Mule ESB- Data Validation- Best Practices

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Mule ESB- Data Validation- Best
Practices

Overview
• Validation of data in ESB application at different layers of message
processing is a requirement which is quite frequent.
• Often, the validation logic is implemented at different layers which
is time consuming and also prone to errors.
• Therefore, it is necessary to separate domain model and the
validation logic, further to it, it also has to be aimed for reuse with
the help of framework.
• This presentation focuses to bring the goodness of JSR303 Bean
Validation model [Hibernate RI], Spring framework’s support for
custom validation and a blend on how it will work in MuleSoft ESB.

Deploying Mule Applications

Validation Requirements
• From an ESB point of view, the validation requirements are:
• Provide uniform approach to validate different type of payloads
supporting REST, SOAP, XML, Java VO and other types of payloads
• Provide support for field level validations (example: validate
inbound message attributes)
• Provide support for custom validations (based on business logic)
• Support context specific messages for validation errors from
configuration files
• Raise validation errors for handling alternate flow of execution
• Inject validators as pluggable components in flow

Mule offerings and shortcomings
• Mule supports validations to an extent but that is not
sufficient; for example
• The validator pattern from Mule supports validation using
MEL which is barely sufficient; forcing to write MEL for every
attribute and has no option to wire to an error code/message
• The JSON validator checks whether the input JSON is
formatted. It does not support features to apply a constraint
like checking the length of an attribute, for null value or for an
empty string, etc.

Benefits of JSR303 specification
• Java Bean Validation (JSR303) is a framework as part of Java EE.
• The bean validation defines meta model and API for data validation.
• The implementation is done through annotations and is extensible, which
can be reused by simply adding annotations to the domain model.
// Example – define constraints to a bean
public class Person {
@NotNull (message=’ERR-BS-001’)
public class Person{
@Size(min=1, max=16)
private String firstName;
@Size(min=1, max=16)
private String lastName;

• Spring framework supports JSR303 bean validations and support for
custom validation. Some of the advantages upon using Spring
Validators are mentioned below:
• Spring framework is a natural choice of Mule for DI – No additional
set-up is required
• Custom Spring Validators can be injected to a Mule ESB flow so as
to validate business logic
• Supports JSR 303 validation by making use of a reference
implementation like Hibernate Validator API or Apache BVal API
• Link validation errors using Spring property placeholders for error
messages which are context specific
7
Benefits of Spring Validators

A validation framework is necessary, which binds annotation
validators, custom validators and error message handler.
8
Blending all together

• To validate annotations, JSR303 RI is required in the
library. Hibernate Validator or Apache’s BVal can be used to
support annotation based validations.
• To validate concrete domain models, Spring framework’s
ValidationUtils class should be used (from
springframework.validation package). The ValidationUtil’s method
should invoke a custom validator thus providing FieldErrors.
• The ExceptionFactory consolidates the FieldErrors from different
validators, fetches the attribute name and message ID and loads the
message from the message source.
• Custom validators to the ValidationUtils should be injected as
Spring beans in Mule.
• Exception factory should use Spring’s PropertiesFactoryBean to load
error messages at runtime.
9
Cont..

• It might be possible to use annotations in order to validate REST
requests by using @Valid annotation.
• Mule ESB 6.1 has upgraded Jersey version 2.11 (RI) which supports
validation using @Valid annotation prior to a REST method
invocation (like in Spring MVC).
// update user profile after validation
@POST
@Consumes( MediaType.APPLICATION_JSON_VALUE )
public boolean updateProfile(
@Valid UserProfile mProfile )
//…
}
10
Go for the extra mile!

Mule ESB- Data Validation- Best Practices

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