Java tutorial
/* * 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.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.Iterator; import java.util.LinkedList; import java.util.List; import java.util.Map; import org.apache.commons.configuration2.event.ConfigurationEvent; import org.apache.commons.configuration2.event.EventListener; import org.apache.commons.configuration2.ex.ConfigurationRuntimeException; import org.apache.commons.configuration2.interpol.ConfigurationInterpolator; import org.apache.commons.configuration2.tree.ConfigurationNodeVisitorAdapter; import org.apache.commons.configuration2.tree.ImmutableNode; import org.apache.commons.configuration2.tree.InMemoryNodeModel; import org.apache.commons.configuration2.tree.InMemoryNodeModelSupport; import org.apache.commons.configuration2.tree.NodeHandler; import org.apache.commons.configuration2.tree.NodeModel; import org.apache.commons.configuration2.tree.NodeSelector; import org.apache.commons.configuration2.tree.NodeTreeWalker; import org.apache.commons.configuration2.tree.QueryResult; import org.apache.commons.configuration2.tree.ReferenceNodeHandler; import org.apache.commons.configuration2.tree.TrackedNodeModel; import org.apache.commons.lang3.ObjectUtils; /** * <p> * A specialized hierarchical configuration implementation that is based on a * structure of {@link ImmutableNode} objects. * </p> * * @version $Id$ */ public class BaseHierarchicalConfiguration extends AbstractHierarchicalConfiguration<ImmutableNode> implements InMemoryNodeModelSupport { /** A listener for reacting on changes caused by sub configurations. */ private final EventListener<ConfigurationEvent> changeListener; /** * Creates a new instance of {@code BaseHierarchicalConfiguration}. */ public BaseHierarchicalConfiguration() { this((HierarchicalConfiguration<ImmutableNode>) null); } /** * Creates a new instance of {@code BaseHierarchicalConfiguration} 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 BaseHierarchicalConfiguration(final HierarchicalConfiguration<ImmutableNode> c) { this(createNodeModel(c)); } /** * Creates a new instance of {@code BaseHierarchicalConfiguration} and * initializes it with the given {@code NodeModel}. * * @param model the {@code NodeModel} */ protected BaseHierarchicalConfiguration(final NodeModel<ImmutableNode> model) { super(model); changeListener = createChangeListener(); } /** * {@inheritDoc} This implementation returns the {@code InMemoryNodeModel} * used by this configuration. */ @Override public InMemoryNodeModel getNodeModel() { return (InMemoryNodeModel) super.getNodeModel(); } /** * Creates a new {@code Configuration} object containing all keys * that start with the specified prefix. This implementation will return a * {@code BaseHierarchicalConfiguration} object so that the structure of * the keys will be saved. The nodes selected by the prefix (it is possible * that multiple nodes are selected) are mapped to the root node of the * returned configuration, i.e. their children and attributes will become * children and attributes of the new root node. However, a value of the root * node is only set if exactly one of the selected nodes contain a value (if * multiple nodes have a value, there is simply no way to decide how these * values are merged together). Note that the returned * {@code Configuration} object is not connected to its source * configuration: updates on the source configuration are not reflected in * the subset and vice versa. The returned configuration uses the same * {@code Synchronizer} as this configuration. * * @param prefix the prefix of the keys for the subset * @return a new configuration object representing the selected subset */ @Override public Configuration subset(final String prefix) { beginRead(false); try { final List<QueryResult<ImmutableNode>> results = fetchNodeList(prefix); if (results.isEmpty()) { return new BaseHierarchicalConfiguration(); } final BaseHierarchicalConfiguration parent = this; final BaseHierarchicalConfiguration result = new BaseHierarchicalConfiguration() { // Override interpolate to always interpolate on the parent @Override protected Object interpolate(final Object value) { return parent.interpolate(value); } @Override public ConfigurationInterpolator getInterpolator() { return parent.getInterpolator(); } }; result.getModel().setRootNode(createSubsetRootNode(results)); if (result.isEmpty()) { return new BaseHierarchicalConfiguration(); } result.setSynchronizer(getSynchronizer()); return result; } finally { endRead(); } } /** * Creates a root node for a subset configuration based on the passed in * query results. This method creates a new root node and adds the children * and attributes of all result nodes to it. If only a single node value is * defined, it is assigned as value of the new root node. * * @param results the collection of query results * @return the root node for the subset configuration */ private ImmutableNode createSubsetRootNode(final Collection<QueryResult<ImmutableNode>> results) { final ImmutableNode.Builder builder = new ImmutableNode.Builder(); Object value = null; int valueCount = 0; for (final QueryResult<ImmutableNode> result : results) { if (result.isAttributeResult()) { builder.addAttribute(result.getAttributeName(), result.getAttributeValue(getModel().getNodeHandler())); } else { if (result.getNode().getValue() != null) { value = result.getNode().getValue(); valueCount++; } builder.addChildren(result.getNode().getChildren()); builder.addAttributes(result.getNode().getAttributes()); } } if (valueCount == 1) { builder.value(value); } return builder.create(); } /** * {@inheritDoc} The result of this implementation depends on the * {@code supportUpdates} flag: If it is <b>false</b>, a plain * {@code BaseHierarchicalConfiguration} is returned using the selected node * as root node. This is suitable for read-only access to properties. * Because the configuration returned in this case is not connected to the * parent configuration, updates on properties made by one configuration are * not reflected by the other one. A value of <b>true</b> for this parameter * causes a tracked node to be created, and result is a * {@link SubnodeConfiguration} based on this tracked node. This * configuration is really connected to its parent, so that updated * properties are visible on both. * * @see SubnodeConfiguration * @throws ConfigurationRuntimeException if the key does not select a single * node */ @Override public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key, final boolean supportUpdates) { beginRead(false); try { return supportUpdates ? createConnectedSubConfiguration(key) : createIndependentSubConfiguration(key); } finally { endRead(); } } /** * Returns the {@code InMemoryNodeModel} to be used as parent model for a * new sub configuration. This method is called whenever a sub configuration * is to be created. This base implementation returns the model of this * configuration. Sub classes with different requirements for the parent * models of sub configurations have to override it. * * @return the parent model for a new sub configuration */ protected InMemoryNodeModel getSubConfigurationParentModel() { return (InMemoryNodeModel) getModel(); } /** * Returns the {@code NodeSelector} to be used for a sub configuration based * on the passed in key. This method is called whenever a sub configuration * is to be created. This base implementation returns a new * {@code NodeSelector} initialized with the passed in key. Sub classes may * override this method if they have a different strategy for creating a * selector. * * @param key the key of the sub configuration * @return a {@code NodeSelector} for initializing a sub configuration * @since 2.0 */ protected NodeSelector getSubConfigurationNodeSelector(final String key) { return new NodeSelector(key); } /** * Creates a connected sub configuration based on a selector for a tracked * node. * * @param selector the {@code NodeSelector} * @param parentModelSupport the {@code InMemoryNodeModelSupport} object for * the parent node model * @return the newly created sub configuration * @since 2.0 */ protected SubnodeConfiguration createSubConfigurationForTrackedNode(final NodeSelector selector, final InMemoryNodeModelSupport parentModelSupport) { final SubnodeConfiguration subConfig = new SubnodeConfiguration(this, new TrackedNodeModel(parentModelSupport, selector, true)); initSubConfigurationForThisParent(subConfig); return subConfig; } /** * Initializes a {@code SubnodeConfiguration} object. This method should be * called for each sub configuration created for this configuration. It * ensures that the sub configuration is correctly connected to its parent * instance and that update events are correctly propagated. * * @param subConfig the sub configuration to be initialized * @since 2.0 */ protected void initSubConfigurationForThisParent(final SubnodeConfiguration subConfig) { initSubConfiguration(subConfig); subConfig.addEventListener(ConfigurationEvent.ANY, changeListener); } /** * Creates a sub configuration from the specified key which is connected to * this configuration. This implementation creates a * {@link SubnodeConfiguration} with a tracked node identified by the passed * in key. * * @param key the key of the sub configuration * @return the new sub configuration */ private BaseHierarchicalConfiguration createConnectedSubConfiguration(final String key) { final NodeSelector selector = getSubConfigurationNodeSelector(key); getSubConfigurationParentModel().trackNode(selector, this); return createSubConfigurationForTrackedNode(selector, this); } /** * Creates a list of connected sub configurations based on a passed in list * of node selectors. * * @param parentModelSupport the parent node model support object * @param selectors the list of {@code NodeSelector} objects * @return the list with sub configurations */ private List<HierarchicalConfiguration<ImmutableNode>> createConnectedSubConfigurations( final InMemoryNodeModelSupport parentModelSupport, final Collection<NodeSelector> selectors) { final List<HierarchicalConfiguration<ImmutableNode>> configs = new ArrayList<>(selectors.size()); for (final NodeSelector selector : selectors) { configs.add(createSubConfigurationForTrackedNode(selector, parentModelSupport)); } return configs; } /** * Creates a sub configuration from the specified key which is independent * on this configuration. This means that the sub configuration operates on * a separate node model (although the nodes are initially shared). * * @param key the key of the sub configuration * @return the new sub configuration */ private BaseHierarchicalConfiguration createIndependentSubConfiguration(final String key) { final List<ImmutableNode> targetNodes = fetchFilteredNodeResults(key); final int size = targetNodes.size(); if (size != 1) { throw new ConfigurationRuntimeException("Passed in key must select exactly one node (found %,d): %s", size, key); } final BaseHierarchicalConfiguration sub = new BaseHierarchicalConfiguration( new InMemoryNodeModel(targetNodes.get(0))); initSubConfiguration(sub); return sub; } /** * Returns an initialized sub configuration for this configuration that is * based on another {@code BaseHierarchicalConfiguration}. Thus, it is * independent from this configuration. * * @param node the root node for the sub configuration * @return the initialized sub configuration */ private BaseHierarchicalConfiguration createIndependentSubConfigurationForNode(final ImmutableNode node) { final BaseHierarchicalConfiguration sub = new BaseHierarchicalConfiguration(new InMemoryNodeModel(node)); initSubConfiguration(sub); return sub; } /** * Executes a query on the specified key and filters it for node results. * * @param key the key * @return the filtered list with result nodes */ private List<ImmutableNode> fetchFilteredNodeResults(final String key) { final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); return resolveNodeKey(handler.getRootNode(), key, handler); } /** * {@inheritDoc} This implementation creates a {@code SubnodeConfiguration} * by delegating to {@code configurationAt()}. Then an immutable wrapper * is created and returned. */ @Override public ImmutableHierarchicalConfiguration immutableConfigurationAt(final String key, final boolean supportUpdates) { return ConfigurationUtils.unmodifiableConfiguration(configurationAt(key, supportUpdates)); } /** * {@inheritDoc} This is a short form for {@code configurationAt(key, * <b>false</b>)}. * @throws ConfigurationRuntimeException if the key does not select a single node */ @Override public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key) { return configurationAt(key, false); } /** * {@inheritDoc} This implementation creates a {@code SubnodeConfiguration} * by delegating to {@code configurationAt()}. Then an immutable wrapper * is created and returned. * @throws ConfigurationRuntimeException if the key does not select a single node */ @Override public ImmutableHierarchicalConfiguration immutableConfigurationAt(final String key) { return ConfigurationUtils.unmodifiableConfiguration(configurationAt(key)); } /** * {@inheritDoc} This implementation creates sub configurations in the same * way as described for {@link #configurationAt(String)}. */ @Override public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt(final String key) { List<ImmutableNode> nodes; beginRead(false); try { nodes = fetchFilteredNodeResults(key); } finally { endRead(); } final List<HierarchicalConfiguration<ImmutableNode>> results = new ArrayList<>(nodes.size()); for (final ImmutableNode node : nodes) { final BaseHierarchicalConfiguration sub = createIndependentSubConfigurationForNode(node); results.add(sub); } return results; } /** * {@inheritDoc} This implementation creates tracked nodes for the specified * key. Then sub configurations for these nodes are created and returned. */ @Override public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt(final String key, final boolean supportUpdates) { if (!supportUpdates) { return configurationsAt(key); } InMemoryNodeModel parentModel; beginRead(false); try { parentModel = getSubConfigurationParentModel(); } finally { endRead(); } final Collection<NodeSelector> selectors = parentModel.selectAndTrackNodes(key, this); return createConnectedSubConfigurations(this, selectors); } /** * {@inheritDoc} This implementation first delegates to * {@code configurationsAt()} to create a list of * {@code SubnodeConfiguration} objects. Then for each element of this list * an unmodifiable wrapper is created. */ @Override public List<ImmutableHierarchicalConfiguration> immutableConfigurationsAt(final String key) { return toImmutable(configurationsAt(key)); } /** * {@inheritDoc} This implementation resolves the node(s) selected by the * given key. If not a single node is selected, an empty list is returned. * Otherwise, sub configurations for each child of the node are created. */ @Override public List<HierarchicalConfiguration<ImmutableNode>> childConfigurationsAt(final String key) { List<ImmutableNode> nodes; beginRead(false); try { nodes = fetchFilteredNodeResults(key); } finally { endRead(); } if (nodes.size() != 1) { return Collections.emptyList(); } final ImmutableNode parent = nodes.get(0); final List<HierarchicalConfiguration<ImmutableNode>> subs = new ArrayList<>(parent.getChildren().size()); for (final ImmutableNode node : parent.getChildren()) { subs.add(createIndependentSubConfigurationForNode(node)); } return subs; } /** * {@inheritDoc} This method works like * {@link #childConfigurationsAt(String)}; however, depending on the value * of the {@code supportUpdates} flag, connected sub configurations may be * created. */ @Override public List<HierarchicalConfiguration<ImmutableNode>> childConfigurationsAt(final String key, final boolean supportUpdates) { if (!supportUpdates) { return childConfigurationsAt(key); } final InMemoryNodeModel parentModel = getSubConfigurationParentModel(); return createConnectedSubConfigurations(this, parentModel.trackChildNodes(key, this)); } /** * {@inheritDoc} This implementation first delegates to * {@code childConfigurationsAt()} to create a list of mutable child * configurations. Then a list with immutable wrapper configurations is * created. */ @Override public List<ImmutableHierarchicalConfiguration> immutableChildConfigurationsAt(final String key) { return toImmutable(childConfigurationsAt(key)); } /** * This method is always called when a subnode configuration created from * this configuration has been modified. This implementation transforms the * received event into an event of type {@code SUBNODE_CHANGED} * and notifies the registered listeners. * * @param event the event describing the change * @since 1.5 */ protected void subnodeConfigurationChanged(final ConfigurationEvent event) { fireEvent(ConfigurationEvent.SUBNODE_CHANGED, null, event, event.isBeforeUpdate()); } /** * Initializes properties of a sub configuration. A sub configuration * inherits some settings from its parent, e.g. the expression engine or the * synchronizer. The corresponding values are copied by this method. * * @param sub the sub configuration to be initialized */ private void initSubConfiguration(final BaseHierarchicalConfiguration sub) { sub.setSynchronizer(getSynchronizer()); sub.setExpressionEngine(getExpressionEngine()); sub.setListDelimiterHandler(getListDelimiterHandler()); sub.setThrowExceptionOnMissing(isThrowExceptionOnMissing()); sub.getInterpolator().setParentInterpolator(getInterpolator()); } /** * Creates a listener which reacts on all changes on this configuration or * one of its {@code SubnodeConfiguration} instances. If such a change is * detected, some updates have to be performed. * * @return the newly created change listener */ private EventListener<ConfigurationEvent> createChangeListener() { return new EventListener<ConfigurationEvent>() { @Override public void onEvent(final ConfigurationEvent event) { subnodeConfigurationChanged(event); } }; } /** * Returns a configuration with the same content as this configuration, but * with all variables replaced by their actual values. This implementation * is specific for hierarchical configurations. It clones the current * configuration and runs a specialized visitor on the clone, which performs * interpolation on the single configuration nodes. * * @return a configuration with all variables interpolated * @since 1.5 */ @Override public Configuration interpolatedConfiguration() { final InterpolatedVisitor visitor = new InterpolatedVisitor(); final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); NodeTreeWalker.INSTANCE.walkDFS(handler.getRootNode(), visitor, handler); final BaseHierarchicalConfiguration c = (BaseHierarchicalConfiguration) clone(); c.getNodeModel().setRootNode(visitor.getInterpolatedRoot()); return c; } /** * {@inheritDoc} This implementation creates a new instance of * {@link InMemoryNodeModel}, initialized with this configuration's root * node. This has the effect that although the same nodes are used, the * original and copied configurations are independent on each other. */ @Override protected NodeModel<ImmutableNode> cloneNodeModel() { return new InMemoryNodeModel(getModel().getNodeHandler().getRootNode()); } /** * Creates a list with immutable configurations from the given input list. * * @param subs a list with mutable configurations * @return a list with corresponding immutable configurations */ private static List<ImmutableHierarchicalConfiguration> toImmutable( final List<? extends HierarchicalConfiguration<?>> subs) { final List<ImmutableHierarchicalConfiguration> res = new ArrayList<>(subs.size()); for (final HierarchicalConfiguration<?> sub : subs) { res.add(ConfigurationUtils.unmodifiableConfiguration(sub)); } return res; } /** * Creates the {@code NodeModel} for this configuration based on a passed in * source configuration. This implementation creates an * {@link InMemoryNodeModel}. If the passed in source configuration is * defined, its root node also becomes the root node of this configuration. * Otherwise, a new, empty root node is used. * * @param c the configuration that is to be copied * @return the {@code NodeModel} for the new configuration */ private static NodeModel<ImmutableNode> createNodeModel(final HierarchicalConfiguration<ImmutableNode> c) { final ImmutableNode root = (c != null) ? obtainRootNode(c) : null; return new InMemoryNodeModel(root); } /** * Obtains the root node from a configuration whose data is to be copied. It * has to be ensured that the synchronizer is called correctly. * * @param c the configuration that is to be copied * @return the root node of this configuration */ private static ImmutableNode obtainRootNode(final HierarchicalConfiguration<ImmutableNode> c) { return c.getNodeModel().getNodeHandler().getRootNode(); } /** * 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()} 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()} * 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 ConfigurationNodeVisitorAdapter<ImmutableNode> { @Override public void visitBeforeChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) { final ReferenceNodeHandler refHandler = (ReferenceNodeHandler) handler; updateNode(node, refHandler); insertNewChildNodes(node, refHandler); } /** * 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. * * @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 * @param refHandler the {@code ReferenceNodeHandler} */ protected abstract void insert(ImmutableNode newNode, ImmutableNode parent, ImmutableNode sibling1, ImmutableNode sibling2, ReferenceNodeHandler refHandler); /** * Updates a node that already existed in the original hierarchy. This * method is called for each node that has an assigned reference object. * A concrete implementation should update the reference according to * the node's current value. * * @param node the current node to be processed * @param reference the reference object for this node * @param refHandler the {@code ReferenceNodeHandler} */ protected abstract void update(ImmutableNode node, Object reference, ReferenceNodeHandler refHandler); /** * Updates the value of a node. If this node is associated with a * reference object, the {@code update()} method is called. * * @param node the current node to be processed * @param refHandler the {@code ReferenceNodeHandler} */ private void updateNode(final ImmutableNode node, final ReferenceNodeHandler refHandler) { final Object reference = refHandler.getReference(node); if (reference != null) { update(node, reference, refHandler); } } /** * Inserts new children that have been added to the specified node. * * @param node the current node to be processed * @param refHandler the {@code ReferenceNodeHandler} */ private void insertNewChildNodes(final ImmutableNode node, final ReferenceNodeHandler refHandler) { final Collection<ImmutableNode> subNodes = new LinkedList<>(refHandler.getChildren(node)); final Iterator<ImmutableNode> children = subNodes.iterator(); ImmutableNode sibling1; ImmutableNode nd = null; while (children.hasNext()) { // find the next new node do { sibling1 = nd; nd = children.next(); } while (refHandler.getReference(nd) != null && children.hasNext()); if (refHandler.getReference(nd) == null) { // find all following new nodes final List<ImmutableNode> newNodes = new LinkedList<>(); newNodes.add(nd); while (children.hasNext()) { nd = children.next(); if (refHandler.getReference(nd) == null) { newNodes.add(nd); } else { break; } } // Insert all new nodes final ImmutableNode sibling2 = (refHandler.getReference(nd) == null) ? null : nd; for (final ImmutableNode insertNode : newNodes) { if (refHandler.getReference(insertNode) == null) { insert(insertNode, node, sibling1, sibling2, refHandler); sibling1 = insertNode; } } } } } } /** * A specialized visitor implementation which constructs the root node of a * configuration with all variables replaced by their interpolated values. */ private class InterpolatedVisitor extends ConfigurationNodeVisitorAdapter<ImmutableNode> { /** A stack for managing node builder instances. */ private final List<ImmutableNode.Builder> builderStack; /** The resulting root node. */ private ImmutableNode interpolatedRoot; /** * Creates a new instance of {@code InterpolatedVisitor}. */ public InterpolatedVisitor() { builderStack = new LinkedList<>(); } /** * Returns the result of this builder: the root node of the interpolated * nodes hierarchy. * * @return the resulting root node */ public ImmutableNode getInterpolatedRoot() { return interpolatedRoot; } @Override public void visitBeforeChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) { if (isLeafNode(node, handler)) { handleLeafNode(node, handler); } else { final ImmutableNode.Builder builder = new ImmutableNode.Builder( handler.getChildrenCount(node, null)).name(handler.nodeName(node)) .value(interpolate(handler.getValue(node))) .addAttributes(interpolateAttributes(node, handler)); push(builder); } } @Override public void visitAfterChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) { if (!isLeafNode(node, handler)) { final ImmutableNode newNode = pop().create(); storeInterpolatedNode(newNode); } } /** * Pushes a new builder on the stack. * * @param builder the builder */ private void push(final ImmutableNode.Builder builder) { builderStack.add(0, builder); } /** * Pops the top-level element from the stack. * * @return the element popped from the stack */ private ImmutableNode.Builder pop() { return builderStack.remove(0); } /** * Returns the top-level element from the stack without removing it. * * @return the top-level element from the stack */ private ImmutableNode.Builder peek() { return builderStack.get(0); } /** * Returns a flag whether the given node is a leaf. This is the case if * it does not have children. * * @param node the node in question * @param handler the {@code NodeHandler} * @return a flag whether this is a leaf node */ private boolean isLeafNode(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) { return handler.getChildren(node).isEmpty(); } /** * Handles interpolation for a node with no children. If interpolation * does not change this node, it is copied as is to the resulting * structure. Otherwise, a new node is created with the interpolated * values. * * @param node the current node to be processed * @param handler the {@code NodeHandler} */ private void handleLeafNode(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) { final Object value = interpolate(node.getValue()); final Map<String, Object> interpolatedAttributes = new HashMap<>(); final boolean attributeChanged = interpolateAttributes(node, handler, interpolatedAttributes); final ImmutableNode newNode = (valueChanged(value, handler.getValue(node)) || attributeChanged) ? new ImmutableNode.Builder().name(handler.nodeName(node)).value(value) .addAttributes(interpolatedAttributes).create() : node; storeInterpolatedNode(newNode); } /** * Stores a processed node. Per default, the node is added to the * current builder on the stack. If no such builder exists, this is the * result node. * * @param node the node to be stored */ private void storeInterpolatedNode(final ImmutableNode node) { if (builderStack.isEmpty()) { interpolatedRoot = node; } else { peek().addChild(node); } } /** * Populates a map with interpolated attributes of the passed in node. * * @param node the current node to be processed * @param handler the {@code NodeHandler} * @param interpolatedAttributes a map for storing the results * @return a flag whether an attribute value was changed by * interpolation */ private boolean interpolateAttributes(final ImmutableNode node, final NodeHandler<ImmutableNode> handler, final Map<String, Object> interpolatedAttributes) { boolean attributeChanged = false; for (final String attr : handler.getAttributes(node)) { final Object attrValue = interpolate(handler.getAttributeValue(node, attr)); if (valueChanged(attrValue, handler.getAttributeValue(node, attr))) { attributeChanged = true; } interpolatedAttributes.put(attr, attrValue); } return attributeChanged; } /** * Returns a map with interpolated attributes of the passed in node. * * @param node the current node to be processed * @param handler the {@code NodeHandler} * @return the map with interpolated attributes */ private Map<String, Object> interpolateAttributes(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) { final Map<String, Object> attributes = new HashMap<>(); interpolateAttributes(node, handler, attributes); return attributes; } /** * Tests whether a value is changed because of interpolation. * * @param interpolatedValue the interpolated value * @param value the original value * @return a flag whether the value was changed */ private boolean valueChanged(final Object interpolatedValue, final Object value) { return ObjectUtils.notEqual(interpolatedValue, value); } } }