Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2094#discussion_r87101256
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/util/typeutils/FieldAccessorFactory.java
---
@@ -0,0 +1,197 @@
+/*
+ * 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.flink.streaming.util.typeutils;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.api.common.ExecutionConfig;
+import org.apache.flink.api.common.typeinfo.BasicArrayTypeInfo;
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.PrimitiveArrayTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.common.typeutils.CompositeType;
+import org.apache.flink.api.java.typeutils.PojoField;
+import org.apache.flink.api.java.typeutils.PojoTypeInfo;
+import org.apache.flink.api.java.typeutils.TupleTypeInfo;
+import org.apache.flink.api.java.typeutils.TupleTypeInfoBase;
+
+import java.io.Serializable;
+
+
+/**
+ * Static factories for the {@link FieldAccessor} utilities.
+ */
+@Internal
+public class FieldAccessorFactory implements Serializable {
+
+ /**
+ * Creates a {@link FieldAccessor} for the given field position, which
can be used to get and set
+ * the specified field on instances of this type.
+ *
+ * @param pos The field position (zero-based)
+ * @param config Configuration object
+ * @param <F> The type of the field to access
+ * @return The created FieldAccessor
+ */
+ @Internal
+ public static <T, F> FieldAccessor<T, F> getAccessor(TypeInformation<T>
typeInfo, int pos, ExecutionConfig config){
+
+ // In case of arrays
+ if (typeInfo instanceof BasicArrayTypeInfo || typeInfo
instanceof PrimitiveArrayTypeInfo) {
+ return new FieldAccessor.ArrayFieldAccessor<>(pos,
typeInfo);
+
+ // In case of basic types
+ } else if (typeInfo instanceof BasicTypeInfo) {
+ if (pos != 0) {
+ throw new
CompositeType.InvalidFieldReferenceException("The " + ((Integer)
pos).toString() + ". field selected on a " +
+ "basic type (" + typeInfo.toString() +
"). A field expression on a basic type can only select " +
+ "the 0th field (which means selecting
the entire basic type).");
+ }
+ return (FieldAccessor<T, F>) new
FieldAccessor.SimpleFieldAccessor<>(typeInfo);
+
+ // In case of case classes
+ } else if (typeInfo.isTupleType() && ((TupleTypeInfoBase)
typeInfo).isCaseClass()) {
+ TupleTypeInfoBase tupleTypeInfo = (TupleTypeInfoBase)
typeInfo;
+ TypeInformation<?>[] types = new
TypeInformation<?>[tupleTypeInfo.getArity()];
+ for (int i = 0; i < types.length; i++) {
+ types[i] = tupleTypeInfo.getTypeAt(i);
+ }
+ return new FieldAccessor.ProductFieldAccessor<>(
+ pos, typeInfo, new
FieldAccessor.SimpleFieldAccessor<>((TypeInformation<F>)types[pos]), config);
+
+ // In case of tuples
+ } else if (typeInfo.isTupleType()) {
+ return new
FieldAccessor.SimpleTupleFieldAccessor<>(pos, typeInfo);
+
+ // Default case, PojoType is directed to this statement
+ } else {
+ throw new
CompositeType.InvalidFieldReferenceException("Cannot reference field by
position on " + typeInfo.toString()
+ + "Referencing a field by position is supported
on tuples, case classes, and arrays. "
+ + "Additionally, you can select the 0th field
of a primitive/basic type (e.g. int).");
+ }
+ }
+
+ /**
+ * Creates a {@link FieldAccessor} for the field that is given by a
field expression,
+ * which can be used to get and set the specified field on instances of
this type.
+ *
+ * @param field The field expression
+ * @param config Configuration object
+ * @param <F> The type of the field to access
+ * @return The created FieldAccessor
+ */
+ @Internal
+ public static <T, F> FieldAccessor<T, F> getAccessor(TypeInformation<T>
typeInfo, String field, ExecutionConfig config) {
+
+ // In case of arrays
+ if (typeInfo instanceof BasicArrayTypeInfo || typeInfo
instanceof PrimitiveArrayTypeInfo) {
+ try {
+ return new
FieldAccessor.ArrayFieldAccessor<>(Integer.parseInt(field), typeInfo);
+ } catch (NumberFormatException ex) {
+ throw new
CompositeType.InvalidFieldReferenceException
+ ("A field expression on an array must
be an integer index (that might be given as a string).");
+ }
+
+ // In case of basic types
+ } else if (typeInfo instanceof BasicTypeInfo) {
+ try {
+ int pos = field.equals("*") ? 0 :
Integer.parseInt(field);
--- End diff --
use `Keys.ExpressionKeys.SELECT_ALL_CHAR` instead of `"*"`?
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