Allow custom JSON adapter specification

In order to decode and encode complex Java POJOs with GSON,
type adapters must be specified. This change allows specification
of GSON type adapters for decoding and encoding of JSON in apex.

Issue-ID: POLICY-954
Change-Id: Ib402d4e82c4f22fa4d532c016f77fb8e7bb568d3
Signed-off-by: liamfallon <liam.fallon@ericsson.com>

6 files changed, 425 insertions, 20 deletions

diff --git a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/BadJsonAdapter.java b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/BadJsonAdapter.java
new file mode 100644
index 000000000..fef69ac33
--- /dev/null
+++ b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/BadJsonAdapter.java
@@ -0,0 +1,63 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.context.impl.schema.java;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+
+import java.lang.reflect.Type;
+
+/**
+ * This class serialises and deserialises various type of event protocol parameters to and from
+ * JSON.
+ *
+ * @author Liam Fallon (liam.fallon@ericsson.com)
+ */
+public class BadJsonAdapter
+        implements JsonSerializer<String>, JsonDeserializer<String> {
+
+    public BadJsonAdapter() throws IllegalAccessException {
+        throw new IllegalAccessException("Test for Bad Adapter");
+    }
+    
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public JsonElement serialize(final String src, final Type typeOfSrc,
+            final JsonSerializationContext context) {
+        return new Gson().toJsonTree(src, String.class);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String deserialize(final JsonElement json, final Type typeOfT,
+            final JsonDeserializationContext context) {
+        
+        return new Gson().fromJson(json, String.class);
+    }
+}
diff --git a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperParametersTest.java b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperParametersTest.java
new file mode 100644
index 000000000..c0287bfe2
--- /dev/null
+++ b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperParametersTest.java
@@ -0,0 +1,101 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.context.impl.schema.java;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.junit.Test;
+
+/**
+ * Test Java schema helper parameters.
+ */
+public class JavaSchemaHelperParametersTest {
+
+    @Test
+    public void testJavaSchemaHelperParameters() {
+        JavaSchemaHelperParameters pars = new JavaSchemaHelperParameters();
+
+        assertEquals("org.onap.policy.apex.context.impl.schema.java.JavaSchemaHelper",
+                        pars.getSchemaHelperPluginClass());
+
+        assertEquals(0, pars.getJsonAdapters().size());
+
+        JavaSchemaHelperJsonAdapterParameters jsonPars = new JavaSchemaHelperJsonAdapterParameters();
+        pars.getJsonAdapters().put("JsonAdapter0", jsonPars);
+
+        assertFalse(pars.validate().isValid());
+
+        jsonPars.setAdaptedClass("AAA");
+        jsonPars.setAdaptorClass("AAA");
+        assertFalse(pars.validate().isValid());
+
+        jsonPars.setAdaptedClass("java.lang.String");
+        jsonPars.setAdaptorClass("AAA");
+        assertFalse(pars.validate().isValid());
+
+        jsonPars.setAdaptedClass("AAA");
+        jsonPars.setAdaptorClass("java.lang.String");
+        assertFalse(pars.validate().isValid());
+
+        jsonPars.setAdaptedClass("java.lang.String");
+        jsonPars.setAdaptorClass("org.onap.policy.apex.context.impl.schema.java.TestJsonDeserializer");
+        assertFalse(pars.validate().isValid());
+
+        jsonPars.setAdaptedClass("java.lang.String");
+        jsonPars.setAdaptorClass("org.onap.policy.apex.context.impl.schema.java.TestJsonSerializer");
+        assertFalse(pars.validate().isValid());
+
+        jsonPars.setAdaptedClass("java.lang.String");
+        jsonPars.setAdaptorClass("org.onap.policy.apex.context.impl.schema.java.TestJsonAdapter");
+        assertTrue(pars.validate().isValid());
+
+        Map<String, JavaSchemaHelperJsonAdapterParameters> adapterMap = new LinkedHashMap<>();
+
+        pars.setJsonAdapters(adapterMap);
+        assertTrue(pars.validate().isValid());
+    }
+
+    @Test
+    public void testJavaSchemaHelperJsonAdapterParameters() {
+        JavaSchemaHelperJsonAdapterParameters pars = new JavaSchemaHelperJsonAdapterParameters();
+
+        assertNull(pars.getName());
+        assertNull(pars.getAdaptedClass());
+        assertNull(pars.getAdaptedClazz());
+        assertNull(pars.getAdaptorClass());
+        assertNull(pars.getAdaptorClazz());
+
+        pars.setName("Zooby");
+        assertEquals("Zooby", pars.getAdaptedClass());
+        assertEquals("Zooby", pars.getName());
+        assertNull(pars.getAdaptedClazz());
+
+        pars.setAdaptorClass("Zooby");
+        assertEquals("Zooby", pars.getAdaptorClass());
+        assertNull(pars.getAdaptorClazz());
+    }
+}
diff --git a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperTest.java b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperTest.java
index 8da6fdab9..c746198e7 100644
--- a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperTest.java
+++ b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/JavaSchemaHelperTest.java
@@ -28,16 +28,44 @@ import com.google.gson.JsonParser;
 import com.google.gson.JsonPrimitive;
 
 import java.math.BigDecimal;
+import java.time.Instant;
 
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
 import org.junit.Test;
 
 import org.onap.policy.apex.context.ContextRuntimeException;
 import org.onap.policy.apex.context.SchemaHelper;
+import org.onap.policy.apex.context.parameters.ContextParameterConstants;
+import org.onap.policy.apex.context.parameters.SchemaParameters;
 import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
 import org.onap.policy.apex.model.contextmodel.concepts.AxContextSchema;
-
+import org.onap.policy.common.parameters.ParameterService;
 
 public class JavaSchemaHelperTest {
+    /**
+     * Initialize JSON adapters.
+     */
+    @BeforeClass
+    public static void registerParameters() {
+        JavaSchemaHelperParameters javaSchemaHelperPars = new JavaSchemaHelperParameters();
+
+        JavaSchemaHelperJsonAdapterParameters stringAdapterPars = new JavaSchemaHelperJsonAdapterParameters();
+        stringAdapterPars.setAdaptedClass("java.lang.String");
+        stringAdapterPars.setAdaptorClass("org.onap.policy.apex.context.impl.schema.java.TestJsonAdapter");
+
+        javaSchemaHelperPars.getJsonAdapters().put("String", stringAdapterPars);
+        
+        SchemaParameters schemaPars = new SchemaParameters();
+        schemaPars.getSchemaHelperParameterMap().put("Java", javaSchemaHelperPars);
+
+        ParameterService.register(schemaPars);
+    }
+
+    @AfterClass
+    public static void deregisterParameters() {
+        ParameterService.clear();
+    }
 
     @Test
     public void testJavaSchemaHelperInit() {
@@ -51,7 +79,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: class/type java.lang.Rubbish for context schema"
-                    + " \"SchemaKey:0.0.1\" not found. Check the class path of the JVM", e.getMessage());
+                            + " \"SchemaKey:0.0.1\" not found. Check the class path of the JVM", e.getMessage());
         }
 
         AxContextSchema builtInJavaTypeSchema = new AxContextSchema(schemaKey, "Java", "short");
@@ -61,8 +89,8 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: class/type short for context schema "
-                    + "\"SchemaKey:0.0.1\" not found. Primitive types are not supported."
-                    + " Use the appropriate Java boxing type instead.", e.getMessage());
+                            + "\"SchemaKey:0.0.1\" not found. Primitive types are not supported."
+                            + " Use the appropriate Java boxing type instead.", e.getMessage());
         }
     }
 
@@ -80,7 +108,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("NULL:0.0.0: could not create an instance, schema class for the schema is null",
-                    e.getMessage());
+                            e.getMessage());
         }
 
         try {
@@ -88,7 +116,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("NULL:0.0.0: could not create an instance, schema class for the schema is null",
-                    e.getMessage());
+                            e.getMessage());
         }
 
         try {
@@ -96,7 +124,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("NULL:0.0.0: could not create an instance, schema class for the schema is null",
-                    e.getMessage());
+                            e.getMessage());
         }
 
         AxArtifactKey schemaKey = new AxArtifactKey("SchemaKey", "0.0.1");
@@ -114,7 +142,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: could not create an instance of class "
-                    + "\"java.lang.Integer\" using the default constructor \"Integer()\"", e.getMessage());
+                            + "\"java.lang.Integer\" using the default constructor \"Integer()\"", e.getMessage());
         }
 
         try {
@@ -122,8 +150,8 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: the object \"1.23\" of type "
-                    + "\"java.lang.Float\" is not an instance of JsonObject and is not "
-                    + "assignable to \"java.lang.Integer\"", e.getMessage());
+                            + "\"java.lang.Float\" is not an instance of JsonObject and is not "
+                            + "assignable to \"java.lang.Integer\"", e.getMessage());
         }
 
         try {
@@ -131,7 +159,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: could not create an instance of class \"java.lang.Integer\" "
-                    + "using the string constructor \"Integer(String)\"", e.getMessage());
+                            + "using the string constructor \"Integer(String)\"", e.getMessage());
         }
 
         JsonElement jsonIntElement = null;
@@ -183,8 +211,8 @@ public class JavaSchemaHelperTest {
         doubleSchemaHelper.init(userKey, doubleSchema);
         stringSchemaHelper.init(userKey, stringSchema);
 
-        AxContextSchema myBaseClassSchema =
-                new AxContextSchema(schemaKey, "Java", "org.onap.policy.apex.context.impl.schema.java.MyBaseClass");
+        AxContextSchema myBaseClassSchema = new AxContextSchema(schemaKey, "Java",
+                        "org.onap.policy.apex.context.impl.schema.java.MyBaseClass");
         SchemaHelper myBaseClassSchemaHelper = new JavaSchemaHelper();
         myBaseClassSchemaHelper.init(userKey, myBaseClassSchema);
 
@@ -201,7 +229,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"one two three\" of class \"java.lang.String\" not "
-                    + "compatible with class \"java.lang.Byte\"", e.getMessage());
+                            + "compatible with class \"java.lang.Byte\"", e.getMessage());
         }
 
         assertEquals(null, shortSchemaHelper.unmarshal(null));
@@ -217,7 +245,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"one two three\" of class \"java.lang.String\" not "
-                    + "compatible with class \"java.lang.Short\"", e.getMessage());
+                            + "compatible with class \"java.lang.Short\"", e.getMessage());
         }
 
         assertEquals(null, intSchemaHelper.unmarshal(null));
@@ -233,7 +261,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"one two three\" of class \"java.lang.String\" not "
-                    + "compatible with class \"java.lang.Integer\"", e.getMessage());
+                            + "compatible with class \"java.lang.Integer\"", e.getMessage());
         }
 
         assertEquals(null, longSchemaHelper.unmarshal(null));
@@ -249,7 +277,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"one two three\" of class \"java.lang.String\" not "
-                    + "compatible with class \"java.lang.Long\"", e.getMessage());
+                            + "compatible with class \"java.lang.Long\"", e.getMessage());
         }
 
         assertEquals(null, floatSchemaHelper.unmarshal(null));
@@ -265,7 +293,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"one two three\" of class \"java.lang.String\" not "
-                    + "compatible with class \"java.lang.Float\"", e.getMessage());
+                            + "compatible with class \"java.lang.Float\"", e.getMessage());
         }
 
         assertEquals(null, doubleSchemaHelper.unmarshal(null));
@@ -282,7 +310,7 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"one two three\" of class \"java.lang.String\" not "
-                    + "compatible with class \"java.lang.Double\"", e.getMessage());
+                            + "compatible with class \"java.lang.Double\"", e.getMessage());
         }
 
         assertEquals("123", stringSchemaHelper.unmarshal(123));
@@ -307,10 +335,74 @@ public class JavaSchemaHelperTest {
             fail("test should throw an exception here");
         } catch (ContextRuntimeException e) {
             assertEquals("UserKey:0.0.1: object \"123.45\" of class \"java.lang.Double\" not "
-                    + "compatible with class \"java.lang.Integer\"", e.getMessage());
+                            + "compatible with class \"java.lang.Integer\"", e.getMessage());
         }
 
         JsonPrimitive intJsonPrimitive = (JsonPrimitive) intSchemaHelper.marshal2Object(123);
         assertEquals(123, intJsonPrimitive.getAsInt());
     }
+
+    @Test
+    public void testJavaSchemaHelperAdapters() {
+        AxArtifactKey schemaKey = new AxArtifactKey("SchemaKey", "0.0.1");
+        AxArtifactKey userKey = new AxArtifactKey("UserKey", "0.0.1");
+
+        AxContextSchema stringSchema = new AxContextSchema(schemaKey, "Java", "java.lang.String");
+        SchemaHelper stringSchemaHelper = new JavaSchemaHelper();
+        stringSchemaHelper.init(userKey, stringSchema);
+
+        assertEquals("null", stringSchemaHelper.marshal2String(null));
+        assertEquals("\"Hello\"", stringSchemaHelper.marshal2String("Hello"));
+        try {
+            stringSchemaHelper.marshal2String(Instant.ofEpochMilli(1000));
+            fail("test should throw an exception here");
+        } catch (ContextRuntimeException e) {
+            assertEquals("UserKey:0.0.1: object \"1970-01-01T00:00:01Z\" of class \"java.time.Instant\" "
+                            + "not compatible with class \"java.lang.String\"", e.getMessage());
+        }
+
+        JsonPrimitive stringJsonPrimitive = (JsonPrimitive) stringSchemaHelper.marshal2Object("Another String");
+        assertEquals("Another String", stringJsonPrimitive.getAsString());
+    }
+
+    @Test
+    public void testJavaSchemaHelperBadAdapter() {
+        AxArtifactKey schemaKey = new AxArtifactKey("SchemaKey", "0.0.1");
+        AxArtifactKey userKey = new AxArtifactKey("UserKey", "0.0.1");
+
+        SchemaParameters pars = ParameterService.get(ContextParameterConstants.SCHEMA_GROUP_NAME);
+        
+        JavaSchemaHelperParameters javaShPars = (JavaSchemaHelperParameters) pars.getSchemaHelperParameterMap()
+                        .get("Java");
+        javaShPars.getJsonAdapters().get("String")
+                        .setAdaptorClass("org.onap.policy.apex.context.impl.schema.java.BadJsonAdapter");
+
+        AxContextSchema stringSchema = new AxContextSchema(schemaKey, "Java", "java.lang.String");
+        SchemaHelper stringSchemaHelper = new JavaSchemaHelper();
+        stringSchemaHelper.init(userKey, stringSchema);
+
+        try {
+            stringSchemaHelper.marshal2String("Hello");
+            fail("test should throw an exception");
+        } catch (ContextRuntimeException pre) {
+            assertEquals("UserKey:0.0.1: instantiation of adapter class "
+                            + "\"org.onap.policy.apex.context.impl.schema.java.BadJsonAdapter\"  "
+                            + "to decode and encode class \"java.lang.String\" failed: Test for Bad Adapter",
+                            pre.getMessage());
+        }
+    }
+
+    @Test
+    public void testJavaSchemaHelperDefaultAdapter() {
+        SchemaParameters pars = ParameterService.get(ContextParameterConstants.SCHEMA_GROUP_NAME);
+
+        JavaSchemaHelperParameters javaShPars = (JavaSchemaHelperParameters) pars.getSchemaHelperParameterMap()
+                        .get("Java");
+        
+        pars.getSchemaHelperParameterMap().clear();
+        
+        testJavaSchemaHelperAdapters();
+
+        pars.getSchemaHelperParameterMap().put("Java", javaShPars);
+    }
 }
diff --git a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonAdapter.java b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonAdapter.java
new file mode 100644
index 000000000..89dfb4c2d
--- /dev/null
+++ b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonAdapter.java
@@ -0,0 +1,55 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.context.impl.schema.java;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+
+import java.lang.reflect.Type;
+
+/**
+ * This class serialises and deserialises various type of event protocol parameters to and from JSON.
+ *
+ * @author Liam Fallon (liam.fallon@ericsson.com)
+ */
+public class TestJsonAdapter implements JsonSerializer<String>, JsonDeserializer<String> {
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public JsonElement serialize(final String src, final Type typeOfSrc, final JsonSerializationContext context) {
+        return new Gson().toJsonTree(src, String.class);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context) {
+
+        return new Gson().fromJson(json, String.class);
+    }
+}
diff --git a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonDeserializer.java b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonDeserializer.java
new file mode 100644
index 000000000..463945872
--- /dev/null
+++ b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonDeserializer.java
@@ -0,0 +1,44 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.context.impl.schema.java;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonElement;
+
+import java.lang.reflect.Type;
+
+/**
+ * This class serialises and deserialises various type of event protocol parameters to and from JSON.
+ *
+ * @author Liam Fallon (liam.fallon@ericsson.com)
+ */
+public class TestJsonDeserializer implements JsonDeserializer<String> {
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public String deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context) {
+
+        return new Gson().fromJson(json, String.class);
+    }
+}
diff --git a/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonSerializer.java b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonSerializer.java
new file mode 100644
index 000000000..d58be6069
--- /dev/null
+++ b/context/context-management/src/test/java/org/onap/policy/apex/context/impl/schema/java/TestJsonSerializer.java
@@ -0,0 +1,50 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.apex.context.impl.schema.java;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+
+import java.lang.reflect.Type;
+
+import org.onap.policy.common.parameters.ParameterRuntimeException;
+import org.slf4j.ext.XLogger;
+import org.slf4j.ext.XLoggerFactory;
+
+/**
+ * This class serialises and deserialises various type of event protocol parameters to and from JSON.
+ *
+ * @author Liam Fallon (liam.fallon@ericsson.com)
+ */
+public class TestJsonSerializer implements JsonSerializer<String> {
+    private static final XLogger LOGGER = XLoggerFactory.getXLogger(TestJsonSerializer.class);
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public JsonElement serialize(final String src, final Type typeOfSrc, final JsonSerializationContext context) {
+        final String returnMessage = "serialization of Apex event protocol parameters to Json is not supported";
+        LOGGER.error(returnMessage);
+        throw new ParameterRuntimeException(returnMessage);
+    }
+}