Q:

javax.validation.ValidationException: Unable to find default provider

I am currently working on Spring MVC web app and trying to hook up validation using the @Valid annotation. When I fire up the application I'm getting the following exception:
javax.validation.ValidationException: Unable to find a default provider

I have Hibernate Validator 3.1.0.GA on the classpath as well as javax validation 1.0.0.GA, Hibernate Core 3.3.1.GA and Hibernate Annotations 3.4.0.GA.
Is there an incompatiblity in those versions that I'm not seeing, or can anyone think of any reason why I'm still getting this exception with Hibernate Validator on the class path?
Cheers,
Caps

A:

See this answer : https://stackoverflow.com/a/3989936/325742
To fix, Add this maven dependency Hibernate Validator Annotation Processor.
<dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate-validator-annotation-processor</artifactId>
  <version>4.1.0.Final</version>
</dependency>

That's the latest stable version of that artifact, as seen from here

 Generic way of finding a dependency 
Let's say that you got a a NoClassDefFoundError stating that the class org.postgresql.Driver was not found. 

Use Jarvana to search for a dependency that can provide org.postgresql.Driver like so : http://www.jarvana.com/jarvana/search?search_type=class&java_class=org.postgresql.Driver which gives

Translate the above dependency into maven dependency format :

<dependency>
    <groupId>postgresql</groupId>
   <artifactId>postgresql</artifactId>
   <version>9.1-901.jdbc4</version>
 </dependency>

Confirm that the above is available at Maven Central by searching like this : g:"postgresql" AND a:"postgresql"
(where g stands for GroupID and a stands for artifactID)
Finally, add it to your pom.xml

Finding Dependencies using m2e 
If you have an approximate idea of the dependency needed or can figure out the one you need given a list, then m2e's dependency search can be the quickest way of adding a dependency to your pom.xml
Steps :

Click on the Dependencies tab (A) in your pom.xml
Click on Add (B)
Search for the dependency by groupId/artifactId (C)
Double click the required one from the search results to have it added directly to your pom.xml (D)

A-D marked in the following snapshot :

Finding dependencies in IntelliJ Idea
In IntelliJ, looking up a dependency is much easier. All you need to do, is to make sure that the maven central repo has been indexed by IntelliJ like so:

And then, go into the pom, do a dep+Tab (or an Alt+Insert as shown here), and this is what you get:

If you are in a class which has an unresolved import, then the quick fix gives you an option of searching and adding the corresponding maven repo by doing an Alt+Enter on the missing Class/Package:

Awesome I say !

A:

Hibernate Validator 3.1 is not a JSR303 provider.  You need to upgrade to Hibernate Validator 4 or later.

A:

This happened to me without Hibernate.
Running great on my PC, it didn't work on my EC2 Linux server.
The reason was an existence of validation-api-1.0.0.GA.jar file under /usr/share/tomcat/lib.
Once validation-api-1.0.0.GA.jar deleted, it worked great.

