Summary: Methods | [Expand All]
public interface

Validator

org.springframework.validation.Validator
Known Indirect Subclasses

Class Overview

A validator for application-specific objects.

This interface is totally divorced from any infrastructure or context; that is to say it is not coupled to validating only objects in the web tier, the data-access tier, or the whatever-tier. As such it is amenable to being used in any layer of an application, and supports the encapsulation of validation logic as a first-class citizen in its own right.

Find below a simple but complete Validator implementation, which validates that the various String properties of a UserLogin instance are not empty (that is they are not null and do not consist wholly of whitespace), and that any password that is present is at least 'MINIMUM_PASSWORD_LENGTH' characters in length. 

 public class UserLoginValidator implements Validator {
 
    private static final int MINIMUM_PASSWORD_LENGTH = 6;
 
    public boolean supports(Class clazz) {
       return UserLogin.class.isAssignableFrom(clazz);
    }
 
    public void validate(Object target, Errors errors) {
       ValidationUtils.rejectIfEmptyOrWhitespace(errors, "userName", "field.required");
       ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "field.required");
       UserLogin login = (UserLogin) target;
       if (login.getPassword() != null
             && login.getPassword().trim().length() < MINIMUM_PASSWORD_LENGTH) {
          errors.rejectValue("password", "field.min.length",
                new Object[]{Integer.valueOf(MINIMUM_PASSWORD_LENGTH)},
                "The password must be at least [" + MINIMUM_PASSWORD_LENGTH + "] characters in length.");
       }
    }
 }

See also the Spring reference manual for a fuller discussion of the Validator interface and it's role in an enterprise application.

See Also

Summary

Public Methods
abstract boolean supports(Class<?> clazz)
Can this Validator validate instances of the supplied clazz?

This method is typically implemented like so: 

return Foo.class.isAssignableFrom(clazz);
(Where Foo is the class (or superclass) of the actual object instance that is to be validated.)
abstract void validate(Object target, Errors errors)
Validate the supplied target object, which must be of a Class for which the supports(Class) method typically has (or would) return true.

Public Methods

public abstract boolean supports (Class<?> clazz)

Can this Validator validate instances of the supplied clazz?

This method is typically implemented like so: 

return Foo.class.isAssignableFrom(clazz);
(Where Foo is the class (or superclass) of the actual object instance that is to be validated.)

Parameters
clazz the Class that this Validator is being asked if it can validate
Returns

public abstract void validate (Object target, Errors errors)

Validate the supplied target object, which must be of a Class for which the supports(Class) method typically has (or would) return true.

The supplied errors instance can be used to report any resulting validation errors.

Parameters
target the object that is to be validated (can be null)
errors contextual state about the validation process (never null)
See Also