Create StandardYamlCoder

Created StandardYamlCoder which is like a StandardCoder, except that
the original converts to/from JSON, while the new class converts to/from
YAML.  Also added YamlMessageBodyHandler and incorporated it into the
http server so that it supports a media type of */yaml.

Change-Id: Ibd83a9f6d355a330f63e435f2bb41affcf1947c2
Issue-ID: POLICY-2065
Signed-off-by: Jim Hahn <jrh3@att.com>

3 files changed, 348 insertions, 0 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 80eddb86..d3d69812 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
@@ -211,6 +211,16 @@ public class StandardCoder implements Coder {
     }
 
     /**
+     * Encodes an object into a json tree, without catching exceptions.
+     *
+     * @param object object to be encoded
+     * @return a json element representing the object
+     */
+    protected JsonElement toJsonTree(Object object) {
+        return GSON.toJsonTree(object);
+    }
+
+    /**
      * Encodes an object into json, without catching exceptions.
      *
      * @param object object to be encoded
@@ -232,6 +242,17 @@ public class StandardCoder implements Coder {
     }
 
     /**
+     * Decodes a json element into an object, without catching exceptions.
+     *
+     * @param json json element to be decoded
+     * @param clazz class of object to be decoded
+     * @return the object represented by the given json element
+     */
+    protected <T> T fromJson(JsonElement json, Class<T> clazz) {
+        return convertFromDouble(clazz, GSON.fromJson(json, clazz));
+    }
+
+    /**
      * Decodes a json string into an object, without catching exceptions.
      *
      * @param json json string to be decoded
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
new file mode 100644
index 00000000..357b106e
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/StandardYamlCoder.java
@@ -0,0 +1,264 @@
+/*-
+ * ============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.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 {
+
+    /**
+     * Constructs the object.
+     */
+    public StandardYamlCoder() {
+        super();
+    }
+
+    @Override
+    protected String toJson(Object object) {
+        StringWriter output = new StringWriter();
+        toJson(output, object);
+        return output.toString();
+    }
+
+    @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);
+        }
+    }
+
+    @Override
+    protected <T> T fromJson(String yaml, Class<T> clazz) {
+        Node node = new Yaml().compose(new StringReader(yaml));
+        return fromJson(makeGson(node), 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());
+        }
+    }
+}
diff --git a/utils/src/main/java/org/onap/policy/common/utils/coder/YamlException.java b/utils/src/main/java/org/onap/policy/common/utils/coder/YamlException.java
new file mode 100644
index 00000000..d6591b3b
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/YamlException.java
@@ -0,0 +1,63 @@
+/*-
+ * ============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 org.yaml.snakeyaml.error.Mark;
+
+/**
+ * Runtime Exception generated by StandardYamlCoder.
+ */
+public class YamlException extends RuntimeException {
+    private static final long serialVersionUID = 1L;
+
+    private final Mark problemMark;
+
+
+    /**
+     * Constructs the object.
+     *
+     * @param reason reason for the exception
+     * @param problemMark where the exception occurred within the input
+     */
+    public YamlException(String reason, Mark problemMark) {
+        super(reason);
+
+        this.problemMark = problemMark;
+    }
+
+    /**
+     * Constructs the object.
+     *
+     * @param reason reason for the exception
+     * @param problemMark where the exception occurred within the input
+     * @param cause cause of the exception
+     */
+    public YamlException(String reason, Mark problemMark, Throwable cause) {
+        super(reason, cause);
+
+        this.problemMark = problemMark;
+    }
+
+    @Override
+    public String getMessage() {
+        return super.getMessage() + problemMark;
+    }
+}