* A namespace is declared on a namespace context. * Namespace contexts are pushed on and popped off the namespace context stack. *
* A declared namespace will be in scope iff the context that it was declared on * has not been popped off the stack. *
* When instantiated the namespace stack consists of the root namespace context, * which contains, by default, the "xml" and "xmlns" declarations. * Namespaces may be declarations may be declared on the root context. * The root context cannot be popped but can be reset to contain just the * "xml" and "xmlns" declarations. *
* Implementation note: determining the prefix from a namespace URI * (or vice versa) is efficient when there are few namespace * declarations i.e. what is considered to be the case for namespace * declarations in 'average' XML documents. The look up of a namespace URI * given a prefix is performed in O(n) time. The look up of a prefix given * a namespace URI is performed in O(2n) time. *
* The implementation does not scale when there are many namespace
* declarations. TODO: Use a hash map when there are many namespace
* declarations.
*
* @author Paul.Sandoz@Sun.Com
*/
final public class NamespaceContexHelper implements NamespaceContextEx {
private static int DEFAULT_SIZE = 8;
// The prefixes of the namespace declarations
private String[] prefixes = new String[DEFAULT_SIZE];
// The URIs of the namespace declarations
private String[] namespaceURIs = new String[DEFAULT_SIZE];
// Current position to store the next namespace declaration
private int namespacePosition;
// The namespace contexts
private int[] contexts = new int[DEFAULT_SIZE];
// Current position to store the next namespace context
private int contextPosition;
/**
* Create a new NamespaceContexHelper.
*
*/
public NamespaceContexHelper() {
// The default namespace declarations that are always in scope
prefixes[0] = "xml";
namespaceURIs[0] = "http://www.w3.org/XML/1998/namespace";
prefixes[1] = "xmlns";
namespaceURIs[1] = "http://www.w3.org/2000/xmlns/";
namespacePosition = 2;
}
// NamespaceContext interface
public String getNamespaceURI(String prefix) {
if (prefix == null) throw new IllegalArgumentException();
prefix = prefix.intern();
for (int i = namespacePosition - 1; i >= 0; i--) {
final String declaredPrefix = prefixes[i];
if (declaredPrefix == prefix) {
return namespaceURIs[i];
}
}
return "";
}
public String getPrefix(String namespaceURI) {
if (namespaceURI == null) throw new IllegalArgumentException();
for (int i = namespacePosition - 1; i >= 0; i--) {
final String declaredNamespaceURI = namespaceURIs[i];
if (declaredNamespaceURI == namespaceURI || declaredNamespaceURI.equals(namespaceURI)) {
final String declaredPrefix = prefixes[i];
// Check if prefix is out of scope
for (++i; i < namespacePosition; i++)
if (declaredPrefix == prefixes[i])
return null;
return declaredPrefix;
}
}
return null;
}
public Iterator getPrefixes(String namespaceURI) {
if (namespaceURI == null) throw new IllegalArgumentException();
List
* @param namespaceURI the namespace URI to declare, may be null.
*/
public void declareDefaultNamespace(String namespaceURI) {
declareNamespace("", namespaceURI);
}
/**
* Declare a namespace.
*
* The namespace will be declared on the current namespace context.
*
* The namespace can be removed by popping the current namespace
* context, or, if the declaration occured in the root context, by
* reseting the namespace context.
*
* A default namespace can be declared by passing
* @param prefix the namespace prefix to declare, may not be null.
* @param namespaceURI the namespace URI to declare, may be null.
* @throws IllegalArgumentException, if the prefix is null.
*/
public void declareNamespace(String prefix, String namespaceURI) {
if (prefix == null) throw new IllegalArgumentException();
prefix = prefix.intern();
// Ignore the "xml" or "xmlns" declarations
if (prefix == "xml" || prefix == "xmlns")
return;
// Check for undeclaration
if (namespaceURI != null)
namespaceURI = namespaceURI.intern();
if (namespacePosition == namespaceURIs.length)
resizeNamespaces();
// Add new declaration
prefixes[namespacePosition] = prefix;
namespaceURIs[namespacePosition++] = namespaceURI;
}
private void resizeNamespaces() {
final int newLength = namespaceURIs.length * 3 / 2 + 1;
String[] newPrefixes = new String[newLength];
System.arraycopy(prefixes, 0, newPrefixes, 0, prefixes.length);
prefixes = newPrefixes;
String[] newNamespaceURIs = new String[newLength];
System.arraycopy(namespaceURIs, 0, newNamespaceURIs, 0, namespaceURIs.length);
namespaceURIs = newNamespaceURIs;
}
/**
* Push a namespace context on the stack.
*/
public void pushContext() {
if (contextPosition == contexts.length)
resizeContexts();
contexts[contextPosition++] = namespacePosition;
}
private void resizeContexts() {
int[] newContexts = new int[contexts.length * 3 / 2 + 1];
System.arraycopy(contexts, 0, newContexts, 0, contexts.length);
contexts = newContexts;
}
/**
* Pop the namespace context off the stack.
*
* Namespaces declared within the context (to be popped)
* will be removed and no longer be in scope.
*/
public void popContext() {
if (contextPosition > 0) {
namespacePosition = contexts[--contextPosition];
}
}
/**
* Reset namespace contexts.
*
* Pop all namespace contexts and reset the root context.
*/
public void resetContexts() {
namespacePosition = 2;
}
}
"" as
* the value of the prefix parameter.
* A namespace may be undeclared by passing null as the
* value of the namespaceURI parameter.
*