Using the ISODateFormatExt Custom XPath Function
This custom XPath function is built into Presto. To use the function in an XPath expression you must:
1. Declare the Presto custom XPath namespace on <mashup> in your mashup script. For example:
<mashup name="dateExample"
xmlns="http://www.openmashup.org/schemas/v1.0/EMML"
xsi:schemaLocation="http://www.openmashup.org/schemas/v1.0/EMML
../xsd/EMMLPrestoSpec.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:fn="java:com.jackbe.jbp.jems.client.EMMLPrestoFunctions">
...
</mashup>
2. Define the to and from formats for the date or time you need to convert.
For example:
<mashup name="dateExample"
xmlns="http://www.openmashup.org/schemas/v1.0/EMML"
xsi:schemaLocation="http://www.openmashup.org/schemas/v1.0/EMML
../xsd/EMMLPrestoSpec.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:fn="java:com.jackbe.jbp.jems.client.EMMLPrestoFunctions">
<output name="result" type="document"/>
<variable name="fromFormat" type="string" default="dd/MM/yyyy"/>
<variable name="isoFormat" type="string" default="yyyy-MM-DD"/>
...
</mashup>
These formats use patterns to identify the various date or time components. Some of the most common include:
Pattern | Usage |
dd | Day of the month such as 05. |
yyyy | Year. |
MM | Numerical month. |
MMM | Text month |
hh | Hour in a 12-hour format (1-12). |
HH | Hour in a 24-hour format (0-23). |
a | AM/PM for 12-hour time formats. |
mm | Minute |
ss | Second |
S | Millisecond |
The complete list of characters and symbols that are valid in patterns are defined in the java.text.SimpleDateFormat class. For detailed information, see Java API documentation for the JDK version used in your environment.
3. Use the function in an XPath expression. In most cases you would use this function along with an XPath constructor function to obtain a date or time.
For example:
<mashup name="dateExample"
xmlns="http://www.openmashup.org/schemas/v1.0/EMML"
xsi:schemaLocation="http://www.openmashup.org/schemas/v1.0/EMML
../xsd/EMMLPrestoSpec.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:fn="java:com.jackbe.jbp.jems.client.EMMLPrestoFunctions">
<output name="result" type="document"/>
<variable name="fromDate" type="string" default="dd/MM/yyyy"/>
<variable name="isoDate" type="string" default="yyyy-MM-DD"/>
<invoke service="YahooRSSFeed" operation="GET"
outputvariable="$stories"/>
<sort inputvariable="$stories" sortexpr="/rss/channel/item"
sortkeys="xs:date(fn:ISODateFormatExt(pubdate, $fromFormat, $isoFormat))"
outputvariable="result" />
</mashup>
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