Activity - xPathStatement

Activity Type: XML

Description

Run an XPath query on an XMLDB data resource. The query can be run upon an individual XMLDB resource contained within a collection in the XMLDB data resource or over an entire collection of XMLDB resources. Please note that XMLDB resources are XML documents which are stored within XMLDB collections (not to be confused with an XMLDB data resource itself or data service resources).

Example

<xPathStatement name="statement">
  <collection>musicians/folksingers</collection>
  <resourceId>someResource</resourceId>
  <namespace prefix="c">http://folksingers/contact-details</namespace>
  <expression>/c:entry/c:address</expression>
  <resourceSetStream name="statementOutput"/>
</xPathStatement>

Specification

Element xPathStatement:

Attribute name - unique name for the activity within the scope of a request.
Element collection (zero or one) - contains the name of the collection that the query will be performed within.
- Relative to the data resource's base collection.
- For example, if a data resource is configured for the db/littleblackbook collection then the example would perform the query within the db/littleblackbook/musicians/folksingers collection.
- If this element is omitted then the query will be performed on the base collection for the data resource.
Element resourceId (zero or one):
- Contains the name of the XMLDB resource in the selected collection over which the query will be run.
- If omitted then the query will be run over all the XMLDB resources in the selected collection.
Element namespace (0 or more) - a namespace prefix declaration.
- Contains a namespace URL.
- Attribute prefix - a prefix for use in the XPath expression and corresponding to the namespace URI.
Element expression (required) - an XPath expression.
- Contains an XPath query statement.
resourceSetStream (required) - output stream.
- Attribute name - name of the activity's output stream.

Input and Output Types

Output: resourceSetStream — sequence of java.lang.String blocks of XML data. The first block is a resource set header in the following format:
```
<resourceSet>
```
The final block is a resource set footer in the following format:
```
</resourceSet>
```
These header and footer blocks will contain no other data. They are terminated by the '\n' character but contain no other whitespace.
The data blocks between the header and footer blocks contain the XML resources returned by the query. Each block will contain a single resource and each resource will be within a single block. The single root element of each XML block will be called resource. An example of a data block is:
```
<resource>
  <entry id="1">
    <name>Ally Antonioletti</name>
    <address>826 Hume Crescent, Southampton</address>
    <phone>01670061244</phone>
  </entry>
</resource>
```

Data Resource Accessor

This activity requires a data resource accessor that implements the following interface: uk.org.ogsadai.dataresource.XMLDBCollectionProvider

Required Libraries

The use of this activity requires the following jar to be loaded on the server:

xmldb.jar (from eXist build 20051203) — handles access to XML database

XML Schema

OGSA-DAI/schema/ogsadai/xsd/activities/xpath_statement.xsd

Class

uk.org.ogsadai.activity.xmldb.XPathStatementActivity

Client Toolkit Class

uk.org.ogsadai.client.toolkit.activity.xmldb.XPathQuery