Problems using JSR-303 ConstraintValidator

[Andrew Swan]

I have a Roo-generated Spring MVC app to which I'm adding web flow. I'm using:

• SWF 2.1.1.RELEASE
• Spring 3.0.4.RELEASE
• Hibernate Validator 4.0.2.GA (JSR-303 provider)
• Roo 1.0.2

Domain Model

I have a simple entity called Book, which has a title and a publisher:

@Entity
@RooJavaBean
@RooToString
@RooEntity
@BookConstraint(message = "Oops!")
public class Book implements Serializable {

    @Column(length = 30)
    @NotNull
    @Size(min = 1, max = 30)
    private String title;

    @ManyToOne(targetEntity = Publisher.class)
    @NotNull
    @JoinColumn
    private Publisher publisher;
}

Validation

Apart from the above field-level JSR-303 annotations, I also have a custom ConstraintValidator with its corresponding annotation, as follows:

public class BookConstraintValidator
    implements ConstraintValidator<BookConstraint, Book>
{
    @Override
    public void initialize(BookConstraint constraintAnnotation) {
        // Empty
    }

    @Override
    public boolean isValid(Book book, ConstraintValidatorContext context) {
        return false;  // i.e. validation is hard-coded to fail for now
    }
}

@Documented
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = BookConstraintValidator.class)
public @interface BookConstraint {
    
    String message() default "{some.error.code}";
    
    Class<?>[] groups() default {};
    
    Class<? extends Payload>[] payload() default {};
}

Works with MVC

This all works nicely when adding a Book via straight Spring MVC (i.e. outside of SWF). The validation fails as expected, and the view displays the configured "Oops!" error message.

Integration of JSR-303 with SWF

Rather than duplicate all the above validation rules in SWF-style validators, I have set up SWF to delegate to my JSR-303 validation logic via a LocalValidatorFactoryBean. However when I add a new Book via SWF, I get this exception:

org.springframework.webflow.execution.FlowExecutionException: Exception thrown in state 'enterBookDetails' of flow 'flows/newBook'
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.wrap(FlowExecutionImpl.java:569)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.resume(FlowExecutionImpl.java:263)
    at org.springframework.webflow.executor.FlowExecutorImpl.resumeExecution(FlowExecutorImpl.java:169)
    at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:183)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:788)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:717)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
...
Caused by: java.lang.IllegalArgumentException: The expression string to parse is required and must not be empty
    at org.springframework.util.Assert.hasText(Assert.java:162)
    at org.springframework.binding.expression.spel.SpringELExpressionParser.parseExpression(SpringELExpressionParser.java:74)
    at org.springframework.binding.message.MessageContextErrors.rejectValue(MessageContextErrors.java:86)
    at org.springframework.validation.beanvalidation.SpringValidatorAdapter.validate(SpringValidatorAdapter.java:92)
    at com.example.books.domain.validate.BookValidator.validate(BookValidator.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:186)
    at org.springframework.webflow.validation.ValidationHelper.invokeValidatorDefaultValidateMethod(ValidationHelper.java:256)
    at org.springframework.webflow.validation.ValidationHelper.invokeModelValidator(ValidationHelper.java:185)
    at org.springframework.webflow.validation.ValidationHelper.validate(ValidationHelper.java:104)
    at org.springframework.webflow.mvc.view.AbstractMvcView.validate(AbstractMvcView.java:625)
    at org.springframework.webflow.mvc.view.AbstractMvcView.processUserEvent(AbstractMvcView.java:217)
    at org.springframework.webflow.engine.ViewState.handleEvent(ViewState.java:224)
    at org.springframework.webflow.engine.ViewState.resume(ViewState.java:196)
    at org.springframework.webflow.engine.Flow.resume(Flow.java:545)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.resume(FlowExecutionImpl.java:259)
    ... 47 more
java.lang.IllegalArgumentException
The expression string to parse is required and must not be empty
java.lang.IllegalArgumentException: The expression string to parse is required and must not be empty
    at org.springframework.util.Assert.hasText(Assert.java:162)
    at org.springframework.binding.expression.spel.SpringELExpressionParser.parseExpression(SpringELExpressionParser.java:74)
    at org.springframework.binding.message.MessageContextErrors.rejectValue(MessageContextErrors.java:86)
    at org.springframework.validation.beanvalidation.SpringValidatorAdapter.validate(SpringValidatorAdapter.java:92)
    at com.example.books.domain.validate.BookValidator.validate(BookValidator.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:186)
    at org.springframework.webflow.validation.ValidationHelper.invokeValidatorDefaultValidateMethod(ValidationHelper.java:256)
    at org.springframework.webflow.validation.ValidationHelper.invokeModelValidator(ValidationHelper.java:185)
    at org.springframework.webflow.validation.ValidationHelper.validate(ValidationHelper.java:104)
    at org.springframework.webflow.mvc.view.AbstractMvcView.validate(AbstractMvcView.java:625)
    at org.springframework.webflow.mvc.view.AbstractMvcView.processUserEvent(AbstractMvcView.java:217)
    at org.springframework.webflow.engine.ViewState.handleEvent(ViewState.java:224)
    at org.springframework.webflow.engine.ViewState.resume(ViewState.java:196)
    at org.springframework.webflow.engine.Flow.resume(Flow.java:545)
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.resume(FlowExecutionImpl.java:259)
    at org.springframework.webflow.executor.FlowExecutorImpl.resumeExecution(FlowExecutorImpl.java:169)
    at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:183)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:788)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:717)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:726)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
    at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:285)
    at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:126)
...

I'm looking into this as we speak, but I'm wondering if anyone else has come across a similar problem, or has managed to get a ConstraintValidator working with SWF.

Thanks in advance for any help.

[Andrew Swan]

From my investigation, it turns out that MessageContextErrors doesn't correctly handle global errors; I've logged this as SWF-1389.

The workaround for SWF users is to extend LocalValidatorFactoryBean as follows:

/**
 * Extends the Spring class to support global errors as well as field errors
 */
public class FixedValidatorFactory extends LocalValidatorFactoryBean {

    @Override
    public void validate(Object target, Errors errors) {
        Set<ConstraintViolation<Object>> result = validate(target);
        for (ConstraintViolation<Object> violation : result) {
            String field = violation.getPropertyPath().toString();
            String errorCode =
                violation.getConstraintDescriptor().getAnnotation()
                .annotationType().getSimpleName(); 
            Object[] errorArgs = getArgumentsForConstraint(
                    errors.getObjectName(), field, violation.getConstraintDescriptor()); 
            String defaultMessage = violation.getMessage();
            FieldError fieldError = errors.getFieldError(field);
            if (fieldError == null) {
                // Global error
                errors.reject(errorCode, errorArgs, defaultMessage);
            }
            else if (!fieldError.isBindingFailure()) {
                // Non-binding field error
                try {
                    errors.rejectValue(field, errorCode, errorArgs, defaultMessage);
                }
                catch (NotReadablePropertyException ex) {
                    throw new IllegalStateException("JSR-303 validated property '" +
                            field + "' does not have a corresponding accessor for" +
                            " Spring data binding - check your DataBinder's" +
                            " configuration (bean property versus direct field" +
                            " access)", ex);
                }
            }
        }
    }
}