001    // Copyright 2006, 2007, 2008, 2011 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.tapestry5.corelib.components;
016    
017    import org.apache.tapestry5.CSSClassConstants;
018    import org.apache.tapestry5.MarkupWriter;
019    import org.apache.tapestry5.ValidationTracker;
020    import org.apache.tapestry5.annotations.Environmental;
021    import org.apache.tapestry5.annotations.Parameter;
022    import org.apache.tapestry5.corelib.internal.InternalMessages;
023    import org.apache.tapestry5.services.FormSupport;
024    
025    import java.util.List;
026    
027    /**
028     * Standard validation error presenter. Must be enclosed by a
029     * {@link org.apache.tapestry5.corelib.components.Form} component. If errors are present, renders a
030     * div element around a banner message and around an unnumbered list of
031     * error messages. Renders nothing if the {@link org.apache.tapestry5.ValidationTracker} shows no
032     * errors.
033     * 
034     * @see Form
035     * @tapestrydoc
036     */
037    public class Errors
038    {
039        /**
040         * The banner message displayed above the errors. The default value is "You must correct the
041         * following errors before
042         * you may continue.".
043         */
044        @Parameter("message:default-banner")
045        private String banner;
046    
047        /**
048         * The CSS class for the div element rendered by the component. The default value is "t-error".
049         */
050        @Parameter(name = "class")
051        private String className = CSSClassConstants.ERROR;
052    
053        // Allow null so we can generate a better error message if missing
054        @Environmental(false)
055        private ValidationTracker tracker;
056    
057        void beginRender(MarkupWriter writer)
058        {
059            if (tracker == null)
060                throw new RuntimeException(InternalMessages.encloseErrorsInForm());
061    
062            if (!tracker.getHasErrors())
063                return;
064    
065            writer.element("div", "class", className);
066    
067            // Inner div for the banner text
068            writer.element("div", "class", "t-banner");
069            writer.write(banner);
070            writer.end();
071    
072            List<String> errors = tracker.getErrors();
073    
074            if (!errors.isEmpty())
075            {
076                // Only write out the <UL> if it will contain <LI> elements. An empty <UL> is not
077                // valid XHTML.
078    
079                writer.element("ul");
080    
081                for (String message : errors)
082                {
083                    writer.element("li");
084                    writer.write(message);
085                    writer.end();
086                }
087    
088                writer.end(); // ul
089            }
090    
091            writer.end(); // div
092    
093        }
094    }