1 files changed, 81 insertions, 0 deletions
diff --git a/gson/src/main/java/com/google/gson/internal/bind/TypeAdapterRuntimeTypeWrapper.java b/gson/src/main/java/com/google/gson/internal/bind/TypeAdapterRuntimeTypeWrapper.java
new file mode 100644
index 00000000..7e52c27d
--- /dev/null
+++ b/gson/src/main/java/com/google/gson/internal/bind/TypeAdapterRuntimeTypeWrapper.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2011 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.google.gson.internal.bind;
+
+import com.google.gson.Gson;
+import com.google.gson.TypeAdapter;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.lang.reflect.TypeVariable;
+
+final class TypeAdapterRuntimeTypeWrapper<T> extends TypeAdapter<T> {
+  private final Gson context;
+  private final TypeAdapter<T> delegate;
+  private final Type type;
+
+  TypeAdapterRuntimeTypeWrapper(Gson context, TypeAdapter<T> delegate, Type type) {
+    this.context = context;
+    this.delegate = delegate;
+    this.type = type;
+  }
+
+  @Override
+  public T read(JsonReader in) throws IOException {
+    return delegate.read(in);
+  }
+
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  @Override
+  public void write(JsonWriter out, T value) throws IOException {
+    // Order of preference for choosing type adapters
+    // First preference: a type adapter registered for the runtime type
+    // Second preference: a type adapter registered for the declared type
+    // Third preference: reflective type adapter for the runtime type (if it is a sub class of the declared type)
+    // Fourth preference: reflective type adapter for the declared type
+
+    TypeAdapter chosen = delegate;
+    Type runtimeType = getRuntimeTypeIfMoreSpecific(type, value);
+    if (runtimeType != type) {
+      TypeAdapter runtimeTypeAdapter = context.getAdapter(TypeToken.get(runtimeType));
+      if (!(runtimeTypeAdapter instanceof ReflectiveTypeAdapterFactory.Adapter)) {
+        // The user registered a type adapter for the runtime type, so we will use that
+        chosen = runtimeTypeAdapter;
+      } else if (!(delegate instanceof ReflectiveTypeAdapterFactory.Adapter)) {
+        // The user registered a type adapter for Base class, so we prefer it over the
+        // reflective type adapter for the runtime type
+        chosen = delegate;
+      } else {
+        // Use the type adapter for runtime type
+        chosen = runtimeTypeAdapter;
+      }
+    }
+    chosen.write(out, value);
+  }
+
+  /**
+   * Finds a compatible runtime type if it is more specific
+   */
+  private Type getRuntimeTypeIfMoreSpecific(Type type, Object value) {
+    if (value != null
+        && (type == Object.class || type instanceof TypeVariable<?> || type instanceof Class<?>)) {
+      type = value.getClass();
+    }
+    return type;
+  }
+}