001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.commons.configuration2; 019 020import java.util.ArrayList; 021import java.util.Collection; 022import java.util.Collections; 023import java.util.HashMap; 024import java.util.Iterator; 025import java.util.LinkedList; 026import java.util.List; 027import java.util.Map; 028 029import org.apache.commons.configuration2.event.ConfigurationEvent; 030import org.apache.commons.configuration2.event.EventListener; 031import org.apache.commons.configuration2.ex.ConfigurationRuntimeException; 032import org.apache.commons.configuration2.interpol.ConfigurationInterpolator; 033import org.apache.commons.configuration2.tree.ConfigurationNodeVisitorAdapter; 034import org.apache.commons.configuration2.tree.ImmutableNode; 035import org.apache.commons.configuration2.tree.InMemoryNodeModel; 036import org.apache.commons.configuration2.tree.InMemoryNodeModelSupport; 037import org.apache.commons.configuration2.tree.NodeHandler; 038import org.apache.commons.configuration2.tree.NodeModel; 039import org.apache.commons.configuration2.tree.NodeSelector; 040import org.apache.commons.configuration2.tree.NodeTreeWalker; 041import org.apache.commons.configuration2.tree.QueryResult; 042import org.apache.commons.configuration2.tree.ReferenceNodeHandler; 043import org.apache.commons.configuration2.tree.TrackedNodeModel; 044import org.apache.commons.lang3.ObjectUtils; 045 046/** 047 * <p> 048 * A specialized hierarchical configuration implementation that is based on a 049 * structure of {@link ImmutableNode} objects. 050 * </p> 051 * 052 */ 053public class BaseHierarchicalConfiguration extends AbstractHierarchicalConfiguration<ImmutableNode> 054 implements InMemoryNodeModelSupport 055{ 056 /** A listener for reacting on changes caused by sub configurations. */ 057 private final EventListener<ConfigurationEvent> changeListener; 058 059 /** 060 * Creates a new instance of {@code BaseHierarchicalConfiguration}. 061 */ 062 public BaseHierarchicalConfiguration() 063 { 064 this((HierarchicalConfiguration<ImmutableNode>) null); 065 } 066 067 /** 068 * Creates a new instance of {@code BaseHierarchicalConfiguration} and 069 * copies all data contained in the specified configuration into the new 070 * one. 071 * 072 * @param c the configuration that is to be copied (if <b>null</b>, this 073 * constructor will behave like the standard constructor) 074 * @since 1.4 075 */ 076 public BaseHierarchicalConfiguration(final HierarchicalConfiguration<ImmutableNode> c) 077 { 078 this(createNodeModel(c)); 079 } 080 081 /** 082 * Creates a new instance of {@code BaseHierarchicalConfiguration} and 083 * initializes it with the given {@code NodeModel}. 084 * 085 * @param model the {@code NodeModel} 086 */ 087 protected BaseHierarchicalConfiguration(final NodeModel<ImmutableNode> model) 088 { 089 super(model); 090 changeListener = createChangeListener(); 091 } 092 093 /** 094 * {@inheritDoc} This implementation returns the {@code InMemoryNodeModel} 095 * used by this configuration. 096 */ 097 @Override 098 public InMemoryNodeModel getNodeModel() 099 { 100 return (InMemoryNodeModel) super.getNodeModel(); 101 } 102 103 /** 104 * Creates a new {@code Configuration} object containing all keys 105 * that start with the specified prefix. This implementation will return a 106 * {@code BaseHierarchicalConfiguration} object so that the structure of 107 * the keys will be saved. The nodes selected by the prefix (it is possible 108 * that multiple nodes are selected) are mapped to the root node of the 109 * returned configuration, i.e. their children and attributes will become 110 * children and attributes of the new root node. However, a value of the root 111 * node is only set if exactly one of the selected nodes contain a value (if 112 * multiple nodes have a value, there is simply no way to decide how these 113 * values are merged together). Note that the returned 114 * {@code Configuration} object is not connected to its source 115 * configuration: updates on the source configuration are not reflected in 116 * the subset and vice versa. The returned configuration uses the same 117 * {@code Synchronizer} as this configuration. 118 * 119 * @param prefix the prefix of the keys for the subset 120 * @return a new configuration object representing the selected subset 121 */ 122 @Override 123 public Configuration subset(final String prefix) 124 { 125 beginRead(false); 126 try 127 { 128 final List<QueryResult<ImmutableNode>> results = fetchNodeList(prefix); 129 if (results.isEmpty()) 130 { 131 return new BaseHierarchicalConfiguration(); 132 } 133 134 final BaseHierarchicalConfiguration parent = this; 135 final BaseHierarchicalConfiguration result = 136 new BaseHierarchicalConfiguration() 137 { 138 // Override interpolate to always interpolate on the parent 139 @Override 140 protected Object interpolate(final Object value) 141 { 142 return parent.interpolate(value); 143 } 144 145 @Override 146 public ConfigurationInterpolator getInterpolator() 147 { 148 return parent.getInterpolator(); 149 } 150 }; 151 result.getModel().setRootNode(createSubsetRootNode(results)); 152 153 if (result.isEmpty()) 154 { 155 return new BaseHierarchicalConfiguration(); 156 } 157 result.setSynchronizer(getSynchronizer()); 158 return result; 159 } 160 finally 161 { 162 endRead(); 163 } 164 } 165 166 /** 167 * Creates a root node for a subset configuration based on the passed in 168 * query results. This method creates a new root node and adds the children 169 * and attributes of all result nodes to it. If only a single node value is 170 * defined, it is assigned as value of the new root node. 171 * 172 * @param results the collection of query results 173 * @return the root node for the subset configuration 174 */ 175 private ImmutableNode createSubsetRootNode( 176 final Collection<QueryResult<ImmutableNode>> results) 177 { 178 final ImmutableNode.Builder builder = new ImmutableNode.Builder(); 179 Object value = null; 180 int valueCount = 0; 181 182 for (final QueryResult<ImmutableNode> result : results) 183 { 184 if (result.isAttributeResult()) 185 { 186 builder.addAttribute(result.getAttributeName(), 187 result.getAttributeValue(getModel().getNodeHandler())); 188 } 189 else 190 { 191 if (result.getNode().getValue() != null) 192 { 193 value = result.getNode().getValue(); 194 valueCount++; 195 } 196 builder.addChildren(result.getNode().getChildren()); 197 builder.addAttributes(result.getNode().getAttributes()); 198 } 199 } 200 201 if (valueCount == 1) 202 { 203 builder.value(value); 204 } 205 return builder.create(); 206 } 207 208 /** 209 * {@inheritDoc} The result of this implementation depends on the 210 * {@code supportUpdates} flag: If it is <b>false</b>, a plain 211 * {@code BaseHierarchicalConfiguration} is returned using the selected node 212 * as root node. This is suitable for read-only access to properties. 213 * Because the configuration returned in this case is not connected to the 214 * parent configuration, updates on properties made by one configuration are 215 * not reflected by the other one. A value of <b>true</b> for this parameter 216 * causes a tracked node to be created, and result is a 217 * {@link SubnodeConfiguration} based on this tracked node. This 218 * configuration is really connected to its parent, so that updated 219 * properties are visible on both. 220 * 221 * @see SubnodeConfiguration 222 * @throws ConfigurationRuntimeException if the key does not select a single 223 * node 224 */ 225 @Override 226 public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key, 227 final boolean supportUpdates) 228 { 229 beginRead(false); 230 try 231 { 232 return supportUpdates ? createConnectedSubConfiguration(key) 233 : createIndependentSubConfiguration(key); 234 } 235 finally 236 { 237 endRead(); 238 } 239 } 240 241 /** 242 * Returns the {@code InMemoryNodeModel} to be used as parent model for a 243 * new sub configuration. This method is called whenever a sub configuration 244 * is to be created. This base implementation returns the model of this 245 * configuration. Sub classes with different requirements for the parent 246 * models of sub configurations have to override it. 247 * 248 * @return the parent model for a new sub configuration 249 */ 250 protected InMemoryNodeModel getSubConfigurationParentModel() 251 { 252 return (InMemoryNodeModel) getModel(); 253 } 254 255 /** 256 * Returns the {@code NodeSelector} to be used for a sub configuration based 257 * on the passed in key. This method is called whenever a sub configuration 258 * is to be created. This base implementation returns a new 259 * {@code NodeSelector} initialized with the passed in key. Sub classes may 260 * override this method if they have a different strategy for creating a 261 * selector. 262 * 263 * @param key the key of the sub configuration 264 * @return a {@code NodeSelector} for initializing a sub configuration 265 * @since 2.0 266 */ 267 protected NodeSelector getSubConfigurationNodeSelector(final String key) 268 { 269 return new NodeSelector(key); 270 } 271 272 /** 273 * Creates a connected sub configuration based on a selector for a tracked 274 * node. 275 * 276 * @param selector the {@code NodeSelector} 277 * @param parentModelSupport the {@code InMemoryNodeModelSupport} object for 278 * the parent node model 279 * @return the newly created sub configuration 280 * @since 2.0 281 */ 282 protected SubnodeConfiguration createSubConfigurationForTrackedNode( 283 final NodeSelector selector, final InMemoryNodeModelSupport parentModelSupport) 284 { 285 final SubnodeConfiguration subConfig = 286 new SubnodeConfiguration(this, new TrackedNodeModel( 287 parentModelSupport, selector, true)); 288 initSubConfigurationForThisParent(subConfig); 289 return subConfig; 290 } 291 292 /** 293 * Initializes a {@code SubnodeConfiguration} object. This method should be 294 * called for each sub configuration created for this configuration. It 295 * ensures that the sub configuration is correctly connected to its parent 296 * instance and that update events are correctly propagated. 297 * 298 * @param subConfig the sub configuration to be initialized 299 * @since 2.0 300 */ 301 protected void initSubConfigurationForThisParent(final SubnodeConfiguration subConfig) 302 { 303 initSubConfiguration(subConfig); 304 subConfig.addEventListener(ConfigurationEvent.ANY, changeListener); 305 } 306 307 /** 308 * Creates a sub configuration from the specified key which is connected to 309 * this configuration. This implementation creates a 310 * {@link SubnodeConfiguration} with a tracked node identified by the passed 311 * in key. 312 * 313 * @param key the key of the sub configuration 314 * @return the new sub configuration 315 */ 316 private BaseHierarchicalConfiguration createConnectedSubConfiguration( 317 final String key) 318 { 319 final NodeSelector selector = getSubConfigurationNodeSelector(key); 320 getSubConfigurationParentModel().trackNode(selector, this); 321 return createSubConfigurationForTrackedNode(selector, this); 322 } 323 324 /** 325 * Creates a list of connected sub configurations based on a passed in list 326 * of node selectors. 327 * 328 * @param parentModelSupport the parent node model support object 329 * @param selectors the list of {@code NodeSelector} objects 330 * @return the list with sub configurations 331 */ 332 private List<HierarchicalConfiguration<ImmutableNode>> createConnectedSubConfigurations( 333 final InMemoryNodeModelSupport parentModelSupport, 334 final Collection<NodeSelector> selectors) 335 { 336 final List<HierarchicalConfiguration<ImmutableNode>> configs = 337 new ArrayList<>( 338 selectors.size()); 339 for (final NodeSelector selector : selectors) 340 { 341 configs.add(createSubConfigurationForTrackedNode(selector, 342 parentModelSupport)); 343 } 344 return configs; 345 } 346 347 /** 348 * Creates a sub configuration from the specified key which is independent 349 * on this configuration. This means that the sub configuration operates on 350 * a separate node model (although the nodes are initially shared). 351 * 352 * @param key the key of the sub configuration 353 * @return the new sub configuration 354 */ 355 private BaseHierarchicalConfiguration createIndependentSubConfiguration( 356 final String key) 357 { 358 final List<ImmutableNode> targetNodes = fetchFilteredNodeResults(key); 359 final int size = targetNodes.size(); 360 if (size != 1) 361 { 362 throw new ConfigurationRuntimeException( 363 "Passed in key must select exactly one node (found %,d): %s", size, key); 364 } 365 final BaseHierarchicalConfiguration sub = 366 new BaseHierarchicalConfiguration(new InMemoryNodeModel( 367 targetNodes.get(0))); 368 initSubConfiguration(sub); 369 return sub; 370 } 371 372 /** 373 * Returns an initialized sub configuration for this configuration that is 374 * based on another {@code BaseHierarchicalConfiguration}. Thus, it is 375 * independent from this configuration. 376 * 377 * @param node the root node for the sub configuration 378 * @return the initialized sub configuration 379 */ 380 private BaseHierarchicalConfiguration createIndependentSubConfigurationForNode( 381 final ImmutableNode node) 382 { 383 final BaseHierarchicalConfiguration sub = 384 new BaseHierarchicalConfiguration(new InMemoryNodeModel(node)); 385 initSubConfiguration(sub); 386 return sub; 387 } 388 389 /** 390 * Executes a query on the specified key and filters it for node results. 391 * 392 * @param key the key 393 * @return the filtered list with result nodes 394 */ 395 private List<ImmutableNode> fetchFilteredNodeResults(final String key) 396 { 397 final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); 398 return resolveNodeKey(handler.getRootNode(), key, handler); 399 } 400 401 /** 402 * {@inheritDoc} This implementation creates a {@code SubnodeConfiguration} 403 * by delegating to {@code configurationAt()}. Then an immutable wrapper 404 * is created and returned. 405 */ 406 @Override 407 public ImmutableHierarchicalConfiguration immutableConfigurationAt( 408 final String key, final boolean supportUpdates) 409 { 410 return ConfigurationUtils.unmodifiableConfiguration(configurationAt( 411 key, supportUpdates)); 412 } 413 414 /** 415 * {@inheritDoc} This is a short form for {@code configurationAt(key, 416 * <b>false</b>)}. 417 * @throws ConfigurationRuntimeException if the key does not select a single node 418 */ 419 @Override 420 public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key) 421 { 422 return configurationAt(key, false); 423 } 424 425 /** 426 * {@inheritDoc} This implementation creates a {@code SubnodeConfiguration} 427 * by delegating to {@code configurationAt()}. Then an immutable wrapper 428 * is created and returned. 429 * @throws ConfigurationRuntimeException if the key does not select a single node 430 */ 431 @Override 432 public ImmutableHierarchicalConfiguration immutableConfigurationAt( 433 final String key) 434 { 435 return ConfigurationUtils.unmodifiableConfiguration(configurationAt( 436 key)); 437 } 438 439 /** 440 * {@inheritDoc} This implementation creates sub configurations in the same 441 * way as described for {@link #configurationAt(String)}. 442 */ 443 @Override 444 public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt( 445 final String key) 446 { 447 List<ImmutableNode> nodes; 448 beginRead(false); 449 try 450 { 451 nodes = fetchFilteredNodeResults(key); 452 } 453 finally 454 { 455 endRead(); 456 } 457 458 final List<HierarchicalConfiguration<ImmutableNode>> results = 459 new ArrayList<>( 460 nodes.size()); 461 for (final ImmutableNode node : nodes) 462 { 463 final BaseHierarchicalConfiguration sub = 464 createIndependentSubConfigurationForNode(node); 465 results.add(sub); 466 } 467 468 return results; 469 } 470 471 /** 472 * {@inheritDoc} This implementation creates tracked nodes for the specified 473 * key. Then sub configurations for these nodes are created and returned. 474 */ 475 @Override 476 public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt( 477 final String key, final boolean supportUpdates) 478 { 479 if (!supportUpdates) 480 { 481 return configurationsAt(key); 482 } 483 484 InMemoryNodeModel parentModel; 485 beginRead(false); 486 try 487 { 488 parentModel = getSubConfigurationParentModel(); 489 } 490 finally 491 { 492 endRead(); 493 } 494 495 final Collection<NodeSelector> selectors = 496 parentModel.selectAndTrackNodes(key, this); 497 return createConnectedSubConfigurations(this, selectors); 498 } 499 500 /** 501 * {@inheritDoc} This implementation first delegates to 502 * {@code configurationsAt()} to create a list of 503 * {@code SubnodeConfiguration} objects. Then for each element of this list 504 * an unmodifiable wrapper is created. 505 */ 506 @Override 507 public List<ImmutableHierarchicalConfiguration> immutableConfigurationsAt( 508 final String key) 509 { 510 return toImmutable(configurationsAt(key)); 511 } 512 513 /** 514 * {@inheritDoc} This implementation resolves the node(s) selected by the 515 * given key. If not a single node is selected, an empty list is returned. 516 * Otherwise, sub configurations for each child of the node are created. 517 */ 518 @Override 519 public List<HierarchicalConfiguration<ImmutableNode>> childConfigurationsAt( 520 final String key) 521 { 522 List<ImmutableNode> nodes; 523 beginRead(false); 524 try 525 { 526 nodes = fetchFilteredNodeResults(key); 527 } 528 finally 529 { 530 endRead(); 531 } 532 533 if (nodes.size() != 1) 534 { 535 return Collections.emptyList(); 536 } 537 538 final ImmutableNode parent = nodes.get(0); 539 final List<HierarchicalConfiguration<ImmutableNode>> subs = 540 new ArrayList<>(parent 541 .getChildren().size()); 542 for (final ImmutableNode node : parent.getChildren()) 543 { 544 subs.add(createIndependentSubConfigurationForNode(node)); 545 } 546 547 return subs; 548 } 549 550 /** 551 * {@inheritDoc} This method works like 552 * {@link #childConfigurationsAt(String)}; however, depending on the value 553 * of the {@code supportUpdates} flag, connected sub configurations may be 554 * created. 555 */ 556 @Override 557 public List<HierarchicalConfiguration<ImmutableNode>> childConfigurationsAt( 558 final String key, final boolean supportUpdates) 559 { 560 if (!supportUpdates) 561 { 562 return childConfigurationsAt(key); 563 } 564 565 final InMemoryNodeModel parentModel = getSubConfigurationParentModel(); 566 return createConnectedSubConfigurations(this, 567 parentModel.trackChildNodes(key, this)); 568 } 569 570 /** 571 * {@inheritDoc} This implementation first delegates to 572 * {@code childConfigurationsAt()} to create a list of mutable child 573 * configurations. Then a list with immutable wrapper configurations is 574 * created. 575 */ 576 @Override 577 public List<ImmutableHierarchicalConfiguration> immutableChildConfigurationsAt( 578 final String key) 579 { 580 return toImmutable(childConfigurationsAt(key)); 581 } 582 583 /** 584 * This method is always called when a subnode configuration created from 585 * this configuration has been modified. This implementation transforms the 586 * received event into an event of type {@code SUBNODE_CHANGED} 587 * and notifies the registered listeners. 588 * 589 * @param event the event describing the change 590 * @since 1.5 591 */ 592 protected void subnodeConfigurationChanged(final ConfigurationEvent event) 593 { 594 fireEvent(ConfigurationEvent.SUBNODE_CHANGED, null, event, event.isBeforeUpdate()); 595 } 596 597 /** 598 * Initializes properties of a sub configuration. A sub configuration 599 * inherits some settings from its parent, e.g. the expression engine or the 600 * synchronizer. The corresponding values are copied by this method. 601 * 602 * @param sub the sub configuration to be initialized 603 */ 604 private void initSubConfiguration(final BaseHierarchicalConfiguration sub) 605 { 606 sub.setSynchronizer(getSynchronizer()); 607 sub.setExpressionEngine(getExpressionEngine()); 608 sub.setListDelimiterHandler(getListDelimiterHandler()); 609 sub.setThrowExceptionOnMissing(isThrowExceptionOnMissing()); 610 sub.getInterpolator().setParentInterpolator(getInterpolator()); 611 } 612 613 /** 614 * Creates a listener which reacts on all changes on this configuration or 615 * one of its {@code SubnodeConfiguration} instances. If such a change is 616 * detected, some updates have to be performed. 617 * 618 * @return the newly created change listener 619 */ 620 private EventListener<ConfigurationEvent> createChangeListener() 621 { 622 return event -> subnodeConfigurationChanged(event); 623 } 624 625 /** 626 * Returns a configuration with the same content as this configuration, but 627 * with all variables replaced by their actual values. This implementation 628 * is specific for hierarchical configurations. It clones the current 629 * configuration and runs a specialized visitor on the clone, which performs 630 * interpolation on the single configuration nodes. 631 * 632 * @return a configuration with all variables interpolated 633 * @since 1.5 634 */ 635 @Override 636 public Configuration interpolatedConfiguration() 637 { 638 final InterpolatedVisitor visitor = new InterpolatedVisitor(); 639 final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); 640 NodeTreeWalker.INSTANCE 641 .walkDFS(handler.getRootNode(), visitor, handler); 642 643 final BaseHierarchicalConfiguration c = 644 (BaseHierarchicalConfiguration) clone(); 645 c.getNodeModel().setRootNode(visitor.getInterpolatedRoot()); 646 return c; 647 } 648 649 /** 650 * {@inheritDoc} This implementation creates a new instance of 651 * {@link InMemoryNodeModel}, initialized with this configuration's root 652 * node. This has the effect that although the same nodes are used, the 653 * original and copied configurations are independent on each other. 654 */ 655 @Override 656 protected NodeModel<ImmutableNode> cloneNodeModel() 657 { 658 return new InMemoryNodeModel(getModel().getNodeHandler().getRootNode()); 659 } 660 661 /** 662 * Creates a list with immutable configurations from the given input list. 663 * 664 * @param subs a list with mutable configurations 665 * @return a list with corresponding immutable configurations 666 */ 667 private static List<ImmutableHierarchicalConfiguration> toImmutable( 668 final List<? extends HierarchicalConfiguration<?>> subs) 669 { 670 final List<ImmutableHierarchicalConfiguration> res = 671 new ArrayList<>(subs.size()); 672 for (final HierarchicalConfiguration<?> sub : subs) 673 { 674 res.add(ConfigurationUtils.unmodifiableConfiguration(sub)); 675 } 676 return res; 677 } 678 679 /** 680 * Creates the {@code NodeModel} for this configuration based on a passed in 681 * source configuration. This implementation creates an 682 * {@link InMemoryNodeModel}. If the passed in source configuration is 683 * defined, its root node also becomes the root node of this configuration. 684 * Otherwise, a new, empty root node is used. 685 * 686 * @param c the configuration that is to be copied 687 * @return the {@code NodeModel} for the new configuration 688 */ 689 private static NodeModel<ImmutableNode> createNodeModel( 690 final HierarchicalConfiguration<ImmutableNode> c) 691 { 692 final ImmutableNode root = c != null ? obtainRootNode(c) : null; 693 return new InMemoryNodeModel(root); 694 } 695 696 /** 697 * Obtains the root node from a configuration whose data is to be copied. It 698 * has to be ensured that the synchronizer is called correctly. 699 * 700 * @param c the configuration that is to be copied 701 * @return the root node of this configuration 702 */ 703 private static ImmutableNode obtainRootNode( 704 final HierarchicalConfiguration<ImmutableNode> c) 705 { 706 return c.getNodeModel().getNodeHandler().getRootNode(); 707 } 708 709 /** 710 * A specialized visitor base class that can be used for storing the tree of 711 * configuration nodes. The basic idea is that each node can be associated 712 * with a reference object. This reference object has a concrete meaning in 713 * a derived class, e.g. an entry in a JNDI context or an XML element. When 714 * the configuration tree is set up, the {@code load()} method is 715 * responsible for setting the reference objects. When the configuration 716 * tree is later modified, new nodes do not have a defined reference object. 717 * This visitor class processes all nodes and finds the ones without a 718 * defined reference object. For those nodes the {@code insert()} 719 * method is called, which must be defined in concrete sub classes. This 720 * method can perform all steps to integrate the new node into the original 721 * structure. 722 */ 723 protected abstract static class BuilderVisitor extends 724 ConfigurationNodeVisitorAdapter<ImmutableNode> 725 { 726 @Override 727 public void visitBeforeChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) 728 { 729 final ReferenceNodeHandler refHandler = (ReferenceNodeHandler) handler; 730 updateNode(node, refHandler); 731 insertNewChildNodes(node, refHandler); 732 } 733 734 /** 735 * Inserts a new node into the structure constructed by this builder. 736 * This method is called for each node that has been added to the 737 * configuration tree after the configuration has been loaded from its 738 * source. These new nodes have to be inserted into the original 739 * structure. The passed in nodes define the position of the node to be 740 * inserted: its parent and the siblings between to insert. 741 * 742 * @param newNode the node to be inserted 743 * @param parent the parent node 744 * @param sibling1 the sibling after which the node is to be inserted; 745 * can be <b>null</b> if the new node is going to be the first 746 * child node 747 * @param sibling2 the sibling before which the node is to be inserted; 748 * can be <b>null</b> if the new node is going to be the last 749 * child node 750 * @param refHandler the {@code ReferenceNodeHandler} 751 */ 752 protected abstract void insert(ImmutableNode newNode, 753 ImmutableNode parent, ImmutableNode sibling1, 754 ImmutableNode sibling2, ReferenceNodeHandler refHandler); 755 756 /** 757 * Updates a node that already existed in the original hierarchy. This 758 * method is called for each node that has an assigned reference object. 759 * A concrete implementation should update the reference according to 760 * the node's current value. 761 * 762 * @param node the current node to be processed 763 * @param reference the reference object for this node 764 * @param refHandler the {@code ReferenceNodeHandler} 765 */ 766 protected abstract void update(ImmutableNode node, Object reference, 767 ReferenceNodeHandler refHandler); 768 769 /** 770 * Updates the value of a node. If this node is associated with a 771 * reference object, the {@code update()} method is called. 772 * 773 * @param node the current node to be processed 774 * @param refHandler the {@code ReferenceNodeHandler} 775 */ 776 private void updateNode(final ImmutableNode node, 777 final ReferenceNodeHandler refHandler) 778 { 779 final Object reference = refHandler.getReference(node); 780 if (reference != null) 781 { 782 update(node, reference, refHandler); 783 } 784 } 785 786 /** 787 * Inserts new children that have been added to the specified node. 788 * 789 * @param node the current node to be processed 790 * @param refHandler the {@code ReferenceNodeHandler} 791 */ 792 private void insertNewChildNodes(final ImmutableNode node, 793 final ReferenceNodeHandler refHandler) 794 { 795 final Collection<ImmutableNode> subNodes = 796 new LinkedList<>(refHandler.getChildren(node)); 797 final Iterator<ImmutableNode> children = subNodes.iterator(); 798 ImmutableNode sibling1; 799 ImmutableNode nd = null; 800 801 while (children.hasNext()) 802 { 803 // find the next new node 804 do 805 { 806 sibling1 = nd; 807 nd = children.next(); 808 } while (refHandler.getReference(nd) != null 809 && children.hasNext()); 810 811 if (refHandler.getReference(nd) == null) 812 { 813 // find all following new nodes 814 final List<ImmutableNode> newNodes = 815 new LinkedList<>(); 816 newNodes.add(nd); 817 while (children.hasNext()) 818 { 819 nd = children.next(); 820 if (refHandler.getReference(nd) == null) 821 { 822 newNodes.add(nd); 823 } 824 else 825 { 826 break; 827 } 828 } 829 830 // Insert all new nodes 831 final ImmutableNode sibling2 = 832 refHandler.getReference(nd) == null ? null : nd; 833 for (final ImmutableNode insertNode : newNodes) 834 { 835 if (refHandler.getReference(insertNode) == null) 836 { 837 insert(insertNode, node, sibling1, sibling2, 838 refHandler); 839 sibling1 = insertNode; 840 } 841 } 842 } 843 } 844 } 845 } 846 847 /** 848 * A specialized visitor implementation which constructs the root node of a 849 * configuration with all variables replaced by their interpolated values. 850 */ 851 private class InterpolatedVisitor extends 852 ConfigurationNodeVisitorAdapter<ImmutableNode> 853 { 854 /** A stack for managing node builder instances. */ 855 private final List<ImmutableNode.Builder> builderStack; 856 857 /** The resulting root node. */ 858 private ImmutableNode interpolatedRoot; 859 860 /** 861 * Creates a new instance of {@code InterpolatedVisitor}. 862 */ 863 public InterpolatedVisitor() 864 { 865 builderStack = new LinkedList<>(); 866 } 867 868 /** 869 * Returns the result of this builder: the root node of the interpolated 870 * nodes hierarchy. 871 * 872 * @return the resulting root node 873 */ 874 public ImmutableNode getInterpolatedRoot() 875 { 876 return interpolatedRoot; 877 } 878 879 @Override 880 public void visitBeforeChildren(final ImmutableNode node, 881 final NodeHandler<ImmutableNode> handler) 882 { 883 if (isLeafNode(node, handler)) 884 { 885 handleLeafNode(node, handler); 886 } 887 else 888 { 889 final ImmutableNode.Builder builder = 890 new ImmutableNode.Builder(handler.getChildrenCount( 891 node, null)) 892 .name(handler.nodeName(node)) 893 .value(interpolate(handler.getValue(node))) 894 .addAttributes( 895 interpolateAttributes(node, handler)); 896 push(builder); 897 } 898 } 899 900 @Override 901 public void visitAfterChildren(final ImmutableNode node, 902 final NodeHandler<ImmutableNode> handler) 903 { 904 if (!isLeafNode(node, handler)) 905 { 906 final ImmutableNode newNode = pop().create(); 907 storeInterpolatedNode(newNode); 908 } 909 } 910 911 /** 912 * Pushes a new builder on the stack. 913 * 914 * @param builder the builder 915 */ 916 private void push(final ImmutableNode.Builder builder) 917 { 918 builderStack.add(0, builder); 919 } 920 921 /** 922 * Pops the top-level element from the stack. 923 * 924 * @return the element popped from the stack 925 */ 926 private ImmutableNode.Builder pop() 927 { 928 return builderStack.remove(0); 929 } 930 931 /** 932 * Returns the top-level element from the stack without removing it. 933 * 934 * @return the top-level element from the stack 935 */ 936 private ImmutableNode.Builder peek() 937 { 938 return builderStack.get(0); 939 } 940 941 /** 942 * Returns a flag whether the given node is a leaf. This is the case if 943 * it does not have children. 944 * 945 * @param node the node in question 946 * @param handler the {@code NodeHandler} 947 * @return a flag whether this is a leaf node 948 */ 949 private boolean isLeafNode(final ImmutableNode node, 950 final NodeHandler<ImmutableNode> handler) 951 { 952 return handler.getChildren(node).isEmpty(); 953 } 954 955 /** 956 * Handles interpolation for a node with no children. If interpolation 957 * does not change this node, it is copied as is to the resulting 958 * structure. Otherwise, a new node is created with the interpolated 959 * values. 960 * 961 * @param node the current node to be processed 962 * @param handler the {@code NodeHandler} 963 */ 964 private void handleLeafNode(final ImmutableNode node, 965 final NodeHandler<ImmutableNode> handler) 966 { 967 final Object value = interpolate(node.getValue()); 968 final Map<String, Object> interpolatedAttributes = 969 new HashMap<>(); 970 final boolean attributeChanged = 971 interpolateAttributes(node, handler, interpolatedAttributes); 972 final ImmutableNode newNode = 973 valueChanged(value, handler.getValue(node)) || attributeChanged ? new ImmutableNode.Builder() 974 .name(handler.nodeName(node)).value(value) 975 .addAttributes(interpolatedAttributes).create() 976 : node; 977 storeInterpolatedNode(newNode); 978 } 979 980 /** 981 * Stores a processed node. Per default, the node is added to the 982 * current builder on the stack. If no such builder exists, this is the 983 * result node. 984 * 985 * @param node the node to be stored 986 */ 987 private void storeInterpolatedNode(final ImmutableNode node) 988 { 989 if (builderStack.isEmpty()) 990 { 991 interpolatedRoot = node; 992 } 993 else 994 { 995 peek().addChild(node); 996 } 997 } 998 999 /** 1000 * Populates a map with interpolated attributes of the passed in node. 1001 * 1002 * @param node the current node to be processed 1003 * @param handler the {@code NodeHandler} 1004 * @param interpolatedAttributes a map for storing the results 1005 * @return a flag whether an attribute value was changed by 1006 * interpolation 1007 */ 1008 private boolean interpolateAttributes(final ImmutableNode node, 1009 final NodeHandler<ImmutableNode> handler, 1010 final Map<String, Object> interpolatedAttributes) 1011 { 1012 boolean attributeChanged = false; 1013 for (final String attr : handler.getAttributes(node)) 1014 { 1015 final Object attrValue = 1016 interpolate(handler.getAttributeValue(node, attr)); 1017 if (valueChanged(attrValue, 1018 handler.getAttributeValue(node, attr))) 1019 { 1020 attributeChanged = true; 1021 } 1022 interpolatedAttributes.put(attr, attrValue); 1023 } 1024 return attributeChanged; 1025 } 1026 1027 /** 1028 * Returns a map with interpolated attributes of the passed in node. 1029 * 1030 * @param node the current node to be processed 1031 * @param handler the {@code NodeHandler} 1032 * @return the map with interpolated attributes 1033 */ 1034 private Map<String, Object> interpolateAttributes(final ImmutableNode node, 1035 final NodeHandler<ImmutableNode> handler) 1036 { 1037 final Map<String, Object> attributes = new HashMap<>(); 1038 interpolateAttributes(node, handler, attributes); 1039 return attributes; 1040 } 1041 1042 /** 1043 * Tests whether a value is changed because of interpolation. 1044 * 1045 * @param interpolatedValue the interpolated value 1046 * @param value the original value 1047 * @return a flag whether the value was changed 1048 */ 1049 private boolean valueChanged(final Object interpolatedValue, final Object value) 1050 { 1051 return ObjectUtils.notEqual(interpolatedValue, value); 1052 } 1053 } 1054}