be
set. For instance with
XPathExpressionEngine
there is an expression engine available that supports configuration keys in
XPATH syntax.
In addition to the events common for all configuration classes, hierarchical
configurations support some more events that correspond to some specific
methods and features. For those events specific event type constants in
ConfigurationEvent
exist:
addNodes()
method was called; the event object contains the
key, to which the nodes were added, and a collection with the new nodes as
value.clearTree()
method was called; the event object stores the
key of the removed sub tree.SubnodeConfiguration
that was created from this configuration
has been changed. The value property of the event object contains the
original event object as it was sent by the subnode configuration.
Whether an AbstractHierarchicalConfiguration
object is thread-safe or
not depends on the underlying NodeModel
and the
Synchronizer
it is associated with. Some NodeModel
implementations are inherently
thread-safe; they do not require a special Synchronizer
. (Per
default, a dummy Synchronizer
is used which is not thread-safe!) The
methods for querying or updating configuration data invoke this
Synchronizer
accordingly. When accessing the configuration's root
node directly, the client application is responsible for proper
synchronization. This is achieved by calling the methods
lock()
,
and unlock()
with a proper
LockMode
argument.
In any case, it is recommended to not access the
root node directly, but to use corresponding methods for querying or updating
configuration data instead. Direct manipulations of a configuration's node
structure circumvent many internal mechanisms and thus can cause undesired
effects. For concrete subclasses dealing with specific node structures, this
situation may be different.
Modifier | Constructor and Description |
---|---|
protected |
AbstractHierarchicalConfiguration(NodeModel<T> nodeModel)
Creates a new instance of
AbstractHierarchicalConfiguration and
sets the NodeModel to be used. |
Modifier and Type | Method and Description |
---|---|
void |
addNodes(String key,
Collection<? extends T> nodes)
Adds a collection of nodes at the specified position of the configuration
tree.
|
protected void |
addNodesInternal(String key,
Collection<? extends T> nodes)
Actually adds a collection of new nodes to this configuration.
|
protected void |
addPropertyDirect(String key,
Object value)
Adds a key/value pair to the Configuration.
|
protected void |
addPropertyInternal(String key,
Object obj)
Adds the property with the specified key.
|
protected void |
clearInternal()
Clears this configuration.
|
protected void |
clearPropertyDirect(String key)
Removes the property with the given key.
|
void |
clearTree(String key)
Removes all values of the property with the given name and of keys that
start with this name.
|
protected Object |
clearTreeInternal(String key)
Actually clears the tree of elements referenced by the given key.
|
Object |
clone()
Creates a copy of this object.
|
protected abstract NodeModel<T> |
cloneNodeModel()
Creates a clone of the node model.
|
protected boolean |
containsKeyInternal(String key)
Checks if the specified key is contained in this configuration.
|
protected List<QueryResult<T>> |
fetchNodeList(String key)
Helper method for resolving the specified key.
|
ExpressionEngine |
getExpressionEngine()
Returns the expression engine used by this configuration.
|
protected Iterator<String> |
getKeysInternal()
Returns an iterator with all keys defined in this configuration.
|
protected Iterator<String> |
getKeysInternal(String prefix)
Returns an iterator with all keys defined in this configuration that
start with the given prefix.
|
int |
getMaxIndex(String key)
Returns the maximum defined index for the given key.
|
protected int |
getMaxIndexInternal(String key)
Actually retrieves the maximum defined index for the given key.
|
protected NodeModel<T> |
getModel()
Returns the
NodeModel used by this configuration. |
NodeModel<T> |
getNodeModel()
Returns the
NodeModel supported by this object. |
protected Object |
getPropertyInternal(String key)
Fetches the specified property.
|
String |
getRootElementName()
Returns the name of the root element of this configuration.
|
protected String |
getRootElementNameInternal()
Actually obtains the name of the root element.
|
protected boolean |
isEmptyInternal()
Checks if this configuration is empty.
|
protected boolean |
nodeDefined(T node)
Checks if the specified node is defined.
|
String |
nodeKey(T node,
Map<T,String> cache,
NodeHandler<T> handler)
Generates a unique key for the specified node.
|
NodeAddData<T> |
resolveAddKey(T root,
String key,
NodeHandler<T> handler)
Resolves a key of an add operation.
|
List<QueryResult<T>> |
resolveKey(T root,
String key,
NodeHandler<T> handler)
Performs a query for the specified key on the given root node.
|
List<T> |
resolveNodeKey(T root,
String key,
NodeHandler<T> handler)
Performs a query for the specified key on the given root node returning
only node results.
|
NodeUpdateData<T> |
resolveUpdateKey(T root,
String key,
Object newValue,
NodeHandler<T> handler)
Resolves a key for an update operation.
|
void |
setExpressionEngine(ExpressionEngine expressionEngine)
Sets the expression engine to be used by this configuration.
|
protected void |
setPropertyInternal(String key,
Object value)
Sets the value of the specified property.
|
protected int |
sizeInternal()
Actually calculates the size of this configuration.
|
String |
toString() |
addErrorLogListener, addProperty, append, beginRead, beginWrite, clear, clearProperty, cloneInterpolator, containsKey, copy, endRead, endWrite, get, get, getArray, getArray, getBigDecimal, getBigDecimal, getBigInteger, getBigInteger, getBoolean, getBoolean, getBoolean, getByte, getByte, getByte, getCollection, getCollection, getConfigurationDecoder, getConversionHandler, getDouble, getDouble, getDouble, getEncodedString, getEncodedString, getFloat, getFloat, getFloat, getInt, getInt, getInteger, getInterpolator, getKeys, getKeys, getList, getList, getList, getList, getListDelimiterHandler, getLogger, getLong, getLong, getLong, getProperties, getProperties, getProperty, getShort, getShort, getShort, getString, getString, getStringArray, getSynchronizer, immutableSubset, initLogger, installInterpolator, interpolate, interpolate, interpolatedConfiguration, isEmpty, isScalarValue, isThrowExceptionOnMissing, lock, setConfigurationDecoder, setConversionHandler, setDefaultLookups, setInterpolator, setListDelimiterHandler, setLogger, setParentInterpolator, setPrefixLookups, setProperty, setSynchronizer, setThrowExceptionOnMissing, size, subset, unlock
addEventListener, clearErrorListeners, clearEventListeners, copyEventListeners, createErrorEvent, createEvent, fireError, fireEvent, getEventListenerRegistrations, getEventListeners, isDetailEvents, removeEventListener, setDetailEvents
equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
childConfigurationsAt, childConfigurationsAt, configurationAt, configurationAt, configurationsAt, configurationsAt
addProperty, clear, clearProperty, getInterpolator, installInterpolator, setInterpolator, setProperty, subset
getSynchronizer, lock, setSynchronizer, unlock
immutableChildConfigurationsAt, immutableConfigurationAt, immutableConfigurationAt, immutableConfigurationsAt
containsKey, get, get, getArray, getArray, getBigDecimal, getBigDecimal, getBigInteger, getBigInteger, getBoolean, getBoolean, getBoolean, getByte, getByte, getByte, getCollection, getCollection, getDouble, getDouble, getDouble, getEncodedString, getEncodedString, getFloat, getFloat, getFloat, getInt, getInt, getInteger, getKeys, getKeys, getList, getList, getList, getList, getLong, getLong, getLong, getProperties, getProperty, getShort, getShort, getShort, getString, getString, getStringArray, immutableSubset, isEmpty, size
public final String getRootElementName()
immutableConfigurationsAt()
method. The exact
meaning of the string returned by this method is specific to a concrete
implementation. For instance, an XML configuration might return the name
of the document element. This implementation handles synchronization and delegates
to getRootElementNameInternal()
.getRootElementName
in interface ImmutableHierarchicalConfiguration
protected String getRootElementNameInternal()
getRootElementName()
. It just returns the name of the root node.
Subclasses that treat the root element name differently can override this
method.public NodeModel<T> getNodeModel()
NodeModel
supported by this object. This implementation returns the configuration's
NodeModel
. It is guarded by the current Synchronizer
.getNodeModel
in interface NodeModelSupport<T>
NodeModel
public ExpressionEngine getExpressionEngine()
getExpressionEngine
in interface ImmutableHierarchicalConfiguration
public void setExpressionEngine(ExpressionEngine expressionEngine)
setExpressionEngine
in interface HierarchicalConfiguration<T>
expressionEngine
- the new expression engine; can be null,
then the default expression engine will be usedprotected Object getPropertyInternal(String key)
getPropertyInternal
in class AbstractConfiguration
key
- the key to be looked upprotected void addPropertyInternal(String key, Object obj)
ExpressionEngine
, so the passed in key
must match the requirements of this implementation.addPropertyInternal
in class AbstractConfiguration
key
- the key of the new propertyobj
- the value of the new propertyprotected void addPropertyDirect(String key, Object value)
addProperty()
for hierarchical configurations because all values
to be added for the property have to be passed to the model in a single
step. However, to allow derived classes to add an arbitrary value as an
object, a special implementation is provided here. The passed in object
is not parsed as a list, but passed directly as only value to the model.addPropertyDirect
in class AbstractConfiguration
key
- key to use for mappingvalue
- object to storepublic final void addNodes(String key, Collection<? extends T> nodes)
addProperty()
, but
instead of a single property a whole collection of nodes can be added -
and thus complete configuration sub trees. E.g. with this method it is
possible to add parts of another BaseHierarchicalConfiguration
object to this object. If the passed in key refers to
an existing and unique node, the new nodes are added to this node.
Otherwise a new node will be created at the specified position in the
hierarchy. Implementation node: This method performs some book-keeping
and then delegates to addNodesInternal()
.addNodes
in interface HierarchicalConfiguration<T>
key
- the key where the nodes are to be added; can be null,
then they are added to the root nodenodes
- a collection with the Node
objects to be
addedprotected void addNodesInternal(String key, Collection<? extends T> nodes)
addNodes()
. It can be overridden by
subclasses that need to adapt this operation.key
- the key where the nodes are to be added; can be null,
then they are added to the root nodenodes
- a collection with the Node
objects to be addedprotected boolean isEmptyInternal()
isEmptyInternal
in class AbstractConfiguration
protected boolean containsKeyInternal(String key)
containsKeyInternal
in class AbstractConfiguration
key
- the key to be checkedprotected void setPropertyInternal(String key, Object value)
setPropertyInternal
in class AbstractConfiguration
key
- the key of the property to setvalue
- the new value of this propertypublic List<QueryResult<T>> resolveKey(T root, String key, NodeHandler<T> handler)
query()
method of an
ExpressionEngine
. This implementation delegates to the expression engine.resolveKey
in interface NodeKeyResolver<T>
root
- the root nodekey
- the key to be resolvedhandler
- the NodeHandler
public List<T> resolveNodeKey(T root, String key, NodeHandler<T> handler)
resolveKey()
, but filters only
for results of type node. This implementation delegates to resolveKey()
and
then filters out attribute results.resolveNodeKey
in interface NodeKeyResolver<T>
root
- the root nodekey
- the key to be resolvedhandler
- the NodeHandler
public NodeAddData<T> resolveAddKey(T root, String key, NodeHandler<T> handler)
NodeAddData
object containing all information for actually performing the add
operation at the specified key. This implementation delegates to the expression engine.resolveAddKey
in interface NodeKeyResolver<T>
root
- the root nodekey
- the key to be resolvedhandler
- the NodeHandler
NodeAddData
object to be used for the add operationpublic NodeUpdateData<T> resolveUpdateKey(T root, String key, Object newValue, NodeHandler<T> handler)
NodeUpdateData
object containing all information for actually
performing the update operation at the specified key using the provided
new value object. This implementation executes a query for the given key and
constructs a NodeUpdateData
object based on the results. It
determines which nodes need to be changed and whether new ones need to be
added or existing ones need to be removed.resolveUpdateKey
in interface NodeKeyResolver<T>
root
- the root nodekey
- the key to be resolvednewValue
- the new value for the key to be updated; this can be a
single value or a container for multiple valueshandler
- the NodeHandler
NodeUpdateData
object to be used for this update
operationpublic String nodeKey(T node, Map<T,String> cache, NodeHandler<T> handler)
nodeKey
in interface NodeKeyResolver<T>
node
- the node in questioncache
- a map serving as cachehandler
- the NodeHandler
protected void clearInternal()
clearInternal
in class AbstractConfiguration
public final void clearTree(String key)
clearTree("foo")
would remove both properties.clearTree
in interface HierarchicalConfiguration<T>
key
- the key of the property to be removedprotected Object clearTreeInternal(String key)
clearTree()
. Subclasses that need to adapt
this operation can override this method. This base implementation
delegates to the node model.key
- the key of the property to be removedprotected void clearPropertyDirect(String key)
clearPropertyDirect
in class AbstractConfiguration
key
- the key of the property to be removedprotected int sizeInternal()
size()
with a read lock held. The base implementation provided
here calculates the size based on the iterator returned by
getKeys()
. Sub classes which can determine the size in a more
efficient way should override this method. This implementation is slightly more efficient than the
default implementation. It does not iterate over the key set, but
directly queries its size after it has been constructed. Note that
constructing the key set is still an O(n) operation.sizeInternal
in class AbstractConfiguration
protected Iterator<String> getKeysInternal()
getKeysInternal
in class AbstractConfiguration
protected Iterator<String> getKeysInternal(String prefix)
getKeysInternal
in class AbstractConfiguration
prefix
- the prefix of the keys to start withpublic final int getMaxIndex(String key)
getMaxIndex
in interface ImmutableHierarchicalConfiguration
key
- the key to be checkedprotected int getMaxIndexInternal(String key)
getMaxIndex()
. Subclasses that need to adapt
this operation have to override this method.key
- the key to be checkedpublic Object clone()
clone
in class BaseEventSource
protected abstract NodeModel<T> cloneNodeModel()
clone()
.NodeModel
protected List<QueryResult<T>> fetchNodeList(String key)
key
- the keyprotected boolean nodeDefined(T node)
node
- the node to be checkedprotected NodeModel<T> getModel()
NodeModel
used by this configuration. This method is
intended for internal use only. Access to the model is granted without
any synchronization. This is in contrast to the "official"
getNodeModel()
method which is guarded by the configuration's
Synchronizer
.Copyright © 2001–2020 The Apache Software Foundation. All rights reserved.