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Posted to commits@commons.apache.org by si...@apache.org on 2011/01/26 17:04:18 UTC
svn commit: r1063770 -
/commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/ExtendedBaseRules.java
Author: simonetripodi
Date: Wed Jan 26 16:04:18 2011
New Revision: 1063770
URL: http://svn.apache.org/viewvc?rev=1063770&view=rev
Log:
first checkin of ExtendedBaseRules class, imported from current proper /trunk
Added:
commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/ExtendedBaseRules.java (with props)
Added: commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/ExtendedBaseRules.java
URL: http://svn.apache.org/viewvc/commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/ExtendedBaseRules.java?rev=1063770&view=auto
==============================================================================
--- commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/ExtendedBaseRules.java (added)
+++ commons/sandbox/digester3/trunk/src/main/java/org/apache/commons/digester3/rules/ExtendedBaseRules.java Wed Jan 26 16:04:18 2011
@@ -0,0 +1,458 @@
+/* $Id$
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.digester3.rules;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.digester3.Rule;
+
+/**
+ * <p>Extension of {@link RulesBase} for complex schema.</p>
+ *
+ * <p>This is an extension of the basic pattern matching scheme
+ * intended to improve support for mapping complex xml-schema.
+ * It is intended to be a minimal extension of the standard rules
+ * big enough to support complex schema but without the full generality
+ * offered by more exotic matching pattern rules.</p>
+ *
+ * <h4>When should you use this rather than the original?</h4>
+ *
+ * <p>
+ * This pattern-matching engine is complex and slower than the basic
+ * default RulesBase class, but offers more functionality:
+ * <ul>
+ * <li>Universal patterns allow patterns to be specified which will match
+ * regardless of whether there are "better matching" patterns available.</li>
+ * <li>Parent-match patterns (eg "a/b/?") allow matching for all direct
+ * children of a specified element.</li>
+ * <li>Ancestor-match patterns (eg "a/b/*") allow matching all elements
+ * nested within a specified element to any nesting depth.</li>
+ * <li>Completely-wild patterns ("*" or "!*") allow matching all elements.</li>
+ * </ul>
+ * </p>
+ *
+ * <h4>Universal Match Patterns</h4>
+ *
+ * <p>The default RulesBase pattern-matching engine always attempts to find
+ * the "best matching pattern", and will ignore rules associated with other
+ * patterns that match but are not "as good". As an example, if the pattern
+ * "a/b/c" is associated with rules 1 and 2, and "*/c" is associated with
+ * rules 3 and 4 then element "a/b/c" will cause only rules 1 and 2 to execute.
+ * Rules 3 and 4 do have matching patterns, but because the patterns are shorter
+ * and include wildcard characters they are regarded as being "not as good" as
+ * a direct match. In general, exact patterns are better than wildcard patterns,
+ * and among multiple patterns with wildcards, the longest is preferred.
+ * See the RulesBase class for more information.</p>
+ *
+ * <p>This feature of preferring "better" patterns can be a powerful tool.
+ * However it also means that patterns can interact in unexpected ways.</p>
+ *
+ * <p>When using the ExtendedBaseRules, any pattern prefixed with '!' bypasses
+ * the "best match" feature. Even if there is an exact match or a longer
+ * wildcard match, patterns prefixed by '!' will still be tested to see if
+ * they match, and if so their associated Rule objects will be included in
+ * the set of rules to be executed in the normal manner.</p>
+ *
+ * <ul>
+ * <li>Pattern <code>"!*/a/b"</code> matches whenever an 'b' element
+ * is inside an 'a'.</li>
+ * <li>Pattern <code>"!a/b/?"</code> matches any child of a parent
+ * matching <code>"a/b"</code> (see "Parent Match Patterns").</li>
+ * <li>Pattern <code>"!*/a/b/?"</code> matches any child of a parent
+ * matching <code>"!*/a/b"</code> (see "Parent Match Patterns").</li>
+ * <li>Pattern <code>"!a/b/*"</code> matches any element whose path
+ * starts with "a" then "b" (see "Ancestor Match Patterns").</li>
+ * <li>Pattern <code>"!*/a/b/*"</code> matches any elements whose path
+ * contains 'a/b' (see "Ancestor Match Patterns").</li>
+ * </ul>
+ *
+ * <h4>Parent Match Patterns</h4>
+ *
+ * <p>
+ * These will match direct child elements of a particular parent element.
+ * <ul>
+ * <li>
+ * <code>"a/b/c/?"</code> matches any child whose parent matches
+ * <code>"a/b/c"</code>. Exact parent rules take precedence over Ancestor
+ * Match patterns.
+ * </li>
+ * <li>
+ * <code>"*/a/b/c/?"</code> matches any child whose parent matches
+ * <code>"*/a/b/c"</code>. The longest matching still applies to parent
+ * matches but the length excludes the '?', which effectively means
+ * that standard wildcard matches with the same level of depth are
+ * chosen in preference.
+ * </li>
+ * </ul>
+ * </p>
+ *
+ * <h4>Ancestor Match Patterns</h4>
+ *
+ * <p>
+ * These will match elements whose parentage includes a particular sequence
+ * of elements.
+ * <ul>
+ * <li>
+ * <code>"a/b/*"</code> matches any element whose path starts with
+ * 'a' then 'b'. Exact parent and parent match rules take precedence.
+ * The longest ancestor match will take precedence.
+ * </li>
+ * <li>
+ * <code>"*/a/b/*"</code> matches any elements whose path contains
+ * an element 'a' followed by an element 'b'. The longest matching still
+ * applies but the length excludes the '*' at the end.
+ * </li>
+ * </ul>
+ * </p>
+ *
+ * <h4>Completely Wild Patterns</h4>
+ *
+ * <p>Pattern <code>"*"</code> matches every pattern that isn't matched by
+ * any other basic rule.</p>
+ *
+ * <p>Pattern <code>"!*"</code> matches every pattern.</p>
+ *
+ * <h4>Using The Extended Rules</h4>
+ *
+ * <p>By default, a Digester instance uses a {@link RulesBase} instance as
+ * its pattern matching engine. To use an ExtendedBaseRules instance, call
+ * the Digester.setRules method before adding any Rule objects to the digester
+ * instance:
+ * <pre>
+ * Digester digester = new Digester();
+ * digester.setRules( new ExtendedBaseRules() );
+ * </pre></p>
+ *
+ * <p>The most important thing to remember when using the extended rules is
+ * that universal and non-universal patterns are completely independent.
+ * Universal patterns are never affected by the addition of new patterns
+ * or the removal of existing ones. Non-universal patterns are never affected
+ * by the addition of new <em>universal</em> patterns or the removal of
+ * existing <em>universal</em> patterns. As in the basic matching rules,
+ * non-universal (basic) patterns <strong>can</strong> be affected by the
+ * addition of new <em>non-universal</em> patterns or the removal of existing
+ * <em>non-universal</em> patterns, because only rules associated with the
+ * "best matching" pattern for each xml element are executed.
+ *
+ * <p> This means that you can use universal patterns to build up the simple
+ * parts of your structure - for example defining universal creation and
+ * property setting rules. More sophisticated and complex mapping will require
+ * non-universal patterns and this might mean that some of the universal rules
+ * will need to be replaced by a series of special cases using non-universal
+ * rules. But by using universal rules as your backbone, these additions
+ * should not break your existing rules.</p>
+ */
+public class ExtendedBaseRules extends BaseRules {
+
+ /**
+ * Counts the entry number for the rules.
+ */
+ private int counter = 0;
+
+ /**
+ * The decision algorithm used (unfortunately) doesn't preserve the entry
+ * order.
+ * This map is used by a comparator which orders the list of matches
+ * before it's returned.
+ * This map stores the entry number keyed by the rule.
+ */
+ private Map<Rule, Integer> order = new HashMap<Rule, Integer>();
+
+ /**
+ * Register a new Rule instance matching the specified pattern.
+ *
+ * @param pattern Nesting pattern to be matched for this Rule
+ * @param rule Rule instance to be registered
+ */
+ @Override
+ public void add(String pattern, Rule rule) {
+ super.add(pattern, rule);
+ this.counter++;
+ this.order.put(rule, this.counter);
+ }
+
+ /**
+ * Return a List of all registered Rule instances that match the specified
+ * nesting pattern, or a zero-length List if there are no matches. If more
+ * than one Rule instance matches, they <strong>must</strong> be returned
+ * in the order originally registered through the <code>add()</code>
+ * method.
+ *
+ * @param pattern Nesting pattern to be matched
+ */
+ @Override
+ public List<Rule> match(String namespace, String pattern) {
+ // calculate the pattern of the parent
+ // (if the element has one)
+ String parentPattern = "";
+ int lastIndex = pattern.lastIndexOf('/');
+
+ boolean hasParent = true;
+
+ if (lastIndex == -1) {
+ // element has no parent
+ hasParent = false;
+ } else {
+ // calculate the pattern of the parent
+ parentPattern = pattern.substring(0, lastIndex);
+ }
+
+ // we keep the list of universal matches separate
+ List<Rule> universalList = new ArrayList<Rule>(counter);
+
+ // Universal all wildards ('!*')
+ // These are always matched so always add them
+ List<Rule> tempList = this.lookup("!*");
+ if (tempList != null) {
+ universalList.addAll(tempList);
+ }
+
+ // Universal exact parent match
+ // need to get this now since only wildcards are considered later
+ tempList = this.lookup("!" + parentPattern + "/?");
+ if (tempList != null) {
+ universalList.addAll(tempList);
+ }
+
+ // base behaviour means that if we certain matches, we don't continue
+ // but we just have a single combined loop and so we have to set
+ // a variable
+ boolean ignoreBasicMatches = false;
+
+ // see if we have an exact basic pattern match
+ List<Rule> rulesList = this.lookup(pattern);
+
+ if (rulesList != null) {
+ // we have a match!
+ // so ignore all basic matches from now on
+ ignoreBasicMatches = true;
+ } else {
+ // see if we have an exact child match
+ if (hasParent) {
+ // matching children takes preference
+ rulesList = this.lookup(parentPattern + "/?");
+ if (rulesList != null) {
+ // we have a match!
+ // so ignore all basic matches from now on
+ ignoreBasicMatches = true;
+
+ } else {
+ // we don't have a match yet - so try exact ancester
+ //
+ rulesList = findExactAncesterMatch(pattern);
+ if (rulesList != null) {
+ // we have a match!
+ // so ignore all basic matches from now on
+ ignoreBasicMatches = true;
+ }
+ }
+ }
+ }
+
+ // OK - we're ready for the big loop!
+ // Unlike the basic rules case,
+ // we have to go through for all those universal rules in all cases.
+
+ // Find the longest key, ie more discriminant
+ String longKey = "";
+ int longKeyLength = 0;
+
+ for (String key : this.patterns()) {
+ // find out if it's a univeral pattern
+ // set a flag
+ boolean isUniversal = key.startsWith("!");
+ if (isUniversal) {
+ // and find the underlying key
+ key = key.substring(1, key.length());
+ }
+
+ // don't need to check exact matches
+ boolean wildcardMatchStart = key.startsWith("*/");
+ boolean wildcardMatchEnd = key.endsWith("/*");
+
+ if (wildcardMatchStart || (isUniversal && wildcardMatchEnd)) {
+ boolean parentMatched = false;
+ boolean basicMatched = false;
+ boolean ancesterMatched = false;
+
+ boolean parentMatchEnd = key.endsWith("/?");
+
+ if (parentMatchEnd) {
+ // try for a parent match
+ parentMatched = parentMatch(key, pattern, parentPattern);
+ } else if (wildcardMatchEnd) {
+ // check for ancester match
+ if (wildcardMatchStart) {
+ String patternBody = key.substring(2, key.length() - 2);
+ if (pattern.endsWith(patternBody)) {
+ ancesterMatched = true;
+ } else {
+ ancesterMatched = (pattern.indexOf(patternBody + "/") > -1);
+ }
+ } else {
+ String bodyPattern = key.substring(0, key.length() - 2);
+ if (pattern.startsWith(bodyPattern)) {
+ if (pattern.length() == bodyPattern.length()) {
+ // exact match
+ ancesterMatched = true;
+ } else {
+ ancesterMatched = ( pattern.charAt(bodyPattern.length()) == '/' );
+ }
+ } else {
+ ancesterMatched = false;
+ }
+ }
+ } else {
+ // try for a base match
+ basicMatched = basicMatch(key, pattern);
+ }
+
+ if (parentMatched || basicMatched || ancesterMatched) {
+ if (isUniversal) {
+ // universal rules go straight in
+ // (no longest matching rule)
+ tempList = this.lookup("!" + key);
+ if (tempList != null) {
+ universalList.addAll(tempList);
+ }
+ } else {
+ if (!ignoreBasicMatches) {
+ // ensure that all parent matches are SHORTER
+ // than rules with same level of matching.
+ //
+ // the calculations below don't work for universal
+ // matching, but we don't care because in that case
+ // this if-stmt is not entered.
+ int keyLength = key.length();
+ if (wildcardMatchStart) {
+ --keyLength;
+ }
+ if (wildcardMatchEnd) {
+ --keyLength;
+ } else if (parentMatchEnd) {
+ --keyLength;
+ }
+
+ if (keyLength > longKeyLength) {
+ rulesList = this.lookup(key);
+ longKey = key;
+ longKeyLength = keyLength;
+ }
+ }
+ }
+ }
+ }
+ }
+
+ // '*' works in practice as a default matching
+ // (this is because anything is a deeper match!)
+ if (rulesList == null) {
+ rulesList = this.lookup("*");
+ }
+
+ // if we've matched a basic pattern, then add to the universal list
+ if (rulesList != null) {
+ universalList.addAll(rulesList);
+ }
+
+ // don't filter if namespace is null
+ if (namespace != null) {
+ // remove invalid namespaces
+ Iterator<Rule> it = universalList.iterator();
+ while (it.hasNext()) {
+ Rule rule = it.next();
+ String ns_uri = rule.getNamespaceURI();
+ if (ns_uri != null && !ns_uri.equals(namespace)) {
+ it.remove();
+ }
+ }
+ }
+
+ // need to make sure that the collection is sort in the order
+ // of addition. We use a custom comparator for this
+ Collections.sort(
+ universalList,
+ new Comparator<Rule>() {
+
+ public int compare(Rule r1, Rule r2) throws ClassCastException {
+ // Get the entry order from the map
+ Integer i1 = order.get(r1);
+ Integer i2 = order.get(r2);
+
+ // and use that to perform the comparison
+ if (i1 == null) {
+ if (i2 == null) {
+
+ return 0;
+
+ } else {
+
+ return -1;
+
+ }
+ } else if (i2 == null) {
+ return 1;
+ }
+
+ return (i1.intValue() - i2.intValue());
+ }
+ });
+
+ return universalList;
+ }
+
+ /**
+ * Matching parent.
+ */
+ private boolean parentMatch(String key, String pattern, String parentPattern) {
+ return parentPattern.endsWith(key.substring(1, key.length() - 2));
+ }
+
+ /**
+ * Standard match.
+ * Matches the end of the pattern to the key.
+ */
+ private boolean basicMatch(String key, String pattern) {
+ return (pattern.equals(key.substring(2)) || pattern.endsWith(key.substring(1)));
+ }
+
+ /**
+ * Finds an exact ancester match for given pattern
+ */
+ private List<Rule> findExactAncesterMatch(String parentPattern) {
+ List<Rule> matchingRules = null;
+ int lastIndex = parentPattern.length();
+ while (lastIndex-- > 0) {
+ lastIndex = parentPattern.lastIndexOf('/', lastIndex);
+ if (lastIndex > 0) {
+ matchingRules = this.lookup(parentPattern.substring(0, lastIndex) + "/*");
+ if (matchingRules != null) {
+ return matchingRules;
+ }
+ }
+ }
+ return null;
+ }
+
+}
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