Created the facilities for transmitting distributed objects and derived

classes over the wire (by inspecting their fields and sending those
directly).


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@8 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/io/FieldMarshallerRegistry.java

@@ -0,0 +1,67 @@
+//
+// $Id: FieldMarshallerRegistry.java,v 1.1 2001/05/30 00:16:00 mdb Exp $
+
+package com.samskivert.cocktail.cher.dobj.net;
+
+import java.lang.reflect.Field;
+import java.util.Hashtable;
+import com.samskivert.cocktail.cher.Log;
+
+/**
+ * Field marshaller instances are registered for each type of field that
+ * is supported in a distributed object.
+ */
+public class FieldMarshallerRegistry
+{
+    /**
+     * Returns a field marshaller that can marshall and unmarshall the
+     * specified type of field. If no marshaller is registered for that
+     * field type, an illegal argument exception will be thrown.
+     * Distributed objects must not contain fields that cannot be
+     * transmitted on the wire.
+     */
+    public static FieldMarshaller getMarshaller (Field field)
+    {
+        Class clazz = field.getType();
+        FieldMarshaller marsh = (FieldMarshaller)_registry.get(clazz);
+        if (marsh == null) {
+            String errmsg = "No field marshaller registered for fields " +
+                "of type " + clazz.getName() + ".";
+            throw new IllegalArgumentException(errmsg);
+        }
+        return marsh;
+    }
+
+    /**
+     * Registers the specified field marshaller as the one to use for
+     * fields of the specified class. This assumes that the field
+     * marshaller implementation provides a prototype field of the type it
+     * knows how to marshall by the name of <code>prototype</code>.
+     *
+     * @param clazz the field marshaller class to be registered.
+     */
+    protected static void registerMarshaller (Class clazz)
+    {
+        try {
+            _registry.put(clazz.getField("prototype").getType(),
+                          clazz.newInstance());
+        } catch (Exception e) {
+            Log.warning("Unable to register field marshaller " +
+                        "[class=" + clazz.getName() + "].");
+            Log.logStackTrace(e);
+        }
+    }
+
+    protected static Hashtable _registry = new Hashtable();
+
+    static {
+        // register our field marshallers
+        registerMarshaller(BooleanFieldMarshaller.class);
+        registerMarshaller(ShortFieldMarshaller.class);
+        registerMarshaller(IntFieldMarshaller.class);
+        registerMarshaller(LongFieldMarshaller.class);
+        registerMarshaller(FloatFieldMarshaller.class);
+        registerMarshaller(DoubleFieldMarshaller.class);
+        registerMarshaller(StringFieldMarshaller.class);
+    }
+}