(On Traditional WebSphere (tWAS) 8.5.5, Java 8, or on WebSphere Liberty 18, currently with Feature webProfile-6.0, in order to match the tWAS spec levels as closely as possible.)

Background

We’re using Spring (4.x) MVC Controllers in several of our applications, for various reasons. I’ve found myself wanting to add basic JSR-303 validations to some of the submitted parameters or objects, and earlier had failed to get this working under WebSphere.

At that time, the need wasn’t that great, so I just manually validated the single parameter and moved on.

But then I hit a case where I wanted to to more sophisticated validation (of REST-style web service controllers), and this would be an easier pattern than the alternatives I was aware of. So I decided to jump in again. After a bit more wrestling, I was starting to think nobody else had done this before, and I was going to have to give up, when I came across a clue that eventually led to success. So I wanted to document that, both for my own future reference, and for anyone else trying to do the same thing.

Context

Spring Validation supports JSR 303 Validation. Using this would allow us to annotate beans with generic javax.validation annotations, not having to tie them specifically to Spring, which is a plus particularly for any classes that aren’t already tied to Spring. POJOs, etc., as opposed to the Controller classes themselves.

Enablement

The first step is to configure Spring to instantiate a MethodValidationPostProcessor. Theoretically, the following is sufficient (for our XML-based configuration):

    <bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor"/>

According to the Spring Javadocs,

The actual provider will be autodetected and automatically adapted.

And according to the WebSphere 8.5.5 documentation, it has such a provider. Should be good to go. Could it be this easy?

The problem

However, enabling this under WebSphere, where our application has only the Spring-core jars, produced the following error:

[8/9/17 10:33:40:588 CDT] 000000a7 ServletWrappe E com.ibm.ws.webcontainer.servlet.ServletWrapper service SRVE0014E: Uncaught service() exception root cause Spring MVC Dispatcher: org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is java.lang.NoClassDefFoundError: org.hibernate.validator.method.MethodConstraintViolationException  
...  
Caused by: java.lang.NoClassDefFoundError: org.hibernate.validator.method.MethodConstraintViolationException  
        at org.springframework.validation.beanvalidation.MethodValidationInterceptor.invoke(MethodValidationInterceptor.java:152)

Hibernate, eh? I don’t have Hibernate, and I don’t want to use Hibernate. I want to use what WebSphere already has.

The solution

I was about on the verge of giving up when web searches caused me to dig deeper into the above Spring and WebSphere Bean Validation documentation and notice that

  1. You can inject a different ValidationFactory into the Spring MethodValidationPostProcessor
  2. WebSphere defines JNDI objects for its ValidationFactory (and Validator) instances. (See section Validation APIs, no anchor to link to.)

Combining those, gets us:

    <jee:jndi-lookup id="validatorFactory" jndi-name="java:comp/ValidatorFactory" resource-ref="false"/>

    <bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor">  
        <property name="validatorFactory" ref="validatorFactory"/>  
    </bean>

Voila! No more NoClassDefFoundError.

Caveat: Maybe there’s a better way to do this. Readers, feel free to point me there.

Side Note

Incidentally, when I use this simple JSP to see what the actual WebSphere-provided ValidatorFactory is, the result is org.apache.bval.jsr303.ApacheValidatorFactory.

Now, to use the validation and ensure it actually works.

Usage

I’m going to validate entire “model” objects being passed into my Spring MVC Controllers. So I have to do two things:

  1. Add JSR 303 field level annotations to the Model POJO fields
  2. Tell the Controllers to apply JSR 303 validations to their inputs

WebSphere supports the JSR 303 Built-in Constraint definitions, so we can use any of those or create our own.

Here’s an excerpt from an annotated model POJO, showing multiple annotation types, both with and without custom error messages:

public class TransactionRequest {  
    @NotNull(message="Business Unit is required")
    private String businessUnit;  

    @NotNull
    @Size(min=1,max=30,message="Application ID must be between 1 and 30 characters")
    private String applicationId;  

    ... getters/setters, etc.

}

And here’s an excerpt from a Controller request-handling method that enables those validations of the incoming request:

@Controller  
public class TransactionController {

    @PostMapping(path = "PostTransaction",  
                 consumes = { MediaType.APPLICATION_JSON_VALUE },  
                 produces = { MediaType.APPLICATION_JSON_VALUE })  
    public ResponseEntity<Object> postTransaction(  
        @Valid @RequestBody TransactionRequest tRequest) {  
            ...  
        }

    ...
}

Where @Controller, @PostMapping, and @RequestBody annotations are from Spring MVC, but @Valid is the JSR 303 generic javax.validation.Valid.

Result

Now, if I call that /PostTransaction URL and provide a JSON request that violates any of those validations - for example is missing the businessUnit - Spring MVC will automatically return an HTTP 400 error.

Improvement Possible

Regrettably, the default 400 error is a generic 400, with Content-Type text/html, with a WebSphere-specific error code in it, and with no information on which validation(s) failed:

HTTP/1.1 400 Bad Request  
Content-Type: text/html;charset=ISO-8859-1  
...  
Error 400: SRVE0295E: Error reported: 400

So in my next post, I describe a Spring MVC way to improve on that.