Convert double to int when decoding via gson

Refactored MapDoubleAdapterFactory, extracting DoubleConverter to be
used by code needing to convert Double to Integer/Long after being
decoded by GSON.
Enhanced StandardCoder to automatically use the above converter if
the desired class is a generic Object.

Change-Id: I1d4e83910de41ceda383f257bfea706db2b8fbbe
Issue-ID: POLICY-1919
Signed-off-by: Jim Hahn <jrh3@att.com>

2 files changed, 141 insertions, 66 deletions

diff --git a/gson/src/main/java/org/onap/policy/common/gson/DoubleConverter.java b/gson/src/main/java/org/onap/policy/common/gson/DoubleConverter.java
new file mode 100644
index 00000000..81803ff2
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/DoubleConverter.java
@@ -0,0 +1,117 @@
+/*
+ * ============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;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+
+/**
+ * Converter for Double values. By default, GSON treats all Objects that are numbers, as
+ * Double. This converts Doubles to Integer or Long, if possible. It converts stand-alone
+ * Doubles, as well as those found within Arrays and Maps.
+ */
+public class DoubleConverter {
+
+    private DoubleConverter() {
+        // do nothing
+    }
+
+    /**
+     * Performs in-place conversion of all values in a list.
+     *
+     * @param list the list whose values are to be converted
+     */
+    public static void convertFromDouble(List<Object> list) {
+        if (list == null) {
+            return;
+        }
+
+        List<Object> original = new ArrayList<>(list);
+
+        list.clear();
+        original.forEach(item -> list.add(convertFromDouble(item)));
+    }
+
+    /**
+     * Performs in-place conversion of all values in a map.
+     *
+     * @param map the map whose values are to be converted
+     */
+    public static void convertFromDouble(Map<String, Object> map) {
+        if (map == null) {
+            return;
+        }
+
+        Set<Entry<String, Object>> set = map.entrySet();
+
+        for (Entry<String, Object> entry : set) {
+            entry.setValue(convertFromDouble(entry.getValue()));
+        }
+    }
+
+    /**
+     * Converts a value. If the value is a List, then it recursively converts the
+     * entries of the List. Likewise with a map, however, the map is converted in place.
+     *
+     * @param value value to be converted
+     * @return the converted value
+     */
+    @SuppressWarnings({"unchecked"})
+    public static Object convertFromDouble(Object value) {
+        if (value == null) {
+            return value;
+        }
+
+        if (value instanceof List) {
+            convertFromDouble((List<Object>) value);
+            return value;
+        }
+
+        if (value instanceof Map) {
+            convertFromDouble((Map<String, Object>) value);
+            return value;
+        }
+
+        if (!(value instanceof Double)) {
+            return value;
+        }
+
+        Double num = (Double) value;
+        long longval = num.longValue();
+
+        if (Double.compare(num.doubleValue(), longval) != 0) {
+            // it isn't integral - return unchanged value
+            return value;
+        }
+
+        // it's integral - determine if it's an integer or a long
+        int intval = (int) longval;
+
+        if (intval == longval) {
+            return intval;
+        }
+
+        return longval;
+    }
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/MapDoubleAdapterFactory.java b/gson/src/main/java/org/onap/policy/common/gson/MapDoubleAdapterFactory.java
index e56f9dd3..bd031999 100644
--- a/gson/src/main/java/org/onap/policy/common/gson/MapDoubleAdapterFactory.java
+++ b/gson/src/main/java/org/onap/policy/common/gson/MapDoubleAdapterFactory.java
@@ -29,33 +29,47 @@ import com.google.gson.stream.JsonWriter;
 import java.io.IOException;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
+import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
-import java.util.Set;
 
 /**
- * Adapter factory for Map&lt;String,Object&gt;. By default, GSON treats all Objects, that
- * are numbers, as Double. This walks the map and converts Doubles to Integer or Long, if
+ * Adapter factory for Map&lt;String,Object&gt; and List&lt;String&gt;. By default, GSON treats all Objects, that
+ * are numbers, as Double. This recursively walks a map/list and converts Doubles to Integer or Long, if
  * possible.
  */
 public class MapDoubleAdapterFactory implements TypeAdapterFactory {
 
     @Override
     public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
-        if (type.getRawType() != Map.class) {
+        if (!isMapType(type) && !isListType(type)) {
             return null;
         }
 
+        TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
+
+        return new MapAdapter<>(delegate);
+    }
+
+    private <T> boolean isMapType(TypeToken<T> type) {
+        if (type.getRawType() != Map.class) {
+            return false;
+        }
+
         Type[] actualParams = ((ParameterizedType) type.getType()).getActualTypeArguments();
 
         // only supports Map<String,Object>
-        if (actualParams[0] != String.class || actualParams[1] != Object.class) {
-            return null;
+        return (actualParams[0] == String.class && actualParams[1] == Object.class);
+    }
+
+    private <T> boolean isListType(TypeToken<T> type) {
+        if (type.getRawType() != List.class) {
+            return false;
         }
 
-        TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
+        Type[] actualParams = ((ParameterizedType) type.getType()).getActualTypeArguments();
 
-        return new MapAdapter<>(delegate);
+        // only supports List<Object>
+        return (actualParams[0] == Object.class);
     }
 
     /**
@@ -88,65 +102,9 @@ public class MapDoubleAdapterFactory implements TypeAdapterFactory {
         public T read(JsonReader in) throws IOException {
             T value = delegate.read(in);
 
-            @SuppressWarnings("rawtypes")
-            Map map = (Map) value;
-
-            convertFromDouble(map);
+            DoubleConverter.convertFromDouble(value);
 
             return value;
         }
-
-        /**
-         * Performs conversion of all values in a map.
-         *
-         * @param map the map whose values are to be converted
-         */
-        @SuppressWarnings("rawtypes")
-        private void convertFromDouble(Map map) {
-
-            @SuppressWarnings("unchecked")
-            Set<Entry> set = map.entrySet();
-
-            for (Entry entry : set) {
-                convertFromDouble(entry);
-            }
-        }
-
-        /**
-         * Converts an entry's value. If the value is a Map, then it recursively converts
-         * the entries of the map.
-         *
-         * @param entry entry whose value is to be converted
-         */
-        @SuppressWarnings({"unchecked", "rawtypes"})
-        private void convertFromDouble(Entry entry) {
-            Object obj = entry.getValue();
-
-            if (obj instanceof Map) {
-                convertFromDouble((Map) obj);
-                return;
-            }
-
-            if (!(obj instanceof Double)) {
-                return;
-            }
-
-            Double num = (Double) obj;
-            long longval = num.longValue();
-
-            if (Double.compare(num.doubleValue(), longval) == 0) {
-                // it's integral - determine if it's an integer or a long
-                int intval = (int) longval;
-
-                if (intval == longval) {
-                    // it fits in an integer
-                    entry.setValue(intval);
-
-                } else {
-                    // doesn't fit in an integer - must be a long
-                    entry.setValue(longval);
-                }
-            }
-        }
     }
 }