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Posted to commits@beam.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2018/04/24 22:55:00 UTC
[jira] [Work logged] (BEAM-4160) Convert JSON objects to Rows
[ https://issues.apache.org/jira/browse/BEAM-4160?focusedWorklogId=94841&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-94841 ]
ASF GitHub Bot logged work on BEAM-4160:
----------------------------------------
Author: ASF GitHub Bot
Created on: 24/Apr/18 22:54
Start Date: 24/Apr/18 22:54
Worklog Time Spent: 10m
Work Description: kennknowles commented on a change in pull request #5120: [BEAM-4160] Add JsonToRow transform
URL: https://github.com/apache/beam/pull/5120#discussion_r183903319
##########
File path: sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/JsonToRow.java
##########
@@ -0,0 +1,122 @@
+/*
+ * 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.beam.sdk.transforms;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import java.io.IOException;
+import javax.annotation.Nullable;
+import org.apache.beam.sdk.schemas.Schema;
+import org.apache.beam.sdk.schemas.Schema.TypeName;
+import org.apache.beam.sdk.util.RowJsonDeserializer;
+import org.apache.beam.sdk.values.PCollection;
+import org.apache.beam.sdk.values.Row;
+
+/**
+ * Creates a {@link PTransform} to convert input JSON objects to {@link Row Rows} with given {@link
+ * Schema}.
+ *
+ * <p>Currently supported {@link Schema} field types are: <ul> <li>{@link Schema.TypeName#BYTE}</li>
+ * <li>{@link Schema.TypeName#INT16}</li> <li>{@link Schema.TypeName#INT32}</li> <li>{@link
+ * Schema.TypeName#INT64}</li> <li>{@link Schema.TypeName#FLOAT}</li> <li>{@link
+ * Schema.TypeName#DOUBLE}</li> <li>{@link Schema.TypeName#BOOLEAN}</li> <li>{@link
+ * Schema.TypeName#STRING}</li> </ul>
+ *
+ * <p>For specifics of JSON deserialization see {@link RowJsonDeserializer}.
+ *
+ * <p>Conversion is strict, with minimal type coercion:
+ *
+ * <p>Booleans are only parsed from {@code true} or {@code false} literals, not from {@code "true"}
+ * or {@code "false"} strings or any other values (exception is thrown in these cases).
+ *
+ * <p>If a JSON number doesn't fit into the corresponding schema field type, an exception is be
+ * thrown. Strings are not auto-converted to numbers. Floating point numbers are not auto-converted
+ * to integral numbers. Precision loss also causes exceptions.
+ *
+ * <p>Only JSON string values can be parsed into {@link TypeName#STRING}. Numbers, booleans are not
+ * automatically converted, exceptions are thrown in these cases.
+ *
+ * <p>If a schema field is missing from the JSON value, an exception will be thrown.
+ *
+ * <p>Explicit {@code null} literals are allowed in JSON objects. No other values are parsed into
+ * {@code null}.
+ */
+public class JsonToRow {
+
+ public static PTransform<PCollection<? extends String>, PCollection<Row>> withSchema(
+ Schema rowSchema) {
+ return JsonToRowFn.forSchema(rowSchema);
+ }
+
+ static class JsonToRowFn extends PTransform<PCollection<? extends String>, PCollection<Row>> {
+ private transient volatile @Nullable ObjectMapper objectMapper;
+ private Schema schema;
+
+ static JsonToRowFn forSchema(Schema rowSchema) {
+ return new JsonToRowFn(rowSchema);
+ }
+
+ private JsonToRowFn(Schema schema) {
+ this.schema = schema;
+ }
+
+ @Override
+ public PCollection<Row> expand(PCollection<? extends String> jsonStrings) {
+ return jsonStrings
+ .apply(
+ ParDo.of(
+ new DoFn<String, Row>() {
+ @ProcessElement
+ public void processElement(ProcessContext context) {
+ context.output(jsonToRow(context.element()));
+ }
+ }))
+ .setCoder(schema.getRowCoder());
+ }
+
+ private Row jsonToRow(String jsonString) {
+ try {
+ return objectMapper().readValue(jsonString, Row.class);
+ } catch (IOException e) {
+ throw new IllegalArgumentException("Unable to parse json object: " + jsonString, e);
+ }
+ }
+
+ private ObjectMapper objectMapper() {
+ if (this.objectMapper == null) {
+ synchronized (this) {
+ if (this.objectMapper == null) {
+ this.objectMapper = newObjectMapperWith(RowJsonDeserializer.forSchema(this.schema));
Review comment:
Just curious - racy lazy initialization looks fine here, and if it double initializes you would just get GC'd. Is the library not safe? I kind of recall that it might not be, but I have forgotten the details.
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Issue Time Tracking
-------------------
Worklog Id: (was: 94841)
Time Spent: 10m
Remaining Estimate: 0h
> Convert JSON objects to Rows
> ----------------------------
>
> Key: BEAM-4160
> URL: https://issues.apache.org/jira/browse/BEAM-4160
> Project: Beam
> Issue Type: New Feature
> Components: dsl-sql, sdk-java-core
> Reporter: Anton Kedin
> Assignee: Anton Kedin
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Automate conversion of JSON objects to Rows to reduce overhead for querying JSON-based sources
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