Genschaw's Tech Blog: Using shale commons-validator with facelets

This entry describes how to integrate the Shale commons-validator tags with facelets. These tags include:

commonsValidator
validatorVar
validatorScript

For example:

...
<h:form onsubmit="return validateForm(this);">
...
  <label for="firstName"
   value="#{bundle['person.firstName']}*" /><br />
  <h:inputText id="firstName" value="#{person.firstName}"
   size="22" maxlength="20">
    <val:commonsValidator type="required"
      arg="#{textBundle['person.firstName']}" client="true" server="true" />
    <val:commonsValidator type="maxlength" maxlength="20"
      arg="#{textBundle['person.firstName']}" client="true" server="true" />
    <val:commonsValidator type="mask"
      arg="#{textBundle['person.firstName']}" client="true" server="true">
      <val:validatorVar name="mask" value="#{validationBundle['regexp.personName']}" />
    </val:commonsValidator>
  </h:inputText>
...
<val:validatorScript functionName="validateForm" />
</h:form>
...

First, you must create a facelets taglib file to tell facelets how to interpret these tags. Within the taglib file, you will refer to specific facelet TagHandler implementation classes that you will provide.

shale-validator-taglib.xml

<?xml version="1.0"?>
<!DOCTYPE facelet-taglib PUBLIC
       "-//Sun Microsystems, Inc.//DTD Facelet Taglib 1.0//EN"
       "http://java.sun.com/dtd/facelet-taglib_1_0.dtd">
<facelet-taglib>

   <namespace>http://shale.apache.org/validator</namespace>

   <tag>
       <tag-name>validatorScript</tag-name>
       <component>
           <component-type>org.apache.shale.ValidatorScript</component-type>
       </component>
   </tag>

   <tag>
       <tag-name>commonsValidator</tag-name>
       <handler-class>net.genschaw.jsf.facelets.CommonsValidatorHandler</handler-class>
   </tag>

   <tag>
       <tag-name>validatorVar</tag-name>
       <handler-class>net.genschaw.jsf.facelets.CommonsValidatorVarHandler</handler-class>
   </tag>

</facelet-taglib>

Save this file in your webapp, commonly under /WEB-INF. The <namespace> element is defining the namespace you will use for prefixing in your facelets templates.
For example:

<html xmlns="http://www.w3.org/1999/xhtml"
 xmlns:ui="http://java.sun.com/jsf/facelets"
 xmlns:h="http://java.sun.com/jsf/html"
 xmlns:f="http://java.sun.com/jsf/core"
 xmlns:c="http://java.sun.com/jstl/core"
 xmlns:val="http://shale.apache.org/validator">
...
...
</html>

The first <tag> element tells facelets to create a ValidatorScript component when it encounters a validatorScript tag. This component is defined in Shale's faces-config.xml.

The second <tag> element tells facelets to invoke a TagHandler when it encounters a commonsValidator tag. The tag handler is a class you need to implement (see below) to create a CommonsValidator instance and attach it to the associated component.

Finally, the third <tag> element tells facelets to also invoke a TagHandler when it encounters a validatorVar tag. This handler needs to expose the name/value pair in the current FaceletContext. The CommonsValidatorHandler will subsequently apply the variable(s) to the CommonsValidator it creates.

CommonsValidatorHandler

package net.genschaw.jsf.facelets;

import java.io.IOException;
import java.util.Map;

import javax.el.ValueExpression;
import javax.faces.component.EditableValueHolder;
import javax.faces.component.UIComponent;
import javax.faces.validator.Validator;

import org.apache.shale.validator.CommonsValidator;

import com.sun.facelets.FaceletContext;
import com.sun.facelets.tag.MetaRuleset;
import com.sun.facelets.tag.MetaTagHandler;
import com.sun.facelets.tag.Metadata;
import com.sun.facelets.tag.TagAttribute;
import com.sun.facelets.tag.TagConfig;
import com.sun.facelets.tag.TagException;

/**
 * Facelets TagHandler for "commonsValidator" tag.
 * 
 * @author Shane Genschaw
 */
public class CommonsValidatorHandler extends MetaTagHandler {
 
 /**
  * Set validatorVar tag variables on commons validator.
  * 
  * @see com.sun.facelets.tag.Metadata
  */
 public static class ValidatorVarMetadata extends Metadata {
  
  /**
   * @see com.sun.facelets.tag.Metadata#applyMetadata(com.sun.facelets.FaceletContext, java.lang.Object)
   */
  @SuppressWarnings("unchecked")
  public void applyMetadata(FaceletContext ctx, Object instance) {
   Map validatorVars = (Map) ctx.getAttribute(CommonsValidatorVarHandler.KEY);
   if (null != validatorVars) {
    CommonsValidator v = (CommonsValidator) instance;
    v.getVars().putAll(validatorVars);
    ctx.setAttribute(CommonsValidatorVarHandler.KEY, null);
   }
  }
 }

 private final TagAttribute binding;

 private String validatorId = "org.apache.shale.CommonsValidator";

 /**
  * @param config
  */
 public CommonsValidatorHandler(TagConfig config) {
  super(config);
  this.binding = this.getAttribute("binding");
 }

 /**
  * @see com.sun.facelets.FaceletHandler#apply(com.sun.facelets.FaceletContext,
  *      javax.faces.component.UIComponent)
  */
 public void apply(FaceletContext ctx, UIComponent parent)
   throws IOException {
  if (parent == null || !(parent instanceof EditableValueHolder)) {
   throw new TagException(this.tag,
     "Parent not an instance of EditableValueHolder: " + parent);
  }

  // process validatorVar tag(s), if present
  if (nextHandler != null) {
   nextHandler.apply(ctx, parent);
  }

  // only process if it's been created
  if (parent.getParent() == null) {
   // cast to a ValueHolder
   EditableValueHolder evh = (EditableValueHolder) parent;
   ValueExpression ve = null;
   Validator v = null;
   if (this.binding != null) {
    ve = this.binding.getValueExpression(ctx, Validator.class);
    v = (Validator) ve.getValue(ctx);
   }
   if (v == null) {
    v = this.createValidator(ctx);
    if (ve != null) {
     ve.setValue(ctx, v);
    }
   }
   if (v == null) {
    throw new TagException(this.tag, "No Validator was created");
   }
   this.setAttributes(ctx, v);
   evh.addValidator(v);
  }
 }

 protected Validator createValidator(FaceletContext ctx) {
  if (this.validatorId == null) {
   throw new TagException(
     this.tag,
     "Default behavior invoked of requiring a validator-id "
       + "passed in the constructor, must override ValidateHandler(ValidatorConfig)");
  }
  return ctx.getFacesContext().getApplication().createValidator(
    this.validatorId);
 }

 // alias the minlength and maxlength attributes
 @SuppressWarnings("unchecked")
 protected MetaRuleset createMetaRuleset(Class type) {
  MetaRuleset metaRuleset = super.createMetaRuleset(type).ignore(
    "binding").alias("minlength", "minLength").alias("maxlength",
    "maxLength").add(new ValidatorVarMetadata());

  return metaRuleset;
 }

}

CommonsValidatorVarHandler

package net.genschaw.jsf.facelets;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import javax.el.ValueExpression;
import javax.faces.component.UIComponent;

import com.sun.facelets.FaceletContext;
import com.sun.facelets.tag.TagAttribute;
import com.sun.facelets.tag.TagConfig;
import com.sun.facelets.tag.TagHandler;

/**
 * Facelets TagHandler for "validatorVar" tag.
 * 
 * @author Shane Genschaw
 */
public class CommonsValidatorVarHandler extends TagHandler {
 
 /** Key under which variable map is stored in FaceletContext. */
 public static final String KEY = "validatorVars";

 // possible attributes
 private final TagAttribute name;
 private final TagAttribute value;

 /**
  * @param config
  */
 public CommonsValidatorVarHandler(TagConfig config) {
  super(config);
  this.name = getRequiredAttribute("name");
  this.value = getRequiredAttribute("value");
 }

 /**
  * @see com.sun.facelets.FaceletHandler#apply(com.sun.facelets.FaceletContext,
  *      javax.faces.component.UIComponent)
  */
 @SuppressWarnings("unchecked")
 public void apply(FaceletContext ctx, UIComponent parent)
   throws IOException {
  String nameStr = this.name.getValue(ctx);
  ValueExpression veObj = this.value
    .getValueExpression(ctx, Object.class);
  if (null != veObj) {
   Map validatorVars = (Map) ctx.getAttribute(KEY);
   if (null == validatorVars) {
    validatorVars = new HashMap();
    ctx.setAttribute(KEY, validatorVars);
   }
   validatorVars.put(nameStr, veObj.getExpressionString());
  }
 }

}

The last step is to add a configuration parameter in your web.xml file to tell facelets to load you're new taglib.

<context-param>
    <param-name>facelets.LIBRARIES</param-name>
    <param-value>/WEB-INF/shale-validator.taglib.xml</param-value>
</context-param>

Additional Resources

Genschaw's Tech Blog

Thursday, May 8, 2008

Using shale commons-validator with facelets

shale-validator-taglib.xml

CommonsValidatorHandler

CommonsValidatorVarHandler

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