XPATH in IIB

In this post, I will provide some example of xpath expression allowing to perform complex transformation within a GDM (Graphical Data Mapper).

I will append this post with new example that I would found that could be of any usage.

For this first post, I will use a sample message having the following structure

<?xml version="1.0" encoding="UTF-8"?>
<Q1:INVOICE xmlns:Q1="http://www.acme.be/acme"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.acme.be/acmeInvoice.xsd ">
<CUSTOMERID>ID001</CUSTOMERID>
<NAME>X</NAME>
<INVOICE_ITEM>
<STOCK>OUT</STOCK>
<EXI>IMPORT</EXI>
<CONTAINER>abc</CONTAINER>
<ISOCODE>2210</ISOCODE>
<QUANTITY>1</QUANTITY>
</INVOICE_ITEM>
<INVOICE_ITEM>
<STOCK>OUT</STOCK>
<EXI>EMPTY</EXI>
<CONTAINER>abcd</CONTAINER>
<ISOCODE>2210</ISOCODE>
<QUANTITY>2</QUANTITY>
</INVOICE_ITEM>
<INVOICE_ITEM>
<STOCK>OUT</STOCK>
<EXI>EMPTY</EXI>
<CONTAINER>abcde</CONTAINER>
<ISOCODE>4532</ISOCODE>
<QUANTITY>4</QUANTITY>
</INVOICE_ITEM>
<INVOICE_ITEM>
<STOCK>OUT</STOCK>
<EXI>EMPTY</EXI>
<CONTAINER>abcdef</CONTAINER>
<ISOCODE>4532</ISOCODE>
<QUANTITY>2</QUANTITY>
</INVOICE_ITEM>
<INVOICE_ITEM>
<STOCK>IN</STOCK>
<EXI>IMPORT</EXI>
<CONTAINER>CONTAINER</CONTAINER>
<ISOCODE>ISOCODE</ISOCODE>
<QUANTITY>2</QUANTITY>
</INVOICE_ITEM>
</Q1:INVOICE>

Sum, Count

It is possible to compute the sum of elements under a repeating node in one expression.
For example if you would like to make the sum of the "Quantity" field of all the INVOICE_ITEM nodes, you could do this by performing the following map:

XPath expression is "fn:sum($INVOICE_ITEM/QUANTITY)"

Count can be used in the same way. Count will provide the number of elements.

Predicates

Predicates allows to select only a subset of nodes based on a criteria.
In the above example, it may be possible to compute the sum of QUANTITY for INVOICE_ITEM having its STOCK child element equal to "OUT".
This could be done by using predicates.
The above xpath expression would be changed with:

fn:sum($INVOICE_ITEM[STOCK='OUT']/QUANTITY)

The predicates here is "[STOCK='OUT']".

It is possible to use an input element within the predicates. For example, imagine that you have a list of Stock. And you would like to make the quantity sum only for the STOCK that are in the list.
This could be achieved by providing as input the stocklist to the xpath transform:

With the XPath expression

fn:sum($INVOICE_ITEM[STOCK=$STOCK1]/QUANTITY)

It is possible to have more than one "where" clause. For example is we would like the sum of  Quantity for STOCK='OUT' and EXI='IMPORT' then the following Xpath could be used:

fn:sum($INVOICE_ITEM[STOCK='OUT' and EXI='IMPORT']/QUANTITY)

be careful that the "and" is case sensitive.

Distinct Values

Last useful xpath expression for this post. Distinct values.
Distinct values could be used to retrieve only elements having distinct values.
For example let's say that the input message where STOCK can have the value "IN', "OUT'.
In the example above there are 4 Invoice Item with Stock equals to "OUT" and only 1 with "IN".

The XPATH expression used here is "fn:distinct-values($INVOICE_ITEM/STOCK)"

The input is the INVOICE_ITEM repeating node and the output is a repeating element STOCK under STOCKLIST.

The Stocklist will be populated by STOCK element having the value "IN" and "OUT":

<STOCKLIST>

        <STOCK>IN</STOCK>

        <STOCK>OUT</STOCK>

</STOCKLIST>

If you need to sort on multiple elements then the option that you may have is first create a concatenation of these fields in a previous map and then use the distinct values xpath expression.

So for example if you need to have the list of invoice items having distinct values for STOCK and EXI, then you may create a first map that concatenates STOCK and EXI using the xpath expression "fn:concat" and place this list in the localenvironment and then in the next map use the disctinct values xpath expression

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