Skip all fields in gson by default

Created an exclusion strategy that will prevent gson from serializing
any fields within a class. The strategy must be registered to take
effect.
Uses lists to identify classes to be excluded when using gson with
the jackson default behavior.

Change-Id: I747fb1159846ad3000f69603f9b5d3f03bc8764f
Issue-ID: POLICY-1428
Signed-off-by: Jim Hahn <jrh3@att.com>

2 files changed, 306 insertions, 0 deletions

diff --git a/utils/src/main/java/org/onap/policy/common/utils/gson/JacksonExclusionStrategy.java b/utils/src/main/java/org/onap/policy/common/utils/gson/JacksonExclusionStrategy.java
new file mode 100644
index 00000000..96213a65
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/gson/JacksonExclusionStrategy.java
@@ -0,0 +1,104 @@
+/*
+ * ============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 com.google.gson.ExclusionStrategy;
+import com.google.gson.FieldAttributes;
+import com.google.gson.JsonElement;
+import java.lang.reflect.GenericArrayType;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Excludes all fields from serialization/deserialization, if the class is managed.
+ */
+public class JacksonExclusionStrategy implements ExclusionStrategy {
+
+    /**
+     * Classes that are explicitly not managed by the GSON jackson adapters.
+     */
+    // @formatter:off
+    private static final Set<Class<?>> unmanaged = new HashSet<>(Arrays.asList(
+                    boolean.class,
+                    byte.class,
+                    short.class,
+                    int.class,
+                    long.class,
+                    float.class,
+                    double.class,
+                    char.class,
+                    Boolean.class,
+                    Byte.class,
+                    Short.class,
+                    Integer.class,
+                    Long.class,
+                    Float.class,
+                    Double.class,
+                    Character.class,
+                    String.class));
+    // @formatter:on
+
+    /**
+     * Classes whose subclasses are explicitly not managed by the GSON jackson adapters.
+     */
+    // @formatter:off
+    private static final Set<Class<?>> unmanagedSuper = new HashSet<>(Arrays.asList(
+                    GenericArrayType.class,
+                    Map.class,
+                    Collection.class,
+                    JsonElement.class));
+    // @formatter:on
+
+    @Override
+    public boolean shouldSkipField(FieldAttributes attrs) {
+        return isManaged(attrs.getDeclaringClass());
+    }
+
+    @Override
+    public boolean shouldSkipClass(Class<?> clazz) {
+        return false;
+    }
+
+    /**
+     * Determines if a class is managed by this adapter, which typically means that it is
+     * <i>not</i> a generic class such as {@link JsonElement} or some type of collection.
+     *
+     * @param clazz the class to be examined
+     * @return {@code true} if the class is managed by this adapter, {@code false}
+     *         otherwise
+     */
+    public static boolean isManaged(Class<?> clazz) {
+        if (clazz.isArray() || clazz.isEnum() || clazz.isPrimitive() || unmanaged.contains(clazz)) {
+            return false;
+        }
+
+        for (Class<?> sup : unmanagedSuper) {
+            if (sup.isAssignableFrom(clazz)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
diff --git a/utils/src/test/java/org/onap/policy/common/utils/gson/JacksonExclusionStrategyTest.java b/utils/src/test/java/org/onap/policy/common/utils/gson/JacksonExclusionStrategyTest.java
new file mode 100644
index 00000000..e8927902
--- /dev/null
+++ b/utils/src/test/java/org/onap/policy/common/utils/gson/JacksonExclusionStrategyTest.java
@@ -0,0 +1,202 @@
+/*
+ * ============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.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import com.google.gson.FieldAttributes;
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonElement;
+import java.lang.reflect.GenericArrayType;
+import java.util.LinkedList;
+import java.util.TreeMap;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class JacksonExclusionStrategyTest {
+
+    private static JacksonExclusionStrategy strategy;
+    private static Gson gson;
+
+    @BeforeClass
+    public static void setUpBeforeClass() {
+        strategy = new JacksonExclusionStrategy();
+        gson = new GsonBuilder().setExclusionStrategies(strategy).create();
+    }
+
+    @Test
+    public void testWithGson() {
+        Derived data = new Derived();
+        data.setId(10);
+        data.setText("some text");
+        data.setValue("some value");
+
+        // no fields should be serialized
+        String result = gson.toJson(data);
+        assertEquals("{}", result);
+
+        // no fields should be deserialized
+        result = "{'id':20, 'text':'my text', 'value':'my value'}".replace('\'', '"');
+        Derived data2 = gson.fromJson(result, Derived.class);
+        assertEquals(new Derived().toString(), data2.toString());
+    }
+
+    @Test
+    public void testShouldSkipField() throws Exception {
+        // should skip every field of Data
+        assertTrue(strategy.shouldSkipField(new FieldAttributes(Data.class.getDeclaredField("id"))));
+        assertTrue(strategy.shouldSkipField(new FieldAttributes(Data.class.getDeclaredField("text"))));
+
+        // should not skip fields in Map
+        assertFalse(strategy.shouldSkipField(new FieldAttributes(MyMap.class.getDeclaredField("mapId"))));
+    }
+
+    @Test
+    public void testShouldSkipClass() {
+        assertFalse(strategy.shouldSkipClass(null));
+        assertFalse(strategy.shouldSkipClass(Object.class));
+    }
+
+    @Test
+    public void testIsManaged() {
+        assertTrue(JacksonExclusionStrategy.isManaged(Data.class));
+        assertTrue(JacksonExclusionStrategy.isManaged(Intfc.class));
+        assertTrue(JacksonExclusionStrategy.isManaged(com.google.gson.TypeAdapter.class));
+
+        // generic classes
+        assertFalse(JacksonExclusionStrategy.isManaged(new Data[0].getClass()));
+        assertFalse(JacksonExclusionStrategy.isManaged(Enum.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(boolean.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(byte.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(short.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(int.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(long.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(float.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(double.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(char.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Boolean.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Byte.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Short.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Integer.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Long.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Float.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Double.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(Character.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(String.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(MyMap.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(MyList.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(MyJson.class));
+        assertFalse(JacksonExclusionStrategy.isManaged(GenericArrayType.class));
+    }
+
+    /**
+     * Used to verify that no fields are exposed.
+     */
+    public static class Data {
+        private int id;
+        public 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 + "]";
+        }
+    }
+
+    public static class Derived extends Data {
+        protected String value;
+
+        public String getValue() {
+            return value;
+        }
+
+        public void setValue(String value) {
+            this.value = value;
+        }
+
+        @Override
+        public String toString() {
+            return "Derived [value=" + value + ", " + super.toString() + "]";
+        }
+    }
+
+    /**
+     * Used to verify that enums are not managed.
+     */
+    public static enum Enum {
+        UP, DOWN,
+    }
+
+    /**
+     * Used to verify that interfaces <i>are</i> managed.
+     */
+    public static interface Intfc {
+        int getId();
+    }
+
+    /**
+     * Used to verify that Maps are not managed.
+     */
+    public static class MyMap extends TreeMap<String, Data> {
+        private static final long serialVersionUID = 1L;
+
+        private int mapId;
+
+        public int getMapId() {
+            return mapId;
+        }
+    }
+
+    /**
+     * Used to verify that Collections are not managed.
+     */
+    public static class MyList extends LinkedList<Data> {
+        private static final long serialVersionUID = 1L;
+    }
+
+    /**
+     * Used to verify that JsonElements are not managed.
+     */
+    public static class MyJson extends JsonElement {
+        @Override
+        public JsonElement deepCopy() {
+            return null;
+        }
+    }
+}