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 new EventListener<ConfigurationEvent>() 623 { 624 @Override 625 public void onEvent(final ConfigurationEvent event) 626 { 627 subnodeConfigurationChanged(event); 628 } 629 }; 630 } 631 632 /** 633 * Returns a configuration with the same content as this configuration, but 634 * with all variables replaced by their actual values. This implementation 635 * is specific for hierarchical configurations. It clones the current 636 * configuration and runs a specialized visitor on the clone, which performs 637 * interpolation on the single configuration nodes. 638 * 639 * @return a configuration with all variables interpolated 640 * @since 1.5 641 */ 642 @Override 643 public Configuration interpolatedConfiguration() 644 { 645 final InterpolatedVisitor visitor = new InterpolatedVisitor(); 646 final NodeHandler<ImmutableNode> handler = getModel().getNodeHandler(); 647 NodeTreeWalker.INSTANCE 648 .walkDFS(handler.getRootNode(), visitor, handler); 649 650 final BaseHierarchicalConfiguration c = 651 (BaseHierarchicalConfiguration) clone(); 652 c.getNodeModel().setRootNode(visitor.getInterpolatedRoot()); 653 return c; 654 } 655 656 /** 657 * {@inheritDoc} This implementation creates a new instance of 658 * {@link InMemoryNodeModel}, initialized with this configuration's root 659 * node. This has the effect that although the same nodes are used, the 660 * original and copied configurations are independent on each other. 661 */ 662 @Override 663 protected NodeModel<ImmutableNode> cloneNodeModel() 664 { 665 return new InMemoryNodeModel(getModel().getNodeHandler().getRootNode()); 666 } 667 668 /** 669 * Creates a list with immutable configurations from the given input list. 670 * 671 * @param subs a list with mutable configurations 672 * @return a list with corresponding immutable configurations 673 */ 674 private static List<ImmutableHierarchicalConfiguration> toImmutable( 675 final List<? extends HierarchicalConfiguration<?>> subs) 676 { 677 final List<ImmutableHierarchicalConfiguration> res = 678 new ArrayList<>(subs.size()); 679 for (final HierarchicalConfiguration<?> sub : subs) 680 { 681 res.add(ConfigurationUtils.unmodifiableConfiguration(sub)); 682 } 683 return res; 684 } 685 686 /** 687 * Creates the {@code NodeModel} for this configuration based on a passed in 688 * source configuration. This implementation creates an 689 * {@link InMemoryNodeModel}. If the passed in source configuration is 690 * defined, its root node also becomes the root node of this configuration. 691 * Otherwise, a new, empty root node is used. 692 * 693 * @param c the configuration that is to be copied 694 * @return the {@code NodeModel} for the new configuration 695 */ 696 private static NodeModel<ImmutableNode> createNodeModel( 697 final HierarchicalConfiguration<ImmutableNode> c) 698 { 699 final ImmutableNode root = (c != null) ? obtainRootNode(c) : null; 700 return new InMemoryNodeModel(root); 701 } 702 703 /** 704 * Obtains the root node from a configuration whose data is to be copied. It 705 * has to be ensured that the synchronizer is called correctly. 706 * 707 * @param c the configuration that is to be copied 708 * @return the root node of this configuration 709 */ 710 private static ImmutableNode obtainRootNode( 711 final HierarchicalConfiguration<ImmutableNode> c) 712 { 713 return c.getNodeModel().getNodeHandler().getRootNode(); 714 } 715 716 /** 717 * A specialized visitor base class that can be used for storing the tree of 718 * configuration nodes. The basic idea is that each node can be associated 719 * with a reference object. This reference object has a concrete meaning in 720 * a derived class, e.g. an entry in a JNDI context or an XML element. When 721 * the configuration tree is set up, the {@code load()} method is 722 * responsible for setting the reference objects. When the configuration 723 * tree is later modified, new nodes do not have a defined reference object. 724 * This visitor class processes all nodes and finds the ones without a 725 * defined reference object. For those nodes the {@code insert()} 726 * method is called, which must be defined in concrete sub classes. This 727 * method can perform all steps to integrate the new node into the original 728 * structure. 729 */ 730 protected abstract static class BuilderVisitor extends 731 ConfigurationNodeVisitorAdapter<ImmutableNode> 732 { 733 @Override 734 public void visitBeforeChildren(final ImmutableNode node, final NodeHandler<ImmutableNode> handler) 735 { 736 final ReferenceNodeHandler refHandler = (ReferenceNodeHandler) handler; 737 updateNode(node, refHandler); 738 insertNewChildNodes(node, refHandler); 739 } 740 741 /** 742 * Inserts a new node into the structure constructed by this builder. 743 * This method is called for each node that has been added to the 744 * configuration tree after the configuration has been loaded from its 745 * source. These new nodes have to be inserted into the original 746 * structure. The passed in nodes define the position of the node to be 747 * inserted: its parent and the siblings between to insert. 748 * 749 * @param newNode the node to be inserted 750 * @param parent the parent node 751 * @param sibling1 the sibling after which the node is to be inserted; 752 * can be <b>null</b> if the new node is going to be the first 753 * child node 754 * @param sibling2 the sibling before which the node is to be inserted; 755 * can be <b>null</b> if the new node is going to be the last 756 * child node 757 * @param refHandler the {@code ReferenceNodeHandler} 758 */ 759 protected abstract void insert(ImmutableNode newNode, 760 ImmutableNode parent, ImmutableNode sibling1, 761 ImmutableNode sibling2, ReferenceNodeHandler refHandler); 762 763 /** 764 * Updates a node that already existed in the original hierarchy. This 765 * method is called for each node that has an assigned reference object. 766 * A concrete implementation should update the reference according to 767 * the node's current value. 768 * 769 * @param node the current node to be processed 770 * @param reference the reference object for this node 771 * @param refHandler the {@code ReferenceNodeHandler} 772 */ 773 protected abstract void update(ImmutableNode node, Object reference, 774 ReferenceNodeHandler refHandler); 775 776 /** 777 * Updates the value of a node. If this node is associated with a 778 * reference object, the {@code update()} method is called. 779 * 780 * @param node the current node to be processed 781 * @param refHandler the {@code ReferenceNodeHandler} 782 */ 783 private void updateNode(final ImmutableNode node, 784 final ReferenceNodeHandler refHandler) 785 { 786 final Object reference = refHandler.getReference(node); 787 if (reference != null) 788 { 789 update(node, reference, refHandler); 790 } 791 } 792 793 /** 794 * Inserts new children that have been added to the specified node. 795 * 796 * @param node the current node to be processed 797 * @param refHandler the {@code ReferenceNodeHandler} 798 */ 799 private void insertNewChildNodes(final ImmutableNode node, 800 final ReferenceNodeHandler refHandler) 801 { 802 final Collection<ImmutableNode> subNodes = 803 new LinkedList<>(refHandler.getChildren(node)); 804 final Iterator<ImmutableNode> children = subNodes.iterator(); 805 ImmutableNode sibling1; 806 ImmutableNode nd = null; 807 808 while (children.hasNext()) 809 { 810 // find the next new node 811 do 812 { 813 sibling1 = nd; 814 nd = children.next(); 815 } while (refHandler.getReference(nd) != null 816 && children.hasNext()); 817 818 if (refHandler.getReference(nd) == null) 819 { 820 // find all following new nodes 821 final List<ImmutableNode> newNodes = 822 new LinkedList<>(); 823 newNodes.add(nd); 824 while (children.hasNext()) 825 { 826 nd = children.next(); 827 if (refHandler.getReference(nd) == null) 828 { 829 newNodes.add(nd); 830 } 831 else 832 { 833 break; 834 } 835 } 836 837 // Insert all new nodes 838 final ImmutableNode sibling2 = 839 (refHandler.getReference(nd) == null) ? null : nd; 840 for (final ImmutableNode insertNode : newNodes) 841 { 842 if (refHandler.getReference(insertNode) == null) 843 { 844 insert(insertNode, node, sibling1, sibling2, 845 refHandler); 846 sibling1 = insertNode; 847 } 848 } 849 } 850 } 851 } 852 } 853 854 /** 855 * A specialized visitor implementation which constructs the root node of a 856 * configuration with all variables replaced by their interpolated values. 857 */ 858 private class InterpolatedVisitor extends 859 ConfigurationNodeVisitorAdapter<ImmutableNode> 860 { 861 /** A stack for managing node builder instances. */ 862 private final List<ImmutableNode.Builder> builderStack; 863 864 /** The resulting root node. */ 865 private ImmutableNode interpolatedRoot; 866 867 /** 868 * Creates a new instance of {@code InterpolatedVisitor}. 869 */ 870 public InterpolatedVisitor() 871 { 872 builderStack = new LinkedList<>(); 873 } 874 875 /** 876 * Returns the result of this builder: the root node of the interpolated 877 * nodes hierarchy. 878 * 879 * @return the resulting root node 880 */ 881 public ImmutableNode getInterpolatedRoot() 882 { 883 return interpolatedRoot; 884 } 885 886 @Override 887 public void visitBeforeChildren(final ImmutableNode node, 888 final NodeHandler<ImmutableNode> handler) 889 { 890 if (isLeafNode(node, handler)) 891 { 892 handleLeafNode(node, handler); 893 } 894 else 895 { 896 final ImmutableNode.Builder builder = 897 new ImmutableNode.Builder(handler.getChildrenCount( 898 node, null)) 899 .name(handler.nodeName(node)) 900 .value(interpolate(handler.getValue(node))) 901 .addAttributes( 902 interpolateAttributes(node, handler)); 903 push(builder); 904 } 905 } 906 907 @Override 908 public void visitAfterChildren(final ImmutableNode node, 909 final NodeHandler<ImmutableNode> handler) 910 { 911 if (!isLeafNode(node, handler)) 912 { 913 final ImmutableNode newNode = pop().create(); 914 storeInterpolatedNode(newNode); 915 } 916 } 917 918 /** 919 * Pushes a new builder on the stack. 920 * 921 * @param builder the builder 922 */ 923 private void push(final ImmutableNode.Builder builder) 924 { 925 builderStack.add(0, builder); 926 } 927 928 /** 929 * Pops the top-level element from the stack. 930 * 931 * @return the element popped from the stack 932 */ 933 private ImmutableNode.Builder pop() 934 { 935 return builderStack.remove(0); 936 } 937 938 /** 939 * Returns the top-level element from the stack without removing it. 940 * 941 * @return the top-level element from the stack 942 */ 943 private ImmutableNode.Builder peek() 944 { 945 return builderStack.get(0); 946 } 947 948 /** 949 * Returns a flag whether the given node is a leaf. This is the case if 950 * it does not have children. 951 * 952 * @param node the node in question 953 * @param handler the {@code NodeHandler} 954 * @return a flag whether this is a leaf node 955 */ 956 private boolean isLeafNode(final ImmutableNode node, 957 final NodeHandler<ImmutableNode> handler) 958 { 959 return handler.getChildren(node).isEmpty(); 960 } 961 962 /** 963 * Handles interpolation for a node with no children. If interpolation 964 * does not change this node, it is copied as is to the resulting 965 * structure. Otherwise, a new node is created with the interpolated 966 * values. 967 * 968 * @param node the current node to be processed 969 * @param handler the {@code NodeHandler} 970 */ 971 private void handleLeafNode(final ImmutableNode node, 972 final NodeHandler<ImmutableNode> handler) 973 { 974 final Object value = interpolate(node.getValue()); 975 final Map<String, Object> interpolatedAttributes = 976 new HashMap<>(); 977 final boolean attributeChanged = 978 interpolateAttributes(node, handler, interpolatedAttributes); 979 final ImmutableNode newNode = 980 (valueChanged(value, handler.getValue(node)) || attributeChanged) ? new ImmutableNode.Builder() 981 .name(handler.nodeName(node)).value(value) 982 .addAttributes(interpolatedAttributes).create() 983 : node; 984 storeInterpolatedNode(newNode); 985 } 986 987 /** 988 * Stores a processed node. Per default, the node is added to the 989 * current builder on the stack. If no such builder exists, this is the 990 * result node. 991 * 992 * @param node the node to be stored 993 */ 994 private void storeInterpolatedNode(final ImmutableNode node) 995 { 996 if (builderStack.isEmpty()) 997 { 998 interpolatedRoot = node; 999 } 1000 else 1001 { 1002 peek().addChild(node); 1003 } 1004 } 1005 1006 /** 1007 * Populates a map with interpolated attributes of the passed in node. 1008 * 1009 * @param node the current node to be processed 1010 * @param handler the {@code NodeHandler} 1011 * @param interpolatedAttributes a map for storing the results 1012 * @return a flag whether an attribute value was changed by 1013 * interpolation 1014 */ 1015 private boolean interpolateAttributes(final ImmutableNode node, 1016 final NodeHandler<ImmutableNode> handler, 1017 final Map<String, Object> interpolatedAttributes) 1018 { 1019 boolean attributeChanged = false; 1020 for (final String attr : handler.getAttributes(node)) 1021 { 1022 final Object attrValue = 1023 interpolate(handler.getAttributeValue(node, attr)); 1024 if (valueChanged(attrValue, 1025 handler.getAttributeValue(node, attr))) 1026 { 1027 attributeChanged = true; 1028 } 1029 interpolatedAttributes.put(attr, attrValue); 1030 } 1031 return attributeChanged; 1032 } 1033 1034 /** 1035 * Returns a map with interpolated attributes of the passed in node. 1036 * 1037 * @param node the current node to be processed 1038 * @param handler the {@code NodeHandler} 1039 * @return the map with interpolated attributes 1040 */ 1041 private Map<String, Object> interpolateAttributes(final ImmutableNode node, 1042 final NodeHandler<ImmutableNode> handler) 1043 { 1044 final Map<String, Object> attributes = new HashMap<>(); 1045 interpolateAttributes(node, handler, attributes); 1046 return attributes; 1047 } 1048 1049 /** 1050 * Tests whether a value is changed because of interpolation. 1051 * 1052 * @param interpolatedValue the interpolated value 1053 * @param value the original value 1054 * @return a flag whether the value was changed 1055 */ 1056 private boolean valueChanged(final Object interpolatedValue, final Object value) 1057 { 1058 return ObjectUtils.notEqual(interpolatedValue, value); 1059 } 1060 } 1061}