Add gson handler and tests

Added JacksonHandler which provides jackson behavior in gson.
Also added classes to facilitate testing of gson serializations.
Added compareGson(xxx, Class).
Removed trailing spaces from some files.
Updated license dates.
Replaced incorrect constant with ${xxx} in json test file.
Fixed typo in test method name.

Change-Id: If05b654d76a4ffc88646f03334be82b32506f28f
Issue-ID: POLICY-1428
Signed-off-by: Jim Hahn <jrh3@att.com>

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}"
+}