Configuring Data Services

Requires Platform 4.5+

Configuring Data Services

Configure data services primarily in the nexaweb-data.xml file.

You also configure the sql data service by defining statementHandlerDefinitions in the nexaweb-sql.xml file

Configuring the nexaweb-data.xml File

The nexaweb-data.xml file contains the following sections:

requestProcessorDefinitions

Processors format data requests or results into the appropriate structures.

In the requestProcessorDefinitions section, you define the pre- and post-processors that you can assign as global processors, data service type processors, or in dataRequestDefinitions.

The requestProcessorDefinitions section includes the following elements:

Use the processorDefinition tag to define a processor in either the preProcessorDefinition or postProcessorDefinition elements.

The following table describes the processorDefinition tag attributes:

Processors use the following implementing classes:

For example:

<requestProcessorDefinitions>
  <preProcessorDefinitions>
    <processorDefinition id="a" class="DataRequestPreProcessor"/> 
    <processorDefinition id="b" class="DataRequestPreProcessor"/> 
  </preProcessorDefinitions>
  <postProcessorDefinitions>
    <processorDefinition id="1" class="DataRequestPostProcessor"/> 
    <processorDefinition id="2" class="DataRequestPostProcessor"/> 
  </postProcessorDefinitions>
</requestProcessorDefinitions>

In addition, you can specify statementHandlerDefinitions in the nexaweb-sql.xml and nexaweb-webservices.xml files to format data for SQL statements or REST or SOAP requests defined in those files.

globalProcessors

This section lists the pre- and post-processors required to format all data accessed through all data service types into the appropriate structures.

The globalProcessors section includes the following elements:

Use the processor tag to specify the ID of a processor defined in the requestProcessorDefinitions element as a pre- or post-processor to use globally.

For example:

<globalProcessors>
  <preProcessors>
    <processor="a"> </processor>
  </preProcessor>
  <postProcessors>
    <processor="1"> </processors>
  </postProcessors>
</globalProcessors>

dataServiceDefinitions

The dataServiceDefinitions section of the nexaweb-data.xml file contains an entry for each type of data service available for accessing external data sources.

Currently, Nexaweb supports the following data service types:

In addition, you can specify pre- and post-processors per data service type to format data for all serviceRequests using that data service type.

The dataServiceDefinitions section includes the following elements:

Use the processor tag to specify the ID of a processor defined in the requestProcessorDefinitions section as a pre- or post-processor for all serviceRequests using the SQL or web services type data service.

For example:

<dataServiceDefinitions>
  <dataService id="sql" 
    class="com.nexaweb.server.data.services.sqlDataService">
    <processors>
      <preProcessors>
        <processor="b"> </processor>
      </preProcessor>
      <postProcessors>
        <processor="2"> </processors>
      </postProcessors>
    </processors>
 </dataService>
</dataServiceDefinitions>

dataRequestDefinitions

In this section you define any dataRequestDefinitions to use to access data sources from the server.

A dataRequestDefintion defines on the server the primary components of a serviceRequest, the information required to access external data, so that you do not need to specify all of this information in the client UI file. In addition, use a dataRequestDefinition to define the primary components of a serviceRequest in order to create a serviceRequest that uses arguments.

The following table describes the elements of a dataRequestDefinition:

The dataRequestDefinitions section includes the following elements:

Use the processor tag to specify the ID of a processor defined in the requestProcessorDefinitions section as a pre- or post-processor for this dataRequestDefinition.

serviceResourceReference Example

Specify a dataRequestDefinition using a serviceResourceDefinition similar to the following: 

<dataRequestDefinition id="FlickrSearchRest">
<serviceResourceReference dataServiceId="WebService" serviceResourceId="searchFlickrParam" />

The nexaweb-data.xml file defines the dataRequestDefinition, FlickrSearchRest, that references a WebService type data service request, searchFlickrParam, defined in the nexweb-webservice.xml file.

serviceResourceDefinition Example

Specify a dataRequestDefinition using a serviceResourceDefinition similar to the following: 

<dataRequestDefinition id=”getDepartments”> 
   <serviceResourceDefinition>
    <sqlStatement connectionId="engineering" 
      xmlns=”http://nexaweb.com/service/data/sql”>
     <statement>
       SELECT * FROM department where dept=’’{0}’’
     </statement> 
    </sqlStatement> 
   </serviceResourceDefinition>

  <parameterMap>
   <parameterMapping name=”deptId”>
    <default>engineering</default>
   </parameterMapping>
  </parameterMap>
</dataRequestDefinition> 

In this example, the dataRequestDefinition, getDepartments, inlcudes a serviceResourceDefinition that accesses an external data source though an SQL statement. The SQL statement selects from deptartment where dept is a variable. The parameterMap provides a means to pass a user-specified value for the dept variable, deptID, or thedefault value of engineering, if a user does not supply a value.

You use a dataRequestDefinition, defined on the server in the nexaweb-data.xml file, in a serviceRequest defined in the client UI file.  You can create a serviceRequest in the client UI file to use this dataRequestDefinition similar to the following:

<serviceRequest id=” getDepartmentRequest” dataRequestId=” 
   getDepartments” xmlns=”http://nexaweb.com/service/data”>
<parameters>
<parameter name=”deptId”>{0}</parameter>
</parameters>
</serviceRequest>

The serviceRequest, getDepartmentRequest, references as the dataRequestID, the dataRequestDefinition, getDepartments. It specifies the parameter, deptId, which accepts user-specified values to pass to the deptID parameter mapping defined in the getDepartments dataRequestDefinition.