Refactor common class from gson code

The TypeAdapters in the gson-jackson code were nearly identical,
so a common class was factored out.  This also enabled junit tests
to attain 100% coverage on that code, whereas there were a couple
of branches that could not be tested previously.
Addressed new sonar issues.
Removed unused import.

Change-Id: Id8e6460c881c6ce0239768f182e4e652cd10645f
Issue-ID: POLICY-1428
Signed-off-by: Jim Hahn <jrh3@att.com>

1 files changed, 108 insertions, 0 deletions

diff --git a/gson/src/main/java/org/onap/policy/common/gson/internal/JacksonTypeAdapter.java b/gson/src/main/java/org/onap/policy/common/gson/internal/JacksonTypeAdapter.java
new file mode 100644
index 00000000..1171fd4d
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/internal/JacksonTypeAdapter.java
@@ -0,0 +1,108 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2019 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.common.gson.internal;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.util.List;
+
+
+/**
+ * Adapter for a single class that implements a jackson-style behavior.
+ *
+ * @param <T> type of class on which the adapter works
+ */
+public class JacksonTypeAdapter<T> extends TypeAdapter<T> {
+
+    /**
+     * Used to create an object of the given class.
+     */
+    private final TypeAdapter<T> delegate;
+
+    /**
+     * Used to serialize/deserialize a JsonElement.
+     */
+    private final TypeAdapter<JsonElement> elementAdapter;
+
+    /**
+     * Serializers for each item within the object.
+     */
+    private final Serializer[] serializers;
+
+    /**
+     * Deserializers for each item within the object.
+     */
+    private final Deserializer[] deserializers;
+
+    /**
+     * Constructs the object.
+     *
+     * @param gson the associated gson object
+     * @param delegate default constructor for the type
+     * @param serializers the serializers to use to serialize items within the object
+     * @param deserializers the deserializers to use to deserialize items into the object
+     */
+    public JacksonTypeAdapter(Gson gson, TypeAdapter<T> delegate, List<Serializer> serializers,
+                    List<Deserializer> deserializers) {
+        this.delegate = delegate;
+        this.elementAdapter = gson.getAdapter(JsonElement.class);
+        this.serializers = serializers.toArray(new Serializer[0]);
+        this.deserializers = deserializers.toArray(new Deserializer[0]);
+    }
+
+    @Override
+    public void write(JsonWriter out, T value) throws IOException {
+        JsonElement tree = delegate.toJsonTree(value);
+
+        if (tree.isJsonObject()) {
+            JsonObject jsonObj = tree.getAsJsonObject();
+
+            // serialize each item from the value into the target tree
+            for (Serializer serializer : serializers) {
+                serializer.addToTree(value, jsonObj);
+            }
+        }
+
+        elementAdapter.write(out, tree);
+    }
+
+    @Override
+    public T read(JsonReader in) throws IOException {
+        JsonElement tree = elementAdapter.read(in);
+        T object = delegate.fromJsonTree(tree);
+
+        if (tree.isJsonObject()) {
+            JsonObject jsonObj = tree.getAsJsonObject();
+
+            // deserialize each item from the tree into the target object
+            for (Deserializer dser : deserializers) {
+                dser.getFromTree(jsonObj, object);
+            }
+        }
+
+        return object;
+    }
+}