Getting Further with Spring RCP

Adding Rules Based Validation

Next we set some rules for field validation.

As the user types, feedback needs to be given about the validity of the entered text.

Spring RCP validation rules are provided separately from the domain object, although they are, in this case, within the same package.

The validation rules need to be registered in the richclient-application-context.xml, as shown at the end of this section.

package domain;

import org.springframework.core.closure.Constraint;
import org.springframework.rules.Rules;
import org.springframework.rules.support.DefaultRulesSource;

public class SimpleValidationRulesSource extends DefaultRulesSource {

    private final Constraint NAME_CONSTRAINT = all(new Constraint[]{required(), minLength(2),
                regexp("[-'.a-zA-Z ]*", "alphabeticConstraint")
            });
    private final Constraint ZIPCODE_CONSTRAINT = all(new Constraint[]{required(), minLength(5), maxLength(10),
                regexp("[0-9]{5}(-[0-9]{4})?", "zipcodeConstraint")
            });

    public SimpleValidationRulesSource() {
        super();
        addRules(createCustomerRules());
    }

    private Rules createCustomerRules() {

        return new Rules(Customer.class) {
            @Override
            protected void initRules() {
                add("firstName", NAME_CONSTRAINT);
                add("lastName", NAME_CONSTRAINT);
                add(not(eqProperty("firstName", "lastName")));
                add("address.street", required());
                add("address.state", required());
                add("address.zip", ZIPCODE_CONSTRAINT);
            }
        };
        
    }
    
}

Now we need to register the class in the richclient-application-context.xml. Anywhere within that file, add the following:

<bean id="rulesSource" class="domain.SimpleValidationRulesSource" />

Validating forms will interrogate the rules source for rules that apply to the class of a form object, which in this case is the "Customer" object. Therefore, when the user types something that breaks the rules, Spring RCP will give a warning and disable the OK button, as shown below:

Conclusion

Though the application is by no means complete (and even the modification code is very rudimentary, just enough is there to perform the modification, but not much more), many of Spring RCP's unique treasures have been covered in this article—in particular, you have seen how the Spring RCP Form Builder and its rules based validation can be used within the context of Swing applications. In general, you have seen how these features fit together within the context of a Spring RCP application that uses views, dialogs, and forms.

(And now continue to the next part!)