streamline rebased Gson into source; rebase was done to prevent conflict with other plugins (like upcoming WorldGuard release) which also use Gson; Bukkit doesn't yet handle such conflicts properly

src/com/bukkit/mcteam/gson/JsonDeserializationVisitor.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2008 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.bukkit.mcteam.gson;
+
+import java.lang.reflect.Type;
+
+/**
+ * Abstract data value container for the {@link ObjectNavigator.Visitor}
+ * implementations.  This class exposes the {@link #getTarget()} method
+ * which returns the class that was visited by this object.
+ *
+ * @author Inderjeet Singh
+ * @author Joel Leitch
+ */
+abstract class JsonDeserializationVisitor<T> implements ObjectNavigator.Visitor {
+
+  protected final ObjectNavigatorFactory factory;
+  protected final ObjectConstructor objectConstructor;
+  protected final ParameterizedTypeHandlerMap<JsonDeserializer<?>> deserializers;
+  protected T target;
+  protected final JsonElement json;
+  protected final Type targetType;
+  protected final JsonDeserializationContext context;
+  protected boolean constructed;
+
+  public JsonDeserializationVisitor(JsonElement json, Type targetType,
+      ObjectNavigatorFactory factory, ObjectConstructor objectConstructor,
+      ParameterizedTypeHandlerMap<JsonDeserializer<?>> deserializers,
+      JsonDeserializationContext context) {
+    Preconditions.checkNotNull(json);
+    this.targetType = targetType;
+    this.factory = factory;
+    this.objectConstructor = objectConstructor;
+    this.deserializers = deserializers;
+    this.json = json;
+    this.context = context;
+    this.constructed = false;
+  }
+
+  public T getTarget() {
+    if (!constructed) {
+      target = constructTarget();
+      constructed = true;
+    }
+    return target;
+  }
+
+  protected abstract T constructTarget();
+
+  public void start(ObjectTypePair node) {
+  }
+
+  public void end(ObjectTypePair node) {
+  }
+
+  @SuppressWarnings("unchecked")
+  public final boolean visitUsingCustomHandler(ObjectTypePair objTypePair) {
+    Pair<JsonDeserializer<?>, ObjectTypePair> pair = objTypePair.getMatchingHandler(deserializers);
+    if (pair == null) {
+      return false;
+    }    
+    Object value = invokeCustomDeserializer(json, pair);
+    target = (T) value;
+    constructed = true;
+    return true;
+  }
+
+  protected Object invokeCustomDeserializer(JsonElement element, 
+      Pair<JsonDeserializer<?>, ObjectTypePair> pair) {
+    if (element == null || element.isJsonNull()) {
+      return null;
+    }
+    Type objType = pair.second.type;
+    return (pair.first).deserialize(element, objType, context);
+  }
+
+  final Object visitChildAsObject(Type childType, JsonElement jsonChild) {
+    JsonDeserializationVisitor<?> childVisitor =
+        new JsonObjectDeserializationVisitor<Object>(jsonChild, childType,
+            factory, objectConstructor, deserializers, context);
+    return visitChild(childType, childVisitor);
+  }
+
+  final Object visitChildAsArray(Type childType, JsonArray jsonChild) {
+    JsonDeserializationVisitor<?> childVisitor =
+        new JsonArrayDeserializationVisitor<Object>(jsonChild.getAsJsonArray(), childType,
+            factory, objectConstructor, deserializers, context);
+    return visitChild(childType, childVisitor);
+  }
+
+  private Object visitChild(Type type, JsonDeserializationVisitor<?> childVisitor) {
+    ObjectNavigator on = factory.create(new ObjectTypePair(null, type, false));
+    on.accept(childVisitor);
+    // the underlying object may have changed during the construction phase
+    // This happens primarily because of custom deserializers
+    return childVisitor.getTarget();
+  }
+}