Merge "Add gson handler and tests"

7 files changed, 804 insertions, 0 deletions

diff --git a/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonSerializer.java b/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonSerializer.java
new file mode 100644
index 00000000..db9c1c7e
--- /dev/null
+++ b/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonSerializer.java
@@ -0,0 +1,37 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * policy-management
+ * ================================================================================
+ * Copyright (C) 2017-2018 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.utils.gson;
+
+import com.google.gson.TypeAdapter;
+import com.google.gson.stream.JsonReader;
+import java.io.IOException;
+
+/**
+ * Gson serializer, providing stub implementation of "read".
+ *
+ * @param <T> type of object that this serializes
+ */
+public abstract class GsonSerializer<T> extends TypeAdapter<T> {
+    @Override
+    public T read(JsonReader in) throws IOException {
+        throw new UnsupportedOperationException("read from pseudo TypeAdapter");
+    }
+}
diff --git a/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonTestUtils.java b/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonTestUtils.java
new file mode 100644
index 00000000..bfdca97c
--- /dev/null
+++ b/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonTestUtils.java
@@ -0,0 +1,314 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * policy-management
+ * ================================================================================
+ * Copyright (C) 2017-2018 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.utils.gson;
+
+import static org.junit.Assert.assertEquals;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map.Entry;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import javax.script.Bindings;
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Utilities used to test encoding and decoding of Policy objects.
+ */
+public class GsonTestUtils {
+
+    private static final Logger logger = LoggerFactory.getLogger(GsonTestUtils.class);
+
+    /**
+     * Matches script items, of the form ${xxx}, within text.
+     */
+    private static final Pattern SCRIPT_PAT = Pattern.compile("\\$\\{([^}]+)\\}");
+
+    /**
+     * Engine used to interpolate strings before they're compared.
+     */
+    private static volatile ScriptEngine engine = null;
+
+    /**
+     * Used to encode and decode an object via gson.
+     */
+    private Gson gson;
+
+    /**
+     * Constructs the object.
+     */
+    public GsonTestUtils() {
+        GsonTestUtils other = new GsonTestUtilsBuilder().build();
+
+        gson = other.gson;
+    }
+
+    /**
+     * Constructs the object.
+     *
+     * @param gson used to encode via gson
+     */
+    protected GsonTestUtils(Gson gson) {
+        this.gson = gson;
+    }
+
+    public Gson getGson() {
+        return gson;
+    }
+
+    /**
+     * Serializes and then deserializes an object using gson.
+     *
+     * @param object the object to be serialized
+     * @param clazz the class of object to deserialize
+     * @return the deserialized object
+     */
+    public <T> T gsonRoundTrip(T object, Class<T> clazz) {
+        String sgson = gsonEncode(object);
+        return gson.fromJson(sgson, clazz);
+    }
+
+    /**
+     * Encodes an object using gson and then compares it to the expected value, after
+     * sorting the elements. The class name is used to find the json file, whose contents
+     * is interpolated (i.e., script elements, of the form ${obj.xxx}, are expanded).
+     *
+     * @param object the object to be encoded
+     * @param expected the expected value
+     * @throws Exception if the file cannot be read
+     */
+    public void compareGson(Object object, Class<?> expected) {
+        compareGson(object, new File(expected.getSimpleName() + ".json"));
+    }
+
+    /**
+     * Encodes an object using gson and then compares it to the expected value, after
+     * sorting the elements. The content of the file is interpolated (i.e., script
+     * elements, of the form ${obj.xxx}, are expanded).
+     *
+     * @param object the object to be encoded
+     * @param expected the expected value
+     * @throws Exception if the file cannot be read
+     */
+    public void compareGson(Object object, File expected) {
+        // file is not required to have a full path - find it via getResource()
+        URL url = object.getClass().getResource(expected.getName());
+        if (url == null) {
+            throw new JsonParseException(new FileNotFoundException(expected.getName()));
+        }
+
+        String expectedText;
+        try {
+            expectedText = readFile(new File(url.getFile()));
+
+        } catch (IOException e) {
+            throw new JsonParseException("error reading: " + expected, e);
+        }
+
+        compareGson(object, expectedText);
+    }
+
+    /**
+     * Encodes an object using gson and then compares it to the expected value, after
+     * sorting the elements. The expected value is interpolated (i.e., script elements, of
+     * the form ${obj.xxx}, are expanded).
+     *
+     * @param object the object to be encoded
+     * @param expected the expected value
+     */
+    public void compareGson(Object object, String expected) {
+        String result = applyScripts(expected, object);
+        compareGson(object, gson.fromJson(result, JsonElement.class));
+    }
+
+    /**
+     * Encodes an object using gson and then compares it to the expected value, after
+     * sorting the elements.
+     *
+     * @param object the object to be encoded
+     * @param expected the expected value
+     */
+    public void compareGson(Object object, JsonElement expected) {
+        String sgson = gsonEncode(object);
+
+        JsonElement gsonjo = reorder(gson.fromJson(sgson, JsonElement.class));
+        JsonElement expjo = reorder(expected);
+
+        assertEquals(expjo.toString(), gsonjo.toString());
+    }
+
+    /**
+     * Reads the content of a file.
+     * @param file file to read
+     * @return the content of the file
+     * @throws IOException if an error occurs
+     */
+    protected String readFile(File file) throws IOException {
+        return new String(Files.readAllBytes(file.toPath()), StandardCharsets.UTF_8);
+    }
+
+
+    /**
+     * Interpolates script elements, of the form ${obj.xxx}, within some text. The script
+     * is evaluated via javascript, where "obj" references the object used by each script
+     * element.
+     *
+     * @param object object to be used by the script
+     * @param text text to be evaluated
+     * @return the text, after interpolating the script elements
+     */
+    public String applyScripts(String text, Object object) {
+        Matcher mat = SCRIPT_PAT.matcher(text);
+        if (!mat.find()) {
+            // contains no script elements - just return it as is
+            return text;
+        }
+
+        // create the engine and bind the object to the variable, "obj"
+        if (engine == null) {
+            // race condition here, but it's ok to overwrite with a new engine
+            engine = new ScriptEngineManager().getEngineByName("javascript");
+        }
+
+        Bindings bindings = engine.createBindings();
+        bindings.put("obj", object);
+
+        // work our way through the text, interpolating script elements as we go
+        StringBuilder bldr = new StringBuilder();
+        int ilast = 0;
+        mat.reset();
+        while (mat.find(ilast)) {
+            // append segment that appears between last match and this
+            int inext = mat.start();
+            bldr.append(text.substring(ilast, inext));
+
+            // next match begins after the current match
+            ilast = mat.end();
+
+            // interpolate the script
+            String script = mat.group(1);
+            try {
+                Object result = engine.eval(script, bindings);
+                bldr.append(result == null ? "null" : result.toString());
+
+            } catch (ScriptException e) {
+                throw new RuntimeException("cannot expand element: " + mat.group(), e);
+            }
+        }
+
+        // append final segment
+        bldr.append(text.substring(ilast));
+
+        return bldr.toString();
+    }
+
+    /**
+     * Encodes an object using gson.
+     *
+     * @param object the object to be encoded
+     * @return the encoded object
+     */
+    public String gsonEncode(Object object) {
+        String sgson = gson.toJson(object);
+        logger.debug("gson=" + sgson);
+        return sgson;
+    }
+
+    /**
+     * Recursively re-orders a json object, arranging the keys alphabetically and removing
+     * null items.
+     *
+     * @param jsonObj object from which nulls are to be removed
+     * @return a new object, without the null items
+     */
+    public JsonObject reorder(JsonObject jsonObj) {
+        JsonObject newjo = new JsonObject();
+
+        // sort the keys before copying to the new object
+        List<Entry<String, JsonElement>> sortedSet = new ArrayList<>(jsonObj.entrySet());
+        Collections.sort(sortedSet, (left, right) -> left.getKey().compareTo(right.getKey()));
+
+        for (Entry<String, JsonElement> ent : sortedSet) {
+            JsonElement val = ent.getValue();
+            if (val.isJsonNull()) {
+                continue;
+            }
+
+            newjo.add(ent.getKey(), reorder(val));
+        }
+
+        return newjo;
+    }
+
+    /**
+     * Recursively re-orders a json array, arranging the keys alphabetically and removing
+     * null items.
+     *
+     * @param jsonArray array from which nulls are to be removed
+     * @return a new array, with null items removed from all elements
+     */
+    public JsonArray reorder(JsonArray jsonArray) {
+        JsonArray newarr = new JsonArray();
+        for (JsonElement ent : jsonArray) {
+            newarr.add(reorder(ent));
+        }
+
+        return newarr;
+    }
+
+    /**
+     * Recursively re-orders a json element, arranging the keys alphabetically and
+     * removing null items.
+     *
+     * @param jsonEl element from which nulls are to be removed
+     * @return a new element, with null items removed
+     */
+    public JsonElement reorder(JsonElement jsonEl) {
+        if (jsonEl == null) {
+            return null;
+
+        } else if (jsonEl.isJsonObject()) {
+            return reorder(jsonEl.getAsJsonObject());
+
+        } else if (jsonEl.isJsonArray()) {
+            return reorder(jsonEl.getAsJsonArray());
+
+        } else {
+            return jsonEl;
+        }
+    }
+}
diff --git a/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonTestUtilsBuilder.java b/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonTestUtilsBuilder.java
new file mode 100644
index 00000000..1f697fdb
--- /dev/null
+++ b/utils-test/src/main/java/org/onap/policy/common/utils/gson/GsonTestUtilsBuilder.java
@@ -0,0 +1,61 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * policy-management
+ * ================================================================================
+ * Copyright (C) 2017-2018 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.utils.gson;
+
+import com.google.gson.GsonBuilder;
+import com.google.gson.TypeAdapterFactory;
+import org.onap.policy.common.gson.JacksonHandler;
+
+/**
+ * Used to builder a utility class.
+ */
+public class GsonTestUtilsBuilder {
+    private final GsonBuilder gsonBldr;
+
+    /**
+     * Constructs the object.
+     */
+    public GsonTestUtilsBuilder() {
+        gsonBldr = new GsonBuilder();
+
+        // register jackson behaviors with the builder
+        new JacksonHandler(gsonBldr);
+    }
+
+    /**
+     * Builds the utility.
+     *
+     * @return a new utility
+     */
+    public GsonTestUtils build() {
+        return new GsonTestUtils(gsonBldr.create());
+    }
+
+    /**
+     * Adds gson support for serializing a mock of a class.
+     *
+     * @param clazz mocked class to be supported
+     * @param sgson gson serializer
+     */
+    protected <T> void addMock(Class<T> clazz, TypeAdapterFactory sgson) {
+        gsonBldr.registerTypeAdapterFactory(sgson);
+    }
+}
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonSerializerTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonSerializerTest.java
new file mode 100644
index 00000000..82f5ede0
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonSerializerTest.java
@@ -0,0 +1,47 @@
+/*
+ * ============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.utils.gson;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.io.StringReader;
+import org.junit.Test;
+
+public class GsonSerializerTest {
+
+    @Test
+    public void testReadJsonReader() {
+        JsonReader rdr = new JsonReader(new StringReader("10"));
+
+        GsonSerializer<Object> ser = new GsonSerializer<Object>() {
+            @Override
+            public void write(JsonWriter out, Object value) throws IOException {
+                // do nothing
+            }
+        };
+
+        assertThatThrownBy(() -> ser.read(rdr)).isInstanceOf(UnsupportedOperationException.class)
+                        .hasMessage("read from pseudo TypeAdapter");
+    }
+}
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonTestUtilsBuilderTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonTestUtilsBuilderTest.java
new file mode 100644
index 00000000..3e4244dd
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonTestUtilsBuilderTest.java
@@ -0,0 +1,93 @@
+/*
+ * ============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.utils.gson;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.gson.Gson;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GsonTestUtilsBuilderTest {
+
+    private GsonTestUtilsBuilder bldr;
+    private GsonTestUtils utils;
+
+    @Before
+    public void setUp() {
+        bldr = new MyBuilder();
+        utils = bldr.build();
+    }
+
+    @Test
+    public void testBuilderAddMock() {
+        PreMock pre = mock(PreMock.class);
+        when(pre.getId()).thenReturn(2000);
+
+        assertEquals("{\"name\":2000}", utils.gsonEncode(pre));
+    }
+
+    /**
+     * Builder that provides an adapter for mock(PreMock.class).
+     */
+    private static class MyBuilder extends GsonTestUtilsBuilder {
+        public MyBuilder() {
+            TypeAdapterFactory sgson = new TypeAdapterFactory() {
+                @Override
+                public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+                    Class<? super T> clazz = type.getRawType();
+
+                    if (PreMock.class.isAssignableFrom(clazz)) {
+                        return new GsonSerializer<T>() {
+                            @Override
+                            public void write(JsonWriter out, T value) throws IOException {
+                                PreMock obj = (PreMock) value;
+                                out.beginObject().name("name").value(obj.getId()).endObject();
+                            }
+                        };
+                    }
+
+                    return null;
+                }
+            };
+
+            addMock(PreMock.class, sgson);
+        }
+    }
+
+    /**
+     * Class that will be mocked.
+     */
+    public static class PreMock {
+        protected int id = 1000;
+
+        public int getId() {
+            return id;
+        }
+    }
+}
diff --git a/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonTestUtilsTest.java b/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonTestUtilsTest.java
new file mode 100644
index 00000000..39cde7dc
--- /dev/null
+++ b/utils-test/src/test/java/org/onap/policy/common/utils/gson/GsonTestUtilsTest.java
@@ -0,0 +1,248 @@
+/*
+ * ============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.utils.gson;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParseException;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import javax.script.ScriptException;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GsonTestUtilsTest {
+    private static final String HELLO = "hello";
+
+    private GsonTestUtils utils;
+
+    @Before
+    public void setUp() {
+        utils = new GsonTestUtils();
+    }
+
+    @Test
+    public void testGetGson() {
+        assertNotNull(utils.getGson());
+    }
+
+    @Test
+    public void testGsonRoundTrip() {
+        Data data = new Data();
+        data.setId(500);
+
+        // try with null text
+        data.setText(null);
+        assertEquals(data.toString(), utils.gsonRoundTrip(data, Data.class).toString());
+
+        // try with non-null text
+        data.setText(HELLO);
+        assertEquals(data.toString(), utils.gsonRoundTrip(data, Data.class).toString());
+    }
+
+    @Test
+    public void testCompareGsonObjectClass_testCompareGsonObjectFile() {
+        Data data = new Data();
+        data.setId(500);
+        data.setText(HELLO);
+
+        utils.compareGson(data, GsonTestUtilsTest.class);
+
+        // file not found
+        assertThatThrownBy(() -> utils.compareGson(data,
+                        new File(GsonTestUtilsTest.class.getSimpleName() + "-NotFound.json")))
+                                        .isInstanceOf(JsonParseException.class)
+                                        .hasCauseInstanceOf(FileNotFoundException.class);
+
+        // force I/O error while reading file
+        GsonTestUtils utils2 = new GsonTestUtils() {
+            @Override
+            protected String readFile(File file) throws IOException {
+                throw new IOException("expected exception");
+            }
+        };
+        assertThatThrownBy(() -> utils2.compareGson(data, GsonTestUtilsTest.class))
+                        .isInstanceOf(JsonParseException.class).hasCauseInstanceOf(IOException.class)
+                        .hasMessage("error reading: GsonTestUtilsTest.json");
+    }
+
+    @Test
+    public void testCompareGsonObjectString() {
+        Data data = new Data();
+        data.setId(600);
+        data.setText(HELLO);
+
+        utils.compareGson(data, "{'id': ${obj.id}, 'text': '${obj.text}'}".replace('\'', '"'));
+    }
+
+    @Test
+    public void testCompareGsonObjectJsonElement() {
+        Data data = new Data();
+        data.setId(650);
+        data.setText(HELLO);
+
+        JsonObject json = new JsonObject();
+        json.addProperty("id", data.getId());
+        json.addProperty("text", data.getText());
+
+        utils.compareGson(data, json);
+
+        // mismatch
+        data.setText("world");
+        assertThatThrownBy(() -> utils.compareGson(data, json)).isInstanceOf(AssertionError.class);
+    }
+
+    @Test
+    public void testApplyScripts() {
+        Data data = new Data();
+        data.setId(700);
+        data.setText(HELLO);
+
+        String result = utils.applyScripts("no interpolation", data);
+        assertEquals("no interpolation", result);
+
+        result = utils.applyScripts("${obj.id} at start, ${obj.text} in middle, and end ${obj.id}", data);
+        assertEquals("700 at start, hello in middle, and end 700", result);
+
+        // try null value
+        data.setText(null);
+        result = utils.applyScripts("use ${obj.text} this", data);
+        assertEquals("use null this", result);
+
+        assertThatThrownBy(() -> utils.applyScripts("use ${obj.text} this", null)).isInstanceOf(RuntimeException.class)
+                        .hasCauseInstanceOf(ScriptException.class).hasMessage("cannot expand element: ${obj.text}");
+    }
+
+    @Test
+    public void testReorderJsonObject() {
+        // insert properties in a non-alphabetical order
+        JsonObject inner = new JsonObject();
+        inner.addProperty("objBint", 100);
+        inner.add("objBNull", JsonNull.INSTANCE);
+        inner.addProperty("objB", true);
+
+        JsonArray arr = new JsonArray();
+        arr.add(110);
+        arr.add(inner);
+        arr.add(false);
+
+        JsonObject outer = new JsonObject();
+        outer.add("objANull", JsonNull.INSTANCE);
+        outer.addProperty("objA", true);
+        outer.addProperty("objAStr", "obj-a-string");
+        outer.add("nested-array", arr);
+
+        outer = utils.reorder(outer);
+        assertEquals("{'nested-array':[110,{'objB':true,'objBint':100},false],'objA':true,'objAStr':'obj-a-string'}"
+                        .replace('\'', '"'), outer.toString());
+    }
+
+    @Test
+    public void testReorderJsonArray() {
+        // insert properties in a non-alphabetical order
+        JsonObject inner = new JsonObject();
+        inner.add("objCNull", JsonNull.INSTANCE);
+        inner.addProperty("objCStr", "obj-c-string");
+        inner.addProperty("objC", true);
+
+        JsonArray arr = new JsonArray();
+        arr.add(200);
+        arr.add(inner);
+        arr.add(false);
+
+        arr = utils.reorder(arr);
+        assertEquals("[200,{'objC':true,'objCStr':'obj-c-string'},false]".replace('\'', '"'), arr.toString());
+    }
+
+    @Test
+    public void testReorderJsonElement() {
+        // null element
+        JsonElement jsonEl = null;
+        assertNull(utils.reorder(jsonEl));
+
+        // object element
+        JsonObject obj = new JsonObject();
+        obj.add("objDNull", JsonNull.INSTANCE);
+        obj.addProperty("objDStr", "obj-d-string");
+        obj.addProperty("objD", true);
+        jsonEl = obj;
+        jsonEl = utils.reorder(jsonEl);
+        assertEquals("{'objD':true,'objDStr':'obj-d-string'}".replace('\'', '"'), jsonEl.toString());
+
+        // boolean
+        jsonEl = obj.get("objD");
+        jsonEl = utils.reorder(jsonEl);
+        assertEquals("true", jsonEl.toString());
+
+        // JsonNull
+        jsonEl = JsonNull.INSTANCE;
+        jsonEl = utils.reorder(jsonEl);
+        assertEquals("null", jsonEl.toString());
+
+        // array element
+        JsonObject inner = new JsonObject();
+        inner.add("objENull", JsonNull.INSTANCE);
+        inner.addProperty("objEStr", "obj-e-string");
+        inner.addProperty("objE", true);
+
+        JsonArray arr = new JsonArray();
+        arr.add(300);
+        arr.add(inner);
+        arr.add(false);
+        jsonEl = arr;
+        jsonEl = utils.reorder(jsonEl);
+        assertEquals("[300,{'objE':true,'objEStr':'obj-e-string'},false]".replace('\'', '"'), jsonEl.toString());
+    }
+
+    public static class Data {
+        private int id;
+        private String text;
+
+        public int getId() {
+            return id;
+        }
+
+        public void setId(int id) {
+            this.id = id;
+        }
+
+        public String getText() {
+            return text;
+        }
+
+        public void setText(String text) {
+            this.text = text;
+        }
+
+        @Override
+        public String toString() {
+            return "Data [id=" + id + ", text=" + text + "]";
+        }
+    }
+}
diff --git a/utils-test/src/test/resources/org/onap/policy/common/utils/gson/GsonTestUtilsTest.json b/utils-test/src/test/resources/org/onap/policy/common/utils/gson/GsonTestUtilsTest.json
new file mode 100644
index 00000000..ff7ed70b
--- /dev/null
+++ b/utils-test/src/test/resources/org/onap/policy/common/utils/gson/GsonTestUtilsTest.json
@@ -0,0 +1,4 @@
+{
+    "id": ${obj.id},
+    "text": "${obj.text}"
+}