CombinedConfiguration.java
/*
* 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.configuration2;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.commons.configuration2.event.ConfigurationEvent;
import org.apache.commons.configuration2.event.EventListener;
import org.apache.commons.configuration2.event.EventSource;
import org.apache.commons.configuration2.event.EventType;
import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
import org.apache.commons.configuration2.sync.LockMode;
import org.apache.commons.configuration2.tree.DefaultConfigurationKey;
import org.apache.commons.configuration2.tree.DefaultExpressionEngine;
import org.apache.commons.configuration2.tree.ExpressionEngine;
import org.apache.commons.configuration2.tree.ImmutableNode;
import org.apache.commons.configuration2.tree.NodeCombiner;
import org.apache.commons.configuration2.tree.NodeTreeWalker;
import org.apache.commons.configuration2.tree.QueryResult;
import org.apache.commons.configuration2.tree.TreeUtils;
import org.apache.commons.configuration2.tree.UnionCombiner;
import org.apache.commons.lang3.StringUtils;
/**
* <p>
* A hierarchical composite configuration class.
* </p>
* <p>
* This class maintains a list of configuration objects, which can be added using the diverse {@code 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 {@link org.apache.commons.configuration2.tree.NodeCombiner NodeCombiner} object can be set. This makes it
* possible to specify different algorithms for the combination process.
* </p>
* <p>
* The big advantage of this class is that it creates a truly 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.
* </p>
* <p>
* The class works by registering itself as an event listener at 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. Note that,
* depending on the used {@code NodeCombiner}, this may be a complex operation.
* </p>
* <p>
* Because of the way a {@code CombinedConfiguration} is working it has more or less view character: it provides a logic
* view on the configurations it contains. In this constellation not all methods defined for hierarchical configurations
* - especially methods that update the stored properties - can be implemented in a consistent manner. Using such
* methods (like {@code addProperty()}, or {@code clearProperty()} on a {@code CombinedConfiguration} is not strictly
* forbidden, however, depending on the current {@link NodeCombiner} and the involved properties, the results may be
* different than expected. Some examples may illustrate this:
* </p>
* <ul>
* <li>Imagine a {@code CombinedConfiguration} <em>cc</em> containing two child configurations with the following
* content:
* <dl>
* <dt>user.properties</dt>
* <dd>
*
* <pre>
* gui.background = blue
* gui.position = (10, 10, 400, 200)
* </pre>
*
* </dd>
* <dt>default.properties</dt>
* <dd>
*
* <pre>
* gui.background = black
* gui.foreground = white
* home.dir = /data
* </pre>
*
* </dd>
* </dl>
* As a {@code NodeCombiner} a {@link org.apache.commons.configuration2.tree.OverrideCombiner OverrideCombiner} is used.
* This combiner will ensure that defined user settings take precedence over the default values. If the resulting
* {@code CombinedConfiguration} is queried for the background color, {@code blue} will be returned because this value
* is defined in {@code user.properties}. Now consider what happens if the key {@code gui.background} is removed from
* the {@code CombinedConfiguration}:
*
* <pre>
* cc.clearProperty("gui.background");
* </pre>
*
* Will a {@code cc.containsKey("gui.background")} now return <b>false</b>? No, it won't! The {@code clearProperty()}
* operation is executed on the node set of the combined configuration, which was constructed from the nodes of the two
* child configurations. It causes the value of the <em>background</em> node to be cleared, which is also part of the
* first child configuration. This modification of one of its child configurations causes the
* {@code CombinedConfiguration} to be re-constructed. This time the {@code OverrideCombiner} cannot find a
* {@code gui.background} property in the first child configuration, but it finds one in the second, and adds it to the
* resulting combined configuration. So the property is still present (with a different value now).</li>
* <li>{@code addProperty()} can also be problematic: Most 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. Using the same configurations as in the last example, the
* statement
*
* <pre>
* addProperty("database.user", "scott");
* </pre>
*
* would cause such a hanging property. If now one of the child configurations is changed and the
* {@code CombinedConfiguration} is re-constructed, this property will disappear! (Add operations are not problematic if
* they result in a child configuration being updated. For instance an {@code addProperty("home.url", "localhost");}
* will alter the second child configuration - because the prefix <em>home</em> is here already present; when the
* {@code CombinedConfiguration} is re-constructed, this change is taken into account.)</li>
* </ul>
* <p>
* Because of such problems it is recommended to perform updates only on the managed child configurations.
* </p>
* <p>
* Whenever the node structure of a {@code CombinedConfiguration} becomes invalid (either because one of the contained
* configurations was modified or because the {@code 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.
* </p>
* <p>
* Notes about thread-safety: This configuration implementation uses a {@code Synchronizer} object to protect instances
* against concurrent access. The concrete {@code Synchronizer} implementation used determines whether an instance of
* this class is thread-safe or not. In contrast to other implementations derived from
* {@link BaseHierarchicalConfiguration}, thread-safety is an issue here because the nodes structure used by this
* configuration has to be constructed dynamically when a child configuration is changed. Therefore, when multiple
* threads are involved which also manipulate one of the child configurations, a proper {@code Synchronizer} object
* should be set. Note that the {@code Synchronizer} objects used by the child configurations do not really matter.
* Because immutable in-memory nodes structures are used for them there is no danger that updates on child
* configurations could interfere with read operations on the combined configuration.
* </p>
*
* @since 1.3
*/
public class CombinedConfiguration extends BaseHierarchicalConfiguration implements EventListener<ConfigurationEvent> {
/**
* An internal helper class for storing information about contained configurations.
*/
private final class ConfigData {
/** Stores a reference to the configuration. */
private final Configuration configuration;
/** Stores the name under which the configuration is stored. */
private final String name;
/** Stores the at information as path of nodes. */
private final Collection<String> atPath;
/** Stores the at string. */
private final String at;
/** Stores the root node for this child configuration. */
private ImmutableNode rootNode;
/**
* Creates a new instance of {@code ConfigData} and initializes it.
*
* @param config the configuration
* @param n the name
* @param at the at position
*/
public ConfigData(final Configuration config, final String n, final String at) {
configuration = config;
name = n;
atPath = parseAt(at);
this.at = at;
}
/**
* Gets the at position of this configuration.
*
* @return the at position
*/
public String getAt() {
return at;
}
/**
* Gets the stored configuration.
*
* @return the configuration
*/
public Configuration getConfiguration() {
return configuration;
}
/**
* Gets the configuration's name.
*
* @return the name
*/
public String getName() {
return name;
}
/**
* Gets the root node for this child configuration.
*
* @return the root node of this child configuration
* @since 1.5
*/
public ImmutableNode getRootNode() {
return rootNode;
}
/**
* Obtains the root node of the wrapped configuration. If necessary, a hierarchical representation of the configuration
* has to be created first.
*
* @return the root node of the associated configuration
*/
private ImmutableNode getRootNodeOfConfiguration() {
getConfiguration().lock(LockMode.READ);
try {
final ImmutableNode root = ConfigurationUtils.convertToHierarchical(getConfiguration(), conversionExpressionEngine).getNodeModel()
.getInMemoryRepresentation();
rootNode = root;
return root;
} finally {
getConfiguration().unlock(LockMode.READ);
}
}
/**
* Gets the transformed root node of the stored configuration. The term "transformed" means that an
* eventually defined at path has been applied.
*
* @return the transformed root node
*/
public ImmutableNode getTransformedRoot() {
final ImmutableNode configRoot = getRootNodeOfConfiguration();
return atPath == null ? configRoot : prependAtPath(configRoot);
}
/**
* Splits the at path into its components.
*
* @param at the at string
* @return a collection with the names of the single components
*/
private Collection<String> parseAt(final String at) {
if (StringUtils.isEmpty(at)) {
return null;
}
final Collection<String> result = new ArrayList<>();
final DefaultConfigurationKey.KeyIterator it = new DefaultConfigurationKey(AT_ENGINE, at).iterator();
while (it.hasNext()) {
result.add(it.nextKey());
}
return result;
}
/**
* Prepends the at path to the given node.
*
* @param node the root node of the represented configuration
* @return the new root node including the at path
*/
private ImmutableNode prependAtPath(final ImmutableNode node) {
final ImmutableNode.Builder pathBuilder = new ImmutableNode.Builder();
final Iterator<String> pathIterator = atPath.iterator();
prependAtPathComponent(pathBuilder, pathIterator.next(), pathIterator, node);
return new ImmutableNode.Builder(1).addChild(pathBuilder.create()).create();
}
/**
* Handles a single component of the at path. A corresponding node is created and added to the hierarchical path to the
* original root node of the configuration.
*
* @param builder the current node builder object
* @param currentComponent the name of the current path component
* @param components an iterator with all components of the at path
* @param orgRoot the original root node of the wrapped configuration
*/
private void prependAtPathComponent(final ImmutableNode.Builder builder, final String currentComponent, final Iterator<String> components,
final ImmutableNode orgRoot) {
builder.name(currentComponent);
if (components.hasNext()) {
final ImmutableNode.Builder childBuilder = new ImmutableNode.Builder();
prependAtPathComponent(childBuilder, components.next(), components, orgRoot);
builder.addChild(childBuilder.create());
} else {
builder.addChildren(orgRoot.getChildren());
builder.addAttributes(orgRoot.getAttributes());
builder.value(orgRoot.getValue());
}
}
}
/**
* Constant for the event type fired when the internal node structure of a combined configuration becomes invalid.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> COMBINED_INVALIDATE = new EventType<>(ConfigurationEvent.ANY, "COMBINED_INVALIDATE");
/** Constant for the expression engine for parsing the at path. */
private static final DefaultExpressionEngine AT_ENGINE = DefaultExpressionEngine.INSTANCE;
/** Constant for the default node combiner. */
private static final NodeCombiner DEFAULT_COMBINER = new UnionCombiner();
/** Constant for a root node for an empty configuration. */
private static final ImmutableNode EMPTY_ROOT = new ImmutableNode.Builder().create();
/** Stores the combiner. */
private NodeCombiner nodeCombiner;
/** Stores a list with the contained configurations. */
private List<ConfigData> configurations;
/** Stores a map with the named configurations. */
private Map<String, Configuration> namedConfigurations;
/**
* An expression engine used for converting child configurations to hierarchical ones.
*/
private ExpressionEngine conversionExpressionEngine;
/** A flag whether this configuration is up-to-date. */
private boolean upToDate;
/**
* Creates a new instance of {@code CombinedConfiguration} that uses a union combiner.
*
* @see org.apache.commons.configuration2.tree.UnionCombiner
*/
public CombinedConfiguration() {
this(null);
}
/**
* Creates a new instance of {@code CombinedConfiguration} and initializes the combiner to be used.
*
* @param comb the node combiner (can be <b>null</b>, then a union combiner is used as default)
*/
public CombinedConfiguration(final NodeCombiner comb) {
nodeCombiner = comb != null ? comb : DEFAULT_COMBINER;
initChildCollections();
}
/**
* Adds a new configuration to this combined configuration. The new configuration is not given a name. Its properties
* will be added under the root of the combined node structure.
*
* @param config the configuration to add (must not be <b>null</b>)
*/
public void addConfiguration(final Configuration config) {
addConfiguration(config, null, null);
}
/**
* Adds a new configuration to this combined configuration with an optional name. The new configuration's properties
* will be added under the root of the combined node structure.
*
* @param config the configuration to add (must not be <b>null</b>)
* @param name the name of this configuration (can be <b>null</b>)
*/
public void addConfiguration(final Configuration config, final String name) {
addConfiguration(config, name, null);
}
/**
* Adds a new configuration to this combined configuration. It is possible (but not mandatory) to give the new
* configuration a name. This name must be unique, otherwise a {@code ConfigurationRuntimeException} will be thrown.
* With the optional {@code 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 {@code "database.tables"}, all properties of the added
* configuration will occur in this branch.
*
* @param config the configuration to add (must not be <b>null</b>)
* @param name the name of this configuration (can be <b>null</b>)
* @param at the position of this configuration in the combined tree (can be <b>null</b>)
*/
public void addConfiguration(final Configuration config, final String name, final String at) {
if (config == null) {
throw new IllegalArgumentException("Added configuration must not be null!");
}
beginWrite(true);
try {
if (name != null && namedConfigurations.containsKey(name)) {
throw new ConfigurationRuntimeException("A configuration with the name '" + name + "' already exists in this combined configuration!");
}
final ConfigData cd = new ConfigData(config, name, at);
if (getLogger().isDebugEnabled()) {
getLogger().debug("Adding configuration " + config + " with name " + name);
}
configurations.add(cd);
if (name != null) {
namedConfigurations.put(name, config);
}
invalidateInternal();
} finally {
endWrite();
}
registerListenerAt(config);
}
/**
* {@inheritDoc} This implementation checks whether a combined root node is available. If not, it is constructed by
* requesting a write lock.
*/
@Override
protected void beginRead(final boolean optimize) {
if (optimize) {
// just need a lock, don't construct configuration
super.beginRead(true);
return;
}
boolean lockObtained = false;
do {
super.beginRead(false);
if (isUpToDate()) {
lockObtained = true;
} else {
// release read lock and try to obtain a write lock
endRead();
beginWrite(false); // this constructs the root node
endWrite();
}
} while (!lockObtained);
}
/**
* {@inheritDoc} This implementation checks whether a combined root node is available. If not, it is constructed now.
*/
@Override
protected void beginWrite(final boolean optimize) {
super.beginWrite(true);
if (optimize) {
// just need a lock, don't construct configuration
return;
}
boolean success = false;
try {
if (!isUpToDate()) {
getSubConfigurationParentModel().replaceRoot(constructCombinedNode(), this);
upToDate = true;
}
success = true;
} finally {
if (!success) {
endWrite();
}
}
}
/**
* Clears this configuration. All contained configurations will be removed.
*/
@Override
protected void clearInternal() {
unregisterListenerAtChildren();
initChildCollections();
invalidateInternal();
}
/**
* Returns a copy of this object. This implementation performs a deep clone, i.e. all contained configurations will be
* cloned, too. For this to work, all contained configurations must be cloneable. Registered event listeners won't be
* cloned. The clone will use the same node combiner than the original.
*
* @return the copied object
*/
@Override
public Object clone() {
beginRead(false);
try {
final CombinedConfiguration copy = (CombinedConfiguration) super.clone();
copy.initChildCollections();
configurations.forEach(cd -> copy.addConfiguration(ConfigurationUtils.cloneConfiguration(cd.getConfiguration()), cd.getName(), cd.getAt()));
return copy;
} finally {
endRead();
}
}
/**
* Creates the root node of this combined configuration.
*
* @return the combined root node
*/
private ImmutableNode constructCombinedNode() {
if (getNumberOfConfigurationsInternal() < 1) {
if (getLogger().isDebugEnabled()) {
getLogger().debug("No configurations defined for " + this);
}
return EMPTY_ROOT;
}
final Iterator<ConfigData> it = configurations.iterator();
ImmutableNode node = it.next().getTransformedRoot();
while (it.hasNext()) {
node = nodeCombiner.combine(node, it.next().getTransformedRoot());
}
if (getLogger().isDebugEnabled()) {
final ByteArrayOutputStream os = new ByteArrayOutputStream();
final PrintStream stream = new PrintStream(os);
TreeUtils.printTree(stream, node);
getLogger().debug(os.toString());
}
return node;
}
/**
* Determines the configurations to which the specified node belongs. This is done by inspecting the nodes structures of
* all child configurations.
*
* @param node the node
* @return a set with the owning configurations
*/
private Set<Configuration> findSourceConfigurations(final ImmutableNode node) {
final Set<Configuration> result = new HashSet<>();
final FindNodeVisitor<ImmutableNode> visitor = new FindNodeVisitor<>(node);
configurations.forEach(cd -> {
NodeTreeWalker.INSTANCE.walkBFS(cd.getRootNode(), visitor, getModel().getNodeHandler());
if (visitor.isFound()) {
result.add(cd.getConfiguration());
visitor.reset();
}
});
return result;
}
/**
* Gets the configuration at the specified index. The contained configurations are numbered in the order they were
* added to this combined configuration. The index of the first configuration is 0.
*
* @param index the index
* @return the configuration at this index
*/
public Configuration getConfiguration(final int index) {
beginRead(true);
try {
final ConfigData cd = configurations.get(index);
return cd.getConfiguration();
} finally {
endRead();
}
}
/**
* Gets the configuration with the given name. This can be <b>null</b> if no such configuration exists.
*
* @param name the name of the configuration
* @return the configuration with this name
*/
public Configuration getConfiguration(final String name) {
beginRead(true);
try {
return namedConfigurations.get(name);
} finally {
endRead();
}
}
/**
* Gets a List of the names of all the configurations that have been added in the order they were added. A NULL value
* will be present in the list for each configuration that was added without a name.
*
* @return A List of all the configuration names.
* @since 1.7
*/
public List<String> getConfigurationNameList() {
beginRead(true);
try {
return configurations.stream().map(ConfigData::getName).collect(Collectors.toList());
} finally {
endRead();
}
}
/**
* Gets a set with the names of all configurations contained in this combined configuration. Of course here are only
* these configurations listed, for which a name was specified when they were added.
*
* @return a set with the names of the contained configurations (never <b>null</b>)
*/
public Set<String> getConfigurationNames() {
beginRead(true);
try {
return namedConfigurations.keySet();
} finally {
endRead();
}
}
/**
* Gets a List of all the configurations that have been added.
*
* @return A List of all the configurations.
* @since 1.7
*/
public List<Configuration> getConfigurations() {
beginRead(true);
try {
return configurations.stream().map(ConfigData::getConfiguration).collect(Collectors.toList());
} finally {
endRead();
}
}
/**
* Gets the {@code ExpressionEngine} for converting flat child configurations to hierarchical ones.
*
* @return the conversion expression engine
* @since 1.6
*/
public ExpressionEngine getConversionExpressionEngine() {
beginRead(true);
try {
return conversionExpressionEngine;
} finally {
endRead();
}
}
/**
* Gets the node combiner that is used for creating the combined node structure.
*
* @return the node combiner
*/
public NodeCombiner getNodeCombiner() {
beginRead(true);
try {
return nodeCombiner;
} finally {
endRead();
}
}
/**
* Gets the number of configurations that are contained in this combined configuration.
*
* @return the number of contained configurations
*/
public int getNumberOfConfigurations() {
beginRead(true);
try {
return getNumberOfConfigurationsInternal();
} finally {
endRead();
}
}
/**
* Gets the number of child configurations in this combined configuration. The internal list of child configurations
* is accessed without synchronization.
*
* @return the number of child configurations
*/
private int getNumberOfConfigurationsInternal() {
return configurations.size();
}
/**
* Gets the configuration source, in which the specified key is defined. This method will determine the configuration
* node that is identified by the given key. The following constellations are possible:
* <ul>
* <li>If no node object is found for this key, <b>null</b> is returned.</li>
* <li>If the key maps to multiple nodes belonging to different configuration sources, a
* {@code IllegalArgumentException} is thrown (in this case no unique source can be determined).</li>
* <li>If exactly one node is found for the key, the (child) configuration object, to which the node belongs is
* determined and returned.</li>
* <li>For keys that have been added directly to this combined configuration and that do not belong to the namespaces
* defined by existing child configurations this configuration will be returned.</li>
* </ul>
*
* @param key the key of a configuration property
* @return the configuration, to which this property belongs or <b>null</b> if the key cannot be resolved
* @throws IllegalArgumentException if the key maps to multiple properties and the source cannot be determined, or if
* the key is <b>null</b>
* @since 1.5
*/
public Configuration getSource(final String key) {
if (key == null) {
throw new IllegalArgumentException("Key must not be null!");
}
final Set<Configuration> sources = getSources(key);
if (sources.isEmpty()) {
return null;
}
final Iterator<Configuration> iterator = sources.iterator();
final Configuration source = iterator.next();
if (iterator.hasNext()) {
throw new IllegalArgumentException("The key " + key + " is defined by multiple sources!");
}
return source;
}
/**
* Gets a set with the configuration sources, in which the specified key is defined. This method determines the
* configuration nodes that are identified by the given key. It then determines the configuration sources to which these
* nodes belong and adds them to the result set. Note the following points:
* <ul>
* <li>If no node object is found for this key, an empty set is returned.</li>
* <li>For keys that have been added directly to this combined configuration and that do not belong to the namespaces
* defined by existing child configurations this combined configuration is contained in the result set.</li>
* </ul>
*
* @param key the key of a configuration property
* @return a set with the configuration sources, which contain this property
* @since 2.0
*/
public Set<Configuration> getSources(final String key) {
beginRead(false);
try {
final List<QueryResult<ImmutableNode>> results = fetchNodeList(key);
final Set<Configuration> sources = new HashSet<>();
results.forEach(result -> {
final Set<Configuration> resultSources = findSourceConfigurations(result.getNode());
if (resultSources.isEmpty()) {
// key must be defined in combined configuration
sources.add(this);
} else {
sources.addAll(resultSources);
}
});
return sources;
} finally {
endRead();
}
}
/**
* Initializes internal data structures for storing information about child configurations.
*/
private void initChildCollections() {
configurations = new ArrayList<>();
namedConfigurations = new HashMap<>();
}
/**
* Invalidates this combined configuration. This means that the next time a property is accessed the combined node
* structure must be re-constructed. Invalidation of a combined configuration also means that an event of type
* {@code 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 invalidate() {
beginWrite(true);
try {
invalidateInternal();
} finally {
endWrite();
}
}
/**
* Marks this configuration as invalid. This means that the next access re-creates the root node. An invalidate event is
* also fired. Note: This implementation expects that an exclusive (write) lock is held on this instance.
*/
private void invalidateInternal() {
upToDate = false;
fireEvent(COMBINED_INVALIDATE, null, null, false);
}
/**
* Returns a flag whether this configuration has been invalidated. This means that the combined nodes structure has to
* be rebuilt before the configuration can be accessed.
*
* @return a flag whether this configuration is invalid
*/
private boolean isUpToDate() {
return upToDate;
}
/**
* Event listener call back for configuration update events. This method is called whenever one of the contained
* configurations was modified. It invalidates this combined configuration.
*
* @param event the update event
*/
@Override
public void onEvent(final ConfigurationEvent event) {
if (event.isBeforeUpdate()) {
invalidate();
}
}
/**
* Registers this combined configuration as listener at the given child configuration.
*
* @param configuration the child configuration
*/
private void registerListenerAt(final Configuration configuration) {
if (configuration instanceof EventSource) {
((EventSource) configuration).addEventListener(ConfigurationEvent.ANY, this);
}
}
/**
* Removes the specified configuration from this combined configuration.
*
* @param config the configuration to be removed
* @return a flag whether this configuration was found and could be removed
*/
public boolean removeConfiguration(final Configuration config) {
for (int index = 0; index < getNumberOfConfigurations(); index++) {
if (configurations.get(index).getConfiguration() == config) {
removeConfigurationAt(index);
return true;
}
}
return false;
}
/**
* Removes the configuration with the specified name.
*
* @param name the name of the configuration to be removed
* @return the removed configuration (<b>null</b> if this configuration was not found)
*/
public Configuration removeConfiguration(final String name) {
final Configuration conf = getConfiguration(name);
if (conf != null) {
removeConfiguration(conf);
}
return conf;
}
/**
* Removes the configuration at the specified index.
*
* @param index the index
* @return the removed configuration
*/
public Configuration removeConfigurationAt(final int index) {
final ConfigData cd = configurations.remove(index);
if (cd.getName() != null) {
namedConfigurations.remove(cd.getName());
}
unregisterListenerAt(cd.getConfiguration());
invalidateInternal();
return cd.getConfiguration();
}
/**
* Sets the {@code ExpressionEngine} for converting flat child configurations to hierarchical ones. When constructing
* the root node for this combined configuration the properties of all child configurations must be combined to a single
* hierarchical node structure. In this process, non hierarchical configurations are converted to hierarchical ones
* first. This can be problematic if a child configuration contains keys that are no compatible with the default
* expression engine used by hierarchical configurations. Therefore it is possible to specify a specific expression
* engine to be used for this purpose.
*
* @param conversionExpressionEngine the conversion expression engine
* @see ConfigurationUtils#convertToHierarchical(Configuration, ExpressionEngine)
* @since 1.6
*/
public void setConversionExpressionEngine(final ExpressionEngine conversionExpressionEngine) {
beginWrite(true);
try {
this.conversionExpressionEngine = conversionExpressionEngine;
} finally {
endWrite();
}
}
/**
* Sets the node combiner. This object will be used when the combined node structure is to be constructed. It must not
* be <b>null</b>, otherwise an {@code IllegalArgumentException} exception is thrown. Changing the node combiner causes
* an invalidation of this combined configuration, so that the new combiner immediately takes effect.
*
* @param nodeCombiner the node combiner
*/
public void setNodeCombiner(final NodeCombiner nodeCombiner) {
if (nodeCombiner == null) {
throw new IllegalArgumentException("Node combiner must not be null!");
}
beginWrite(true);
try {
this.nodeCombiner = nodeCombiner;
invalidateInternal();
} finally {
endWrite();
}
}
/**
* Removes this combined configuration as listener from the given child configuration.
*
* @param configuration the child configuration
*/
private void unregisterListenerAt(final Configuration configuration) {
if (configuration instanceof EventSource) {
((EventSource) configuration).removeEventListener(ConfigurationEvent.ANY, this);
}
}
/**
* Removes this combined configuration as listener from all child configurations. This method is called on a clear()
* operation.
*/
private void unregisterListenerAtChildren() {
if (configurations != null) {
configurations.forEach(child -> unregisterListenerAt(child.getConfiguration()));
}
}
}