<html2> Tag Library for Struts

Downloads:
html2.zip- the jar file and the Validator rules xml file.
html2-src.zip - all source files.
html2demo.war - the demo file.

All files are distributed under the Apache 2.0 License.

The html2 tag library provides an alternate way of handling invalid (and valid) form input.

Features

• error tag provides an easy way to display errors related to a specific form property.
• label tag takes advantage of the HTML label tag to provide a label associated with the input control for a form property. The style for this tag can be modified when its associated field is invalid.
• field tag conveniently wraps label, error, and HTML input control tags to associate them with a property on the form bean.
• Custom field handling allows the developer to provide a custom JavaScript function that gets called after a field has been validated, whether the field is valid or not.

Combined with some CSS style definitions, your form fields can be declared like this:

    <html:field property="salary">
        <html:label/>
        <html:text/>
        <html:error styleClass="myCssStyleClass"/>
    </html:field>

There are two modes provided, one for forms not using the Validator support, and another for those using Validator.

html2 without Validator

Without Validator's client-side validation, <html2> tags will call the ActionForm's validate() method. This is done through an XMLHttpRequest to an action mapping created by the Html2Plugin.

To enable this:

1. Include html2.jar in your web application.

2. Declare the Html2PlugIn in your struts-config.xml:
   

           <plug-in className="net.rabago.struts.html2.Html2PlugIn"/>
           

3. Use <html2> tags for form fields. (See below)

4. Call the html2Validate() javascript method when the form is submitted:
   

           <html2:form action="/submitForm" onsubmit="return html2Validate(this)">
           

5. Include the <html2:html2Javascript/> tag in the page.

Using html2 with Validator

The javascript code in the current Validator plugin hardcodes its handling of validation results. This prevents applications (or add-ons like this one) from customizing its behavior. To solve this, we use the validatorjs extension by Niall Pemberton (proposed as a commons-validator enhancement here).

To use this:

1. Include html2.jar and validatorjs_struts.jar in your web application.

2. Use <html2> tags for form fields. (See below)

3. Call the validate[FormName]() javascript method when the form is submitted:
   

           <html2:form action="/submitForm" onsubmit="return validateEmployeeForm(this)">
           

   ... the way you do now with Validator-supported forms, or use the new validatorForm attribute provided by the validatorjs extension:

           <html2:form action="/submit" validatorForm="employeeForm">
           

4. Include the <html2:html2Javascript/> tag in the page. If all forms on this page are Validator-supported, you can turn html2 XMLHttpRequest support off:

           <html2:html2Javascript xmlHttpRequest="false"/>
           

Since Validator provides client-side validation, I was able to save the generated HTML code and provide it here:
validatorDemo.htm - Struts Validator + ValidatorJS extension + html2
customHandlingDemo.htm - same as above, plus custom field handling.

Using the right TLD

The use of <html2> tags for form fields are needed for html2 functionality. There are two sets of tags that are provided, one for use without Validator, the other for use with Validator:

<%@ taglib uri="http://www.rabago.net/tags-html2" prefix="html2" %>
<%@ taglib uri="http://www.rabago.net/tags-valid2" prefix="html2" %>

Each set contains about 10 custom implementations of existing Struts tags, plus about 4 new tags (field, label, error, and html2Javascript).

You'll only need to use one set in a given JSP, of course. You can continue to use the standard HTML tag library for those not customized by <html2>, but for convenience, those same tags were declared in these TLD files so you can stick to just one set of HTML tags.

The demo application shows examples of mixing <html2> tags with the standard Struts HTML tags in both actionFormDemo.jsp and validatorDemo.jsp. In these files you'll see a mix of <html2> tags and the usual Struts <html> tags.

The customHandlingDemo.jsp file shows an example of using the <html2> TLD for both <html2> and Struts <html> tags.

A note on HTML ID attributes

The Javascript generated by the <html2> tags use the ID attribute of HTML tags to find the labels and error tags associated with valid and invalid fields. For this reason, forms that need to specify their own ID value may not be able to use <html2> tags.

The ID values used are:

Element	ID format
Form	[beanName]
Input control	[beanName].[fieldName]
Input label	[beanName].[fieldName].label
Error display <span> tag	[beanName].[fieldName].error

Next up

If I find the time, that is. Or someone else volunteers and picks this up.

• Code reviews. It might help if someone who knows Javascript really well can see what I've done and either suggest improvements or say all is well.
• More testing. I haven't spent a lot of time testing the other tags yet. Multipart forms, type=file fields, and indexed fields, all need testing.
• If someone was interested, a port to Struts 1.2.7. There really isn't anything preventing it. All it'd need are 1.2.7-compatible TLD and validator-rules.xml files.
• Documentation. There are a few more tag attributes that need to be documented. The TLD has the description, but you don't wanna dig through that just to read what the "errorDisplay" attribute is for, do you? (Btw, that's the value for the "display" style of the <span> used for the error display, with a default value of "inline".)
• Oh, and if Bug 32343 gets resolved (and the patch is applied), then some adjustments on the tags and the javascript would be needed.
• Maybe repackage everything from "net.rabago.etc.etc". I always start using this package by default now, but I don't want that to prevent someone else from using this extension.