001    // Copyright 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry.form.validator;
016    
017    import java.util.Collection;
018    
019    import org.apache.tapestry.IMarkupWriter;
020    import org.apache.tapestry.IRequestCycle;
021    import org.apache.tapestry.TapestryUtils;
022    import org.apache.tapestry.form.FormComponentContributorContext;
023    import org.apache.tapestry.form.IFormComponent;
024    import org.apache.tapestry.form.ValidationMessages;
025    import org.apache.tapestry.valid.ValidationConstants;
026    import org.apache.tapestry.valid.ValidationConstraint;
027    import org.apache.tapestry.valid.ValidationStrings;
028    import org.apache.tapestry.valid.ValidatorException;
029    
030    /**
031     * {@link org.apache.tapestry.form.validator.Validator} that ensures a value was supplied.
032     * 
033     * @author Howard Lewis Ship
034     * @since 4.0
035     */
036    public class Required extends BaseValidator
037    {
038        public Required()
039        {
040        }
041    
042        public Required(String initializer)
043        {
044            super(initializer);
045        }
046    
047        public boolean getAcceptsNull()
048        {
049            return true;
050        }
051    
052        public void validate(IFormComponent field, ValidationMessages messages, Object object)
053                throws ValidatorException
054        {
055            if ((object == null)
056                    || (String.class.isInstance(object) && (((String) object).length() == 0))
057                    || (Collection.class.isInstance(object) && ((Collection) object).isEmpty()))
058            {
059                String message = buildMessage(messages, field);
060                throw new ValidatorException(message, ValidationConstraint.REQUIRED);
061            }
062        }
063    
064        private String buildMessage(ValidationMessages messages, IFormComponent field)
065        {
066            return messages.formatValidationMessage(
067                    getMessage(),
068                    ValidationStrings.REQUIRED_FIELD,
069                    new Object[]
070                    { field.getDisplayName() });
071        }
072    
073        public void renderContribution(IMarkupWriter writer, IRequestCycle cycle,
074                FormComponentContributorContext context, IFormComponent field)
075        {
076            context.registerForFocus(ValidationConstants.REQUIRED_FIELD);
077    
078            StringBuffer buffer = new StringBuffer("function(event) { Tapestry.require_field(event, '");
079            buffer.append(field.getClientId());
080            buffer.append("', ");
081            buffer.append(TapestryUtils.enquote(buildMessage(context, field)));
082            buffer.append("); }");
083    
084            context.addSubmitHandler(buffer.toString());
085        }
086    
087        /**
088         * Returns true, that's what Required means!
089         */
090        public boolean isRequired()
091        {
092            return true;
093        }
094    }