org.apache.taglibs.standard.lang.jstl.EnumeratedMap Maven / Gradle / Ivy
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package org.apache.taglibs.standard.lang.jstl;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
/**
*
* This is a Map implementation driven by a data source that only
* provides an enumeration of keys and a getValue(key) method. This
* class must be subclassed to implement those methods.
*
*
Some of the methods may incur a performance penalty that
* involves enumerating the entire data source. In these cases, the
* Map will try to save the results of that enumeration, but only if
* the underlying data source is immutable.
*
* @author Nathan Abramson - Art Technology Group
* @version $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: kchung $
**/
public abstract class EnumeratedMap
implements Map
{
//-------------------------------------
// Member variables
//-------------------------------------
Map mMap;
//-------------------------------------
public void clear ()
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public boolean containsKey (Object pKey)
{
return getValue (pKey) != null;
}
//-------------------------------------
public boolean containsValue (Object pValue)
{
return getAsMap ().containsValue (pValue);
}
//-------------------------------------
public Set entrySet ()
{
return getAsMap ().entrySet ();
}
//-------------------------------------
public Object get (Object pKey)
{
return getValue (pKey);
}
//-------------------------------------
public boolean isEmpty ()
{
return !enumerateKeys ().hasMoreElements ();
}
//-------------------------------------
public Set keySet ()
{
return getAsMap ().keySet ();
}
//-------------------------------------
public Object put (Object pKey, Object pValue)
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public void putAll (Map pMap)
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public Object remove (Object pKey)
{
throw new UnsupportedOperationException ();
}
//-------------------------------------
public int size ()
{
return getAsMap ().size ();
}
//-------------------------------------
public Collection values ()
{
return getAsMap ().values ();
}
//-------------------------------------
// Abstract methods
//-------------------------------------
/**
*
* Returns an enumeration of the keys
**/
public abstract Enumeration enumerateKeys ();
//-------------------------------------
/**
*
* Returns true if it is possible for this data source to change
**/
public abstract boolean isMutable ();
//-------------------------------------
/**
*
* Returns the value associated with the given key, or null if not
* found.
**/
public abstract Object getValue (Object pKey);
//-------------------------------------
/**
*
* Converts the MapSource to a Map. If the map is not mutable, this
* is cached
**/
public Map getAsMap ()
{
if (mMap != null) {
return mMap;
}
else {
Map m = convertToMap ();
if (!isMutable ()) {
mMap = m;
}
return m;
}
}
//-------------------------------------
/**
*
* Converts to a Map
**/
Map convertToMap ()
{
Map ret = new HashMap ();
for (Enumeration e = enumerateKeys (); e.hasMoreElements (); ) {
Object key = e.nextElement ();
Object value = getValue (key);
ret.put (key, value);
}
return ret;
}
//-------------------------------------
}