Use Jackson for JSON de/serialization

This involves a major refactor of all message representations.
The main motivation for this change is to simplify the logic to
enforce type safety, such that we no longer depend on the behavior
of all the scala class magic we used to rely on.

This commit also introduces a differentiation between request
and response messages to provide further type safety. This would
have introduced much additional complexity without the refactor.

core/src/main/scala/org/apache/spark/deploy/rest/DriverStatusRequest.scala

@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.spark.deploy.rest
+
+class DriverStatusRequest extends SubmitRestProtocolRequest {
+  protected override val action = SubmitRestProtocolAction.DRIVER_STATUS_REQUEST
+  private val driverId = new SubmitRestProtocolField[String]
+
+  def getDriverId: String = driverId.toString
+  def setDriverId(s: String): this.type = setField(driverId, s)
+
+  override def validate(): Unit = {
+    super.validate()
+    assertFieldIsSet(driverId, "driver_id")
+  }
+}

core/src/main/scala/org/apache/spark/deploy/rest/DriverStatusResponse.scala

@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.spark.deploy.rest
+
+class DriverStatusResponse extends SubmitRestProtocolResponse {
+  protected override val action = SubmitRestProtocolAction.DRIVER_STATUS_RESPONSE
+  private val driverId = new SubmitRestProtocolField[String]
+  private val success = new SubmitRestProtocolField[Boolean]
+  private val driverState = new SubmitRestProtocolField[String]
+  private val workerId = new SubmitRestProtocolField[String]
+  private val workerHostPort = new SubmitRestProtocolField[String]
+
+  def getDriverId: String = driverId.toString
+  def getSuccess: String = success.toString
+  def getDriverState: String = driverState.toString
+  def getWorkerId: String = workerId.toString
+  def getWorkerHostPort: String = workerHostPort.toString
+
+  def setDriverId(s: String): this.type = setField(driverId, s)
+  def setSuccess(s: String): this.type = setBooleanField(success, s)
+  def setDriverState(s: String): this.type = setField(driverState, s)
+  def setWorkerId(s: String): this.type = setField(workerId, s)
+  def setWorkerHostPort(s: String): this.type = setField(workerHostPort, s)
+
+  override def validate(): Unit = {
+    super.validate()
+    assertFieldIsSet(driverId, "driver_id")
+    assertFieldIsSet(success, "success")
+  }
+}

core/src/main/scala/org/apache/spark/deploy/rest/ErrorResponse.scala

@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.spark.deploy.rest
+
+class ErrorResponse extends SubmitRestProtocolResponse {
+  protected override val action = SubmitRestProtocolAction.ERROR
+  override def validate(): Unit = {
+    super.validate()
+    assertFieldIsSet(message, "message")
+  }
+}

core/src/main/scala/org/apache/spark/deploy/rest/KillDriverRequest.scala

@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.spark.deploy.rest
+
+class KillDriverRequest extends SubmitRestProtocolRequest {
+  protected override val action = SubmitRestProtocolAction.KILL_DRIVER_REQUEST
+  private val driverId = new SubmitRestProtocolField[String]
+
+  def getDriverId: String = driverId.toString
+  def setDriverId(s: String): this.type = setField(driverId, s)
+
+  override def validate(): Unit = {
+    super.validate()
+    assertFieldIsSet(driverId, "driver_id")
+  }
+}

core/src/main/scala/org/apache/spark/deploy/rest/KillDriverResponse.scala

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.
+ */
+
+package org.apache.spark.deploy.rest
+
+class KillDriverResponse extends SubmitRestProtocolResponse {
+  protected override val action = SubmitRestProtocolAction.KILL_DRIVER_RESPONSE
+  private val driverId = new SubmitRestProtocolField[String]
+  private val success = new SubmitRestProtocolField[Boolean]
+
+  def getDriverId: String = driverId.toString
+  def getSuccess: String = success.toString
+
+  def setDriverId(s: String): this.type = setField(driverId, s)
+  def setSuccess(s: String): this.type = setBooleanField(success, s)
+
+  override def validate(): Unit = {
+    super.validate()
+    assertFieldIsSet(driverId, "driver_id")
+    assertFieldIsSet(success, "success")
+  }
+}