Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/5240#discussion_r163007886
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/descriptors/JSON.scala
---
@@ -0,0 +1,140 @@
+/*
+ * 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.table.descriptors
+
+import java.util
+
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.table.api.TableSchema
+
+import scala.collection.mutable
+import scala.collection.JavaConverters._
+
+/**
+ * Encoding descriptor for JSON.
+ */
+class JSON extends EncodingDescriptor("json") {
+
+ private val encodingSchema: mutable.LinkedHashMap[String, String] =
+ mutable.LinkedHashMap[String, String]()
+ private var fieldMapping: Option[util.Map[String, String]] = None
+ private var failOnMissingField: Option[Boolean] = None
+
+ /**
+ * Sets the JSON schema with field names and the types for the
JSON-encoded input.
+ * The JSON schema must not contain nested fields.
+ *
+ * This method overwrites existing fields added with [[field()]].
+ *
+ * @param schema the table schema
+ */
+ def schema(schema: TableSchema): JSON = {
+ this.encodingSchema.clear()
+ NormalizedProperties.normalizeTableSchema(schema).foreach {
+ case (n, t) => field(n, t)
+ }
+ this
+ }
+
+ /**
+ * Adds a JSON field with the field name and the type information for
the JSON-encoding.
+ * This method can be called multiple times. The call order of this
method defines
+ * also the order of the fields in the JSON-encoding.
+ *
+ * @param fieldName the field name
+ * @param fieldType the type information of the field
+ */
+ def field(fieldName: String, fieldType: TypeInformation[_]): JSON = {
+ field(fieldName, NormalizedProperties.normalizeTypeInfo(fieldType))
+ this
+ }
+
+ /**
+ * Adds a JSON field with the field name and the type string for the
JSON-encoding.
+ * This method can be called multiple times. The call order of this
method defines
+ * also the order of the fields in the JSON-encoding.
+ *
+ * @param fieldName the field name
+ * @param fieldType the type string of the field
+ */
+ def field(fieldName: String, fieldType: String): JSON = {
+ if (encodingSchema.contains(fieldName)) {
+ throw new IllegalArgumentException(s"Duplicate field name
$fieldName.")
+ }
+ encodingSchema += (fieldName -> fieldType)
+ this
+ }
+
+ /**
+ * Sets a mapping from schema fields to fields of the JSON schema.
+ *
+ * A field mapping is required if the fields of produced tables should
be named different than
+ * the fields of the JSON records.
+ * The key of the provided Map refers to the field of the table schema,
+ * the value to the field in the JSON schema.
+ *
+ * @param tableToJsonMapping A mapping from table schema fields to JSON
schema fields.
+ * @return The builder.
+ */
+ def tableToJsonMapping(tableToJsonMapping: util.Map[String, String]):
JSON = {
+ this.fieldMapping = Some(tableToJsonMapping)
+ this
+ }
+
+ /**
+ * Sets flag whether to fail if a field is missing or not.
+ *
+ * @param failOnMissingField If set to true, the operation fails if
there is a missing field.
+ * If set to false, a missing field is set to
null.
+ * @return The builder.
+ */
+ def failOnMissingField(failOnMissingField: Boolean): JSON = {
+ this.failOnMissingField = Some(failOnMissingField)
+ this
+ }
+
+ /**
+ * Internal method for encoding properties conversion.
+ */
+ override protected def addEncodingProperties(properties:
NormalizedProperties): Unit = {
+ properties.putIndexedFixedProperties(
--- End diff --
Maybe add support for nested fields to utils.
Other encodings will need this as well.
---
