XmlSink (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Cloud Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. See Migrating from Cloud Dataflow SDK 1.x for Java for migration guidance.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

com.google.cloud.dataflow.sdk.io

Class XmlSink

• java.lang.Object
• • com.google.cloud.dataflow.sdk.io.XmlSink

• ---

  
  

  public class XmlSink
  extends Object

  A Sink that outputs records as XML-formatted elements. Writes a PCollection of records from JAXB-annotated classes to a single file location.

  Given a PCollection containing records of type T that can be marshalled to XML elements, this Sink will produce a single file consisting of a single root element that contains all of the elements in the PCollection.

  XML Sinks are created with a base filename to write to, a root element name that will be used for the root element of the output files, and a class to bind to an XML element. This class will be used in the marshalling of records in an input PCollection to their XML representation and must be able to be bound using JAXB annotations (checked at pipeline construction time).

  XML Sinks can be written to using the Write transform:

   p.apply(Write.to(
        XmlSink.ofRecordClass(Type.class)
            .withRootElementName(root_element)
            .toFilenamePrefix(output_filename)));
   

  For example, consider the following class with JAXB annotations:

     @XmlRootElement(name = "word_count_result")
     @XmlType(propOrder = {"word", "frequency"})
    public class WordFrequency {
      private String word;
      private long frequency;
  
      public WordFrequency() { }
  
      public WordFrequency(String word, long frequency) {
        this.word = word;
        this.frequency = frequency;
      }
  
      public void setWord(String word) {
        this.word = word;
      }
  
      public void setFrequency(long frequency) {
        this.frequency = frequency;
      }
  
      public long getFrequency() {
        return frequency;
      }
  
      public String getWord() {
        return word;
      }
    }
   

  The following will produce XML output with a root element named "words" from a PCollection of WordFrequency objects:

   p.apply(Write.to(
    XmlSink.ofRecordClass(WordFrequency.class)
        .withRootElement("words")
        .toFilenamePrefix(output_file)));
   

  The output of which will look like:

   
   <words>
  
    <word_count_result>
      <word>decreased</word>
      <frequency>1</frequency>
    </word_count_result>
  
    <word_count_result>
      <word>War</word>
      <frequency>4</frequency>
    </word_count_result>
  
    <word_count_result>
      <word>empress'</word>
      <frequency>14</frequency>
    </word_count_result>
  
    <word_count_result>
      <word>stoops</word>
      <frequency>6</frequency>
    </word_count_result>
  
    ...
   </words>
   

• • Nested Class Summary

    Nested Classes 

    Modifier and Type	Class and Description
    static class	XmlSink.Bound<T> A FileBasedSink that writes objects as XML elements.
    protected static class	XmlSink.XmlWriteOperation<T> Sink.WriteOperation for XML Sinks.
    protected static class	XmlSink.XmlWriter<T> A Sink.Writer that can write objects as XML elements.

  • Field Summary

    Fields 

    Modifier and Type	Field and Description
    protected static String	XML_EXTENSION

  • Constructor Summary

    Constructors 

    Constructor and Description
    XmlSink()

  • Method Summary

    All Methods Static Methods Concrete Methods 

    Modifier and Type	Method and Description
    static XmlSink.Bound<?>	write() Returns a builder for an XmlSink.
    static <T> XmlSink.Bound<T>	writeOf(Class<T> klass, String rootElementName, String baseOutputFilename) Returns an XmlSink that writes objects as XML entities.

    • Methods inherited from class java.lang.Object

      clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

• • Field Detail

    • XML_EXTENSION

      protected static final String XML_EXTENSION

      See Also:

      Constant Field Values

  • Constructor Detail

    • XmlSink

      public XmlSink()

  • Method Detail

    • write

      public static XmlSink.Bound<?> write()

      Returns a builder for an XmlSink. You'll need to configure the class to bind, the root element name, and the output file prefix with XmlSink.Bound.ofRecordClass(java.lang.Class<T>), XmlSink.Bound.withRootElement(java.lang.String), and XmlSink.Bound.toFilenamePrefix(java.lang.String), respectively.

    • writeOf

      public static <T> XmlSink.Bound<T> writeOf(Class<T> klass,
                                                 String rootElementName,
                                                 String baseOutputFilename)

      Returns an XmlSink that writes objects as XML entities.

      Output files will have the name {baseOutputFilename}-0000i-of-0000n.xml where n is the number of output bundles that the Dataflow service divides the output into.

      Parameters:

      klass - the class of the elements to write.

      rootElementName - the enclosing root element.

      baseOutputFilename - the output filename prefix.