Validation - SwitchYard 0.7

Validation feature provides a functionality for message content validation.

Take the following message content:

<MyBook xmlns="example">
  <Chapter1/>
  <Chapter2/>
</MyBook>

And follwing XML Schema definition:

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
        targetNamespace="example"
        xmlns:orders="example">
        <element name="MyBook" type="example:MyBook"/>
        <complexType name="MyBook">
            <sequence>
                <element name="Chapter1" type="string"/>
            </sequence>
        </complexType>
</schema>

The XML content is still Well-Formed, but it has a Chapter2 element that is not declared as the child of MyBook element in the XML Schema, So the content is not Valid against this XML Schema. We often need to perform this kind of validation before processing its data in service logic, but implementing the validation logic directly in the consumer or provider pollutes the service logic and can lead to tight coupling. SwitchYard allows for the validation logic to declared outside the service logic and injected into the mediation layer at runtime.

Adding Validation to Your Application

Validation of message content is specified in the descriptor of your SwitchYard application (switchyard.xml). The qualified name of the type being validated name is defined along with the validator implementation. This allows validation to be a declarative aspect of a SwitchYard application, as the runtime will automatically register and execute validators in the course of a message exchange.

<validates>
   <validate.xml schemaType="XML_SCHEMA"
                   name="{urn:example}MyBook
                   schemaFile="/xsd/orders.xsd"/>
</validates>

Content Type Names

Since validations occur with named type (i.e. type A) as well as transformations, it's important to understand how the type names are derived. Please refer to the Content Type Names section in the Transformation chapter if you have not ever seen it.

Java Validator

There are two methods available for creating a Java-based validator in SwitchYard:

Implement the org.switchyard.validate.Validator interface and add a <validate.java> definition to your switchyard.xml.
Annotate one or more methods on your Java class with @Validator.

When using the @Validator annotation, the SwitchYard maven plugin will automatically generate the <validate.java> definition(s) for you and add them to the switchyard.xml packaged in your application.

public class MyValidator {
    @Validator(name = "{urn:switchyard-quickstart-demo:orders:1.0}submitOrder")
    public boolean validate(Element from) {
       // handle validation here
    }
}

The above Java class would produce the <validate.java> definition as following:

<validate.java class="org.switchyard.quickstarts.demos.orders.MyValidator"
               name="{urn:switchyard-quickstart-demo:orders:1.0}submitOrder"/>

The optional name element of the @Validator annotation can be used to specify the qualified type name used during validator registration. If not supplied, the full class name of the method parameter will be used as the type.

XML Validator

The XML validator allows you to perform a validation against its schema definition. Supported schema types are DTD, XML_SCHEMA, and RELAX_NG. It is configured simply by specifying the schema Type, the name QName, and the path to the schema file.

<validate.xml schemaType="XML_SCHEMA" name="{http://acme/}A" schemaFile="com/acme/xsd/A.xsd"/>