Version

    XMLReader

    XMLXPathReader 64x64

    Short Description

    Ports

    Metadata

    XMLReader Attributes

    Details

    Examples

    Best Practices

    Compatibility

    See also

    Short Description

    XMLReader reads data from XML files using DOM technology. It can also read data from compressed files, input port, and dictionary.

    Which XML Component?

    Generally, use XMLExtract. It is fast and has GUI to map elements to records. It is based on SAX.

    XMLReader can use more complex XPath expressions than XMLExtract; for example, it allows you to reference siblings. On the other hand, XMLReader is slower and needs more memory than XMLExtract. XMLReader is based on DOM.

    XMLReader supersedes the original XMLXPathReader. XMLXPathReader can use more complex XPath expressions than XMLExtract. XMLXPathReader uses DOM.
    Component Data source Input ports Output ports Each to all outputs Different to different outputs[1] Transformation Transf. req. Java CTL Auto-propagated metadata

    XMLReader

    XML file

    0-1

    1-n

    ⨯

    ✓

    ⨯

    ⨯

    ⨯

    ⨯

    ⨯
    1

     XMLReader, XMLExtract and XMLXPathReader send data to ports as defined in their Mapping or Mapping URL attribute.

    Ports

    Port type Number Required Description Metadata

    Input

    0

    ⨯

    For port reading. See Reading from Input Port.

    One field (byte, cbyte,string).

    Output

    0 …​ n-1

    ✓

    For correct data records. Connect more than one output ports if your mapping requires that.

    Any

    n

    ⨯

    Error port

    Restricted format. See Metadata.

    Metadata

    Metadata Propagation

    XMLReader does not propagate metadata.

    Metadata Templates

    XMLReader has metadata templates on the error port. There are two templates: XMLReader_TreeReader_ErrPortWithoutFile and XMLReader_TreeReader_ErrPortWithFile.

    Table 42. Error Metadata for XMLReader
    Field number Field name Data type Description

    0

    port

    integer

    The number of the output port where errors occurred.

    1

    recordNumber

    integer

    Record number (per source and port).

    2

    fieldNumber

    integer

    Field number

    3

    fieldName

    string

    Field name

    4

    value

    string

    The value which caused the error.

    5

    message

    string

    Error message

    6

    file

    string

    Source name; This field is optional
    Requirements on Metadata

    Input metadata has one field with datatype byte, cbyte or string.

    The metadata on each of the output ports does not need to be the same. Each of these metadata can use Autofilling Functions.

    If you intend to use the last output port for error logging, metadata must have a fixed format. Field names can be arbitrary, field types must be same as from the template.

    XMLReader Attributes

    Attribute Req Description Possible values

    Basic

    File URL

    yes

    Specifies which data source(s) will be read (XML file, input port, dictionary). See Supported File URL Formats for Readers.

    Charset

    Encoding of records that are read. When reading from files, the charset is detected automatically (unless you specify it yourself).

    Important: if you are reading from a port or dictionary, always set Charset explicitly (otherwise errors will occur). There is no autodetection as in reading from files.

    ISO-8859-1 (default) | <other encodings>

    Data policy

    Determines what should be done when an error occurs. For more information, see Data Policy

    Strict (default) | Controlled | Lenient

    Mapping

    [1]

    The mapping of the input XML structure to output ports. For more information, see Mapping Definition.

    Mapping URL

    [1]

    An external text file containing the mapping definition. For more information, see Mapping Definition.

    Implicit mapping

    If true, map element values to the fields having a same name in record. Example: An element (salary) is automatically mapped onto field of the same name (salary).

    false (default) | true

    Advanced

    XML features

    A sequence of individual true/false expressions related to XML features which should be validated. The expressions are separated from each other by a semicolon. For more information, see XML Features.
    1

     One of these has to be specified. If both are specified, Mapping URL has a higher priority.

    Details

    Mapping Definition

    Context Tag Attributes

    Mapping Tag Attributes

    Input Mapping Attributes

    Reading Multivalue Fields

    Mapping Input Fields

    Records and fields to be send out to the output ports are specified using XML elements and attributes. Each Context element corresponds to one output port attached. Each Mapping element defines a mapping to one field. See the example below.

    Example 25. Mapping in XMLReader
    <Context xpath="/employees/employee" outPort="0">
    <Mapping nodeName="salary" cloverField="basic_salary"/>
    <Mapping xpath="name/firstname" cloverField="firstname"/>
    <Mapping xpath="name/surname" cloverField="surname"/>
    <Context xpath="child" outPort="1" parentKey="empID" generatedKey="parentID"/>
    <Context xpath="benefits" outPort="2" parentKey="empID;jobID" generatedKey="empID;jobID"
            sequenceField="seqKey" sequenceId="Sequence0">
        <Context xpath="financial" outPort="3" parentKey="seqKey" generatedKey="seqKey"/>
    </Context>
    <Context xpath="project" outPort="4" parentKey="empID;jobID" generatedKey="empID;jobID">
        <Context xpath="customer" outPort="5" parentKey="projName;projManager;inProjectID;Start"
                generatedKey="joinedKey"/>
    </Context>
</Context>

    The nested structure of <Context> tags is similar to the nested structure of XML elements in input XML files.

    However, the Mapping attribute does not need to copy whole XML structure, it can start at the specified level inside the whole XML file.

    Defining the Mapping

    • The Mapping definition is specified in the Mapping URL attribute or in the Mapping attribute.

    • Every Mapping definition consists of <Context> tags. Each <Context> tag defines a mapping of particular XML subtree to record being sent to the specified output port.

    • Each <Context> tag can surround a serie of nested <Mapping> tags. These allow to map XML elements or attributes to Clover fields.

    • Each of these <Context> and <Mapping> tags contains some Context Tag Attributes and Mapping Tag Attributes, respectively.

    XMLReader Context Tags and Mapping Tags

    • Empty Context Tag (Without a Child)

      <Context xpath="xpathexpression" />

      See Context Tag Attributes.

    • Non-Empty Context Tag (Parent with a Child)

      <Context xpath="xpathexpression">

      (nested Context and Mapping elements (only children, parents with one or more children, etc.)

      </Context>

      See Context Tag Attributes.

    • Empty Mapping Tag (Renaming Tag)

      • xpath is used:

        <Mapping xpath="xpathexpression" />

      • nodeName is used:

        <Mapping nodeName="elementname" />

      Mapping Tag Attributes

    XMLReader Context Tag Attributes

    xpath

    outPort

    parentKey

    generatedKey

    sequenceId

    sequenceField

    namespacesPath

    • xpath

      Required

      The xpath expression can be any XPath query.

      Example: xpath="/tagA/…​/tagJ"

    • outPort

      Optional

      The number of an output port to which data is sent. If not defined, no data from this level of Mapping is sent out using such level of Mapping.

      Example: outPort="2"

    • parentKey

      Both parentKey and generatedKey must be specified.

      The sequence of metadata fields on the next parent level separated by a semicolon, colon, or pipe. Number and data types of all these fields must be the same in the generatedKey attribute or all values are concatenated to create a unique string value. In such a case, the key has only one field.

      Example: parentKey="first_name;last_name"

      Equal values of these attributes assure that such records can be joined in the future.

    • generatedKey

      Both parentKey and generatedKey must be specified.

      The sequence of metadata fields on the specified level separated by a semicolon, colon, or pipe. Number and data types of all these fields must be the same in the parentKey attribute or all values are concatenated to create a unique string value. In such a case, the key has only one field.

      Example: generatedKey="f_name;l_name"

      Equal values of these attributes assure that such records can be joined in the future.

    • sequenceId

      When a pair of parentKey and generatedKey does not insure a unique identification of records, a sequence can be defined and used.

      Id of the sequence.

      Example: sequenceId="Sequence0"

    • sequenceField

      When a pair of parentKey and generatedKey does not insure a unique identification of records, a sequence can be defined and used.

      A metadata field on the specified level in which the sequence values are written. Can serve as parentKey for the next nested level.

      Example: sequenceField="sequenceKey"

    • namespacePaths

      Optional

      Default namespaces that should be used for the xpath attribute specified in the <Context> tag.

      Pattern: namespacePaths='prefix1="URI1";…​;prefixN="URIN"'

      Example: namespacePaths='n1="http://www.w3.org/TR/html4/";n2="http://ops.com/"'.

      Remember that if the input XML file contains a default namespace, this namespacePaths must be specified in the corresponding place of the Mapping attribute. In addition, namespacePaths is inherited from the <Context> element and used by the <Mapping> elements.
    XMLReader Mapping Tag Attributes

    xpath

    nodeName

    cloverField

    trim

    namespacePaths

    • xpath

      Either xpath or nodeName must be specified in the <Mapping> tag.

      XPath query.

      Example: xpath="tagA/…​/salary"

    • nodeName

      Either xpath or nodeName must be specified in the <Mapping> tag. Using nodeName is faster than using xpath.

      XML node that should be mapped to Clover field.

      Example: nodeName="salary"

    • cloverField

      Required

      A Clover field to which XML node should be mapped.

      The name of the field in the corresponding level.

      Example: cloverField="SALARY"

    • trim

      Optional

      Specifies whether leading and trailing white spaces should be removed. By default, it removes both leading and trailing white spaces.

      Example: trim="false" (white spaces will not be removed)

    • namespacePaths.

      Optional

      Default namespaces that should be used for the xpath attribute specified in the <Mapping> tag.

      Pattern:¨namespacePaths='prefix1="URI1";…​;prefixN="URIN"'

      Example: namespacePaths='n1="http://www.w3.org/TR/html4/";n2="http://ops.com/"'

      Remember that if the input XML file contains a default namespace, this namespacePaths must be specified in the corresponding place of the Mapping attribute. In addition, namespacePaths is inherited from the <Context> element and used by the <Mapping> elements.
    XMLReader Input Mapping Attributes

    • cloverField

      Required

      Output Clover field to input should be mapped.

      Example: cloverField="SALARY"

    • inputField

      Required

      Input field to be used.

      Example: inputField="SALARY"

    Reading Multivalue Fields

    You can read only lists, however (see Multivalue Fields).

    Reading maps is handled as reading pure string (for all data types as map’s values).
    Example 26. Reading lists with XMLReader

    An example input file containing these elements (just a code snippet):

    ...
<attendees>John</attendees>
<attendees>Vicky</attendees>
<attendees>Brian</attendees>
...

    can be read back by the component with this mapping:

    <Mapping xpath="attendees" cloverField="attendanceList"/>

    where attendanceList is a field of your metadata. The metadata has to be assigned to the component’s output edge. After you run the graph, the field gets populated by XML data like this (this will be seen in View data):

    [John,Vicky,Brian]

    Mapping Input Fields

    If you use input port reading in discrete or source mode, you can map particular input fields to output fields using the inputField attribute.

    <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Context xpath="/rootPath" outPort="0">
 	<Mapping cloverField="field2" inputField="field2"/>
</Context>

    Examples

    Reading an XML File

    Mapping Input Fields to Output

    Sending Nested Elements to Different Output Ports

    Reading XML with Namespace
    Reading an XML File

    This example shows the basic usage of XMLReader.

    You have a retail.xml file with data about your retail sale.

    <?xml version="1.0" ?>
<orders>
    <order id="1">
        <firstname>John</firstname>
        <surname>Smith</surname>
        <emails>
            <email>john.black@example.com</email>
            <email>jblack@example.info</email>
        </emails>
        <item>
            <goodName>table</goodName>
            <items>1</items>
        </item>
    </order>
    <order id="2">
        <firstname>Ellen</firstname>
        <surname>Smith</surname>
        <emails>
            <email>e-tailor@example.net</email>
        </emails>
        <item>
            <goodName>chair</goodName>
            <items>3</items>
        </item>
        <item>
            <goodName>tablecloth</goodName>
            <item>2</item>
        </item>
    </order>
</orders>

    Create a list containing order_id, customer first name, surname and email(s).

    Solution

    Create a metadata having 4 fields: order_id (integer), name (string), surname (string), email (string[]).

    Set up the attributes File URL, Implicit mapping and Mapping.

    Attribute Value

    File URL

    ${DATAIN_DIR}/retail.xml

    Mapping

    See the xml below.

    Implicit mapping

    true

    If you set Implicit mapping to true, fields name and surname are populated by values of corresponding elements.

    Content of the Mapping attribute:

    <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Context xpath="/orders/order" outPort="0">
    <Mapping cloverField="order_id" xpath="@id"/>
    <Mapping cloverField="email" xpath="./emails/email"/>
</Context>

    The XMLReader will send following 2 records to its first output port.

    1  John   Smith  [john.black@example.com, jblack@example.info]
2  Ellen  Smith  [e-tailor@example.net]
    Mapping Input Fields to Output

    This example shows reading an input file while some input fields are mapped to an output.

    Given a list of customers and paths to the files with orders.

    C001|./file001.xml
C002|./file002.xml

    Each file can contain one or more products:

    <?xml version="1.0" ?>
<products>
    <product>A</product>
    <product>B</product>
</products>

    Create a list with customers and products:

    C001|A
C001|B
C002|E
    Solution

    Use the File URL, Charset and Mapping attributes.

    Attribute Value

    File URL

    port:$0.filename:source

    Charset

    UTF-8

    Mapping

    See the code below

    		 
    <?xml version="1.0" encoding="UTF-8" standalone="no"?>

<Context xpath="/products/product" outPort="0">
    <Mapping cloverField="productID" xpath="."/>
    <Mapping cloverField="customerID" inputField="ID"/>
</Context>
    Sending Nested Elements to Different Output Ports

    This example shows reading of an input file with nested elements. The nested elements on different levels are sent out to the different output ports.

    The input file countries-and-counties.xml contains a list of countries. Each country has a name and contains several counties. Each county has a name.

    <?xml version="1.0"?>
<countries>
    <country>
        <name>England</name>
        <county>
            <name>Bristol</name>
        </county>
        <county>
            <name>Cumbria</name>
        </county>
        <county>
            <name>Devon</name>
        </county>
    </country>
    <country>
        <name>Scotland</name>
        <county>
            <name>Edinburgh</name>
        </county>
        <county>
            <name>Fife</name>
        </county>
    </country>
</countries>

    Make a list of countries, and a list of counties with corresponding countries.

    Solution

    Assign metadata country with the field countryName to the edge on the first output port.

    Assign metadata county with the fields countryName and countyName to the edge on the second output port.

    Use the File URL, Charset and Mapping attributes.

    Attribute Value

    File URL

    ${DATAIN_DIR}/countries-and-counties.xml

    Charset

    UTF-8

    Mapping

    See the code below

    		 
    <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Context xpath="/countries/country" outPort="0">
    <Mapping cloverField="countryName" xpath="name"/>
    <Context xpath="./county" outPort="1">
        <Mapping cloverField="countryName" xpath="../name" />
        <Mapping cloverField="countyName" xpath="name"/>
    </Context>
</Context>

    The records sent to the first output port are:

    England
Scotland

    The records sent to the second output port are:

    England	 | Bristol
England  | Cumbria
England  | Devon
Scotland | Edinburgh
Scotland | Fife
    Reading XML with Namespace

    This example shows you how to read XML that contains different namespaces.

    A web page contains SVG graphics and links to other web pages. The links (<a>) are of two namespaces: xhtml and svg. Get URLs of the links from SVG image.

    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    </head>
    <body>
        <svg width="1024" height="768"
            xmlns="http://www.w3.org/2000/svg" version="1.1">
            <a href="http://www.cloverdx.com">
                <circle cx="512" cy="384" r="80"/>
            </a>
        </svg>
        <p>
            <a href="http://www.example.com">www.example.com</a>
        </p>
    </body>
</html>
    Solution

    Use the File URL, Charset and Mapping attributes.

    Attribute Value

    File URL

    ${DATAIN_DIR}/page.xhtml

    Charset

    UTF-8

    Mapping

    See the code below

    		 
    <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Context xpath="/xhtml:html//svg:a"
         namespacePaths='xhtml="http://www.w3.org/1999/xhtml";svg="http://www.w3.org/2000/svg"'
         outPort="0">
    <Mapping cloverField="field1" xpath="@href"/>
</Context>

    The output contains URL:

    http://www.cloverdx.com

    Best Practices

    Implicit Mapping

    To avoid typing lines like:

    <Mapping xpath="salary" cloverField="salary"/>

    Switch on the implicit mapping and use explicit mapping only to populate fields with data from distinct elements.

    Avoid Unnecessary Context Elements

    The <Context> element should be used only if you intend to send record corresponding to subtree to the output.

    Use

    <Context xpath="/elem1/elem11" outPort="0">
    <Mapping cloverField="field1" xpath="elem111"/>
</Context>

    instead of

    <Context xpath="/elem1">
    <Context xpath="elem11" outPort="0">
        <Mapping cloverField="field1" xpath="elem111"/>
    </Context>
</Context>
    Specify Charset

    We recommend users to explicitly specify Charset.

    Compatibility

    Version Compatibility Notice

    3.3

    XMLReader is available since 3.3.x.

    Reading multivalue fields is now supported; however, you can read only lists (see Multivalue Fields).

    4.1.0-M1

    You can now assign values of fields from an input port to fields on an output port.

    See also

    JSONReader

    XMLExtract

    XMLXPathReader

    XMLWriter

    Common Properties of Components

    Specific Attribute Types

    Common Properties of Readers

    Readers Comparison