Thursday, January 2, 2020

12c SOA - Oracle Mediator part8 - Schematron or Payload validation

Schematron Basics:
  • Schematron is an XML schema language, and it can be used to validate XML contents in an XML payload. Schematron defines a set of rules and checks that are applied to an XML instance. 
  • Schematron relies almost entirely on XPath query patterns for defining these rules and checks. 
  • The schematron validation allows loose coupling of Semantic validation of the incoming/outgoing mediator payload.This is accommodated while defining the routing rule for mediator payloads.
  • The Schematron file is created with a file type having an .sch extension.
Schematron Structure:
  • A Schematron XML document consist of a schema element in the Schematron namespace:
  • The schema element contains one or more pattern elements. Pattern elements allow the user to group schema constraints logically. Some examples of logical groupings are: Text Only Elements, Valid Root Element, Check for ID Attribute. Pattern elements have a name attribute. 
  • Rule elements define a collection of constraints on a particular context in a document instance (for example, on an element or collection of elements). This is very similar to XSLT templates, which are fired with respect to a node or group of nodes returned by an XPath expression.
  • The Schematron standard defines two types of rules: assert and report. The assert rule returns your error message when the test condition fails (returns false), whereas the report rule returns your error message when the test conditions succeeds (returns true). The Schematron implementation in the SOA Suite only supports the assert rule, so you have to rewrite your report rules. This is not much of a problem, because the assert rule is just the logical complement (inversion) of the report rule, so the logical “not” function solves this issue. In case of just a logical comparison in the test condition, you also can invert it by replacing a = operator, etc.
The namespaces of our input payload (“”) have to be declared. The solution is to use the “ns” element with attributes “uri” and “prefix”:
<ns uri="" prefix="emp" />

XSD used:
<?xml version="1.0" encoding="windows-1252" ?>
<xsd:schema xmlns:xsd="" xmlns="" targetNamespace=""
  <xsd:element name="Employees">
        <xsd:element name="Employee" maxOccurs="unbounded">
              <xsd:element name="Name" type="xsd:string"/>
              <xsd:element name="Id" type="xsd:integer"/>
              <xsd:element name="Salary" type="xsd:integer"/>
              <xsd:element name="Type" type="xsd:string"/>
              <xsd:element name="ManagerName" type="xsd:string"/>
              <xsd:element name="ManagerId" type="xsd:integer"/>

 Schematron created:
<?xml version="1.0" encoding="UTF-8" ?>
<schema xmlns="">
    <ns uri="" prefix="emp" />
    <pattern name="Employee may not be the manager of himself">
        <rule context="/emp:Employees/emp:Employee">
            <assert test="emp:Id != emp:ManagerId">Employee may not be the manager of himself</assert>
    <pattern name="Validate Employee Type">
        <rule context="/emp:Employees/emp:Employee">
            <assert test="emp:Type = 'PERM'">Not a permanent employee</assert>
Rule1: if Emp id != manager id condition fails then it throws the error "Employee may not be the manager of himself"
Rule2: if EMp type = 'PERM' fails then it throws the error "Not a permanent employee".

Double Click on the Mediator component. Check the ‘Validate Syntax (XSD)’ option. Click on the image icon at ‘Validate Semantic’ and use the schematron.sch file for Schematron validation.

Deploy and test.
Tested with keeping the following:
-Employee1 is TMP type
-EMployee2 is sharing same id with manager.

Error details:
The selected operation execute could not be invoked.
A fault occurred while invoking the webservice operation. The fault is : <env:Fault xmlns:env="">
<faultstring>oracle.tip.mediator.infra.exception.MediatorException: ORAMED-01301:[Payload custom validation]Schematron validation fails with error "<ns1:ValidationErrors xmlns:emp="" xmlns:ns1="">
<error>Employee may not be the manager of himself</error>
<error>Not a permanent employee</error>

".Possible Fix:Fix the payload.</faultstring>

oracle.sysman.emInternalSDK.webservices.util.SoapTestException: Client received SOAP Fault from server : oracle.tip.mediator.infra.exception.MediatorException: ORAMED-01301:[Payload custom validation]Schematron validation fails with error "
Employee may not be the manager of himself
Not a permanent employee

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