Github user markap14 commented on a diff in the pull request:

    https://github.com/apache/nifi/pull/2587#discussion_r179824910
  
    --- Diff: 
nifi-nar-bundles/nifi-standard-services/nifi-record-serialization-services-bundle/nifi-record-serialization-services/src/main/java/org/apache/nifi/xml/XMLRecordReader.java
 ---
    @@ -0,0 +1,502 @@
    +/*
    + * 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.nifi.xml;
    +
    +import org.apache.nifi.logging.ComponentLog;
    +import org.apache.nifi.serialization.MalformedRecordException;
    +import org.apache.nifi.serialization.RecordReader;
    +import org.apache.nifi.serialization.SimpleRecordSchema;
    +import org.apache.nifi.serialization.record.DataType;
    +import org.apache.nifi.serialization.record.MapRecord;
    +import org.apache.nifi.serialization.record.Record;
    +import org.apache.nifi.serialization.record.RecordField;
    +import org.apache.nifi.serialization.record.RecordSchema;
    +import org.apache.nifi.serialization.record.type.ArrayDataType;
    +import org.apache.nifi.serialization.record.type.RecordDataType;
    +import org.apache.nifi.serialization.record.util.DataTypeUtils;
    +
    +import javax.xml.stream.XMLEventReader;
    +import javax.xml.stream.XMLInputFactory;
    +import javax.xml.stream.XMLStreamException;
    +import javax.xml.stream.events.Attribute;
    +import javax.xml.stream.events.Characters;
    +import javax.xml.stream.events.StartElement;
    +import javax.xml.stream.events.XMLEvent;
    +import java.io.IOException;
    +import java.io.InputStream;
    +import java.text.DateFormat;
    +import java.util.ArrayList;
    +import java.util.Collections;
    +import java.util.HashMap;
    +import java.util.Iterator;
    +import java.util.List;
    +import java.util.Map;
    +import java.util.Optional;
    +import java.util.function.Supplier;
    +
    +public class XMLRecordReader implements RecordReader {
    +
    +    private final ComponentLog logger;
    +    private final RecordSchema schema;
    +    private final String recordName;
    +    private final String attributePrefix;
    +    private final String contentFieldName;
    +
    +    // thread safety required?
    +    private StartElement currentRecordStartTag;
    +
    +    private final XMLEventReader xmlEventReader;
    +
    +    private final Supplier<DateFormat> LAZY_DATE_FORMAT;
    +    private final Supplier<DateFormat> LAZY_TIME_FORMAT;
    +    private final Supplier<DateFormat> LAZY_TIMESTAMP_FORMAT;
    +
    +    public XMLRecordReader(InputStream in, RecordSchema schema, String 
rootName, String recordName, String attributePrefix, String contentFieldName,
    +                           final String dateFormat, final String 
timeFormat, final String timestampFormat, final ComponentLog logger) throws 
MalformedRecordException {
    +        this.schema = schema;
    +        this.recordName = recordName;
    +        this.attributePrefix = attributePrefix;
    +        this.contentFieldName = contentFieldName;
    +        this.logger = logger;
    +
    +        final DateFormat df = dateFormat == null ? null : 
DataTypeUtils.getDateFormat(dateFormat);
    +        final DateFormat tf = timeFormat == null ? null : 
DataTypeUtils.getDateFormat(timeFormat);
    +        final DateFormat tsf = timestampFormat == null ? null : 
DataTypeUtils.getDateFormat(timestampFormat);
    +
    +        LAZY_DATE_FORMAT = () -> df;
    +        LAZY_TIME_FORMAT = () -> tf;
    +        LAZY_TIMESTAMP_FORMAT = () -> tsf;
    +
    +        try {
    +            final XMLInputFactory xmlInputFactory = 
XMLInputFactory.newInstance();
    +
    +            // Avoid namespace replacements
    +            
xmlInputFactory.setProperty(XMLInputFactory.IS_NAMESPACE_AWARE, false);
    --- End diff --
    
    I think this approach may lead to some odd behaviors if the incoming XML is 
actually namespace aware. For example, if an element looks like:
    ```
    <ns:myElement xmlns:ns="urn:nifi"><child /></ns:myElement>
    ```
    Then the name of the element in the schema would have to be "ns:myElement" 
in order to match. But I think that's not what we want. Instead, in the schema, 
I would want to use the name "myElement".
    
    So I think the approach that I would use here instead would be to set 
IS_NAMESPACE_AWARE to true. Then, when we have a StartElement object, instead 
of calling StartElement.getName().toString() I would call 
StartElement.getName().getLocalPart()
    
    In that case, we would get "myElement" as the name of the outer element and 
"child" as the name of the inner element. I.e., we would basically just ignore 
the namespaces. In either case, it will be very important that we explain 
clearly how this behaves in the documentation.


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