Big cleanups and fixes:

- Groupby-Nodes with prototype now use an internal DbMapping object
with the specified prototype's DbMapping as parent mapping. This is
necessary because the groupby prototype may be used in different places
and with different relational constraints.
- Cleaned up and reduced duplcate code in Getters for Property Relations
and DbMappings. Now everything is based on getExactPropertyRelation(str)
and getPropertyRelation() methods.
- Replaced Hashtables with HashMaps for performance reasons after
noticing that they are accessed quite often within a single request.

src/helma/objectmodel/db/DbMapping.java

@@ -6,7 +6,7 @@ package helma.objectmodel.db;
 import helma.framework.core.Application;
 import helma.util.Updatable;
 import helma.util.SystemProperties;
-import java.util.Hashtable;
+import java.util.HashMap;
 import java.util.Enumeration;
 import java.util.StringTokenizer;
 import java.sql.*;
@@ -49,9 +49,9 @@ public class DbMapping implements Updatable {
     DbMapping groupbyMapping;
 
      // Map of property names to Relations objects
-    Hashtable prop2db;
+    HashMap prop2db;
      // Map of db columns to Relations objects
-    Hashtable db2prop;
+    HashMap db2prop;
 
     // db field used as primary key
     String idField;
@@ -64,7 +64,6 @@ public class DbMapping implements Updatable {
     String extendsProto;
     // dbmapping of parent prototype, if any
     DbMapping parentMapping;
-    boolean inheritsMapping;
 
     // db field that specifies the prototype of an object
     String prototypeField;
@@ -92,8 +91,8 @@ public class DbMapping implements Updatable {
 
 	this.app = app;
 
-	prop2db = new Hashtable ();
-	db2prop = new Hashtable ();
+	prop2db = new HashMap ();
+	db2prop = new HashMap ();
 
 	parent = null;
 	// subnodes = null;
@@ -109,8 +108,8 @@ public class DbMapping implements Updatable {
 	this.app = app;
 	this.typename = typename;
 
-	prop2db = new Hashtable ();
-	db2prop = new Hashtable ();
+	prop2db = new HashMap ();
+	db2prop = new HashMap ();
 
 	parent = null;
 	// subnodes = null;
@@ -199,8 +198,8 @@ public class DbMapping implements Updatable {
 	
 	// if (table != null && source != null) {
 	// app.logEvent ("set data source for "+typename+" to "+source);
-	Hashtable p2d = new Hashtable ();
-	Hashtable d2p = new Hashtable ();
+	HashMap p2d = new HashMap ();
+	HashMap d2p = new HashMap ();
 
 	for (Enumeration e=props.keys(); e.hasMoreElements(); ) {
 	    String propName = (String) e.nextElement ();
@@ -268,8 +267,7 @@ public class DbMapping implements Updatable {
 	    propertiesRel = null;
 
 	if (groupbyMapping != null) {
-	    groupbyMapping.subnodesRel = subnodesRel == null ? null : subnodesRel.getGroupbySubnodeRelation ();
-	    groupbyMapping.propertiesRel = propertiesRel == null ? null : propertiesRel.getGroupbyPropertyRelation ();
+	    initGroupbyMapping ();
 	    groupbyMapping.lastTypeChange = this.lastTypeChange;
 	}
     }
@@ -458,23 +456,12 @@ public class DbMapping implements Updatable {
 
 
     public DbMapping getExactPropertyMapping (String propname) {
-	if (propname == null)
-	    return null;
-	Relation rel = (Relation) prop2db.get (propname.toLowerCase());
-	if (rel == null && parentMapping != null)
-	    return parentMapping.getExactPropertyMapping (propname);
+	Relation rel = getExactPropertyRelation (propname);
 	return rel != null ? rel.otherType : null;
     }
 
     public DbMapping getPropertyMapping (String propname) {
-	if (propname == null) {
-	    if (propertiesRel != null)
-	        return propertiesRel.otherType;
-	    if (parentMapping != null)
-	        return parentMapping.getPropertyMapping (null);
-	}
-
-	Relation rel = (Relation) prop2db.get (propname.toLowerCase());
+	Relation rel = getPropertyRelation (propname);
 	if (rel != null) {
 	    // if this is a virtual node, it doesn't have a dbmapping
 	    if (rel.virtual && rel.prototype == null)
@@ -482,11 +469,6 @@ public class DbMapping implements Updatable {
 	    else
 	        return rel.otherType;
 	}
-
-	if (propertiesRel != null)
-	    return propertiesRel.otherType;
-	if (parentMapping != null)
-	    return parentMapping.getPropertyMapping (propname);
 	return null;
     }
 
@@ -498,13 +480,22 @@ public class DbMapping implements Updatable {
 	if (subnodesRel == null || subnodesRel.groupby == null)
 	    return null;
 	if (groupbyMapping == null) {
+	    initGroupbyMapping ();
+	}
+	return groupbyMapping;
+    }
+
+    /**
+     * Initialize the dbmapping used for group-by nodes.
+     */
+    private void initGroupbyMapping () {
 	// if a prototype is defined for groupby nodes, use that
-	    // DbMapping instead of creating a new one
-	    if (subnodesRel.groupbyprototype != null)
-	        groupbyMapping = app.getDbMapping (subnodesRel.groupbyprototype);
 	// if mapping doesn' exist or isn't defined, create a new (anonymous internal) one
-	    if (groupbyMapping == null)
 	groupbyMapping = new DbMapping (app);
+	// If a mapping is defined, make the internal mapping inherit from
+	// the defined named prototype.
+	if (subnodesRel.groupbyprototype != null)
+	    groupbyMapping.parentMapping = app.getDbMapping (subnodesRel.groupbyprototype);
 	groupbyMapping.subnodesRel = subnodesRel.getGroupbySubnodeRelation ();
 	if (propertiesRel != null)
 	    groupbyMapping.propertiesRel = propertiesRel.getGroupbyPropertyRelation ();
@@ -512,16 +503,14 @@ public class DbMapping implements Updatable {
 	    groupbyMapping.propertiesRel = subnodesRel.getGroupbyPropertyRelation ();
 	groupbyMapping.typename = subnodesRel.groupbyprototype;
     }
-	return groupbyMapping;
-    }
 
     /* public void setPropertyMapping (DbMapping pm) {
 	properties = pm;
     } */
 
-    public void setSubnodeRelation (Relation rel) {
+    /* public void setSubnodeRelation (Relation rel) {
 	subnodesRel = rel;
-    }
+    } */
 
     public void setPropertyRelation (Relation rel) {
 	propertiesRel = rel;
@@ -542,10 +531,21 @@ public class DbMapping implements Updatable {
     public Relation getPropertyRelation (String propname) {
 	if (propname == null)
 	    return getPropertyRelation ();
+	// first try finding an exact match for the property name
+	Relation rel = getExactPropertyRelation (propname);
+	// if not defined, return the generic property mapping
+	if (rel == null)
+	    rel = getPropertyRelation ();
+	return rel;
+    }
+
+    public Relation getExactPropertyRelation (String propname) {
+	if (propname == null)
+	    return null;
 	Relation rel = (Relation) prop2db.get (propname.toLowerCase());
-	if (rel == null && propertiesRel == null && parentMapping != null)
-	    return parentMapping.getPropertyRelation (propname);
-	return rel != null ? rel : propertiesRel;
+	if (rel == null && parentMapping != null)
+	    rel = parentMapping.getExactPropertyRelation (propname);
+	return rel;
     }
 
     public String getSubnodeGroupby () {
@@ -614,7 +614,7 @@ public class DbMapping implements Updatable {
     }
 
     public String toString () {
-	if (app == null)
+	if (typename == null)
 	    return "[unspecified internal DbMapping]";
 	else
 	    return ("["+app.getName()+"."+typename+"]");
@@ -642,13 +642,13 @@ public class DbMapping implements Updatable {
 	return lastID;
     }
 
-    public Hashtable getProp2DB () {
+    public HashMap getProp2DB () {
 	if (table == null && parentMapping != null)
 	    return parentMapping.getProp2DB ();
 	return prop2db;
     }
 
-    public Hashtable getDB2Prop () {
+    public HashMap getDB2Prop () {
 	if (table == null && parentMapping != null)
 	    return parentMapping.getDB2Prop ();
 	return db2prop;
@@ -694,5 +694,10 @@ public class DbMapping implements Updatable {
 	return false;
     }
 
+
+    public DbMapping getParentMapping () {
+	return parentMapping;
+    }
+
 }