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 * @version $Id: BaseHierarchicalConfiguration.java 1842194 2018-09-27 22:24:23Z ggregory $ 053 */ 054public class BaseHierarchicalConfiguration extends AbstractHierarchicalConfiguration<ImmutableNode> 055 implements InMemoryNodeModelSupport 056{ 057 /** A listener for reacting on changes caused by sub configurations. */ 058 private final EventListener<ConfigurationEvent> changeListener; 059 060 /** 061 * Creates a new instance of {@code BaseHierarchicalConfiguration}. 062 */ 063 public BaseHierarchicalConfiguration() 064 { 065 this((HierarchicalConfiguration<ImmutableNode>) null); 066 } 067 068 /** 069 * Creates a new instance of {@code BaseHierarchicalConfiguration} and 070 * copies all data contained in the specified configuration into the new 071 * one. 072 * 073 * @param c the configuration that is to be copied (if <b>null</b>, this 074 * constructor will behave like the standard constructor) 075 * @since 1.4 076 */ 077 public BaseHierarchicalConfiguration(final HierarchicalConfiguration<ImmutableNode> c) 078 { 079 this(createNodeModel(c)); 080 } 081 082 /** 083 * Creates a new instance of {@code BaseHierarchicalConfiguration} and 084 * initializes it with the given {@code NodeModel}. 085 * 086 * @param model the {@code NodeModel} 087 */ 088 protected BaseHierarchicalConfiguration(final NodeModel<ImmutableNode> model) 089 { 090 super(model); 091 changeListener = createChangeListener(); 092 } 093 094 /** 095 * {@inheritDoc} This implementation returns the {@code InMemoryNodeModel} 096 * used by this configuration. 097 */ 098 @Override 099 public InMemoryNodeModel getNodeModel() 100 { 101 return (InMemoryNodeModel) super.getNodeModel(); 102 } 103 104 /** 105 * Creates a new {@code Configuration} object containing all keys 106 * that start with the specified prefix. This implementation will return a 107 * {@code BaseHierarchicalConfiguration} object so that the structure of 108 * the keys will be saved. The nodes selected by the prefix (it is possible 109 * that multiple nodes are selected) are mapped to the root node of the 110 * returned configuration, i.e. their children and attributes will become 111 * children and attributes of the new root node. However, a value of the root 112 * node is only set if exactly one of the selected nodes contain a value (if 113 * multiple nodes have a value, there is simply no way to decide how these 114 * values are merged together). Note that the returned 115 * {@code Configuration} object is not connected to its source 116 * configuration: updates on the source configuration are not reflected in 117 * the subset and vice versa. The returned configuration uses the same 118 * {@code Synchronizer} as this configuration. 119 * 120 * @param prefix the prefix of the keys for the subset 121 * @return a new configuration object representing the selected subset 122 */ 123 @Override 124 public Configuration subset(final String prefix) 125 { 126 beginRead(false); 127 try 128 { 129 final List<QueryResult<ImmutableNode>> results = fetchNodeList(prefix); 130 if (results.isEmpty()) 131 { 132 return new BaseHierarchicalConfiguration(); 133 } 134 135 final BaseHierarchicalConfiguration parent = this; 136 final BaseHierarchicalConfiguration result = 137 new BaseHierarchicalConfiguration() 138 { 139 // Override interpolate to always interpolate on the parent 140 @Override 141 protected Object interpolate(final Object value) 142 { 143 return parent.interpolate(value); 144 } 145 146 @Override 147 public ConfigurationInterpolator getInterpolator() 148 { 149 return parent.getInterpolator(); 150 } 151 }; 152 result.getModel().setRootNode(createSubsetRootNode(results)); 153 154 if (result.isEmpty()) 155 { 156 return new BaseHierarchicalConfiguration(); 157 } 158 result.setSynchronizer(getSynchronizer()); 159 return result; 160 } 161 finally 162 { 163 endRead(); 164 } 165 } 166 167 /** 168 * Creates a root node for a subset configuration based on the passed in 169 * query results. This method creates a new root node and adds the children 170 * and attributes of all result nodes to it. If only a single node value is 171 * defined, it is assigned as value of the new root node. 172 * 173 * @param results the collection of query results 174 * @return the root node for the subset configuration 175 */ 176 private ImmutableNode createSubsetRootNode( 177 final Collection<QueryResult<ImmutableNode>> results) 178 { 179 final ImmutableNode.Builder builder = new ImmutableNode.Builder(); 180 Object value = null; 181 int valueCount = 0; 182 183 for (final QueryResult<ImmutableNode> result : results) 184 { 185 if (result.isAttributeResult()) 186 { 187 builder.addAttribute(result.getAttributeName(), 188 result.getAttributeValue(getModel().getNodeHandler())); 189 } 190 else 191 { 192 if (result.getNode().getValue() != null) 193 { 194 value = result.getNode().getValue(); 195 valueCount++; 196 } 197 builder.addChildren(result.getNode().getChildren()); 198 builder.addAttributes(result.getNode().getAttributes()); 199 } 200 } 201 202 if (valueCount == 1) 203 { 204 builder.value(value); 205 } 206 return builder.create(); 207 } 208 209 /** 210 * {@inheritDoc} The result of this implementation depends on the 211 * {@code supportUpdates} flag: If it is <b>false</b>, a plain 212 * {@code BaseHierarchicalConfiguration} is returned using the selected node 213 * as root node. This is suitable for read-only access to properties. 214 * Because the configuration returned in this case is not connected to the 215 * parent configuration, updates on properties made by one configuration are 216 * not reflected by the other one. A value of <b>true</b> for this parameter 217 * causes a tracked node to be created, and result is a 218 * {@link SubnodeConfiguration} based on this tracked node. This 219 * configuration is really connected to its parent, so that updated 220 * properties are visible on both. 221 * 222 * @see SubnodeConfiguration 223 * @throws ConfigurationRuntimeException if the key does not select a single 224 * node 225 */ 226 @Override 227 public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key, 228 final boolean supportUpdates) 229 { 230 beginRead(false); 231 try 232 { 233 return supportUpdates ? createConnectedSubConfiguration(key) 234 : createIndependentSubConfiguration(key); 235 } 236 finally 237 { 238 endRead(); 239 } 240 } 241 242 /** 243 * Returns the {@code InMemoryNodeModel} to be used as parent model for a 244 * new sub configuration. This method is called whenever a sub configuration 245 * is to be created. This base implementation returns the model of this 246 * configuration. Sub classes with different requirements for the parent 247 * models of sub configurations have to override it. 248 * 249 * @return the parent model for a new sub configuration 250 */ 251 protected InMemoryNodeModel getSubConfigurationParentModel() 252 { 253 return (InMemoryNodeModel) getModel(); 254 } 255 256 /** 257 * Returns the {@code NodeSelector} to be used for a sub configuration based 258 * on the passed in key. This method is called whenever a sub configuration 259 * is to be created. This base implementation returns a new 260 * {@code NodeSelector} initialized with the passed in key. Sub classes may 261 * override this method if they have a different strategy for creating a 262 * selector. 263 * 264 * @param key the key of the sub configuration 265 * @return a {@code NodeSelector} for initializing a sub configuration 266 * @since 2.0 267 */ 268 protected NodeSelector getSubConfigurationNodeSelector(final String key) 269 { 270 return new NodeSelector(key); 271 } 272 273 /** 274 * Creates a connected sub configuration based on a selector for a tracked 275 * node. 276 * 277 * @param selector the {@code NodeSelector} 278 * @param parentModelSupport the {@code InMemoryNodeModelSupport} object for 279 * the parent node model 280 * @return the newly created sub configuration 281 * @since 2.0 282 */ 283 protected SubnodeConfiguration createSubConfigurationForTrackedNode( 284 final NodeSelector selector, final InMemoryNodeModelSupport parentModelSupport) 285 { 286 final SubnodeConfiguration subConfig = 287 new SubnodeConfiguration(this, new TrackedNodeModel( 288 parentModelSupport, selector, true)); 289 initSubConfigurationForThisParent(subConfig); 290 return subConfig; 291 } 292 293 /** 294 * Initializes a {@code SubnodeConfiguration} object. This method should be 295 * called for each sub configuration created for this configuration. It 296 * ensures that the sub configuration is correctly connected to its parent 297 * instance and that update events are correctly propagated. 298 * 299 * @param subConfig the sub configuration to be initialized 300 * @since 2.0 301 */ 302 protected void initSubConfigurationForThisParent(final SubnodeConfiguration subConfig) 303 { 304 initSubConfiguration(subConfig); 305 subConfig.addEventListener(ConfigurationEvent.ANY, changeListener); 306 } 307 308 /** 309 * Creates a sub configuration from the specified key which is connected to 310 * this configuration. This implementation creates a 311 * {@link SubnodeConfiguration} with a tracked node identified by the passed 312 * in key. 313 * 314 * @param key the key of the sub configuration 315 * @return the new sub configuration 316 */ 317 private BaseHierarchicalConfiguration createConnectedSubConfiguration( 318 final String key) 319 { 320 final NodeSelector selector = getSubConfigurationNodeSelector(key); 321 getSubConfigurationParentModel().trackNode(selector, this); 322 return createSubConfigurationForTrackedNode(selector, this); 323 } 324 325 /** 326 * Creates a list of connected sub configurations based on a passed in list 327 * of node selectors. 328 * 329 * @param parentModelSupport the parent node model support object 330 * @param selectors the list of {@code NodeSelector} objects 331 * @return the list with sub configurations 332 */ 333 private List<HierarchicalConfiguration<ImmutableNode>> createConnectedSubConfigurations( 334 final InMemoryNodeModelSupport parentModelSupport, 335 final Collection<NodeSelector> selectors) 336 { 337 final List<HierarchicalConfiguration<ImmutableNode>> configs = 338 new ArrayList<>( 339 selectors.size()); 340 for (final NodeSelector selector : selectors) 341 { 342 configs.add(createSubConfigurationForTrackedNode(selector, 343 parentModelSupport)); 344 } 345 return configs; 346 } 347 348 /** 349 * Creates a sub configuration from the specified key which is independent 350 * on this configuration. This means that the sub configuration operates on 351 * a separate node model (although the nodes are initially shared). 352 * 353 * @param key the key of the sub configuration 354 * @return the new sub configuration 355 */ 356 private BaseHierarchicalConfiguration createIndependentSubConfiguration( 357 final String key) 358 { 359 final List<ImmutableNode> targetNodes = fetchFilteredNodeResults(key); 360 final int size = targetNodes.size(); 361 if (size != 1) 362 { 363 throw new ConfigurationRuntimeException( 364 "Passed in key must select exactly one node (found %,d): %s", size, key); 365 } 366 final BaseHierarchicalConfiguration sub = 367 new BaseHierarchicalConfiguration(new InMemoryNodeModel( 368 targetNodes.get(0))); 369 initSubConfiguration(sub); 370 return sub; 371 } 372 373 /** 374 * Returns an initialized sub configuration for this configuration that is 375 * based on another {@code BaseHierarchicalConfiguration}. Thus, it is 376 * independent from this configuration. 377 * 378 * @param node the root node for the sub configuration 379 * @return the initialized sub configuration 380 */ 381 private BaseHierarchicalConfiguration createIndependentSubConfigurationForNode( 382 final ImmutableNode node) 383 { 384 final BaseHierarchicalConfiguration sub = 385 new BaseHierarchicalConfiguration(new InMemoryNodeModel(node)); 386 initSubConfiguration(sub); 387 return sub; 388 } 389 390 /** 391 * Executes a query on the specified key and filters it for node results. 392 * 393 * @param key the key 394 * @return the filtered list with result nodes 395 */ 396 private List<ImmutableNode> fetchFilteredNodeResults(final String key) 397 { 398 final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); 399 return resolveNodeKey(handler.getRootNode(), key, handler); 400 } 401 402 /** 403 * {@inheritDoc} This implementation creates a {@code SubnodeConfiguration} 404 * by delegating to {@code configurationAt()}. Then an immutable wrapper 405 * is created and returned. 406 */ 407 @Override 408 public ImmutableHierarchicalConfiguration immutableConfigurationAt( 409 final String key, final boolean supportUpdates) 410 { 411 return ConfigurationUtils.unmodifiableConfiguration(configurationAt( 412 key, supportUpdates)); 413 } 414 415 /** 416 * {@inheritDoc} This is a short form for {@code configurationAt(key, 417 * <b>false</b>)}. 418 * @throws ConfigurationRuntimeException if the key does not select a single node 419 */ 420 @Override 421 public HierarchicalConfiguration<ImmutableNode> configurationAt(final String key) 422 { 423 return configurationAt(key, false); 424 } 425 426 /** 427 * {@inheritDoc} This implementation creates a {@code SubnodeConfiguration} 428 * by delegating to {@code configurationAt()}. Then an immutable wrapper 429 * is created and returned. 430 * @throws ConfigurationRuntimeException if the key does not select a single node 431 */ 432 @Override 433 public ImmutableHierarchicalConfiguration immutableConfigurationAt( 434 final String key) 435 { 436 return ConfigurationUtils.unmodifiableConfiguration(configurationAt( 437 key)); 438 } 439 440 /** 441 * {@inheritDoc} This implementation creates sub configurations in the same 442 * way as described for {@link #configurationAt(String)}. 443 */ 444 @Override 445 public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt( 446 final String key) 447 { 448 List<ImmutableNode> nodes; 449 beginRead(false); 450 try 451 { 452 nodes = fetchFilteredNodeResults(key); 453 } 454 finally 455 { 456 endRead(); 457 } 458 459 final List<HierarchicalConfiguration<ImmutableNode>> results = 460 new ArrayList<>( 461 nodes.size()); 462 for (final ImmutableNode node : nodes) 463 { 464 final BaseHierarchicalConfiguration sub = 465 createIndependentSubConfigurationForNode(node); 466 results.add(sub); 467 } 468 469 return results; 470 } 471 472 /** 473 * {@inheritDoc} This implementation creates tracked nodes for the specified 474 * key. Then sub configurations for these nodes are created and returned. 475 */ 476 @Override 477 public List<HierarchicalConfiguration<ImmutableNode>> configurationsAt( 478 final String key, final boolean supportUpdates) 479 { 480 if (!supportUpdates) 481 { 482 return configurationsAt(key); 483 } 484 485 InMemoryNodeModel parentModel; 486 beginRead(false); 487 try 488 { 489 parentModel = getSubConfigurationParentModel(); 490 } 491 finally 492 { 493 endRead(); 494 } 495 496 final Collection<NodeSelector> selectors = 497 parentModel.selectAndTrackNodes(key, this); 498 return createConnectedSubConfigurations(this, selectors); 499 } 500 501 /** 502 * {@inheritDoc} This implementation first delegates to 503 * {@code configurationsAt()} to create a list of 504 * {@code SubnodeConfiguration} objects. Then for each element of this list 505 * an unmodifiable wrapper is created. 506 */ 507 @Override 508 public List<ImmutableHierarchicalConfiguration> immutableConfigurationsAt( 509 final String key) 510 { 511 return toImmutable(configurationsAt(key)); 512 } 513 514 /** 515 * {@inheritDoc} This implementation resolves the node(s) selected by the 516 * given key. If not a single node is selected, an empty list is returned. 517 * Otherwise, sub configurations for each child of the node are created. 518 */ 519 @Override 520 public List<HierarchicalConfiguration<ImmutableNode>> childConfigurationsAt( 521 final String key) 522 { 523 List<ImmutableNode> nodes; 524 beginRead(false); 525 try 526 { 527 nodes = fetchFilteredNodeResults(key); 528 } 529 finally 530 { 531 endRead(); 532 } 533 534 if (nodes.size() != 1) 535 { 536 return Collections.emptyList(); 537 } 538 539 final ImmutableNode parent = nodes.get(0); 540 final List<HierarchicalConfiguration<ImmutableNode>> subs = 541 new ArrayList<>(parent 542 .getChildren().size()); 543 for (final ImmutableNode node : parent.getChildren()) 544 { 545 subs.add(createIndependentSubConfigurationForNode(node)); 546 } 547 548 return subs; 549 } 550 551 /** 552 * {@inheritDoc} This method works like 553 * {@link #childConfigurationsAt(String)}; however, depending on the value 554 * of the {@code supportUpdates} flag, connected sub configurations may be 555 * created. 556 */ 557 @Override 558 public List<HierarchicalConfiguration<ImmutableNode>> childConfigurationsAt( 559 final String key, final boolean supportUpdates) 560 { 561 if (!supportUpdates) 562 { 563 return childConfigurationsAt(key); 564 } 565 566 final InMemoryNodeModel parentModel = getSubConfigurationParentModel(); 567 return createConnectedSubConfigurations(this, 568 parentModel.trackChildNodes(key, this)); 569 } 570 571 /** 572 * {@inheritDoc} This implementation first delegates to 573 * {@code childConfigurationsAt()} to create a list of mutable child 574 * configurations. Then a list with immutable wrapper configurations is 575 * created. 576 */ 577 @Override 578 public List<ImmutableHierarchicalConfiguration> immutableChildConfigurationsAt( 579 final String key) 580 { 581 return toImmutable(childConfigurationsAt(key)); 582 } 583 584 /** 585 * This method is always called when a subnode configuration created from 586 * this configuration has been modified. This implementation transforms the 587 * received event into an event of type {@code SUBNODE_CHANGED} 588 * and notifies the registered listeners. 589 * 590 * @param event the event describing the change 591 * @since 1.5 592 */ 593 protected void subnodeConfigurationChanged(final ConfigurationEvent event) 594 { 595 fireEvent(ConfigurationEvent.SUBNODE_CHANGED, null, event, event.isBeforeUpdate()); 596 } 597 598 /** 599 * Initializes properties of a sub configuration. A sub configuration 600 * inherits some settings from its parent, e.g. the expression engine or the 601 * synchronizer. The corresponding values are copied by this method. 602 * 603 * @param sub the sub configuration to be initialized 604 */ 605 private void initSubConfiguration(final BaseHierarchicalConfiguration sub) 606 { 607 sub.setSynchronizer(getSynchronizer()); 608 sub.setExpressionEngine(getExpressionEngine()); 609 sub.setListDelimiterHandler(getListDelimiterHandler()); 610 sub.setThrowExceptionOnMissing(isThrowExceptionOnMissing()); 611 sub.getInterpolator().setParentInterpolator(getInterpolator()); 612 } 613 614 /** 615 * Creates a listener which reacts on all changes on this configuration or 616 * one of its {@code SubnodeConfiguration} instances. If such a change is 617 * detected, some updates have to be performed. 618 * 619 * @return the newly created change listener 620 */ 621 private EventListener<ConfigurationEvent> createChangeListener() 622 { 623 return new EventListener<ConfigurationEvent>() 624 { 625 @Override 626 public void onEvent(final ConfigurationEvent event) 627 { 628 subnodeConfigurationChanged(event); 629 } 630 }; 631 } 632 633 /** 634 * Returns a configuration with the same content as this configuration, but 635 * with all variables replaced by their actual values. This implementation 636 * is specific for hierarchical configurations. It clones the current 637 * configuration and runs a specialized visitor on the clone, which performs 638 * interpolation on the single configuration nodes. 639 * 640 * @return a configuration with all variables interpolated 641 * @since 1.5 642 */ 643 @Override 644 public Configuration interpolatedConfiguration() 645 { 646 final InterpolatedVisitor visitor = new InterpolatedVisitor(); 647 final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); 648 NodeTreeWalker.INSTANCE 649 .walkDFS(handler.getRootNode(), visitor, handler); 650 651 final BaseHierarchicalConfiguration c = 652 (BaseHierarchicalConfiguration) clone(); 653 c.getNodeModel().setRootNode(visitor.getInterpolatedRoot()); 654 return c; 655 } 656 657 /** 658 * {@inheritDoc} This implementation creates a new instance of 659 * {@link InMemoryNodeModel}, initialized with this configuration's root 660 * node. This has the effect that although the same nodes are used, the 661 * original and copied configurations are independent on each other. 662 */ 663 @Override 664 protected NodeModel<ImmutableNode> cloneNodeModel() 665 { 666 return new InMemoryNodeModel(getModel().getNodeHandler().getRootNode()); 667 } 668 669 /** 670 * Creates a list with immutable configurations from the given input list. 671 * 672 * @param subs a list with mutable configurations 673 * @return a list with corresponding immutable configurations 674 */ 675 private static List<ImmutableHierarchicalConfiguration> toImmutable( 676 final List<? extends HierarchicalConfiguration<?>> subs) 677 { 678 final List<ImmutableHierarchicalConfiguration> res = 679 new ArrayList<>(subs.size()); 680 for (final HierarchicalConfiguration<?> sub : subs) 681 { 682 res.add(ConfigurationUtils.unmodifiableConfiguration(sub)); 683 } 684 return res; 685 } 686 687 /** 688 * Creates the {@code NodeModel} for this configuration based on a passed in 689 * source configuration. This implementation creates an 690 * {@link InMemoryNodeModel}. If the passed in source configuration is 691 * defined, its root node also becomes the root node of this configuration. 692 * Otherwise, a new, empty root node is used. 693 * 694 * @param c the configuration that is to be copied 695 * @return the {@code NodeModel} for the new configuration 696 */ 697 private static NodeModel<ImmutableNode> createNodeModel( 698 final HierarchicalConfiguration<ImmutableNode> c) 699 { 700 final ImmutableNode root = (c != null) ? obtainRootNode(c) : null; 701 return new InMemoryNodeModel(root); 702 } 703 704 /** 705 * Obtains the root node from a configuration whose data is to be copied. It 706 * has to be ensured that the synchronizer is called correctly. 707 * 708 * @param c the configuration that is to be copied 709 * @return the root node of this configuration 710 */ 711 private static ImmutableNode obtainRootNode( 712 final HierarchicalConfiguration<ImmutableNode> c) 713 { 714 return c.getNodeModel().getNodeHandler().getRootNode(); 715 } 716 717 /** 718 * A specialized visitor base class that can be used for storing the tree of 719 * configuration nodes. The basic idea is that each node can be associated 720 * with a reference object. This reference object has a concrete meaning in 721 * a derived class, e.g. an entry in a JNDI context or an XML element. When 722 * the configuration tree is set up, the {@code load()} method is 723 * responsible for setting the reference objects. When the configuration 724 * tree is later modified, new nodes do not have a defined reference object. 725 * This visitor class processes all nodes and finds the ones without a 726 * defined reference object. For those nodes the {@code insert()} 727 * method is called, which must be defined in concrete sub classes. This 728 * method can perform all steps to integrate the new node into the original 729 * structure. 730 */ 731 protected abstract static class BuilderVisitor extends 732 ConfigurationNodeVisitorAdapter<ImmutableNode> 733 { 734 @Override 735 public void visitBeforeChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) 736 { 737 final ReferenceNodeHandler refHandler = (ReferenceNodeHandler) handler; 738 updateNode(node, refHandler); 739 insertNewChildNodes(node, refHandler); 740 } 741 742 /** 743 * Inserts a new node into the structure constructed by this builder. 744 * This method is called for each node that has been added to the 745 * configuration tree after the configuration has been loaded from its 746 * source. These new nodes have to be inserted into the original 747 * structure. The passed in nodes define the position of the node to be 748 * inserted: its parent and the siblings between to insert. 749 * 750 * @param newNode the node to be inserted 751 * @param parent the parent node 752 * @param sibling1 the sibling after which the node is to be inserted; 753 * can be <b>null</b> if the new node is going to be the first 754 * child node 755 * @param sibling2 the sibling before which the node is to be inserted; 756 * can be <b>null</b> if the new node is going to be the last 757 * child node 758 * @param refHandler the {@code ReferenceNodeHandler} 759 */ 760 protected abstract void insert(ImmutableNode newNode, 761 ImmutableNode parent, ImmutableNode sibling1, 762 ImmutableNode sibling2, ReferenceNodeHandler refHandler); 763 764 /** 765 * Updates a node that already existed in the original hierarchy. This 766 * method is called for each node that has an assigned reference object. 767 * A concrete implementation should update the reference according to 768 * the node's current value. 769 * 770 * @param node the current node to be processed 771 * @param reference the reference object for this node 772 * @param refHandler the {@code ReferenceNodeHandler} 773 */ 774 protected abstract void update(ImmutableNode node, Object reference, 775 ReferenceNodeHandler refHandler); 776 777 /** 778 * Updates the value of a node. If this node is associated with a 779 * reference object, the {@code update()} method is called. 780 * 781 * @param node the current node to be processed 782 * @param refHandler the {@code ReferenceNodeHandler} 783 */ 784 private void updateNode(final ImmutableNode node, 785 final ReferenceNodeHandler refHandler) 786 { 787 final Object reference = refHandler.getReference(node); 788 if (reference != null) 789 { 790 update(node, reference, refHandler); 791 } 792 } 793 794 /** 795 * Inserts new children that have been added to the specified node. 796 * 797 * @param node the current node to be processed 798 * @param refHandler the {@code ReferenceNodeHandler} 799 */ 800 private void insertNewChildNodes(final ImmutableNode node, 801 final ReferenceNodeHandler refHandler) 802 { 803 final Collection<ImmutableNode> subNodes = 804 new LinkedList<>(refHandler.getChildren(node)); 805 final Iterator<ImmutableNode> children = subNodes.iterator(); 806 ImmutableNode sibling1; 807 ImmutableNode nd = null; 808 809 while (children.hasNext()) 810 { 811 // find the next new node 812 do 813 { 814 sibling1 = nd; 815 nd = children.next(); 816 } while (refHandler.getReference(nd) != null 817 && children.hasNext()); 818 819 if (refHandler.getReference(nd) == null) 820 { 821 // find all following new nodes 822 final List<ImmutableNode> newNodes = 823 new LinkedList<>(); 824 newNodes.add(nd); 825 while (children.hasNext()) 826 { 827 nd = children.next(); 828 if (refHandler.getReference(nd) == null) 829 { 830 newNodes.add(nd); 831 } 832 else 833 { 834 break; 835 } 836 } 837 838 // Insert all new nodes 839 final ImmutableNode sibling2 = 840 (refHandler.getReference(nd) == null) ? null : nd; 841 for (final ImmutableNode insertNode : newNodes) 842 { 843 if (refHandler.getReference(insertNode) == null) 844 { 845 insert(insertNode, node, sibling1, sibling2, 846 refHandler); 847 sibling1 = insertNode; 848 } 849 } 850 } 851 } 852 } 853 } 854 855 /** 856 * A specialized visitor implementation which constructs the root node of a 857 * configuration with all variables replaced by their interpolated values. 858 */ 859 private class InterpolatedVisitor extends 860 ConfigurationNodeVisitorAdapter<ImmutableNode> 861 { 862 /** A stack for managing node builder instances. */ 863 private final List<ImmutableNode.Builder> builderStack; 864 865 /** The resulting root node. */ 866 private ImmutableNode interpolatedRoot; 867 868 /** 869 * Creates a new instance of {@code InterpolatedVisitor}. 870 */ 871 public InterpolatedVisitor() 872 { 873 builderStack = new LinkedList<>(); 874 } 875 876 /** 877 * Returns the result of this builder: the root node of the interpolated 878 * nodes hierarchy. 879 * 880 * @return the resulting root node 881 */ 882 public ImmutableNode getInterpolatedRoot() 883 { 884 return interpolatedRoot; 885 } 886 887 @Override 888 public void visitBeforeChildren(final ImmutableNode node, 889 final NodeHandler<ImmutableNode> handler) 890 { 891 if (isLeafNode(node, handler)) 892 { 893 handleLeafNode(node, handler); 894 } 895 else 896 { 897 final ImmutableNode.Builder builder = 898 new ImmutableNode.Builder(handler.getChildrenCount( 899 node, null)) 900 .name(handler.nodeName(node)) 901 .value(interpolate(handler.getValue(node))) 902 .addAttributes( 903 interpolateAttributes(node, handler)); 904 push(builder); 905 } 906 } 907 908 @Override 909 public void visitAfterChildren(final ImmutableNode node, 910 final NodeHandler<ImmutableNode> handler) 911 { 912 if (!isLeafNode(node, handler)) 913 { 914 final ImmutableNode newNode = pop().create(); 915 storeInterpolatedNode(newNode); 916 } 917 } 918 919 /** 920 * Pushes a new builder on the stack. 921 * 922 * @param builder the builder 923 */ 924 private void push(final ImmutableNode.Builder builder) 925 { 926 builderStack.add(0, builder); 927 } 928 929 /** 930 * Pops the top-level element from the stack. 931 * 932 * @return the element popped from the stack 933 */ 934 private ImmutableNode.Builder pop() 935 { 936 return builderStack.remove(0); 937 } 938 939 /** 940 * Returns the top-level element from the stack without removing it. 941 * 942 * @return the top-level element from the stack 943 */ 944 private ImmutableNode.Builder peek() 945 { 946 return builderStack.get(0); 947 } 948 949 /** 950 * Returns a flag whether the given node is a leaf. This is the case if 951 * it does not have children. 952 * 953 * @param node the node in question 954 * @param handler the {@code NodeHandler} 955 * @return a flag whether this is a leaf node 956 */ 957 private boolean isLeafNode(final ImmutableNode node, 958 final NodeHandler<ImmutableNode> handler) 959 { 960 return handler.getChildren(node).isEmpty(); 961 } 962 963 /** 964 * Handles interpolation for a node with no children. If interpolation 965 * does not change this node, it is copied as is to the resulting 966 * structure. Otherwise, a new node is created with the interpolated 967 * values. 968 * 969 * @param node the current node to be processed 970 * @param handler the {@code NodeHandler} 971 */ 972 private void handleLeafNode(final ImmutableNode node, 973 final NodeHandler<ImmutableNode> handler) 974 { 975 final Object value = interpolate(node.getValue()); 976 final Map<String, Object> interpolatedAttributes = 977 new HashMap<>(); 978 final boolean attributeChanged = 979 interpolateAttributes(node, handler, interpolatedAttributes); 980 final ImmutableNode newNode = 981 (valueChanged(value, handler.getValue(node)) || attributeChanged) ? new ImmutableNode.Builder() 982 .name(handler.nodeName(node)).value(value) 983 .addAttributes(interpolatedAttributes).create() 984 : node; 985 storeInterpolatedNode(newNode); 986 } 987 988 /** 989 * Stores a processed node. Per default, the node is added to the 990 * current builder on the stack. If no such builder exists, this is the 991 * result node. 992 * 993 * @param node the node to be stored 994 */ 995 private void storeInterpolatedNode(final ImmutableNode node) 996 { 997 if (builderStack.isEmpty()) 998 { 999 interpolatedRoot = node; 1000 } 1001 else 1002 { 1003 peek().addChild(node); 1004 } 1005 } 1006 1007 /** 1008 * Populates a map with interpolated attributes of the passed in node. 1009 * 1010 * @param node the current node to be processed 1011 * @param handler the {@code NodeHandler} 1012 * @param interpolatedAttributes a map for storing the results 1013 * @return a flag whether an attribute value was changed by 1014 * interpolation 1015 */ 1016 private boolean interpolateAttributes(final ImmutableNode node, 1017 final NodeHandler<ImmutableNode> handler, 1018 final Map<String, Object> interpolatedAttributes) 1019 { 1020 boolean attributeChanged = false; 1021 for (final String attr : handler.getAttributes(node)) 1022 { 1023 final Object attrValue = 1024 interpolate(handler.getAttributeValue(node, attr)); 1025 if (valueChanged(attrValue, 1026 handler.getAttributeValue(node, attr))) 1027 { 1028 attributeChanged = true; 1029 } 1030 interpolatedAttributes.put(attr, attrValue); 1031 } 1032 return attributeChanged; 1033 } 1034 1035 /** 1036 * Returns a map with interpolated attributes of the passed in node. 1037 * 1038 * @param node the current node to be processed 1039 * @param handler the {@code NodeHandler} 1040 * @return the map with interpolated attributes 1041 */ 1042 private Map<String, Object> interpolateAttributes(final ImmutableNode node, 1043 final NodeHandler<ImmutableNode> handler) 1044 { 1045 final Map<String, Object> attributes = new HashMap<>(); 1046 interpolateAttributes(node, handler, attributes); 1047 return attributes; 1048 } 1049 1050 /** 1051 * Tests whether a value is changed because of interpolation. 1052 * 1053 * @param interpolatedValue the interpolated value 1054 * @param value the original value 1055 * @return a flag whether the value was changed 1056 */ 1057 private boolean valueChanged(final Object interpolatedValue, final Object value) 1058 { 1059 return ObjectUtils.notEqual(interpolatedValue, value); 1060 } 1061 } 1062}