SimpleNamespaceContext implements all subtleties of the NamespaceContext contract

Issue: SPR-13713

Author: jhoeller

spring-core/src/main/java/org/springframework/util/xml/SimpleNamespaceContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,66 +16,85 @@
 
 package org.springframework.util.xml;
 
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
-import java.util.List;
+import java.util.LinkedHashSet;
 import java.util.Map;
+import java.util.Set;
 import javax.xml.XMLConstants;
 import javax.xml.namespace.NamespaceContext;
 
 import org.springframework.util.Assert;
 
 /**
- * Simple {@code javax.xml.namespace.NamespaceContext} implementation. Follows the standard
- * {@code NamespaceContext} contract, and is loadable via a {@code java.util.Map} or
- * {@code java.util.Properties} object
+ * Simple {@code javax.xml.namespace.NamespaceContext} implementation.
+ * Follows the standard {@code NamespaceContext} contract, and is loadable
+ * via a {@code java.util.Map} or {@code java.util.Properties} object
  *
  * @author Arjen Poutsma
+ * @author Juergen Hoeller
  * @since 3.0
  */
 public class SimpleNamespaceContext implements NamespaceContext {
 
-	private Map<String, String> prefixToNamespaceUri = new HashMap<String, String>();
+	private final Map<String, String> prefixToNamespaceUri = new HashMap<String, String>();
 
-	private Map<String, List<String>> namespaceUriToPrefixes = new HashMap<String, List<String>>();
+	private final Map<String, Set<String>> namespaceUriToPrefixes = new HashMap<String, Set<String>>();
 
 	private String defaultNamespaceUri = "";
 
+
 	@Override
 	public String getNamespaceURI(String prefix) {
-		Assert.notNull(prefix, "prefix is null");
+		Assert.notNull(prefix, "No prefix given");
 		if (XMLConstants.XML_NS_PREFIX.equals(prefix)) {
 			return XMLConstants.XML_NS_URI;
 		}
 		else if (XMLConstants.XMLNS_ATTRIBUTE.equals(prefix)) {
 			return XMLConstants.XMLNS_ATTRIBUTE_NS_URI;
 		}
 		else if (XMLConstants.DEFAULT_NS_PREFIX.equals(prefix)) {
-			return defaultNamespaceUri;
+			return this.defaultNamespaceUri;
 		}
-		else if (prefixToNamespaceUri.containsKey(prefix)) {
-			return prefixToNamespaceUri.get(prefix);
+		else if (this.prefixToNamespaceUri.containsKey(prefix)) {
+			return this.prefixToNamespaceUri.get(prefix);
 		}
 		return "";
 	}
 
 	@Override
 	public String getPrefix(String namespaceUri) {
-		List<?> prefixes = getPrefixesInternal(namespaceUri);
-		return prefixes.isEmpty() ? null : (String) prefixes.get(0);
+		Set<String> prefixes = getPrefixesSet(namespaceUri);
+		return (!prefixes.isEmpty() ? prefixes.iterator().next() : null);
 	}
 
 	@Override
 	public Iterator<String> getPrefixes(String namespaceUri) {
-		return getPrefixesInternal(namespaceUri).iterator();
+		return getPrefixesSet(namespaceUri).iterator();
 	}
 
+	private Set<String> getPrefixesSet(String namespaceUri) {
+		Assert.notNull(namespaceUri, "No namespaceUri given");
+		if (this.defaultNamespaceUri.equals(namespaceUri)) {
+			return Collections.singleton(XMLConstants.DEFAULT_NS_PREFIX);
+		}
+		else if (XMLConstants.XML_NS_URI.equals(namespaceUri)) {
+			return Collections.singleton(XMLConstants.XML_NS_PREFIX);
+		}
+		else if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(namespaceUri)) {
+			return Collections.singleton(XMLConstants.XMLNS_ATTRIBUTE);
+		}
+		else {
+			Set<String> prefixes = this.namespaceUriToPrefixes.get(namespaceUri);
+			return (prefixes != null ?  Collections.unmodifiableSet(prefixes) : Collections.<String>emptySet());
+		}
+	}
+
+
 	/**
-	 * Sets the bindings for this namespace context. The supplied map must consist of string key value pairs.
-	 *
-	 * @param bindings the bindings
+	 * Set the bindings for this namespace context.
+	 * The supplied map must consist of string key value pairs.
 	 */
 	public void setBindings(Map<String, String> bindings) {
 		for (Map.Entry<String, String> entry : bindings.entrySet()) {
@@ -84,79 +103,70 @@ public void setBindings(Map<String, String> bindings) {
 	}
 
 	/**
-	 * Binds the given namespace as default namespace.
-	 *
+	 * Bind the given namespace as default namespace.
 	 * @param namespaceUri the namespace uri
 	 */
 	public void bindDefaultNamespaceUri(String namespaceUri) {
 		bindNamespaceUri(XMLConstants.DEFAULT_NS_PREFIX, namespaceUri);
 	}
 
 	/**
-	 * Binds the given prefix to the given namespace.
-	 *
-	 * @param prefix	   the namespace prefix
+	 * Bind the given prefix to the given namespace.
+	 * @param prefix the namespace prefix
 	 * @param namespaceUri the namespace uri
 	 */
 	public void bindNamespaceUri(String prefix, String namespaceUri) {
 		Assert.notNull(prefix, "No prefix given");
 		Assert.notNull(namespaceUri, "No namespaceUri given");
 		if (XMLConstants.DEFAULT_NS_PREFIX.equals(prefix)) {
-			defaultNamespaceUri = namespaceUri;
+			this.defaultNamespaceUri = namespaceUri;
 		}
 		else {
-			prefixToNamespaceUri.put(prefix, namespaceUri);
-			getPrefixesInternal(namespaceUri).add(prefix);
+			this.prefixToNamespaceUri.put(prefix, namespaceUri);
+			Set<String> prefixes = this.namespaceUriToPrefixes.get(namespaceUri);
+			if (prefixes == null) {
+				prefixes = new LinkedHashSet<String>();
+				this.namespaceUriToPrefixes.put(namespaceUri, prefixes);
+			}
+			prefixes.add(prefix);
 		}
 	}
 
-	/** Removes all declared prefixes. */
-	public void clear() {
-		prefixToNamespaceUri.clear();
-	}
-
 	/**
-	 * Returns all declared prefixes.
-	 *
-	 * @return the declared prefixes
+	 * Remove the given prefix from this context.
+	 * @param prefix the prefix to be removed
 	 */
-	public Iterator<String> getBoundPrefixes() {
-		return prefixToNamespaceUri.keySet().iterator();
-	}
-
-	private List<String> getPrefixesInternal(String namespaceUri) {
-		if (defaultNamespaceUri.equals(namespaceUri)) {
-			return Collections.singletonList(XMLConstants.DEFAULT_NS_PREFIX);
-		}
-		else if (XMLConstants.XML_NS_URI.equals(namespaceUri)) {
-			return Collections.singletonList(XMLConstants.XML_NS_PREFIX);
-		}
-		else if (XMLConstants.XMLNS_ATTRIBUTE_NS_URI.equals(namespaceUri)) {
-			return Collections.singletonList(XMLConstants.XMLNS_ATTRIBUTE);
+	public void removeBinding(String prefix) {
+		if (XMLConstants.DEFAULT_NS_PREFIX.equals(prefix)) {
+			this.defaultNamespaceUri = "";
 		}
-		else {
-			List<String> list = namespaceUriToPrefixes.get(namespaceUri);
-			if (list == null) {
-				list = new ArrayList<String>();
-				namespaceUriToPrefixes.put(namespaceUri, list);
+		else if (prefix != null) {
+			String namespaceUri = this.prefixToNamespaceUri.remove(prefix);
+			if (namespaceUri != null) {
+				Set<String> prefixes = this.namespaceUriToPrefixes.get(namespaceUri);
+				if (prefixes != null) {
+					prefixes.remove(prefix);
+					if (prefixes.isEmpty()) {
+						this.namespaceUriToPrefixes.remove(namespaceUri);
+					}
+				}
 			}
-			return list;
 		}
 	}
 
 	/**
-	 * Removes the given prefix from this context.
-	 *
-	 * @param prefix the prefix to be removed
+	 * Remove all declared prefixes.
 	 */
-	public void removeBinding(String prefix) {
-		if (XMLConstants.DEFAULT_NS_PREFIX.equals(prefix)) {
-			defaultNamespaceUri = "";
-		}
-		else {
-			String namespaceUri = prefixToNamespaceUri.remove(prefix);
-			List<String> prefixes = getPrefixesInternal(namespaceUri);
-			prefixes.remove(prefix);
-		}
+	public void clear() {
+		this.prefixToNamespaceUri.clear();
+		this.namespaceUriToPrefixes.clear();
+	}
+
+	/**
+	 * Return all declared prefixes.
+	 */
+	public Iterator<String> getBoundPrefixes() {
+		return this.prefixToNamespaceUri.keySet().iterator();
 	}
+
 }