Jwickers: Protected "Opentaps 2 Service Validation": Sysop page [edit=sysop:move=sysop]

2012-01-30T14:50:21Z

Protected "Opentaps 2 Service Validation": Sysop page [edit=sysop:move=sysop]

Jwickers: New page: There are currently two level of validations, one at the service level which validates the parameters given, and one at the persistence level. == General Concept == Validation at those l...

2012-01-30T14:50:21Z

New page: There are currently two level of validations, one at the service level which validates the parameters given, and one at the persistence level. == General Concept == Validation at those l...

New page

There are currently two level of validations, one at the service level which validates the parameters given, and one at the persistence level.

== General Concept ==

Validation at those levels is implemented using Bean Validation (JSR-303), which simply consist of annotations on a POJO's properties or accessors. There are numerous online articles to learn more about it, eg: http://java.dzone.com/articles/bean-validation-made-simple

Some validators are quite simple, like ''javax.validation.constraints.NotNull'', and it is also very easy to define your own, like for example ''org.opentaps.validation.contraints.NotEmpty''.

A Validator can also be set on a class itself when complex validation involving multiple properties is needed.

== Validation on Entities ==

JPA supports Bean Validation internally so an entity which is annotated will only be persisted if it is valid.

== Validation in the Services ==

Validation in the Services is done in a similar manner, the Input and Output objects are annotated and the service implementation is responsible for calling the validator.

For this the ''validation.api'' bundle defines a ''ValidationService'' which is provided by the ''validation.impl'' bundle which itself simply expose the implementation given by Geronimo.

A typical pattern in the service implementation can be seen in ''org.opentaps.notes.services.impl.CreateNoteServiceImpl'' and is basically:

Set<ConstraintViolation<MyServiceInput>> inputViolations = validationService.getValidator().validate(input);
if (inputViolations.size() > 0) {
throw new ServiceValidationException("My service failed.", (Set) inputViolations);
}

try {
// do something involving persistence
...
} catch (ConstraintViolationException e) {
throw new ServiceValidationException("My service failed.", e);
} catch (PersistenceException e) {
throw new ServiceException("My service failed.", e);
}

// populate the output
MyServiceOutput out = new MyServiceOutput();
...

Set<ConstraintViolation<MyServiceOutput>> outputViolations = validationService.getValidator().validate(out);
if (outputViolations.size() > 0) {
throw new ServiceValidationException("My service failed.", (Set) outputViolations);
}

== Sending Validation Errors to the Client ==

As an example the Note rest service `org.opentaps.notes.rest.NoteResource` simply extends `org.opentaps.rest.ServerResource` which implements an exception handler that translates a `ServiceValidationException` into a JSON structure.

Part of the JSON response includes a `errorDetail` object which is an array of `ServiceValidationException.FieldError` which contains 3 fields:
* ''field'' which is the field name in the service interface that was not valid
* ''message'' which is the error message returned by the validator
* ''value'' which was the value given that failed validation

The client can then read that response to present the errors to the user.

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Opentaps 2 Service Validation - Revision history

Jwickers: Protected "Opentaps 2 Service Validation": Sysop page [edit=sysop:move=sysop]

Jwickers: New page: There are currently two level of validations, one at the service level which validates the parameters given, and one at the persistence level. == General Concept == Validation at those l...