Spring Framework example source code file (Validator.java)

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Java - Spring Framework tags/keywords

errors, errors, validator, validator

The Spring Framework Validator.java source code

/*
 * Copyright 2002-2007 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.validation;

/**
 * A validator for application-specific objects.
 * 
 * <p>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 first-class citizens in their own right.
 * 
 * <p>Find below a simple but complete Validator
 * implementation, which validates that the various {@link String}
 * properties of a <code>UserLogin instance are not empty
 * (that is they are not <code>null and do not consist
 * wholly of whitespace), and that any password that is present is
 * at least <code>'MINIMUM_PASSWORD_LENGTH' characters in length.
 * 
 * <pre class="code"> 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.");
 *       }
 *    }
 * }</pre>
 * 
 * <p>See also the Spring reference manual for a fuller discussion of
 * the <code>Validator interface and it's role in a enterprise
 * application. 
 * 
 * @author Rod Johnson
 * @see Errors
 * @see ValidationUtils
 */
public interface Validator {
	
	/**
	 * Can this {@link Validator} {@link #validate(Object, Errors) validate}
	 * instances of the supplied <code>clazz?
	 * <p>This method is typically implemented like so:
	 * <pre class="code">return Foo.class.isAssignableFrom(clazz);

* (Where <code>Foo is the class (or superclass) of the actual * object instance that is to be {@link #validate(Object, Errors) validated}.) * @param clazz the {@link Class} that this {@link Validator} is * being asked if it can {@link #validate(Object, Errors) validate} * @return <code>true if this {@link Validator} can indeed * {@link #validate(Object, Errors) validate} instances of the * supplied <code>clazz */ boolean supports(Class clazz); /** * Validate the supplied <code>target object, which must be * of a {@link Class} for which the {@link #supports(Class)} method * typically has (or would) return <code>true. * <p>The supplied {@link Errors errors} instance can be used to report * any resulting validation errors. * @param target the object that is to be validated (can be <code>null) * @param errors contextual state about the validation process (never <code>null) * @see ValidationUtils */ void validate(Object target, Errors errors); }