Include PdxFieldNotWritableException, RuntimeException class to indicate a PDX field on a PdxInstance is not modifiable.

apache-geode-extensions/src/main/java/org/springframework/geode/pdx/PdxFieldNotWritableException.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * 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
+ *
+ *     https://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.springframework.geode.pdx;
+
+import org.apache.geode.pdx.PdxInstance;
+
+/**
+ * A {@link RuntimeException} thrown to indicate that a PDX field of a {@link PdxInstance} is not writable.
+ *
+ * @author John Blum
+ * @see java.lang.RuntimeException
+ * @see org.apache.geode.pdx.PdxInstance
+ * @since 1.3.0
+ */
+@SuppressWarnings("unused")
+public class PdxFieldNotWritableException extends RuntimeException {
+
+	public PdxFieldNotWritableException() { }
+
+	public PdxFieldNotWritableException(String message) {
+		super(message);
+	}
+
+	public PdxFieldNotWritableException(Throwable cause) {
+		super(cause);
+	}
+
+	public PdxFieldNotWritableException(String message, Throwable cause) {
+		super(message, cause);
+	}
+}