/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.configuration;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.Stack;
import org.apache.commons.collections.set.ListOrderedSet;
import org.apache.commons.collections.iterators.SingletonIterator;
import org.apache.commons.configuration.tree.ConfigurationNode;
import org.apache.commons.configuration.tree.ConfigurationNodeVisitorAdapter;
import org.apache.commons.configuration.tree.DefaultConfigurationNode;
import org.apache.commons.configuration.tree.DefaultExpressionEngine;
import org.apache.commons.configuration.tree.ExpressionEngine;
import org.apache.commons.configuration.tree.NodeAddData;
import org.apache.commons.lang.StringUtils;
/**
* <p>A specialized configuration class that extends its base class by the
* ability of keeping more structure in the stored properties.</p><p>There
* are some sources of configuration data that cannot be stored very well in a
* <code>BaseConfiguration</code> object because then their structure is lost.
* This is especially true for XML documents. This class can deal with such
* structured configuration sources by storing the properties in a tree-like
* organization.</p><p>The internal used storage form allows for a more
* sophisticated access to single properties. As an example consider the
* following XML document:</p><p>
*
* <pre>
* <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>
* </pre>
*
* </p><p>If this document is parsed and stored in a
* <code>HierarchicalConfiguration</code> object (which can be done by one of
* the sub classes), there are enhanced possibilities of accessing properties.
* The keys for querying information can contain indices that select a certain
* element if there are multiple hits.</p><p>For instance the key
* <code>tables.table(0).name</code> can be used to find out the name of the
* first table. In opposite <code>tables.table.name</code> would return a
* collection with the names of all available tables. Similarily the key
* <code>tables.table(1).fields.field.name</code> returns a collection with
* the names of all fields of the second table. If another index is added after
* the <code>field</code> element, a single field can be accessed:
* <code>tables.table(1).fields.field(0).name</code>.</p><p>There is a
* <code>getMaxIndex()</code> 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.</p>
*
* @author <a href="mailto:oliver.heger@t-online.de">Oliver Heger </a>
* @version $Id: HierarchicalConfiguration.java,v 1.14 2004/12/02 22:05:52
* ebourg Exp $
*/
public class HierarchicalConfiguration extends AbstractConfiguration implements Serializable, Cloneable
{
/** Constant for the clear tree event.*/
public static final int EVENT_CLEAR_TREE = 10;
/** Constant for the add nodes event.*/
public static final int EVENT_ADD_NODES = 11;
/**
* The serial version UID.
*/
private static final long serialVersionUID = 3373812230395363192L;
/** Stores the default expression engine to be used for new objects.*/
private static ExpressionEngine defaultExpressionEngine = new DefaultExpressionEngine();
/** Stores the root node of this configuration. This field is required for
* backwards compatibility only.
*/
private Node root;
/** Stores the root configuration node.*/
private ConfigurationNode rootNode;
/** Stores the expression engine for this instance.*/
private ExpressionEngine expressionEngine;
/**
* Creates a new instance of <code>HierarchicalConfiguration</code>.
*/
public HierarchicalConfiguration()
{
setRootNode(new Node());
}
/**
* Creates a new instance of <code>HierarchicalConfiguration</code> and
* copies all data contained in the specified configuration into the new
* one.
*
* @param c the configuration that is to be copied (if <b>null</b>, this
* constructor will behave like the standard constructor)
* @since 1.4
*/
public HierarchicalConfiguration(HierarchicalConfiguration c)
{
this();
if (c != null)
{
CloneVisitor visitor = new CloneVisitor();
c.getRootNode().visit(visitor);
setRootNode(visitor.getClone());
}
}
/**
* Returns the root node of this hierarchical configuration. This method
* exists for backwards compatibility only. New code should use the
* <code>{@link #getRootNode()}</code> method instead, which operates on
* the preferred data type <code>ConfigurationNode</code>.
*
* @return the root node
*/
public Node getRoot()
{
return root;
}
/**
* Sets the root node of this hierarchical configuration. This method
* exists for backwards compatibility only. New code should use the
* <code>{@link #setRootNode(ConfigurationNode)}</code> method instead,
* which operates on the preferred data type <code>ConfigurationNode</code>.
*
* @param node the root node
*/
public void setRoot(Node node)
{
if (node == null)
{
throw new IllegalArgumentException("Root node must not be null!");
}
root = node;
rootNode = null;
}
/**
* Returns the root node of this hierarchical configuration.
*
* @return the root node
* @since 1.3
*/
public ConfigurationNode getRootNode()
{
return (rootNode != null) ? rootNode : root;
}
/**
* Sets the root node of this hierarchical configuration.
*
* @param rootNode the root node
* @since 1.3
*/
public void setRootNode(ConfigurationNode rootNode)
{
if (rootNode == null)
{
throw new IllegalArgumentException("Root node must not be null!");
}
this.rootNode = rootNode;
// For backward compatibility also set the old root field.
root = (rootNode instanceof Node) ? (Node) rootNode : new Node(rootNode);
}
/**
* Returns the default expression engine.
*
* @return the default expression engine
* @since 1.3
*/
public static ExpressionEngine getDefaultExpressionEngine()
{
return defaultExpressionEngine;
}
/**
* Sets the default expression engine. This expression engine will be used
* if no specific engine was set for an instance. It is shared between all
* hierarchical configuration instances. So modifying its properties will
* impact all instances, for which no specific engine is set.
*
* @param engine the new default expression engine
* @since 1.3
*/
public static void setDefaultExpressionEngine(ExpressionEngine engine)
{
if (engine == null)
{
throw new IllegalArgumentException(
"Default expression engine must not be null!");
}
defaultExpressionEngine = engine;
}
/**
* Returns the expression engine used by this configuration. This method
* will never return <b>null</b>; if no specific expression engine was set,
* the default expression engine will be returned.
*
* @return the current expression engine
* @since 1.3
*/
public ExpressionEngine getExpressionEngine()
{
return (expressionEngine != null) ? expressionEngine
: getDefaultExpressionEngine();
}
/**
* Sets the expression engine to be used by this configuration. All property
* keys this configuration has to deal with will be interpreted by this
* engine.
*
* @param expressionEngine the new expression engine; can be <b>null</b>,
* then the default expression engine will be used
* @since 1.3
*/
public void setExpressionEngine(ExpressionEngine expressionEngine)
{
this.expressionEngine = expressionEngine;
}
/**
* Fetches the specified property. This task is delegated to the associated
* expression engine.
*
* @param key the key to be looked up
* @return the found value
*/
public Object getProperty(String key)
{
List nodes = fetchNodeList(key);
if (nodes.size() == 0)
{
return null;
}
else
{
List list = new ArrayList();
for (Iterator it = nodes.iterator(); it.hasNext();)
{
ConfigurationNode node = (ConfigurationNode) it.next();
if (node.getValue() != null)
{
list.add(node.getValue());
}
}
if (list.size() < 1)
{
return null;
}
else
{
return (list.size() == 1) ? list.get(0) : list;
}
}
}
/**
* Adds the property with the specified key. This task will be delegated to
* the associated <code>ExpressionEngine</code>, so the passed in key
* must match the requirements of this implementation.
*
* @param key the key of the new property
* @param obj the value of the new property
*/
protected void addPropertyDirect(String key, Object obj)
{
NodeAddData data = getExpressionEngine().prepareAdd(getRootNode(), key);
ConfigurationNode node = processNodeAddData(data);
node.setValue(obj);
}
/**
* Adds a collection of nodes at the specified position of the configuration
* tree. This method works similar to <code>addProperty()</code>, 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 <code>HierarchicalConfiguration</code>
* 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.
*
* @param key the key where the nodes are to be added; can be <b>null </b>,
* then they are added to the root node
* @param nodes a collection with the <code>Node</code> objects to be
* added
*/
public void addNodes(String key, Collection nodes)
{
if (nodes == null || nodes.isEmpty())
{
return;
}
fireEvent(EVENT_ADD_NODES, key, nodes, true);
ConfigurationNode parent;
List target = fetchNodeList(key);
if (target.size() == 1)
{
// existing unique key
parent = (ConfigurationNode) target.get(0);
}
else
{
// otherwise perform an add operation
parent = processNodeAddData(getExpressionEngine().prepareAdd(
getRootNode(), key));
}
if (parent.isAttribute())
{
throw new IllegalArgumentException(
"Cannot add nodes to an attribute node!");
}
for (Iterator it = nodes.iterator(); it.hasNext();)
{
ConfigurationNode child = (ConfigurationNode) it.next();
if (child.isAttribute())
{
parent.addAttribute(child);
}
else
{
parent.addChild(child);
}
}
fireEvent(EVENT_ADD_NODES, key, nodes, false);
}
/**
* Checks if this configuration is empty. Empty means that there are no keys
* with any values, though there can be some (empty) nodes.
*
* @return a flag if this configuration is empty
*/
public boolean isEmpty()
{
return !nodeDefined(getRootNode());
}
/**
* Creates a new <code>Configuration</code> object containing all keys
* that start with the specified prefix. This implementation will return a
* <code>HierarchicalConfiguration</code> object so that the structure of
* the keys will be saved.
*
* @param prefix the prefix of the keys for the subset
* @return a new configuration object representing the selected subset
*/
public Configuration subset(String prefix)
{
Collection nodes = fetchNodeList(prefix);
if (nodes.isEmpty())
{
return new HierarchicalConfiguration();
}
final HierarchicalConfiguration parent = this;
HierarchicalConfiguration result = new HierarchicalConfiguration()
{
// Override interpolate to always interpolate on the parent
protected Object interpolate(Object value)
{
return parent.interpolate(value);
}
};
CloneVisitor visitor = new CloneVisitor();
for (Iterator it = nodes.iterator(); it.hasNext();)
{
ConfigurationNode nd = (ConfigurationNode) it.next();
nd.visit(visitor);
for (Iterator it2 = visitor.getClone().getChildren().iterator(); it2.hasNext();)
{
result.getRootNode().addChild((ConfigurationNode) it2.next());
}
for (Iterator it2 = visitor.getClone().getAttributes().iterator(); it2.hasNext();)
{
result.getRootNode().addAttribute((ConfigurationNode) it2.next());
}
}
return (result.isEmpty()) ? new HierarchicalConfiguration() : result;
}
/**
* <p>
* Returns a hierarchical subnode configuration object that wraps the
* configuration node specified by the given key. This method provides an
* easy means of accessing sub trees of a hierarchical configuration. In the
* returned configuration the sub tree can directly be accessed, it becomes
* the root node of this configuration. Because of this the passed in key
* must select exactly one configuration node; otherwise an
* <code>IllegalArgumentException</code> will be thrown.
* </p>
* <p>
* The difference between this method and the
* <code>{@link #subset(String)}</code> method is that
* <code>subset()</code> supports arbitrary subsets of configuration nodes
* while <code>configurationAt()</code> only returns a single sub tree.
* Please refer to the documentation of the
* <code>SubnodeConfiguration</code> class to obtain further information
* about subnode configurations and when they should be used.
* </p>
*
* @param key the key that selects the sub tree
* @return a hierarchical configuration that contains this sub tree
* @see SubnodeConfiguration
* @since 1.3
*/
public SubnodeConfiguration configurationAt(String key)
{
List nodes = fetchNodeList(key);
if (nodes.size() != 1)
{
throw new IllegalArgumentException(
"Passed in key must select exactly one node: " + key);
}
return createSubnodeConfiguration((ConfigurationNode) nodes.get(0));
}
/**
* Returns a list of sub configurations for all configuration nodes selected
* by the given key. This method will evaluate the passed in key (using the
* current <code>ExpressionEngine</code>) and then create a subnode
* configuration for each returned node (like
* <code>{@link #configurationAt(String)}</code>}). This is especially
* useful when dealing with list-like structures. As an example consider the
* configuration that contains data about database tables and their fields.
* If you need access to all fields of a certain table, you can simply do
*
* <pre>
* List fields = config.configurationsAt("tables.table(0).fields.field");
* for(Iterator it = fields.iterator(); it.hasNext();)
* {
* HierarchicalConfiguration sub = (HierarchicalConfiguration) it.next();
* // now the children and attributes of the field node can be
* // directly accessed
* String fieldName = sub.getString("name");
* String fieldType = sub.getString("type");
* ...
* </pre>
*
* @param key the key for selecting the desired nodes
* @return a list with hierarchical configuration objects; each
* configuration represents one of the nodes selected by the passed in key
* @since 1.3
*/
public List configurationsAt(String key)
{
List nodes = fetchNodeList(key);
List configs = new ArrayList(nodes.size());
for (Iterator it = nodes.iterator(); it.hasNext();)
{
configs.add(createSubnodeConfiguration((ConfigurationNode) it.next()));
}
return configs;
}
/**
* Creates a subnode configuration for the specified node. This method is
* called by <code>configurationAt()</code> and
* <code>configurationsAt()</code>.
*
* @param node the node, for which a subnode configuration is to be created
* @return the configuration for the given node
* @since 1.3
*/
protected SubnodeConfiguration createSubnodeConfiguration(ConfigurationNode node)
{
return new SubnodeConfiguration(this, node);
}
/**
* Checks if the specified key is contained in this configuration. Note that
* for this configuration the term "contained" means that the key
* has an associated value. If there is a node for this key that has no
* value but children (either defined or undefined), this method will still
* return <b>false </b>.
*
* @param key the key to be chekced
* @return a flag if this key is contained in this configuration
*/
public boolean containsKey(String key)
{
return getProperty(key) != null;
}
/**
* Sets the value of the specified property.
*
* @param key the key of the property to set
* @param value the new value of this property
*/
public void setProperty(String key, Object value)
{
fireEvent(EVENT_SET_PROPERTY, key, value, true);
Iterator itNodes = fetchNodeList(key).iterator();
Iterator itValues;
if (!isDelimiterParsingDisabled())
{
itValues = PropertyConverter.toIterator(value, getListDelimiter());
}
else
{
itValues = new SingletonIterator(value);
}
while (itNodes.hasNext() && itValues.hasNext())
{
((ConfigurationNode) itNodes.next()).setValue(itValues.next());
}
// Add additional nodes if necessary
while (itValues.hasNext())
{
addPropertyDirect(key, itValues.next());
}
// Remove remaining nodes
while (itNodes.hasNext())
{
clearNode((ConfigurationNode) itNodes.next());
}
fireEvent(EVENT_SET_PROPERTY, key, value, false);
}
/**
* Removes all values of the property with the given name and of keys that
* start with this name. So if there is a property with the key
* "foo" and a property with the key "foo.bar", a call
* of <code>clearTree("foo")</code> would remove both properties.
*
* @param key the key of the property to be removed
*/
public void clearTree(String key)
{
fireEvent(EVENT_CLEAR_TREE, key, null, true);
List nodes = fetchNodeList(key);
for (Iterator it = nodes.iterator(); it.hasNext();)
{
removeNode((ConfigurationNode) it.next());
}
fireEvent(EVENT_CLEAR_TREE, key, nodes, false);
}
/**
* Removes the property with the given key. Properties with names that start
* with the given key (i.e. properties below the specified key in the
* hierarchy) won't be affected.
*
* @param key the key of the property to be removed
*/
public void clearProperty(String key)
{
fireEvent(EVENT_CLEAR_PROPERTY, key, null, true);
List nodes = fetchNodeList(key);
for (Iterator it = nodes.iterator(); it.hasNext();)
{
clearNode((ConfigurationNode) it.next());
}
fireEvent(EVENT_CLEAR_PROPERTY, key, null, false);
}
/**
* Returns an iterator with all keys defined in this configuration.
* Note that the keys returned by this method will not contain any
* indices. This means that some structure will be lost.</p>
*
* @return an iterator with the defined keys in this configuration
*/
public Iterator getKeys()
{
DefinedKeysVisitor visitor = new DefinedKeysVisitor();
getRootNode().visit(visitor);
return visitor.getKeyList().iterator();
}
/**
* Returns an iterator with all keys defined in this configuration that
* start with the given prefix. The returned keys will not contain any
* indices.
*
* @param prefix the prefix of the keys to start with
* @return an iterator with the found keys
*/
public Iterator getKeys(String prefix)
{
DefinedKeysVisitor visitor = new DefinedKeysVisitor(prefix);
List nodes = fetchNodeList(prefix);
for (Iterator itNodes = nodes.iterator(); itNodes.hasNext();)
{
ConfigurationNode node = (ConfigurationNode) itNodes.next();
for (Iterator it = node.getChildren().iterator(); it.hasNext();)
{
((ConfigurationNode) it.next()).visit(visitor);
}
for (Iterator it = node.getAttributes().iterator(); it.hasNext();)
{
((ConfigurationNode) it.next()).visit(visitor);
}
}
return visitor.getKeyList().iterator();
}
/**
* Returns the maximum defined index for the given key. This is useful if
* there are multiple values for this key. They can then be addressed
* separately by specifying indices from 0 to the return value of this
* method.
*
* @param key the key to be checked
* @return the maximum defined index for this key
*/
public int getMaxIndex(String key)
{
return fetchNodeList(key).size() - 1;
}
/**
* Creates a copy of this object. This new configuration object will contain
* copies of all nodes in the same structure. Registered event listeners
* won't be cloned; so they are not registered at the returned copy.
*
* @return the copy
* @since 1.2
*/
public Object clone()
{
try
{
HierarchicalConfiguration copy = (HierarchicalConfiguration) super
.clone();
// clone the nodes, too
CloneVisitor v = new CloneVisitor();
getRootNode().visit(v);
copy.setRootNode(v.getClone());
return copy;
}
catch (CloneNotSupportedException cex)
{
// should not happen
throw new ConfigurationRuntimeException(cex);
}
}
/**
* Helper method for fetching a list of all nodes that are addressed by the
* specified key.
*
* @param key the key
* @return a list with all affected nodes (never <b>null </b>)
*/
protected List fetchNodeList(String key)
{
return getExpressionEngine().query(getRootNode(), key);
}
/**
* Recursive helper method for fetching a property. This method processes
* all facets of a configuration key, traverses the tree of properties and
* fetches the the nodes of all matching properties.
*
* @param keyPart the configuration key iterator
* @param node the actual node
* @param nodes here the found nodes are stored
* @deprecated Property keys are now evaluated by the expression engine
* associated with the configuration; this method will no longer be called.
* If you want to modify the way properties are looked up, consider
* implementing you own <code>ExpressionEngine</code> implementation.
*/
protected void findPropertyNodes(ConfigurationKey.KeyIterator keyPart,
Node node, Collection nodes)
{
}
/**
* Checks if the specified node is defined.
*
* @param node the node to be checked
* @return a flag if this node is defined
* @deprecated Use the method <code>{@link #nodeDefined(ConfigurationNode)}</code>
* instead.
*/
protected boolean nodeDefined(Node node)
{
return nodeDefined((ConfigurationNode) node);
}
/**
* Checks if the specified node is defined.
*
* @param node the node to be checked
* @return a flag if this node is defined
*/
protected boolean nodeDefined(ConfigurationNode node)
{
DefinedVisitor visitor = new DefinedVisitor();
node.visit(visitor);
return visitor.isDefined();
}
/**
* Removes the specified node from this configuration. This method ensures
* that parent nodes that become undefined by this operation are also
* removed.
*
* @param node the node to be removed
* @deprecated Use the method <code>{@link #removeNode(ConfigurationNode)}</code>
* instead.
*/
protected void removeNode(Node node)
{
removeNode((ConfigurationNode) node);
}
/**
* Removes the specified node from this configuration. This method ensures
* that parent nodes that become undefined by this operation are also
* removed.
*
* @param node the node to be removed
*/
protected void removeNode(ConfigurationNode node)
{
ConfigurationNode parent = node.getParentNode();
if (parent != null)
{
parent.removeChild(node);
if (!nodeDefined(parent))
{
removeNode(parent);
}
}
}
/**
* Clears the value of the specified node. If the node becomes undefined by
* this operation, it is removed from the hierarchy.
*
* @param node the node to be cleard
* @deprecated Use the method <code>{@link #clearNode(ConfigurationNode)}</code>
* instead
*/
protected void clearNode(Node node)
{
clearNode((ConfigurationNode) node);
}
/**
* Clears the value of the specified node. If the node becomes undefined by
* this operation, it is removed from the hierarchy.
*
* @param node the node to be cleard
*/
protected void clearNode(ConfigurationNode node)
{
node.setValue(null);
if (!nodeDefined(node))
{
removeNode(node);
}
}
/**
* Returns a reference to the parent node of an add operation. Nodes for new
* properties can be added as children of this node. If the path for the
* specified key does not exist so far, it is created now.
*
* @param keyIt the iterator for the key of the new property
* @param startNode the node to start the search with
* @return the parent node for the add operation
* @deprecated Adding new properties is now to a major part delegated to the
* <code>ExpressionEngine</code> associated with this configuration instance.
* This method will no longer be called. Developers who want to modify the
* process of adding new properties should consider implementing their own
* expression engine.
*/
protected Node fetchAddNode(ConfigurationKey.KeyIterator keyIt, Node startNode)
{
return null;
}
/**
* Finds the last existing node for an add operation. This method traverses
* the configuration tree along the specified key. The last existing node on
* this path is returned.
*
* @param keyIt the key iterator
* @param node the actual node
* @return the last existing node on the given path
* @deprecated Adding new properties is now to a major part delegated to the
* <code>ExpressionEngine</code> associated with this configuration instance.
* This method will no longer be called. Developers who want to modify the
* process of adding new properties should consider implementing their own
* expression engine.
*/
protected Node findLastPathNode(ConfigurationKey.KeyIterator keyIt, Node node)
{
return null;
}
/**
* Creates the missing nodes for adding a new property. This method ensures
* that there are corresponding nodes for all components of the specified
* configuration key.
*
* @param keyIt the key iterator
* @param root the base node of the path to be created
* @return the last node of the path
* @deprecated Adding new properties is now to a major part delegated to the
* <code>ExpressionEngine</code> associated with this configuration instance.
* This method will no longer be called. Developers who want to modify the
* process of adding new properties should consider implementing their own
* expression engine.
*/
protected Node createAddPath(ConfigurationKey.KeyIterator keyIt, Node root)
{
return null;
}
/**
* Creates a new <code>Node</code> object with the specified name. This
* method can be overloaded in derived classes if a specific node type is
* needed. This base implementation always returns a new object of the
* <code>Node</code> class.
*
* @param name the name of the new node
* @return the new node
*/
protected Node createNode(String name)
{
return new Node(name);
}
/**
* Helper method for processing a node add data object obtained from the
* expression engine. This method will create all new nodes.
*
* @param data the data object
* @return the new node
* @since 1.3
*/
private ConfigurationNode processNodeAddData(NodeAddData data)
{
ConfigurationNode node = data.getParent();
// Create missing nodes on the path
for (Iterator it = data.getPathNodes().iterator(); it.hasNext();)
{
ConfigurationNode child = createNode((String) it.next());
node.addChild(child);
node = child;
}
// Add new target node
ConfigurationNode child = createNode(data.getNewNodeName());
if (data.isAttribute())
{
node.addAttribute(child);
}
else
{
node.addChild(child);
}
return child;
}
/**
* Clears all reference fields in a node structure. A configuration node can
* store a so-called "reference". The meaning of this data is
* determined by a concrete sub class. Typically such references are
* specific for a configuration instance. If this instance is cloned or
* copied, they must be cleared. This can be done using this method.
*
* @param node the root node of the node hierarchy, in which the references
* are to be cleared
* @since 1.4
*/
protected static void clearReferences(ConfigurationNode node)
{
node.visit(new ConfigurationNodeVisitorAdapter()
{
public void visitBeforeChildren(ConfigurationNode node)
{
node.setReference(null);
}
});
}
/**
* A data class for storing (hierarchical) property information. A property
* can have a value and an arbitrary number of child properties. From
* version 1.3 on this class is only a thin wrapper over the
* <code>{@link org.apache.commons.configuration.tree.DefaultConfigurationNode DefaultconfigurationNode}</code>
* class that exists mainly for the purpose of backwards compatibility.
*/
public static class Node extends DefaultConfigurationNode implements Serializable
{
/**
* The serial version UID.
*/
private static final long serialVersionUID = -6357500633536941775L;
/**
* Creates a new instance of <code>Node</code>.
*/
public Node()
{
super();
}
/**
* Creates a new instance of <code>Node</code> and sets the name.
*
* @param name the node's name
*/
public Node(String name)
{
super(name);
}
/**
* Creates a new instance of <code>Node</code> and sets the name and the value.
*
* @param name the node's name
* @param value the value
*/
public Node(String name, Object value)
{
super(name, value);
}
/**
* Creates a new instance of <code>Node</code> based on the given
* source node. All properties of the source node, including its
* children and attributes, will be copied.
*
* @param src the node to be copied
*/
public Node(ConfigurationNode src)
{
this(src.getName(), src.getValue());
setReference(src.getReference());
for (Iterator it = src.getChildren().iterator(); it.hasNext();)
{
addChild((ConfigurationNode) it.next());
}
for (Iterator it = src.getAttributes().iterator(); it.hasNext();)
{
addAttribute((ConfigurationNode) it.next());
}
}
/**
* Returns the parent of this node.
*
* @return this node's parent (can be <b>null</b>)
*/
public Node getParent()
{
return (Node) getParentNode();
}
/**
* Sets the parent of this node.
*
* @param node the parent node
*/
public void setParent(Node node)
{
setParentNode(node);
}
/**
* Adds the given node to the children of this node.
*
* @param node the child to be added
*/
public void addChild(Node node)
{
addChild((ConfigurationNode) node);
}
/**
* Returns a flag whether this node has child elements.
*
* @return <b>true</b> if there is a child node, <b>false</b> otherwise
*/
public boolean hasChildren()
{
return getChildrenCount() > 0 || getAttributeCount() > 0;
}
/**
* Removes the specified child from this node.
*
* @param child the child node to be removed
* @return a flag if the child could be found
*/
public boolean remove(Node child)
{
return child.isAttribute() ? removeAttribute(child) : removeChild(child);
}
/**
* Removes all children with the given name.
*
* @param name the name of the children to be removed
* @return a flag if children with this name existed
*/
public boolean remove(String name)
{
boolean childrenRemoved = removeChild(name);
boolean attrsRemoved = removeAttribute(name);
return childrenRemoved || attrsRemoved;
}
/**
* A generic method for traversing this node and all of its children.
* This method sends the passed in visitor to this node and all of its
* children.
*
* @param visitor the visitor
* @param key here a configuration key with the name of the root node of
* the iteration can be passed; if this key is not <b>null </b>, the
* full pathes to the visited nodes are builded and passed to the
* visitor's <code>visit()</code> methods
*/
public void visit(NodeVisitor visitor, ConfigurationKey key)
{
int length = 0;
if (key != null)
{
length = key.length();
if (getName() != null)
{
key
.append(StringUtils
.replace(
isAttribute() ? ConfigurationKey
.constructAttributeKey(getName())
: getName(),
String
.valueOf(ConfigurationKey.PROPERTY_DELIMITER),
ConfigurationKey.ESCAPED_DELIMITER));
}
}
visitor.visitBeforeChildren(this, key);
for (Iterator it = getChildren().iterator(); it.hasNext()
&& !visitor.terminate();)
{
((Node) it.next()).visit(visitor, key);
}
for (Iterator it = getAttributes().iterator(); it.hasNext()
&& !visitor.terminate();)
{
((Node) it.next()).visit(visitor, key);
}
if (key != null)
{
key.setLength(length);
}
visitor.visitAfterChildren(this, key);
}
}
/**
* <p>Definition of a visitor class for traversing a node and all of its
* children.</p><p>This class defines the interface of a visitor for
* <code>Node</code> objects and provides a default implementation. The
* method <code>visit()</code> of <code>Node</code> implements a generic
* iteration algorithm based on the <em>Visitor</em> pattern. By providing
* different implementations of visitors it is possible to collect different
* data during the iteration process.</p>
*
*/
public static class NodeVisitor
{
/**
* Visits the specified node. This method is called during iteration for
* each node before its children have been visited.
*
* @param node the actual node
* @param key the key of this node (may be <b>null </b>)
*/
public void visitBeforeChildren(Node node, ConfigurationKey key)
{
}
/**
* Visits the specified node after its children have been processed.
* This gives a visitor the opportunity of collecting additional data
* after the child nodes have been visited.
*
* @param node the node to be visited
* @param key the key of this node (may be <b>null </b>)
*/
public void visitAfterChildren(Node node, ConfigurationKey key)
{
}
/**
* Returns a flag that indicates if iteration should be stopped. This
* method is called after each visited node. It can be useful for
* visitors that search a specific node. If this node is found, the
* whole process can be stopped. This base implementation always returns
* <b>false </b>.
*
* @return a flag if iteration should be stopped
*/
public boolean terminate()
{
return false;
}
}
/**
* A specialized visitor that checks if a node is defined.
* "Defined" in this terms means that the node or at least one of
* its sub nodes is associated with a value.
*
*/
static class DefinedVisitor extends ConfigurationNodeVisitorAdapter
{
/** Stores the defined flag. */
private boolean defined;
/**
* Checks if iteration should be stopped. This can be done if the first
* defined node is found.
*
* @return a flag if iteration should be stopped
*/
public boolean terminate()
{
return isDefined();
}
/**
* Visits the node. Checks if a value is defined.
*
* @param node the actual node
*/
public void visitBeforeChildren(ConfigurationNode node)
{
defined = node.getValue() != null;
}
/**
* Returns the defined flag.
*
* @return the defined flag
*/
public boolean isDefined()
{
return defined;
}
}
/**
* A specialized visitor that fills a list with keys that are defined in a
* node hierarchy.
*/
class DefinedKeysVisitor extends ConfigurationNodeVisitorAdapter
{
/** Stores the list to be filled. */
private Set keyList;
/** A stack with the keys of the already processed nodes. */
private Stack parentKeys;
/**
* Default constructor.
*/
public DefinedKeysVisitor()
{
keyList = new ListOrderedSet();
parentKeys = new Stack();
}
/**
* Creates a new <code>DefinedKeysVisitor</code> instance and sets the
* prefix for the keys to fetch.
*
* @param prefix the prefix
*/
public DefinedKeysVisitor(String prefix)
{
this();
parentKeys.push(prefix);
}
/**
* Returns the list with all defined keys.
*
* @return the list with the defined keys
*/
public Set getKeyList()
{
return keyList;
}
/**
* Visits the node after its children has been processed. Removes this
* node's key from the stack.
*
* @param node the node
*/
public void visitAfterChildren(ConfigurationNode node)
{
parentKeys.pop();
}
/**
* Visits the specified node. If this node has a value, its key is added
* to the internal list.
*
* @param node the node to be visited
*/
public void visitBeforeChildren(ConfigurationNode node)
{
String parentKey = parentKeys.isEmpty() ? null
: (String) parentKeys.peek();
String key = getExpressionEngine().nodeKey(node, parentKey);
parentKeys.push(key);
if (node.getValue() != null)
{
keyList.add(key);
}
}
}
/**
* A specialized visitor that is able to create a deep copy of a node
* hierarchy.
*/
static class CloneVisitor extends ConfigurationNodeVisitorAdapter
{
/** A stack with the actual object to be copied. */
private Stack copyStack;
/** Stores the result of the clone process. */
private ConfigurationNode result;
/**
* Creates a new instance of <code>CloneVisitor</code>.
*/
public CloneVisitor()
{
copyStack = new Stack();
}
/**
* Visits the specified node after its children have been processed.
*
* @param node the node
*/
public void visitAfterChildren(ConfigurationNode node)
{
ConfigurationNode copy = (ConfigurationNode) copyStack.pop();
if (copyStack.isEmpty())
{
result = copy;
}
}
/**
* Visits and copies the specified node.
*
* @param node the node
*/
public void visitBeforeChildren(ConfigurationNode node)
{
ConfigurationNode copy = (ConfigurationNode) node.clone();
copy.setParentNode(null);
if (!copyStack.isEmpty())
{
if (node.isAttribute())
{
((ConfigurationNode) copyStack.peek()).addAttribute(copy);
}
else
{
((ConfigurationNode) copyStack.peek()).addChild(copy);
}
}
copyStack.push(copy);
}
/**
* Returns the result of the clone process. This is the root node of the
* cloned node hierarchy.
*
* @return the cloned root node
*/
public ConfigurationNode getClone()
{
return result;
}
}
/**
* A specialized visitor base class that can be used for storing the tree of
* configuration nodes. The basic idea is that each node can be associated
* with a reference object. This reference object has a concrete meaning in
* a derived class, e.g. an entry in a JNDI context or an XML element. When
* the configuration tree is set up, the <code>load()</code> method is
* responsible for setting the reference objects. When the configuration
* tree is later modified, new nodes do not have a defined reference object.
* This visitor class processes all nodes and finds the ones without a
* defined reference object. For those nodes the <code>insert()</code>
* method is called, which must be defined in concrete sub classes. This
* method can perform all steps to integrate the new node into the original
* structure.
*
*/
protected abstract static class BuilderVisitor extends NodeVisitor
{
/**
* Visits the specified node before its children have been traversed.
*
* @param node the node to visit
* @param key the current key
*/
public void visitBeforeChildren(Node node, ConfigurationKey key)
{
Collection subNodes = new LinkedList(node.getChildren());
subNodes.addAll(node.getAttributes());
Iterator children = subNodes.iterator();
Node sibling1 = null;
Node nd = null;
while (children.hasNext())
{
// find the next new node
do
{
sibling1 = nd;
nd = (Node) children.next();
} while (nd.getReference() != null && children.hasNext());
if (nd.getReference() == null)
{
// find all following new nodes
List newNodes = new LinkedList();
newNodes.add(nd);
while (children.hasNext())
{
nd = (Node) children.next();
if (nd.getReference() == null)
{
newNodes.add(nd);
}
else
{
break;
}
}
// Insert all new nodes
Node sibling2 = (nd.getReference() == null) ? null : nd;
for (Iterator it = newNodes.iterator(); it.hasNext();)
{
Node insertNode = (Node) it.next();
if (insertNode.getReference() == null)
{
Object ref = insert(insertNode, node, sibling1, sibling2);
if (ref != null)
{
insertNode.setReference(ref);
}
sibling1 = insertNode;
}
}
}
}
}
/**
* Inserts a new node into the structure constructed by this builder.
* This method is called for each node that has been added to the
* configuration tree after the configuration has been loaded from its
* source. These new nodes have to be inserted into the original
* structure. The passed in nodes define the position of the node to be
* inserted: its parent and the siblings between to insert. The return
* value is interpreted as the new reference of the affected
* <code>Node</code> object; if it is not <b>null </b>, it is passed
* to the node's <code>setReference()</code> method.
*
* @param newNode the node to be inserted
* @param parent the parent node
* @param sibling1 the sibling after which the node is to be inserted;
* can be <b>null </b> if the new node is going to be the first child
* node
* @param sibling2 the sibling before which the node is to be inserted;
* can be <b>null </b> if the new node is going to be the last child
* node
* @return the reference object for the node to be inserted
*/
protected abstract Object insert(Node newNode, Node parent, Node sibling1, Node sibling2);
}
}