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Chapter 12. Validators
12.1. What is a Validator
A Validator provides message content checking functionality. SwitchYard allows you to declare the validation logic outside the service logic and inject it into the mediation layer at runtime.
12.2. Message Validation
Here is a sample that depicts message validation.
Message Content:
<MyBook xmlns="example"> <Chapter1/> <Chapter2/> </MyBook>
This is the associated 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. Hence the content cannot be validated against the schema.
12.3. Add Validation to Your Application
Procedure 12.1. Add Validation to Your Application
- Specify message validation in the descriptor of your SwitchYard application by editing the
switchyard.xml
file using the JBoss Developer Studio SwitchYard Editor.The qualified name of the type being validated 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"> <schemaFiles><entry file="/xsd/orders.xsd"/></schemaFiles> </validate.xml> </validates>
12.4. Supported Validators
12.4.1. Java
12.4.1.1. Use a Java Validator
Procedure 12.2. Create a Java Validator
- Implement the
org.switchyard.validate.Validator
interface. - Add a <validate.java> definition to your
switchyard.xml
file. - Alternatively, annotate one or more methods to your Java class with @Validator:
@Named("MyValidatorBean") public class MyValidator { @Validator(name = "{urn:switchyard-quickstart-demo:orders:1.0}submitOrder") public ValidationResult validate(Element from) { // handle validation here } }
When using the @Validator annotation, the SwitchYard Maven plug-in automatically generates the <validate.java> definitions for you and add them to theswitchyard.xml
file packaged in your application.The Java class above produces this <validate.java> definition:<validate.java bean="MyValidatorBean" name="{urn:switchyard-quickstart-demo:orders:1.0}submitOrder"/>
12.4.1.2. Java Validator Reference
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 is used as the type.
The CDI bean name specified by @Named annotation is used to resolve validator class. If you fail to specify it, then the validator's class name is used instead:
<validates> <validate.java class="org.switchyard.quickstarts.demos.orders.MyValidator" name="{urn:switchyard-quickstart-demo:orders:1.0}submitOrder"/> </transforms>
Note
Each of the <validate.java> definitions have either a bean attribute or a class attribute. These two attributes are mutually exclusive.
12.4.1.3. ValidationResult
ValidationResult is a simple interface which represents the result of validation. It has two methods,
isValid()
and getDetail()
.
12.4.1.4. Java Validation Failure
If Java validation fails, the message exchange process stops immediately and a
HandlerException
is thrown along with a validation failure message which is returned by ValidationResult.getDetail()
. Make sure that you return a ValidationResult
with failure detail message when you want to indicate a validation failure in your Java Validator, instead of throwing a RuntimeException
.
12.4.1.5. ValidationResult Properties
isValid()
returns whether the validation succeeded or not. _getDetail()
returns an error message if validation fails.
package org.switchyard.validate; public interface ValidationResult { boolean isValid(); String getDetail(); }
There are three convenience methods available for
org.switchyard.validate.BaseValidator
. These are validResult()
, invalidResult()
and invalidResult(String)
Use them to generate ValidationResult objects.
12.4.2. XML
12.4.2.1. Use an XML Validator
The XML validator allows you to perform a validation against its schema definition. It support DTD, XML_SCHEMA, and RELAX_NG schema types. You can configure an XML validator by specifying the schema Type, the name QName, and the path to the schema file. Here is an example:
<validate.xml schemaType="XML_SCHEMA" name="{urn:switchyard-quickstart:validate-xml:0.1.0}order" failOnWarning="true" namespaceAware="true"> <schemaFiles> <entry file="/xsd/orders.xsd"/> </schemaFiles> <schemaCatalogs> <entry file="/xsd/catalog.xml"/> </schemaCatalogs> </validate.xml>If you specify the
failOnWarning
attribute as true, the validation fails if any warning is detected during validation. If the XML content to be validated has namespace prefix, then you need to specify namespaceAware
as true.
12.4.2.2. XML Catalog
You can use XML catalog to decouple the schema file location from schema definition itself. This schema is
orders.xsd
which has a import element. It refers to logical name orders.base by the schemaLocation
attribute:
<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="urn:switchyard-quickstart:validate-xml:0.1.0" xmlns:base="urn:switchyard-quickstart:validate-xml-base:0.1.0" xmlns:orders="urn:switchyard-quickstart:validate-xml:0.1.0"> <import namespace="urn:switchyard-quickstart:validate-xml-base:0.1.0" schemaLocation="orders.base"/> ...Here is the
catalog.xml
file that resolves actual schema location from logical name orders.base:
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> <system systemId="orders.base" uri="orders-base.xsd"/> </catalog>
12.4.2.3. XML Validation Failure
If XML validation fails, the message exchange process stops immediately and a
HandlerException
is thrown along with a validation failure message. XMLValidator collects a set of validation failures through the SAX ErrorHandler
, and uses the getMessage()
of each received SAXParseException
as a failure detail with extracting root cause, if exists.