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NamespaceSupport2.javaAPI DocJava SE 5 API24481Fri Aug 26 14:56:04 BST 2005com.sun.org.apache.xml.internal.utils

NamespaceSupport2

public class NamespaceSupport2 extends NamespaceSupport
Encapsulate Namespace tracking logic for use by SAX drivers.

This class is an attempt to rewrite the SAX NamespaceSupport "helper" class for improved efficiency. It can be used to track the namespace declarations currently in scope, providing lookup routines to map prefixes to URIs and vice versa.

ISSUE: For testing purposes, I've extended NamespaceSupport even though I'm completely reasserting all behaviors and fields. Wasteful.... But SAX did not put an interface under that object and we seem to have written that SAX class into our APIs... and I don't want to argue with it right now.

see
org.xml.sax.helpers.NamespaceSupport

Fields Summary
private Context2
currentContext
public static final String
XMLNS
The XML Namespace as a constant.

This is the Namespace URI that is automatically mapped to the "xml" prefix.

Constructors Summary
public NamespaceSupport2()
Create a new Namespace support object.



    ////////////////////////////////////////////////////////////////////
    // Constructor.
    ////////////////////////////////////////////////////////////////////


               
      
    
        reset();
    
Methods Summary
public booleandeclarePrefix(java.lang.String prefix, java.lang.String uri)
Declare a Namespace prefix.

This method declares a prefix in the current Namespace context; the prefix will remain in force until this context is popped, unless it is shadowed in a descendant context.

To declare a default Namespace, use the empty string. The prefix must not be "xml" or "xmlns".

Note that you must not declare a prefix after you've pushed and popped another Namespace.

Note that there is an asymmetry in this library: while {@link #getPrefix getPrefix} will not return the default "" prefix, even if you have declared one; to check for a default prefix, you have to look it up explicitly using {@link #getURI getURI}. This asymmetry exists to make it easier to look up prefixes for attribute names, where the default prefix is not allowed.

param
prefix The prefix to declare, or null for the empty string.
param
uri The Namespace URI to associate with the prefix.
return
true if the prefix was legal, false otherwise
see
#processName
see
#getURI
see
#getPrefix

        if (prefix.equals("xml") || prefix.equals("xmlns")) {
            return false;
        } else {
            currentContext.declarePrefix(prefix, uri);
            return true;
        }
    
public java.util.EnumerationgetDeclaredPrefixes()
Return an enumeration of all prefixes declared in this context.

The empty (default) prefix will be included in this enumeration; note that this behaviour differs from that of {@link #getPrefix} and {@link #getPrefixes}.

return
An enumeration of all prefixes declared in this context.
see
#getPrefixes
see
#getURI

        return currentContext.getDeclaredPrefixes();
    
public java.lang.StringgetPrefix(java.lang.String uri)
Return one of the prefixes mapped to a Namespace URI.

If more than one prefix is currently mapped to the same URI, this method will make an arbitrary selection; if you want all of the prefixes, use the {@link #getPrefixes} method instead.

Note: this will never return the empty (default) prefix; to check for a default prefix, use the {@link #getURI getURI} method with an argument of "".

param
uri The Namespace URI.
return
One of the prefixes currently mapped to the URI supplied, or null if none is mapped or if the URI is assigned to the default Namespace.
see
#getPrefixes(java.lang.String)
see
#getURI

        return currentContext.getPrefix(uri);
    
public java.util.EnumerationgetPrefixes(java.lang.String uri)
Return an enumeration of all prefixes currently declared for a URI.

This method returns prefixes mapped to a specific Namespace URI. The xml: prefix will be included. If you want only one prefix that's mapped to the Namespace URI, and you don't care which one you get, use the {@link #getPrefix getPrefix} method instead.

Note: the empty (default) prefix is never included in this enumeration; to check for the presence of a default Namespace, use the {@link #getURI getURI} method with an argument of "".

param
uri The Namespace URI.
return
An enumeration of all prefixes declared in the current context.
see
#getPrefix
see
#getDeclaredPrefixes
see
#getURI

        // JJK: The old code involved creating a vector, filling it
        // with all the matching prefixes, and then getting its
        // elements enumerator. Wastes storage, wastes cycles if we
        // don't actually need them all. Better to either implement
        // a specific enumerator for these prefixes... or a filter
        // around the all-prefixes enumerator, which comes out to
        // roughly the same thing.
        //
        // **** Currently a filter. That may not be most efficient
        // when I'm done restructuring storage!
        return new PrefixForUriEnumerator(this,uri,getPrefixes());       
    
public java.util.EnumerationgetPrefixes()
Return an enumeration of all prefixes currently declared.

Note: if there is a default prefix, it will not be returned in this enumeration; check for the default prefix using the {@link #getURI getURI} with an argument of "".

return
An enumeration of all prefixes declared in the current context except for the empty (default) prefix.
see
#getDeclaredPrefixes
see
#getURI

        return currentContext.getPrefixes();
    
public java.lang.StringgetURI(java.lang.String prefix)
Look up a prefix and get the currently-mapped Namespace URI.

This method looks up the prefix in the current context. Use the empty string ("") for the default Namespace.

param
prefix The prefix to look up.
return
The associated Namespace URI, or null if the prefix is undeclared in this context.
see
#getPrefix
see
#getPrefixes

        return currentContext.getURI(prefix);
    
public voidpopContext()
Revert to the previous Namespace context.

Normally, you should pop the context at the end of each XML element. After popping the context, all Namespace prefix mappings that were previously in force are restored.

You must not attempt to declare additional Namespace prefixes after popping a context, unless you push another context first.

see
#pushContext

        Context2 parentContext=currentContext.getParent();
        if(parentContext==null)
            throw new EmptyStackException();
        else
            currentContext = parentContext;
    
public java.lang.String[]processName(java.lang.String qName, java.lang.String[] parts, boolean isAttribute)
Process a raw XML 1.0 name.

This method processes a raw XML 1.0 name in the current context by removing the prefix and looking it up among the prefixes currently declared. The return value will be the array supplied by the caller, filled in as follows:

parts[0]
The Namespace URI, or an empty string if none is in use.
parts[1]
The local name (without prefix).
parts[2]
The original raw name.

All of the strings in the array will be internalized. If the raw name has a prefix that has not been declared, then the return value will be null.

Note that attribute names are processed differently than element names: an unprefixed element name will received the default Namespace (if any), while an unprefixed element name will not.

param
qName The raw XML 1.0 name to be processed.
param
parts A string array supplied by the caller, capable of holding at least three members.
param
isAttribute A flag indicating whether this is an attribute name (true) or an element name (false).
return
The supplied array holding three internalized strings representing the Namespace URI (or empty string), the local name, and the raw XML 1.0 name; or null if there is an undeclared prefix.
see
#declarePrefix
see
java.lang.String#intern

        String[] name=currentContext.processName(qName, isAttribute);
        if(name==null)
            return null;

        // JJK: This recopying is required because processName may return
        // a cached result. I Don't Like It. *****
        System.arraycopy(name,0,parts,0,3);
        return parts;
    
public voidpushContext()
Start a new Namespace context.

Normally, you should push a new context at the beginning of each XML element: the new context will automatically inherit the declarations of its parent context, but it will also keep track of which declarations were made within this context.

The Namespace support object always starts with a base context already in force: in this context, only the "xml" prefix is declared.

see
#popContext

        // JJK: Context has a parent pointer.
        // That means we don't need a stack to pop.
        // We may want to retain for reuse, but that can be done via
        // a child pointer.

        Context2 parentContext=currentContext;
        currentContext = parentContext.getChild();
        if (currentContext == null){
                currentContext = new Context2(parentContext);
            }
        else{
            // JJK: This will wipe out any leftover data
            // if we're reusing a previously allocated Context.
            currentContext.setParent(parentContext);
        }
    
public voidreset()
Reset this Namespace support object for reuse.

It is necessary to invoke this method before reusing the Namespace support object for a new session.

        // Discarding the whole stack doesn't save us a lot versus
        // creating a new NamespaceSupport. Do we care, or should we
        // change this to just reset the root context?
        currentContext = new Context2(null);
        currentContext.declarePrefix("xml", XMLNS);