add applicationfailureexception class and let data converter to fallback on this exception instead

Signed-off-by: Shijie Sheng <liouvetren@gmail.com>

Author: shijiesheng

src/main/java/com/uber/cadence/client/ApplicationFailureException.java

@@ -0,0 +1,43 @@
+/**
+ * Copyright 2012-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * <p>Modifications copyright (C) 2017 Uber Technologies, Inc.
+ *
+ * <p>Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file
+ * except in compliance with the License. A copy of the License is located at
+ *
+ * <p>http://aws.amazon.com/apache2.0
+ *
+ * <p>or in the "license" file accompanying this file. This file 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.
+ */
+package com.uber.cadence.client;
+
+import com.uber.cadence.CadenceError;
+import java.util.Objects;
+
+public final class ApplicationFailureException extends CadenceError {
+
+  public ApplicationFailureException(String message) {
+    super(message);
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (this == obj) {
+      return true;
+    }
+    if (obj == null || getClass() != obj.getClass()) {
+      return false;
+    }
+    ApplicationFailureException that = (ApplicationFailureException) obj;
+    return Objects.equals(getMessage(), that.getMessage())
+        && Objects.equals(getCause(), that.getCause());
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(getMessage(), getCause());
+  }
+}

src/main/java/com/uber/cadence/converter/CustomThrowableTypeAdapter.java

@@ -22,6 +22,7 @@
 import com.google.gson.reflect.TypeToken;
 import com.google.gson.stream.JsonReader;
 import com.google.gson.stream.JsonWriter;
+import com.uber.cadence.client.ApplicationFailureException;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringWriter;
@@ -137,7 +138,7 @@ public T read(JsonReader jsonReader) throws IOException {
       try {
         classType = Class.forName(className);
       } catch (ClassNotFoundException e) {
-        return null;
+        return (T) new ApplicationFailureException("Class not found: " + className);
       }
       if (!Throwable.class.isAssignableFrom(classType)) {
         throw new IOException("Expected type that extends Throwable: " + className);

src/test/java/com/uber/cadence/converter/JsonDataConverterTest.java

@@ -27,6 +27,7 @@
 import com.uber.cadence.WorkflowExecutionStartedEventAttributes;
 import com.uber.cadence.WorkflowType;
 import com.uber.cadence.activity.Activity;
+import com.uber.cadence.client.ApplicationFailureException;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
@@ -285,6 +286,9 @@ public void testExceptionNotFound() {
             convertedString.getBytes(StandardCharsets.UTF_8),
             RuntimeException.class,
             RuntimeException.class);
-    assertNull(fromConverted);
+    assertEquals(ApplicationFailureException.class, fromConverted.getClass());
+    assertEquals(
+        "Class not found: com.uber.cadence.converter.ExceptionNotFound",
+        fromConverted.getMessage());
   }
 }