Extract YamlJsonTranslator from StandardYamlCoder

Refactored StandardYamlCoder, extracting a new class, YamlJsonTranslator,
from it.  This facilitates performing yaml translation when not using a
standard "gson" coder.
Added YamlJacksonHandler which supports YAML translation layered on
top of a JacksonHandler instead of a GsonMessageBodyHandler.
Also added junit tests to complete coverage of StandardCoder.
Also added public APPLICATION_YAML to YamlMessageBodyHandler.

Change-Id: Ia470fa194661fbf1aebeaf0f18b57f2a984cb64b
Issue-ID: POLICY-2081
Signed-off-by: Jim Hahn <jrh3@att.com>

3 files changed, 330 insertions, 211 deletions

diff --git a/utils/src/main/java/org/onap/policy/common/utils/coder/StandardCoder.java b/utils/src/main/java/org/onap/policy/common/utils/coder/StandardCoder.java
index d3d69812..c3f2d993 100644
--- a/utils/src/main/java/org/onap/policy/common/utils/coder/StandardCoder.java
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/StandardCoder.java
@@ -38,6 +38,8 @@ import java.io.OutputStreamWriter;
 import java.io.Reader;
 import java.io.Writer;
 import java.nio.charset.StandardCharsets;
+import lombok.AccessLevel;
+import lombok.Getter;
 import org.onap.policy.common.gson.DoubleConverter;
 import org.onap.policy.common.gson.MapDoubleAdapterFactory;
 
@@ -49,6 +51,7 @@ public class StandardCoder implements Coder {
     /**
      * Gson object used to encode and decode messages.
      */
+    @Getter(AccessLevel.PROTECTED)
     private static final Gson GSON =
                     new GsonBuilder().registerTypeAdapter(StandardCoderObject.class, new StandardTypeAdapter())
                                     .registerTypeAdapterFactory(new MapDoubleAdapterFactory()).create();
diff --git a/utils/src/main/java/org/onap/policy/common/utils/coder/StandardYamlCoder.java b/utils/src/main/java/org/onap/policy/common/utils/coder/StandardYamlCoder.java
index 357b106e..36f15b96 100644
--- a/utils/src/main/java/org/onap/policy/common/utils/coder/StandardYamlCoder.java
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/StandardYamlCoder.java
@@ -20,245 +20,40 @@
 
 package org.onap.policy.common.utils.coder;
 
-import com.google.gson.JsonArray;
-import com.google.gson.JsonElement;
-import com.google.gson.JsonNull;
-import com.google.gson.JsonObject;
-import com.google.gson.JsonPrimitive;
-import java.io.IOException;
 import java.io.Reader;
-import java.io.StringReader;
-import java.io.StringWriter;
 import java.io.Writer;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Map.Entry;
-import org.yaml.snakeyaml.DumperOptions;
-import org.yaml.snakeyaml.Yaml;
-import org.yaml.snakeyaml.emitter.Emitter;
-import org.yaml.snakeyaml.error.YAMLException;
-import org.yaml.snakeyaml.nodes.MappingNode;
-import org.yaml.snakeyaml.nodes.Node;
-import org.yaml.snakeyaml.nodes.NodeTuple;
-import org.yaml.snakeyaml.nodes.ScalarNode;
-import org.yaml.snakeyaml.nodes.SequenceNode;
-import org.yaml.snakeyaml.nodes.Tag;
-import org.yaml.snakeyaml.resolver.Resolver;
-import org.yaml.snakeyaml.serializer.Serializer;
 
 /**
  * YAML encoder and decoder using the "standard" mechanism, which is currently gson. All
  * of the methods perform conversion to/from YAML (instead of JSON).
  */
 public class StandardYamlCoder extends StandardCoder {
+    private final YamlJsonTranslator translator;
 
     /**
      * Constructs the object.
      */
     public StandardYamlCoder() {
-        super();
+        translator = new YamlJsonTranslator(getGSON());
     }
 
     @Override
     protected String toJson(Object object) {
-        StringWriter output = new StringWriter();
-        toJson(output, object);
-        return output.toString();
+        return translator.toYaml(object);
     }
 
     @Override
     protected void toJson(Writer target, Object object) {
-        DumperOptions dumper = new DumperOptions();
-        Serializer serializer = new Serializer(new Emitter(target, dumper), new Resolver(), dumper, null);
-
-        try {
-            serializer.open();
-            serializer.serialize(makeYaml(toJsonTree(object)));
-            serializer.close();
-
-        } catch (IOException e) {
-            throw new YAMLException(e);
-        }
+        translator.toYaml(target, object);
     }
 
     @Override
     protected <T> T fromJson(String yaml, Class<T> clazz) {
-        Node node = new Yaml().compose(new StringReader(yaml));
-        return fromJson(makeGson(node), clazz);
+        return translator.fromYaml(yaml, clazz);
     }
 
     @Override
     protected <T> T fromJson(Reader source, Class<T> clazz) {
-        Node node = new Yaml().compose(source);
-        return fromJson(makeGson(node), clazz);
-    }
-
-    /**
-     * Converts an arbitrary gson element into a corresponding Yaml node.
-     *
-     * @param jel gson element to be converted
-     * @return a yaml node corresponding to the element
-     */
-    private Node makeYaml(JsonElement jel) {
-        if (jel.isJsonArray()) {
-            return makeYamlSequence((JsonArray) jel);
-
-        } else if (jel.isJsonObject()) {
-            return makeYamlMap((JsonObject) jel);
-
-        } else if (jel.isJsonPrimitive()) {
-            return makeYamlPrim((JsonPrimitive) jel);
-
-        } else {
-            return new ScalarNode(Tag.NULL, "", null, null, DumperOptions.ScalarStyle.PLAIN);
-        }
-    }
-
-    /**
-     * Converts an arbitrary gson array into a corresponding Yaml sequence.
-     *
-     * @param jel gson element to be converted
-     * @return a yaml node corresponding to the element
-     */
-    private Node makeYamlSequence(JsonArray jel) {
-        List<Node> nodes = new ArrayList<>(jel.size());
-        jel.forEach(item -> nodes.add(makeYaml(item)));
-
-        return new SequenceNode(Tag.SEQ, true, nodes, null, null, DumperOptions.FlowStyle.AUTO);
-    }
-
-    /**
-     * Converts an arbitrary gson object into a corresponding Yaml map.
-     *
-     * @param jel gson element to be converted
-     * @return a yaml node corresponding to the element
-     */
-    private Node makeYamlMap(JsonObject jel) {
-        List<NodeTuple> nodes = new ArrayList<>(jel.size());
-
-        for (Entry<String, JsonElement> entry : jel.entrySet()) {
-            Node key = new ScalarNode(Tag.STR, entry.getKey(), null, null, DumperOptions.ScalarStyle.PLAIN);
-            Node value = makeYaml(entry.getValue());
-
-            nodes.add(new NodeTuple(key, value));
-        }
-
-        return new MappingNode(Tag.MAP, true, nodes, null, null, DumperOptions.FlowStyle.AUTO);
-    }
-
-    /**
-     * Converts an arbitrary gson primitive into a corresponding Yaml scalar.
-     *
-     * @param jel gson element to be converted
-     * @return a yaml node corresponding to the element
-     */
-    private Node makeYamlPrim(JsonPrimitive jel) {
-        Tag tag;
-        if (jel.isNumber()) {
-            Class<? extends Number> clazz = jel.getAsNumber().getClass();
-
-            if (clazz == Double.class || clazz == Float.class) {
-                tag = Tag.FLOAT;
-
-            } else {
-                tag = Tag.INT;
-            }
-
-        } else if (jel.isBoolean()) {
-            tag = Tag.BOOL;
-
-        } else {
-            // treat anything else as a string
-            tag = Tag.STR;
-        }
-
-        return new ScalarNode(tag, jel.getAsString(), null, null, DumperOptions.ScalarStyle.PLAIN);
-    }
-
-    /**
-     * Converts an arbitrary Yaml node into a corresponding gson element.
-     *
-     * @param node node to be converted
-     * @return a gson element corresponding to the node
-     */
-    private JsonElement makeGson(Node node) {
-        if (node instanceof MappingNode) {
-            return makeGsonObject((MappingNode) node);
-
-        } else if (node instanceof SequenceNode) {
-            return makeGsonArray((SequenceNode) node);
-
-        } else {
-            return makeGsonPrim((ScalarNode) node);
-        }
-
-        // yaml doesn't appear to use anchor nodes when decoding so ignore them for now
-    }
-
-    /**
-     * Converts a Yaml sequence into a corresponding gson array.
-     *
-     * @param node node to be converted
-     * @return a gson element corresponding to the node
-     */
-    private JsonElement makeGsonArray(SequenceNode node) {
-        List<Node> nodes = node.getValue();
-
-        JsonArray array = new JsonArray(nodes.size());
-        nodes.forEach(subnode -> array.add(makeGson(subnode)));
-
-        return array;
-    }
-
-    /**
-     * Converts a Yaml map into a corresponding gson object.
-     *
-     * @param node node to be converted
-     * @return a gson element corresponding to the node
-     */
-    private JsonElement makeGsonObject(MappingNode node) {
-        JsonObject obj = new JsonObject();
-
-        for (NodeTuple tuple : node.getValue()) {
-            Node key = tuple.getKeyNode();
-            String skey = ((ScalarNode) key).getValue();
-
-            obj.add(skey, makeGson(tuple.getValueNode()));
-        }
-
-        return obj;
-    }
-
-    /**
-     * Converts a Yaml scalar into a corresponding gson primitive.
-     *
-     * @param node node to be converted
-     * @return a gson element corresponding to the node
-     */
-    private JsonElement makeGsonPrim(ScalarNode node) {
-        try {
-            Tag tag = node.getTag();
-
-            if (tag == Tag.INT) {
-                return new JsonPrimitive(Long.valueOf(node.getValue()));
-
-            } else if (tag == Tag.FLOAT) {
-                return new JsonPrimitive(Double.valueOf(node.getValue()));
-
-            } else if (tag == Tag.BOOL) {
-                return new JsonPrimitive(Boolean.valueOf(node.getValue()));
-
-            } else if (tag == Tag.NULL) {
-                return JsonNull.INSTANCE;
-
-            } else {
-                // treat anything else as a string
-                return new JsonPrimitive(node.getValue());
-            }
-
-        } catch (NumberFormatException ex) {
-            // just treat it as a string
-            return new JsonPrimitive(node.getValue());
-        }
+        return translator.fromYaml(source, clazz);
     }
 }
diff --git a/utils/src/main/java/org/onap/policy/common/utils/coder/YamlJsonTranslator.java b/utils/src/main/java/org/onap/policy/common/utils/coder/YamlJsonTranslator.java
new file mode 100644
index 00000000..906c9fdd
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/YamlJsonTranslator.java
@@ -0,0 +1,321 @@
+/*-
+ * ============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.coder;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonPrimitive;
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.io.Writer;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map.Entry;
+import org.yaml.snakeyaml.DumperOptions;
+import org.yaml.snakeyaml.Yaml;
+import org.yaml.snakeyaml.emitter.Emitter;
+import org.yaml.snakeyaml.error.YAMLException;
+import org.yaml.snakeyaml.nodes.MappingNode;
+import org.yaml.snakeyaml.nodes.Node;
+import org.yaml.snakeyaml.nodes.NodeTuple;
+import org.yaml.snakeyaml.nodes.ScalarNode;
+import org.yaml.snakeyaml.nodes.SequenceNode;
+import org.yaml.snakeyaml.nodes.Tag;
+import org.yaml.snakeyaml.resolver.Resolver;
+import org.yaml.snakeyaml.serializer.Serializer;
+
+/**
+ * YAML-JSON translator. The methods may throw either of the runtime exceptions,
+ * YAMLException or JsonSyntaxException.
+ */
+public class YamlJsonTranslator {
+
+    /**
+     * Object to be used to translate between YAML and JsonElement.
+     */
+    private final Gson gson;
+
+    /**
+     * Constructs the object.
+     */
+    public YamlJsonTranslator() {
+        this(new Gson());
+    }
+
+    /**
+     * Constructs the object.
+     *
+     * @param gson the Gson object to be used to serialize and de-serialize
+     */
+    public YamlJsonTranslator(Gson gson) {
+        this.gson = gson;
+    }
+
+    /**
+     * Translates a POJO into a YAML String.
+     *
+     * @param object POJO to be translated
+     * @return YAML representing the original object
+     */
+    public String toYaml(Object object) {
+        StringWriter output = new StringWriter();
+        toYaml(output, object);
+        return output.toString();
+    }
+
+    /**
+     * Serializes a POJO to a writer, as YAML.
+     *
+     * @param target target writer
+     * @param object POJO to be translated
+     */
+    public void toYaml(Writer target, Object object) {
+        DumperOptions dumper = new DumperOptions();
+        Serializer serializer = new Serializer(new Emitter(target, dumper), new Resolver(), dumper, null);
+
+        try {
+            serializer.open();
+            serializer.serialize(makeYaml(toJsonTree(object)));
+            serializer.close();
+
+        } catch (IOException e) {
+            throw new YAMLException(e);
+        }
+    }
+
+    /**
+     * Translates a POJO into a JsonElement.
+     *
+     * @param object POJO to be translated
+     * @return a JsonElement representing the original object
+     */
+    protected JsonElement toJsonTree(Object object) {
+        return gson.toJsonTree(object);
+    }
+
+    /**
+     * Translates a YAML string to a POJO.
+     *
+     * @param yaml YAML string to be translated
+     * @param clazz class of POJO to be created
+     * @return a POJO representing the original YAML
+     */
+    public <T> T fromYaml(String yaml, Class<T> clazz) {
+        return fromYaml(new StringReader(yaml), clazz);
+    }
+
+    /**
+     * Translates a YAML string, read from a reader, into a POJO.
+     *
+     * @param source source of the YAML string to be translated
+     * @param clazz class of POJO to be created
+     * @return a POJO representing the YAML read from the reader
+     */
+    public <T> T fromYaml(Reader source, Class<T> clazz) {
+        Node node = new Yaml().compose(source);
+        return fromJson(makeJson(node), clazz);
+    }
+
+    /**
+     * Translates a JsonElement to a POJO of the given class.
+     *
+     * @param jel element to be translated
+     * @param clazz class of POJO to be created
+     * @return a POJO representing the original element
+     */
+    protected <T> T fromJson(JsonElement jel, Class<T> clazz) {
+        return gson.fromJson(jel, clazz);
+    }
+
+    /**
+     * Converts an arbitrary gson element into a corresponding Yaml node.
+     *
+     * @param jel gson element to be converted
+     * @return a yaml node corresponding to the element
+     */
+    protected Node makeYaml(JsonElement jel) {
+        if (jel.isJsonArray()) {
+            return makeYamlSequence((JsonArray) jel);
+
+        } else if (jel.isJsonObject()) {
+            return makeYamlMap((JsonObject) jel);
+
+        } else if (jel.isJsonPrimitive()) {
+            return makeYamlPrim((JsonPrimitive) jel);
+
+        } else {
+            return new ScalarNode(Tag.NULL, "", null, null, DumperOptions.ScalarStyle.PLAIN);
+        }
+    }
+
+    /**
+     * Converts an arbitrary gson array into a corresponding Yaml sequence.
+     *
+     * @param jel gson element to be converted
+     * @return a yaml node corresponding to the element
+     */
+    protected SequenceNode makeYamlSequence(JsonArray jel) {
+        List<Node> nodes = new ArrayList<>(jel.size());
+        jel.forEach(item -> nodes.add(makeYaml(item)));
+
+        return new SequenceNode(Tag.SEQ, true, nodes, null, null, DumperOptions.FlowStyle.AUTO);
+    }
+
+    /**
+     * Converts an arbitrary gson object into a corresponding Yaml map.
+     *
+     * @param jel gson element to be converted
+     * @return a yaml node corresponding to the element
+     */
+    protected MappingNode makeYamlMap(JsonObject jel) {
+        List<NodeTuple> nodes = new ArrayList<>(jel.size());
+
+        for (Entry<String, JsonElement> entry : jel.entrySet()) {
+            Node key = new ScalarNode(Tag.STR, entry.getKey(), null, null, DumperOptions.ScalarStyle.PLAIN);
+            Node value = makeYaml(entry.getValue());
+
+            nodes.add(new NodeTuple(key, value));
+        }
+
+        return new MappingNode(Tag.MAP, true, nodes, null, null, DumperOptions.FlowStyle.AUTO);
+    }
+
+    /**
+     * Converts an arbitrary gson primitive into a corresponding Yaml scalar.
+     *
+     * @param jel gson element to be converted
+     * @return a yaml node corresponding to the element
+     */
+    protected ScalarNode makeYamlPrim(JsonPrimitive jel) {
+        Tag tag;
+        if (jel.isNumber()) {
+            Class<? extends Number> clazz = jel.getAsNumber().getClass();
+
+            if (clazz == Double.class || clazz == Float.class) {
+                tag = Tag.FLOAT;
+
+            } else {
+                tag = Tag.INT;
+            }
+
+        } else if (jel.isBoolean()) {
+            tag = Tag.BOOL;
+
+        } else {
+            // treat anything else as a string
+            tag = Tag.STR;
+        }
+
+        return new ScalarNode(tag, jel.getAsString(), null, null, DumperOptions.ScalarStyle.PLAIN);
+    }
+
+    /**
+     * Converts an arbitrary Yaml node into a corresponding gson element.
+     *
+     * @param node node to be converted
+     * @return a gson element corresponding to the node
+     */
+    protected JsonElement makeJson(Node node) {
+        if (node instanceof MappingNode) {
+            return makeJsonObject((MappingNode) node);
+
+        } else if (node instanceof SequenceNode) {
+            return makeJsonArray((SequenceNode) node);
+
+        } else {
+            return makeJsonPrim((ScalarNode) node);
+        }
+
+        // yaml doesn't appear to use anchor nodes when decoding so ignore them for now
+    }
+
+    /**
+     * Converts a Yaml sequence into a corresponding gson array.
+     *
+     * @param node node to be converted
+     * @return a gson element corresponding to the node
+     */
+    protected JsonArray makeJsonArray(SequenceNode node) {
+        List<Node> nodes = node.getValue();
+
+        JsonArray array = new JsonArray(nodes.size());
+        nodes.forEach(subnode -> array.add(makeJson(subnode)));
+
+        return array;
+    }
+
+    /**
+     * Converts a Yaml map into a corresponding gson object.
+     *
+     * @param node node to be converted
+     * @return a gson element corresponding to the node
+     */
+    protected JsonObject makeJsonObject(MappingNode node) {
+        JsonObject obj = new JsonObject();
+
+        for (NodeTuple tuple : node.getValue()) {
+            Node key = tuple.getKeyNode();
+            String skey = ((ScalarNode) key).getValue();
+
+            obj.add(skey, makeJson(tuple.getValueNode()));
+        }
+
+        return obj;
+    }
+
+    /**
+     * Converts a Yaml scalar into a corresponding gson primitive.
+     *
+     * @param node node to be converted
+     * @return a gson element corresponding to the node
+     */
+    protected JsonElement makeJsonPrim(ScalarNode node) {
+        try {
+            Tag tag = node.getTag();
+
+            if (tag == Tag.INT) {
+                return new JsonPrimitive(Long.valueOf(node.getValue()));
+
+            } else if (tag == Tag.FLOAT) {
+                return new JsonPrimitive(Double.valueOf(node.getValue()));
+
+            } else if (tag == Tag.BOOL) {
+                return new JsonPrimitive(Boolean.valueOf(node.getValue()));
+
+            } else if (tag == Tag.NULL) {
+                return JsonNull.INSTANCE;
+
+            } else {
+                // treat anything else as a string
+                return new JsonPrimitive(node.getValue());
+            }
+
+        } catch (NumberFormatException ex) {
+            // just treat it as a string
+            return new JsonPrimitive(node.getValue());
+        }
+    }
+}