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, 206 insertions, 0 deletions

diff --git a/gson/src/test/java/org/onap/policy/common/gson/internal/JacksonTypeAdapterTest.java b/gson/src/test/java/org/onap/policy/common/gson/internal/JacksonTypeAdapterTest.java
new file mode 100644
index 00000000..a75fe17e
--- /dev/null
+++ b/gson/src/test/java/org/onap/policy/common/gson/internal/JacksonTypeAdapterTest.java
@@ -0,0 +1,206 @@
+/*
+ * ============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 static org.junit.Assert.assertEquals;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonObject;
+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.StringReader;
+import java.io.StringWriter;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Before;
+import org.junit.Test;
+
+public class JacksonTypeAdapterTest {
+    private static final String HELLO = "hello";
+    private static final String WORLD = "world";
+
+    /**
+     * Gson object that excludes fields, as we're going to process the fields ourselves.
+     */
+    private static Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create();
+
+    private JacksonTypeAdapter<Data> adapter;
+    private List<Serializer> sers;
+    private List<Deserializer> desers;
+
+    /**
+     * Initializes the previously defined fields.
+     */
+    @Before
+    public void setUp() {
+        // create list of serializers, one for "id" and one for "value"
+        sers = new ArrayList<>(2);
+        sers.add(new NamedSer(HELLO) {
+            @Override
+            protected String getValue(Data data) {
+                return data.id;
+            }
+        });
+        sers.add(new NamedSer(WORLD) {
+            @Override
+            protected String getValue(Data data) {
+                return data.value;
+            }
+        });
+
+        // create list of deserializers, one for "id" and one for "value"
+        desers = new ArrayList<>(2);
+        desers.add(new NamedDeser(HELLO) {
+            @Override
+            protected void setValue(Data data, String value) {
+                data.id = value;
+            }
+        });
+        desers.add(new NamedDeser(WORLD) {
+            @Override
+            protected void setValue(Data data, String value) {
+                data.value = value;
+            }
+        });
+
+        TypeAdapter<Data> delegate = gson.getDelegateAdapter(null, TypeToken.get(Data.class));
+
+        adapter = new JacksonTypeAdapter<>(gson, delegate, sers, desers);
+    }
+
+    @Test
+    public void testWriteJsonWriterT() throws Exception {
+        Data data = new Data("abc", "def");
+
+        StringWriter wtr = new StringWriter();
+        adapter.write(new JsonWriter(wtr), data);
+
+        assertEquals("{'hello':'abc','world':'def'}".replace('\'', '"'), wtr.toString());
+    }
+
+    /**
+     * Tests the case where the delegate does not return a JsonObject.
+     *
+     * @throws Exception if an error occurs
+     */
+    @Test
+    public void testWriteJsonWriterT_NotAnObject() throws Exception {
+        TypeAdapter<String> delegate = gson.getAdapter(String.class);
+        JacksonTypeAdapter<String> stringAdapter = new JacksonTypeAdapter<>(gson, delegate, sers, desers);
+
+        StringWriter wtr = new StringWriter();
+        stringAdapter.write(new JsonWriter(wtr), "write text");
+
+        assertEquals("'write text'".replace('\'', '"'), wtr.toString());
+    }
+
+    @Test
+    public void testReadJsonReader() throws Exception {
+        Data data = adapter
+                        .read(new JsonReader(new StringReader("{'hello':'four','world':'score'}".replace('\'', '"'))));
+
+        assertEquals(new Data("four", "score").toString(), data.toString());
+    }
+
+    /**
+     * Tests the case where the delegate does not use a JsonObject.
+     *
+     * @throws Exception if an error occurs
+     */
+    @Test
+    public void testReadJsonReader_NotAnObject() throws Exception {
+        TypeAdapter<String> delegate = gson.getAdapter(String.class);
+        JacksonTypeAdapter<String> stringAdapter = new JacksonTypeAdapter<>(gson, delegate, sers, desers);
+
+        String data = stringAdapter.read(new JsonReader(new StringReader("'read text'".replace('\'', '"'))));
+
+        assertEquals("read text", data.toString());
+    }
+
+    private static class Data {
+        private String id;
+        private String value;
+
+        /*
+         * This is invoked by gson via reflection, thus no direct invocation. Hence it has
+         * to be labeled "unused".
+         */
+        @SuppressWarnings("unused")
+        public Data() {
+            super();
+        }
+
+        public Data(String id, String value) {
+            this.id = id;
+            this.value = value;
+        }
+
+        @Override
+        public String toString() {
+            return "Data [id=" + id + ", value=" + value + "]";
+        }
+    }
+
+    private abstract static class NamedSer implements Serializer {
+        private final String name;
+
+        /**
+         * Constructs the object.
+         *
+         * @param name the name of the field, when stored in a JsonObject
+         */
+        public NamedSer(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public void addToTree(Object source, JsonObject target) {
+            Data data = (Data) source;
+            target.addProperty(name, getValue(data));
+        }
+
+        protected abstract String getValue(Data data);
+    }
+
+    private abstract static class NamedDeser implements Deserializer {
+        private final String name;
+
+        /**
+         * Constructs the object.
+         *
+         * @param name the name of the field, when stored in a JsonObject
+         */
+        public NamedDeser(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public void getFromTree(JsonObject source, Object target) {
+            Data data = (Data) target;
+            setValue(data, source.get(name).getAsString());
+        }
+
+        protected abstract void setValue(Data data, String value);
+    }
+}