Add superclasses for gson-jackson migration

Added common classes needed by other gson-jackson code.
Modified some logic to make it more maintainable or perform better.
Updated comments and spacing.
Fix another comment.
Moved gson classes from utils to a separate gson project.
Added GsonXxx annotations to mirror jackson annotations.
Removed unneeded dependencies from gson pom.
Removed old GsonMessage class from policy-endpoints.
Removed trailing spaces.
Updated licenses.
Removed more trailing spaces.
Removed unneeded checkstyle suppression file from utils.

Change-Id: I1a285500faeb0a0b6a1467d09b92ecd3cded713e
Issue-ID: POLICY-1428
Signed-off-by: Jim Hahn <jrh3@att.com>

9 files changed, 1154 insertions, 0 deletions

diff --git a/gson/src/main/java/org/onap/policy/common/gson/GsonMessageBodyHandler.java b/gson/src/main/java/org/onap/policy/common/gson/GsonMessageBodyHandler.java
new file mode 100644
index 00000000..2112c97c
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/GsonMessageBodyHandler.java
@@ -0,0 +1,124 @@
+/*
+ * ============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 com.google.gson.Gson;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Type;
+import java.nio.charset.StandardCharsets;
+import javax.ws.rs.Consumes;
+import javax.ws.rs.Produces;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.ext.MessageBodyReader;
+import javax.ws.rs.ext.MessageBodyWriter;
+import javax.ws.rs.ext.Provider;
+
+/**
+ * Provider that serializes and de-serializes JSON via gson.
+ */
+@Provider
+@Consumes(MediaType.WILDCARD)
+@Produces(MediaType.WILDCARD)
+public class GsonMessageBodyHandler implements MessageBodyReader<Object>, MessageBodyWriter<Object> {
+
+    /**
+     * Object to be used to serialize and de-serialize.
+     */
+    private Gson gson;
+
+    /**
+     * Constructs the object, using a plain Gson object.
+     */
+    public GsonMessageBodyHandler() {
+        this(new Gson());
+    }
+
+    /**
+     * Constructs the object.
+     *
+     * @param gson the Gson object to be used to serialize and de-serialize
+     */
+    public GsonMessageBodyHandler(Gson gson) {
+        this.gson = gson;
+    }
+
+    @Override
+    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
+        return canHandle(mediaType);
+    }
+
+    @Override
+    public long getSize(Object object, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
+        return -1;
+    }
+
+    @Override
+    public void writeTo(Object object, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType,
+                    MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream)
+                    throws IOException, WebApplicationException {
+
+        try (OutputStreamWriter writer = new OutputStreamWriter(entityStream, StandardCharsets.UTF_8)) {
+            Type jsonType = (type.equals(genericType) ? type : genericType);
+            gson.toJson(object, jsonType, writer);
+        }
+    }
+
+    @Override
+    public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
+        return canHandle(mediaType);
+    }
+
+    /**
+     * Determines if this provider can handle the given media type.
+     *
+     * @param mediaType the media type of interest
+     * @return {@code true} if this provider handles the given media type, {@code false}
+     *         otherwise
+     */
+    private boolean canHandle(MediaType mediaType) {
+        if (mediaType == null) {
+            return true;
+        }
+
+        String subtype = mediaType.getSubtype();
+
+        return "json".equalsIgnoreCase(subtype) || subtype.endsWith("+json") || "javascript".equals(subtype)
+                        || "x-javascript".equals(subtype) || "x-json".equals(subtype);
+    }
+
+    @Override
+    public Object readFrom(Class<Object> type, Type genericType, Annotation[] annotations, MediaType mediaType,
+                    MultivaluedMap<String, String> httpHeaders, InputStream entityStream)
+                    throws IOException, WebApplicationException {
+
+        try (InputStreamReader streamReader = new InputStreamReader(entityStream, StandardCharsets.UTF_8)) {
+            Type jsonType = (type.equals(genericType) ? type : genericType);
+            return gson.fromJson(streamReader, jsonType);
+        }
+    }
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/JacksonExclusionStrategy.java b/gson/src/main/java/org/onap/policy/common/gson/JacksonExclusionStrategy.java
new file mode 100644
index 00000000..cb959c43
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/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.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/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonAnyGetter.java b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonAnyGetter.java
new file mode 100644
index 00000000..859f5386
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonAnyGetter.java
@@ -0,0 +1,38 @@
+/*
+ * ============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.annotation;
+
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Mimics Jackson JsonAnyGetter annotation, but used by gson. This requires the gson
+ * object to be configured with the jackson default behaviors (i.e., the associated
+ * JacksonXxx strategy and adapters must be registered with the gson object).
+ */
+@Retention(RUNTIME)
+@Target(METHOD)
+public @interface GsonJsonAnyGetter {
+
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonAnySetter.java b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonAnySetter.java
new file mode 100644
index 00000000..87e0f330
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonAnySetter.java
@@ -0,0 +1,38 @@
+/*
+ * ============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.annotation;
+
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Mimics Jackson JsonAnySetter annotation, but used by gson. This requires the gson
+ * object to be configured with the jackson default behaviors (i.e., the associated
+ * JacksonXxx strategy and adapters must be registered with the gson object).
+ */
+@Retention(RUNTIME)
+@Target(METHOD)
+public @interface GsonJsonAnySetter {
+
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonIgnore.java b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonIgnore.java
new file mode 100644
index 00000000..cf2d4394
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonIgnore.java
@@ -0,0 +1,39 @@
+/*
+ * ============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.annotation;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Mimics Jackson JsonIgnore annotation, but used by gson. This requires the gson object
+ * to be configured with the jackson default behaviors (i.e., the associated JacksonXxx
+ * strategy and adapters must be registered with the gson object).
+ */
+@Retention(RUNTIME)
+@Target({FIELD, METHOD})
+public @interface GsonJsonIgnore {
+
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonProperty.java b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonProperty.java
new file mode 100644
index 00000000..c31c19bb
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/annotation/GsonJsonProperty.java
@@ -0,0 +1,44 @@
+/*
+ * ============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.annotation;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Mimics Jackson JsonProperty annotation, but used by gson. This requires the gson object
+ * to be configured with the jackson default behaviors (i.e., the associated JacksonXxx
+ * strategy and adapters must be registered with the gson object).
+ */
+@Retention(RUNTIME)
+@Target({FIELD, METHOD})
+public @interface GsonJsonProperty {
+
+    /**
+     * Property name of this item when placed into a JsonObject.
+     * @return the item's serialized name
+     */
+    String value() default "";
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/internal/Adapter.java b/gson/src/main/java/org/onap/policy/common/gson/internal/Adapter.java
new file mode 100644
index 00000000..b4ef53f7
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/internal/Adapter.java
@@ -0,0 +1,339 @@
+/*
+ * ============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 com.google.gson.Gson;
+import com.google.gson.JsonElement;
+import com.google.gson.TypeAdapter;
+import com.google.gson.reflect.TypeToken;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.lang.reflect.Type;
+import java.util.function.Supplier;
+import java.util.regex.Pattern;
+import org.onap.policy.common.gson.annotation.GsonJsonProperty;
+
+/**
+ * Super class of adapters used to serialize and de-serialize an item.
+ */
+public class Adapter {
+
+    /**
+     * Pattern to match valid identifiers.
+     */
+    private static final Pattern VALID_NAME_PAT = Pattern.compile("[a-zA-Z_]\\w*");
+
+    /**
+     * Name of the property within the json structure containing the item.
+     */
+    private final String propName;
+
+    /**
+     * Gson object that will provide the type converter.
+     */
+    private final Gson gson;
+
+    /**
+     * Converter used when reading.
+     */
+    private final ConvInfo reader;
+
+    /**
+     * Converter used when writing, allocated lazily, once an actual type is determined.
+     */
+    private volatile ConvInfo writer = null;
+
+    /**
+     * Name of the item being lifted - used when throwing exceptions.
+     */
+    private final String fullName;
+
+    /**
+     * Constructs the object.
+     *
+     * @param gson Gson object providing type adapters
+     * @param field field used to access the item from within an object
+     */
+    public Adapter(Gson gson, Field field) {
+        this.propName = detmPropName(field);
+        this.reader = new ConvInfo(TypeToken.get(field.getGenericType()));
+        this.gson = gson;
+        this.fullName = getQualifiedName(field);
+
+        field.setAccessible(true);
+    }
+
+    /**
+     * Constructs the object.
+     *
+     * @param gson Gson object providing type adapters
+     * @param accessor method used to access the item from within an object
+     * @param forGetter {@code true} if the name is for a "getter" method, {@code false}
+     *        if for a "setter"
+     * @param valueType the class of value on which this operates
+     */
+    public Adapter(Gson gson, Method accessor, boolean forGetter, Type valueType) {
+        this.propName = (forGetter ? detmGetterPropName(accessor) : detmSetterPropName(accessor));
+        this.reader = new ConvInfo(TypeToken.get(valueType));
+        this.gson = gson;
+        this.fullName = getQualifiedName(accessor);
+
+        accessor.setAccessible(true);
+    }
+
+    /**
+     * Converts an object to a json tree.
+     *
+     * @param object the object to be converted
+     * @return a json tree representing the object
+     */
+    @SuppressWarnings("unchecked")
+    public JsonElement toJsonTree(Object object) {
+        // always use a converter for the specific subclass
+        Class<? extends Object> clazz = object.getClass();
+
+        if (writer == null) {
+            // race condition here, but it's ok to overwrite a previous value
+            writer = new ConvInfo(TypeToken.get(clazz));
+        }
+
+        ConvInfo wtr = writer;
+        TypeAdapter<Object> conv =
+                        (TypeAdapter<Object>) (wtr.clazz == clazz ? wtr.getConverter() : gson.getAdapter(clazz));
+
+        return conv.toJsonTree(object);
+    }
+
+    /**
+     * Converts a json tree to an object.
+     *
+     * @param tree the tree to be converted
+     * @return the object represented by the tree
+     */
+    public Object fromJsonTree(JsonElement tree) {
+        return reader.getConverter().fromJsonTree(tree);
+    }
+
+    public final String getPropName() {
+        return propName;
+    }
+
+    public final String getFullName() {
+        return fullName;
+    }
+
+    /**
+     * Makes an error message, appending the item's full name to the message prefix.
+     *
+     * @param prefix the message prefix
+     * @return the error message
+     */
+    public String makeError(String prefix) {
+        return (prefix + fullName);
+    }
+
+    /**
+     * Determines if the field is managed by the walker.
+     *
+     * @param field the field to examine
+     * @return {@code true} if the field is managed by the walker, {@code false} otherwise
+     */
+    public static boolean isManaged(Field field) {
+        return VALID_NAME_PAT.matcher(field.getName()).matches();
+    }
+
+    /**
+     * Determines if the method is managed by the walker.
+     *
+     * @param method the method to examine
+     * @return {@code true} if the method is managed by the walker, {@code false}
+     *         otherwise
+     */
+    public static boolean isManaged(Method method) {
+        return VALID_NAME_PAT.matcher(method.getName()).matches();
+    }
+
+    /**
+     * Determines the property name of an item within the json structure.
+     *
+     * @param field the item within the object
+     * @return the json property name for the item or {@code null} if the name is invalid
+     */
+    public static String detmPropName(Field field) {
+        // use the serialized name, if specified
+        GsonJsonProperty prop = field.getAnnotation(GsonJsonProperty.class);
+        if (prop != null && !prop.value().isEmpty()) {
+            return prop.value();
+        }
+
+        // no name provided - use it as is
+        return (isManaged(field) ? field.getName() : null);
+    }
+
+    /**
+     * Determines the property name of an item, within the json structure, associated with
+     * a "get" method.
+     *
+     * @param method method to be invoked to get the item within the object
+     * @return the json property name for the item, or {@code null} if the method name is
+     *         not valid
+     */
+    public static String detmGetterPropName(Method method) {
+
+        return detmPropNameCommon(method, () -> {
+
+            if (!isManaged(method)) {
+                return null;
+            }
+
+            String name = method.getName();
+
+            if (name.startsWith("get")) {
+                return name.substring(3);
+
+            } else if (name.startsWith("is")) {
+                Class<?> treturn = method.getReturnType();
+
+                if (treturn == boolean.class || treturn == Boolean.class) {
+                    return name.substring(2);
+                }
+            }
+
+            // not a valid name for a "getter" method
+            return null;
+        });
+    }
+
+    /**
+     * Determines the property name of an item, within the json structure, associated with
+     * a "set" method.
+     *
+     * @param method method to be invoked to set the item within the object
+     * @return the json property name for the item, or {@code null} if the method name is
+     *         not valid
+     */
+    public static String detmSetterPropName(Method method) {
+
+        return detmPropNameCommon(method, () -> {
+
+            if (!isManaged(method)) {
+                return null;
+            }
+
+            String name = method.getName();
+
+            if (name.startsWith("set")) {
+                return name.substring(3);
+            }
+
+            // not a valid name for a "setter" method
+            return null;
+        });
+    }
+
+    /**
+     * Determines the property name of an item within the json structure.
+     *
+     * @param method method to be invoked to get/set the item within the object
+     * @param extractor function to extract the name directly from the method name
+     * @return the json property name for the item, or {@code null} if the method name is
+     *         not valid
+     */
+    private static String detmPropNameCommon(Method method, Supplier<String> extractor) {
+
+        // use the property name, if specified
+        GsonJsonProperty propName = method.getAnnotation(GsonJsonProperty.class);
+        if (propName != null && !propName.value().isEmpty()) {
+            return propName.value();
+        }
+
+        // no name provided - must compute it from the method name
+        String name = extractor.get();
+
+        if (name == null || name.isEmpty()) {
+            // nothing left after stripping the prefix - invalid name
+            return null;
+        }
+
+        // translate the first letter to lower-case
+        return name.substring(0, 1).toLowerCase() + name.substring(1);
+    }
+
+    /**
+     * Gets the fully qualified name of a field.
+     *
+     * @param field field whose name is desired
+     * @return the field fully qualified name
+     */
+    public static String getQualifiedName(Field field) {
+        return (field.getDeclaringClass().getName() + "." + field.getName());
+    }
+
+    /**
+     * Gets the fully qualified name of a method.
+     *
+     * @param method method whose name is desired
+     * @return the method's fully qualified name
+     */
+    public static String getQualifiedName(Method method) {
+        return (method.getDeclaringClass().getName() + "." + method.getName());
+    }
+
+    /**
+     * Converter info.
+     */
+    private class ConvInfo {
+
+        /**
+         * Type on which the converter works.
+         */
+        private TypeToken<?> type;
+
+        /**
+         * Class of object on which the converter works.
+         */
+        private Class<?> clazz;
+
+        /**
+         * Converter to use, initialized lazily.
+         */
+        private volatile TypeAdapter<?> conv = null;
+
+        /**
+         * Constructs the object.
+         *
+         * @param type type of object to be converted
+         */
+        public ConvInfo(TypeToken<?> type) {
+            this.type = type;
+            this.clazz = type.getRawType();
+        }
+
+        public final TypeAdapter<?> getConverter() {
+            if (conv == null) {
+                // race condition here, but it's ok to overwrite a previous value
+                this.conv = gson.getAdapter(type);
+            }
+
+            return conv;
+        }
+    }
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/internal/ClassWalker.java b/gson/src/main/java/org/onap/policy/common/gson/internal/ClassWalker.java
new file mode 100644
index 00000000..e985d98a
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/internal/ClassWalker.java
@@ -0,0 +1,389 @@
+/*
+ * ============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 com.google.gson.JsonParseException;
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import org.onap.policy.common.gson.annotation.GsonJsonAnyGetter;
+import org.onap.policy.common.gson.annotation.GsonJsonAnySetter;
+import org.onap.policy.common.gson.annotation.GsonJsonIgnore;
+import org.onap.policy.common.gson.annotation.GsonJsonProperty;
+
+/**
+ * Data populated while walking the hierarchy of a class.
+ */
+public class ClassWalker {
+
+    public static final String ANY_GETTER_MISMATCH_ERR =
+                    GsonJsonAnyGetter.class.getSimpleName() + " parameter mismatch for: ";
+
+    public static final String ANY_SETTER_MISMATCH_ERR =
+                    GsonJsonAnySetter.class.getSimpleName() + " parameter mismatch for: ";
+
+    public static final String ANY_SETTER_TYPE_ERR =
+                    GsonJsonAnySetter.class.getSimpleName() + " first parameter must be a string: ";
+
+    /**
+     * Maps an input property name to an item within the class, where item is one of:
+     * {@link Field}, {@link Method}, or {@code null}. Entries are overwritten as new
+     * items are added.
+     */
+    private final Map<String, Object> inProps = new HashMap<>();
+
+    /**
+     * Maps an output property name to an item within the class, where item is one of:
+     * {@link Field}, {@link Method}, or {@code null}. Entries are overwritten as new
+     * items are added.
+     */
+    private final Map<String, Object> outProps = new HashMap<>();
+
+    /**
+     * Maps a method name to a "get" method. Used when overriding properties associated
+     * with a method.
+     */
+    private final Map<String, Method> getters = new HashMap<>();
+
+    /**
+     * Maps a method name to a "set" method. Used when overriding properties associated
+     * with a method.
+     */
+    private final Map<String, Method> setters = new HashMap<>();
+
+    /**
+     * Method having {@link GsonJsonAnyGetter} annotation. Overwritten as new "any-getters"
+     * are identified.
+     */
+    private Method anyGetter = null;
+
+    /**
+     * Method having {@link GsonJsonAnySetter} annotation. Overwritten as new "any-setters"
+     * are identified.
+     */
+    private Method anySetter = null;
+
+
+    public Method getAnyGetter() {
+        return anyGetter;
+    }
+
+    public Method getAnySetter() {
+        return anySetter;
+    }
+
+    /**
+     * Gets the names of input properties that are not being ignored.
+     *
+     * @return the non-ignored input property names
+     */
+    public List<String> getInNotIgnored() {
+        return getNonNull(inProps);
+    }
+
+    /**
+     * Gets the names of output properties that are not being ignored.
+     *
+     * @return the non-ignored output property names
+     */
+    public List<String> getOutNotIgnored() {
+        return getNonNull(outProps);
+    }
+
+    /**
+     * Gets the property names, associated with a non-null value, from a set of
+     * properties.
+     *
+     * @param props set of properties from which to extract the names
+     * @return the property names having a non-null value
+     */
+    private List<String> getNonNull(Map<String, Object> props) {
+        List<String> lst = new ArrayList<String>(props.size());
+
+        for (Entry<String, Object> ent : props.entrySet()) {
+            if (ent.getValue() != null) {
+                lst.add(ent.getKey());
+            }
+        }
+
+        return lst;
+    }
+
+    /**
+     * Gets the input properties whose values are of the given class.
+     *
+     * @param clazz class of properties to get
+     * @return the input properties of the given class
+     */
+    public <T> List<T> getInProps(Class<T> clazz) {
+        return getProps(clazz, inProps.values());
+    }
+
+    /**
+     * Gets the output properties whose values are of the given class.
+     *
+     * @param clazz class of properties to get
+     * @return the output properties of the given class
+     */
+    public <T> List<T> getOutProps(Class<T> clazz) {
+        return getProps(clazz, outProps.values());
+    }
+
+    /**
+     * Gets the properties whose values are of the given class.
+     *
+     * @param clazz class of properties to get
+     * @param values values from which to select
+     * @return the output properties of the given class
+     */
+    @SuppressWarnings("unchecked")
+    private <T> List<T> getProps(Class<T> clazz, Collection<Object> values) {
+        List<T> lst = new ArrayList<T>(values.size());
+
+        for (Object val : values) {
+            if (val != null && val.getClass() == clazz) {
+                lst.add((T) val);
+            }
+        }
+
+        return lst;
+    }
+
+    /**
+     * Recursively walks a class hierarchy, including super classes and interfaces,
+     * examining each class for various annotations.
+     *
+     * @param clazz class whose hierarchy is to be walked
+     */
+    public void walkClassHierarchy(Class<?> clazz) {
+        if (clazz == Object.class) {
+            return;
+        }
+
+        // walk interfaces first
+        for (Class<?> intfc : clazz.getInterfaces()) {
+            walkClassHierarchy(intfc);
+        }
+
+        // walk superclass next, overwriting previous items
+        Class<?> sup = clazz.getSuperclass();
+        if (sup != null) {
+            walkClassHierarchy(sup);
+        }
+
+        // finally, examine this class, overwriting previous items
+        examine(clazz);
+    }
+
+    /**
+     * Examines a class for annotations, examining fields and then methods.
+     *
+     * @param clazz class to be examined
+     */
+    protected void examine(Class<?> clazz) {
+        for (Field field : clazz.getDeclaredFields()) {
+            examine(field);
+        }
+
+        for (Method method : clazz.getDeclaredMethods()) {
+            examine(method);
+        }
+    }
+
+    /**
+     * Examines a field for annotations.
+     *
+     * @param field field to be examined
+     */
+    protected void examine(Field field) {
+        if (field.isSynthetic()) {
+            return;
+        }
+
+        int mod = field.getModifiers();
+
+        if (Modifier.isStatic(mod)) {
+            // skip static fields
+            return;
+        }
+
+        if (!Modifier.isPublic(mod) && field.getAnnotation(GsonJsonProperty.class) == null) {
+            // private/protected - skip it unless explicitly exposed
+            return;
+        }
+
+        if (Modifier.isTransient(mod) && field.getAnnotation(GsonJsonProperty.class) == null) {
+            // transient - skip it unless explicitly exposed
+            return;
+        }
+
+        String name = Adapter.detmPropName(field);
+        if (name == null) {
+            // invalid name
+            return;
+        }
+
+        // if ignoring, then insert null into the map, otherwise insert the field
+        Field annotField = (field.getAnnotation(GsonJsonIgnore.class) != null ? null : field);
+
+        // a field can be both an input and an output
+
+        inProps.put(name, annotField);
+        outProps.put(name, annotField);
+    }
+
+    /**
+     * Examines a method for annotations.
+     *
+     * @param method method to be examined
+     */
+    protected void examine(Method method) {
+        if (method.isSynthetic()) {
+            return;
+        }
+
+        int mod = method.getModifiers();
+
+        if (Modifier.isStatic(mod)) {
+            // static methods are not exposed
+            return;
+        }
+
+        GsonJsonProperty prop = method.getAnnotation(GsonJsonProperty.class);
+        GsonJsonAnyGetter get = method.getAnnotation(GsonJsonAnyGetter.class);
+        GsonJsonAnySetter set = method.getAnnotation(GsonJsonAnySetter.class);
+
+        if (!Modifier.isPublic(mod) && prop == null && get == null && set == null) {
+            // private/protected methods are not exposed, unless annotated
+            return;
+        }
+
+
+        if (method.getReturnType() == void.class) {
+            // "void" return type - must be a "setter" method
+            if (set == null) {
+                examineSetter(method);
+
+            } else {
+                examineAnySetter(method);
+            }
+
+        } else {
+            // must be a "getter" method
+            if (get == null) {
+                examineGetter(method);
+
+            } else {
+                examineAnyGetter(method);
+            }
+        }
+    }
+
+    /**
+     * Examines a "setter" method.
+     *
+     * @param method method to be examined
+     */
+    private void examineSetter(Method method) {
+        String name = Adapter.detmSetterPropName(method);
+        if (name != null && method.getParameterCount() == 1) {
+            // remove old name mapping, if any
+            Method old = setters.get(method.getName());
+            if (old != null) {
+                inProps.remove(Adapter.detmSetterPropName(old));
+            }
+
+            setters.put(method.getName(), method);
+
+            // if ignoring, then insert null into the map, otherwise insert the method
+            inProps.put(name, (method.getAnnotation(GsonJsonIgnore.class) != null ? null : method));
+        }
+    }
+
+    /**
+     * Examines a "getter" method.
+     *
+     * @param method method to be examined
+     */
+    private void examineGetter(Method method) {
+        String name = Adapter.detmGetterPropName(method);
+        if (name != null && method.getParameterCount() == 0) {
+            // remove old name mapping, if any
+            Method old = getters.get(method.getName());
+            if (old != null) {
+                outProps.remove(Adapter.detmGetterPropName(old));
+            }
+
+            getters.put(method.getName(), method);
+
+            // if ignoring, then insert null into the map, otherwise insert the method
+            outProps.put(name, (method.getAnnotation(GsonJsonIgnore.class) != null ? null : method));
+        }
+    }
+
+    /**
+     * Examines a method having a {@link GsonJsonAnySetter} annotation.
+     *
+     * @param method method to be examined
+     */
+    private void examineAnySetter(Method method) {
+        if (method.getParameterCount() != 2) {
+            throw new JsonParseException(ANY_SETTER_MISMATCH_ERR + getFqdn(method));
+        }
+
+        if (method.getParameterTypes()[0] != String.class) {
+            throw new JsonParseException(ANY_SETTER_TYPE_ERR + getFqdn(method));
+        }
+
+        // if ignoring, then use null, otherwise use the method
+        anySetter = (method.getAnnotation(GsonJsonIgnore.class) != null ? null : method);
+    }
+
+    /**
+     * Examines a method having a {@link GsonJsonAnyGetter} annotation.
+     *
+     * @param method method to be examined
+     */
+    private void examineAnyGetter(Method method) {
+        if (method.getParameterCount() != 0) {
+            throw new JsonParseException(ANY_GETTER_MISMATCH_ERR + getFqdn(method));
+        }
+
+        // if ignoring, then use null, otherwise use the method
+        anyGetter = (method.getAnnotation(GsonJsonIgnore.class) != null ? null : method);
+    }
+
+    /**
+     * Gets the fully qualified name of a method.
+     *
+     * @param method method whose name is desired
+     * @return the fully qualified method name
+     */
+    private String getFqdn(Method method) {
+        return (method.getDeclaringClass().getName() + "." + method.getName());
+    }
+}
diff --git a/gson/src/main/java/org/onap/policy/common/gson/internal/Deserializer.java b/gson/src/main/java/org/onap/policy/common/gson/internal/Deserializer.java
new file mode 100644
index 00000000..f2975860
--- /dev/null
+++ b/gson/src/main/java/org/onap/policy/common/gson/internal/Deserializer.java
@@ -0,0 +1,39 @@
+/*
+ * ============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 com.google.gson.JsonObject;
+
+/**
+ * Super class of all de-serializers.
+ */
+public interface Deserializer {
+
+    String INVOKE_ERR = "cannot invoke method to deserialize: ";
+
+    /**
+     * Gets an value from a tree, converts it, and puts it into a target object.
+     *
+     * @param source tree from which to get the value
+     * @param target where to place the converted value
+     */
+    void getFromTree(JsonObject source, Object target);
+}