JSF 2.2 Tip of the Day: Using Hibernate Validators with JSF

Introduction

Hibernate validators offer a plethora of validators to make your development work much easier. Some of the common ones that are used are @NotNull, @NotBlank, and @NotEmpty. To take advantage of these validators, and avoid some misconceptions, a little information needs to be provided.

@NotNull

Everyone likes this particular annotation, and it can be a real life saver. However something that often catches developers using it on JSF is that JSF treats empty form fields as empty strings. This is not the same as null. So if you want JSF to capture these values and treat them as null values, you need to tell JSF to do so. This is accomplished by adding the following context parameter to the web.xml file.

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<context-param>      <param-name>javax.faces.INTERPRET_EMPTY_STRING_SUBMITTED_VALUES_AS_NULL</param-name>      <param-value>true</param-value> </context-param>

Once this is added to the context, all blanks will be treated as null values. Be mindful of any side effects created from this change.

@NotEmpty

This validator causes a lot of confusion. The value can not be null, but can be any character including whitespace, e.g. You can enter a space, and it will accept it.

@NotEmpty

This is the most useful annotation from my standpoint. This makes sure that the input is not null, and is not an empty string like white spaces. This is really what I think most developers are really after anyway. They want to make sure that users fill in form fields.

Code

The code for this project can be found on Github, and includes some additional bonus code such as using locales, and custom messages. The code can be found here: jsf-hibernate-validator.

JSF 2.2 Tip of the Day: Using ValueExpressions and VariableMapper to set EL using a PhaseListener

The title seems like a mouthful, and it is. I had some code which I used to demonstrate how to set EL values using a PhaseListener. I was going to delete the code when I decided that it was the second time someone in a short span of time asked me the same question, and I should post how to do it.

The use of a PhaseListener to set EL values seems to the casual observer like Voodoo magic. You will see the EL expressions on the page, and they magically seem to populate. In some ways it is like a classical interceptor which can make your code really seem magical, and lead to confusion. This approach though has its place, and if used correctly can solve a lot of issues. One example is determining if a <ui:include src="XXX" rendered="#{EL_VARIABLE_HERE}" /> should render.

It can also be used to set the src value on the fly. An always popular question on how to resolve.

The project can be found on GitHub here: jsf-ve-phaselistener

So the output looks like a nice set of name value pairs using the Greek alphabet as variable names.

Google Guava IP and Hostname Validation

I was trying to come up with a way to validate hostnames and IP addresses. I didn't want to spend time trying to do it myself. I figured that this should be a common situation, and likely someone had already written a tool to do just such a thing. I was right. Google Guava has a couple of interesting classes that do exactly what I was looking for.

For folks who may not be familiar with Guava, it is a framework of really helpful utilities that can be used for a variety of situations. Most folks who use Guava in my experience use the collections classes. However, there is a boon for anyone who digs a little deeper.

We will use two specific classes from the Guava framework to do our validations. The first is InternetDomainName which is used to validate the domain name. The other is InetAddresses to check our IP address for validity.

There are some caveats to the InternetDomainName class which are explained here: InternetDomainNameExplained.

In the code below, we see that it is very easy to use and it works very well.

	/*
	* Copyright 2015-2016 Blue Lotus Software, LLC.
	*
	* 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 com.bluelotussoftware.example;
	import com.google.common.net.InetAddresses;
	import com.google.common.net.InternetDomainName;
	import java.text.MessageFormat;
	/**
	*
	* @author John Yeary <jyeary@bluelotussoftware.com>
	* @version 1.0
	*/
	public class HostIPValidation {
	public static void main(String[] args) {
	String hostname = "www.bluelotussoftware.com";
	boolean result = InternetDomainName.isValid(hostname);
	System.out.println(MessageFormat.format("Is Internet Domain Name: {0} valid? {1}", hostname, result));
	hostname = "bluelotussoftware.com";
	result = InternetDomainName.isValid(hostname);
	System.out.println(MessageFormat.format("Is Internet Domain Name: {0} valid? {1}", hostname, result));
	hostname = "bluelotussoftware";
	result = InternetDomainName.isValid(hostname);
	System.out.println(MessageFormat.format("Is Internet Domain Name: {0} valid? {1}", hostname, result));
	hostname = "256.0.0.0";
	result = InternetDomainName.isValid(hostname);
	System.out.println(MessageFormat.format("Is Internet Domain Name: {0} valid? {1}", hostname, result));
	result = InetAddresses.isInetAddress(hostname);
	System.out.println(MessageFormat.format("Is Internet Address: {0} valid? {1}", hostname, result));
	hostname = "255.255.255.0";
	result = InternetDomainName.isValid(hostname);
	System.out.println(MessageFormat.format("Is Internet Domain Name: {0} valid? {1}", hostname, result));
	result = InetAddresses.isInetAddress(hostname);
	System.out.println(MessageFormat.format("Is Internet Address: {0} valid? {1}", hostname, result));
	hostname = "_xyz.bluelotussoftware.com";
	result = InternetDomainName.isValid(hostname);
	System.out.println(MessageFormat.format("Is Internet Domain Name: {0} valid? {1}", hostname, result));
	}
	}

view raw HostIPValidation.java hosted with ❤ by GitHub

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Is Internet Domain Name: www.bluelotussoftware.com valid? true Is Internet Domain Name: bluelotussoftware.com valid? true Is Internet Domain Name: bluelotussoftware valid? true Is Internet Domain Name: 256.0.0.0 valid? false Is Internet Address: 256.0.0.0 valid? false Is Internet Domain Name: 255.255.255.0 valid? false Is Internet Address: 255.255.255.0 valid? true Is Internet Domain Name: _xyz.bluelotussoftware.com valid? false