Github user chinmaykolhatkar commented on a diff in the pull request:
https://github.com/apache/incubator-apex-malhar/pull/217#discussion_r56805377
--- Diff:
library/src/main/java/com/datatorrent/lib/projection/ProjectionOperator.java ---
@@ -0,0 +1,303 @@
+/**
+ * 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 com.datatorrent.lib.projection;
+
+import java.lang.reflect.Field;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.commons.lang3.ClassUtils;
+
+import com.datatorrent.api.AutoMetric;
+import com.datatorrent.api.Context;
+import com.datatorrent.api.Context.PortContext;
+import com.datatorrent.api.DefaultInputPort;
+import com.datatorrent.api.DefaultOutputPort;
+
+import com.datatorrent.api.Operator;
+import com.datatorrent.api.annotation.InputPortFieldAnnotation;
+import com.datatorrent.api.annotation.OutputPortFieldAnnotation;
+
+import com.datatorrent.common.util.BaseOperator;
+
+import com.datatorrent.lib.util.PojoUtils;
+
+/**
+ * <b>ProjectionOperator</b>
+ * Projection Operator projects defined set of fields from given
selectFields/dropFields
+ *
+ * <b>Parameters</b>
+ * - selectFields: comma separated list of fields to be selected from
input tuples
+ * - dropFields: comma separated list of fields to be dropped from input
tuples
+ * selectFields and dropFields are optional and either of them shall be
specified
+ * When both are not specified, all fields shall be projected to
downstream operator
+ *
+ * <b>Input Port</b> takes POJOs as an input
+ *
+ * <b>Output Ports</b>
+ * - projected port emits POJOs with projected fields from input POJOs
+ * - remainder port, if connected, emits POJOs with remainder fields from
input POJOs
+ * - error port emits input POJOs as is upon error situations
+ *
+ * <b>Examples</b>
+ * For {a, b, c} type of input tuples
+ * - when selectFields = "" and dropFields = "", projected port shall
emit {a, b, c}
+ * - when selectFields = "b", projected port shall emit {b} and remainder
port shall emit {a, c}
+ * - when dropFields = "b", projected port shall emit {a, c} and
remainder port shall emit {b}
+ *
+ */
+
+public class ProjectionOperator extends BaseOperator implements
Operator.ActivationListener<Context>
+{
+ protected String selectFields;
+ protected String dropFields;
+ protected String condition;
+
+ static class TypeInfo
+ {
+ String name;
+ Class type;
+ PojoUtils.Setter setter;
+ PojoUtils.Getter getter;
+
+ public TypeInfo(String name, Class<?> type)
+ {
+ this.name = name;
+ this.type = type;
+ }
+
+ public String toString()
+ {
+ String s = new String("'name': " + name + " 'type': " + type);
+ return s;
+ }
+ }
+
+ protected transient List<TypeInfo> projectedFields = new ArrayList<>();
--- End diff --
Unless there is a immediate need for a projectedFields & remainderFields to
be used by subclass, I'll suggest to make these fields private.
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