Removing a node from node-list

With the bpelx: extensions in BPEL you are able to insert and update nodes in a node list. A node-list is an XML message that contains a set of records. In this article I use the following example:

<BookList xmlns="http://message.vijfhuizen.com">
<Book>
  <title>The Lord Of The Rings</title>
  <author>J.R.R. Tolkien</author>
</Book>
<Book>
  <title>Harry Potter</title>
  <author>J.R.R. Tolkien</author>
</Book>
<Book>
  <title>The Hobbit</title>
  <author>J.R.R. Tolkien</author>
</Book>
<Book>
  <title>Storm; Chronicals of Pandarve</title>
  <author>Don Lawrence</author>
</Book>
</BookList>

For creating and updating node lists the bpelx: functions are enough to handle this. But when you want to remove a particular node, you can use the bpelx:remove function. But this function can only remove a node from a particular position. For example removing the second node you code:

<bpel:assign>
  <bpelx:remove>
     <bpelx:target variable="VarBookList" query="/Booklist/Book[2]" />
  </bpelx:append>
</bpel:assign>

It is hard to code the bpelx:remove to create a xpath to dynamicly remove node. You would like to remove the second node based on the xpath:

/Booklist/Book[title="Harry Potter" and author="J.R.R. Tolkien"]

You can add the above xpath in the bpelx:remove, but you are not able to make this dynamically.

There is a solution. The trick is to create a stylesheet that copies the data into a new message, but removing that particular records. Create a stylesheet that does the normal copy of the XML message. Then add a <choose> element in the stylsheet to filter that particular record.

  <xsl:template match="/">
<BookList>
  <xsl:for-each select="/BookList/Book">
    <xsl:choose>
      <xsl:when test="title='Harry Potter' and author='J.R.R. Tolkien'"/>
      <xsl:otherwise>
        <Book>
          <title>
           <xsl:value-of select="title"/>
          </title>
          <author>
            <xsl:value-of select="author"/>
          </author>
        </Book>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:for-each>
</BookList>

Now we have a XSL stylesheet that removes a particular record, but this is not variable. This can be done via XSLT parameters.

  <xsl:param name="pTitle"/>
<xsl:param name="pAuthor"/>
<xsl:template match="/">
<BookList>
  <xsl:for-each select="/BookList/Book">
    <xsl:choose>
      <xsl:when test="title=$pTitle and author=$pAuthor"/>
      <xsl:otherwise>
        <Book>
          <title>
           <xsl:value-of select="title"/>
          </title>
          <author>
            <xsl:value-of select="author"/>
          </author>
        </Book>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:for-each>
</BookList>
</xsl:template>

Now we are able to use this stylesheet in BPEL. In general BPEL create the following code:

  <assign name="Transform">
  <bpelx:annotation>
    <bpelx:pattern>transformation</bpelx:pattern>
  </bpelx:annotation>
  <copy>
    <from expression="ora:processXSLT('RemoveNode.xsl'
                     , bpws:getVariableData('Variable_BookList','payload')" />
    <to variable="Variable_BookListTemp" part="payload"/>
  </copy>
</assign>

But this code does not pass parameters to the stylesheet. The ora:processXSLT() can do this it has an additional parameter in this function:

  <assign name="Transform">
  <bpelx:annotation>
    <bpelx:pattern>transformation</bpelx:pattern>
  </bpelx:annotation>
  <copy>
    <from expression="ora:processXSLT('RemoveNode.xsl'
                     , bpws:getVariableData('Variable_BookList','payload')" />
                     , bpws:getVariableData('BPELxslparameters'))"/>
    <to variable="Variable_BookListTemp" part="payload"/>
  </copy>
</assign>

Now only you have to create the BPELxslparameters variable and assign it with the correct name/value pairs. The structure of the this variable is as follows:

  <?xml version="1.0" encoding="windows-1252" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns="http://schemas.oracle.com/service/bpel/common"
            targetNamespace="http://schemas.oracle.com/service/bpel/common"
            elementFormDefault="qualified">
  <xsd:element name="parameters">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:element name="item" minOccurs="1" maxOccurs="unbounded">
          <xsd:complexType>
            <xsd:sequence>
              <xsd:element name="name" type="xsd:string"/>
              <xsd:element name="value" type="xsd:string"/>
            </xsd:sequence>
          </xsd:complexType>
        </xsd:element>
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>
</xsd:schema>

Create in BPEL the variable BPELxslparameters and let it point to this strucure:

    <process ....
  xmlns:common="http://schemas.oracle.com/service/bpel/common"
  .../>
  <variable name="BPELparameters" element="common:parameters"/>

Now we can in BPEL create an empty XML message, based on this strcuture and assign the values to these parameters and then call the processXSLT function.

  <bpelx:assign name="Assign_GenerateEmptyParameterSet">
  <copy>
    <from>
      <parameters xmlns="http://schemas.oracle.com/service/bpel/common">
        <item>
          <name>pTitle</name>
          <value/>
        </item>
        <item>
          <name>pAutor</name>
          <value/>
        </item>
      </parameters>
    </from>
    <to variable="BPELparameters" query="/common:parameters"/>
  </copy>
</bpelx:assign>
<assign name="Assign_setXSLTParameters">
  <copy>
    <from expression="'Harry Potter'"/>
    <to variable="BPELparameters" query="/common:parameters/common:item[1]/common:value"/>
  </copy>
  <copy>
    <from expression="'J.R.R. Tolkien'"/>
    <to variable="BPELparameters" query="/common:parameters/common:item[1]/common:value"/>
  </copy>
 </assign>