Add common coder classes

Added coder classes as a common utility that can be used to encode
and decode json data.  Currently, it uses gson, but that can be
changed.

Separated the Coder interface from implementation.

Used assertSame to compare references.
Used numbers instead of strings so don't have to deal with escaping quotes
in the test cases.

Change-Id: Iea9001d2adc5a3150b3367619b5f43e96b5f8b41
Issue-ID: POLICY-1444
Signed-off-by: Jim Hahn <jrh3@att.com>

3 files changed, 174 insertions, 0 deletions

diff --git a/utils/src/main/java/org/onap/policy/common/utils/coder/Coder.java b/utils/src/main/java/org/onap/policy/common/utils/coder/Coder.java
new file mode 100644
index 00000000..41db218b
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/Coder.java
@@ -0,0 +1,46 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * 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;
+
+/**
+ * JSON encoder and decoder.
+ */
+public interface Coder {
+
+    /**
+     * Encodes an object into json.
+     *
+     * @param object object to be encoded
+     * @return a json string representing the object
+     * @throws CoderException if an error occurs
+     */
+    String encode(Object object) throws CoderException;
+
+    /**
+     * Decodes a json string into an object.
+     *
+     * @param json json string to be decoded
+     * @param clazz class of object to be decoded
+     * @return the object represented by the given json string
+     * @throws CoderException if an error occurs
+     */
+    <T> T decode(String json, Class<T> clazz) throws CoderException;
+}
diff --git a/utils/src/main/java/org/onap/policy/common/utils/coder/CoderException.java b/utils/src/main/java/org/onap/policy/common/utils/coder/CoderException.java
new file mode 100644
index 00000000..60e85733
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/CoderException.java
@@ -0,0 +1,44 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * 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;
+
+/**
+ * Exceptions generated by coders.
+ */
+public class CoderException extends Exception {
+    private static final long serialVersionUID = 1L;
+
+    public CoderException() {
+        super();
+    }
+
+    public CoderException(String message) {
+        super(message);
+    }
+
+    public CoderException(Throwable cause) {
+        super(cause);
+    }
+
+    public CoderException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}
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
new file mode 100644
index 00000000..4c7a55c2
--- /dev/null
+++ b/utils/src/main/java/org/onap/policy/common/utils/coder/StandardCoder.java
@@ -0,0 +1,84 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP PAP
+ * ================================================================================
+ * 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;
+
+/**
+ * JSON encoder and decoder using the "standard" mechanism, which is currently gson.
+ */
+public class StandardCoder implements Coder {
+
+    /**
+     * Gson object used to encode and decode messages.
+     */
+    private static final Gson GSON = new Gson();
+
+    /**
+     * Constructs the object.
+     */
+    public StandardCoder() {
+        super();
+    }
+
+    @Override
+    public String encode(Object object) throws CoderException {
+        try {
+            return toJson(object);
+
+        } catch (RuntimeException e) {
+            throw new CoderException(e);
+        }
+    }
+
+    @Override
+    public <T> T decode(String json, Class<T> clazz) throws CoderException {
+        try {
+            return fromJson(json, clazz);
+
+        } catch (RuntimeException e) {
+            throw new CoderException(e);
+        }
+    }
+
+    // the remaining methods are wrappers that can be overridden by junit tests
+
+    /**
+     * Encodes an object into json, without catching exceptions.
+     *
+     * @param object object to be encoded
+     * @return a json string representing the object
+     */
+    protected String toJson(Object object) {
+        return GSON.toJson(object);
+    }
+
+    /**
+     * Decodes a json string into an object, without catching exceptions.
+     *
+     * @param json json string to be decoded
+     * @param clazz class of object to be decoded
+     * @return the object represented by the given json string
+     */
+    protected <T> T fromJson(String json, Class<T> clazz) {
+        return GSON.fromJson(json, clazz);
+    }
+}