Nikos Maravitsas

About Nikos Maravitsas

Nikos has graduated from the Department of Informatics and Telecommunications of The National and Kapodistrian University of Athens. Currently, his main interests are system’s security, parallel systems, artificial intelligence, operating systems, system programming, telecommunications, web applications, human – machine interaction and mobile development.

Validate HTML Tag with Java Regular Expression example

In this tutorial we are going to see how to validate HTML Tag format. In general, validating HTML with regular expressions in not the optimal method. You should use an HTML parser for that matter. But when you want to validate the basic HTML format, quickly in your application, Regular Expressions will do. So the basic policy of HTML tags format.

So this is the regular expression we are going to use for 12 hours format validation:
 
 
 
 

<(\"[^\"]*\"|'[^']*'|[^'\">])*>

You can take a look at the Pattern class documentation to learn how to construct your own regular expressions according to your policy.

1. Validator clas.

This is the class that we are going to use for HTML tag format validation.

HtmlTagValidator.java:

package com.javacodegeeks.java.core;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class HtmlTagValidator{
 
   private Pattern pattern;
   private Matcher matcher;
 
   private static final String HTML_TAG_FORMAT_PATTERN = "<(\"[^\"]*\"|'[^']*'|[^'\">])*>";
 
   public HtmlTagValidator(){
	  pattern = Pattern.compile(HTML_TAG_FORMAT_PATTERN);
   }
 
 
  public boolean validate(final String tag){
 
	  matcher = pattern.matcher(tag);
	  return matcher.matches();
 
  }
}

2. Unit Testing our HtmlTagValidator class

For unit testing we are going to use JUnit. Unit testing is very important in these situations because they provide good feedback about the correctness of our regular expressions. You can test your program and reassure that your regular expression meets the rules on your policy about the form of HTML Tag format.

This is a basic test class:

HtmlTagValidatorTest.java:

package com.javacodegeeks.java.core;

import static org.junit.Assert.*;

import java.util.Arrays;
import java.util.Collection;

import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class HtmlTagValidatorTest {

	private String arg;
	private static HtmlTagValidator htmlTagValidator;
	private Boolean expectedValidation;

	public HtmlTagValidatorTest(String str, Boolean expectedValidation) {
		this.arg = str;
		this.expectedValidation = expectedValidation;
	}

	@BeforeClass
	public static void initialize() {
		htmlTagValidator = new HtmlTagValidator();
	}

	@Parameters
	public static Collection<Object[]> data() {
		Object[][] data = new Object[][] {
				{ "<'br />", false },              // wrong format
				{ "img src=\"ar.jpg\">" , false }, // wrong format
				{ "<input => />", false },         // wrong format
								
				
				{ "<br />", true },                         
				{ "<img src=\"a.png\" />", true },
				{ "</a>", true } };
		    
		return Arrays.asList(data);
	}
	
	@Test
	public void test() {
		Boolean res = htmlTagValidator.validate(this.arg);
		String validv = (res) ? "valid" : "invalid";
		System.out.println("HTML tag Format "+arg+ " is " + validv);
		assertEquals("Result", this.expectedValidation, res);

	}

}

Output:

HTML tag Format <'br /> is invalid
HTML tag Format img src="ar.jpg"> is invalid
HTML tag Format <input => /> is invalid
HTML tag Format <br /> is valid
HTML tag Format <img src="a.png" /> is valid
HTML tag Format </a> is valid

 
This was an exampl on how to validate date format with Java Regular Expression.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you two of our best selling eBooks for FREE!

JPA Mini Book

Learn how to leverage the power of JPA in order to create robust and flexible Java applications. With this Mini Book, you will get introduced to JPA and smoothly transition to more advanced concepts.

JVM Troubleshooting Guide

The Java virtual machine is really the foundation of any Java EE platform. Learn how to master it with this advanced guide!

Given email address is already subscribed, thank you!
Oops. Something went wrong. Please try again later.
Please provide a valid email address.
Thank you, your sign-up request was successful! Please check your e-mail inbox.
Please complete the CAPTCHA.
Please fill in the required fields.
Examples Java Code Geeks and all content copyright © 2010-2014, Exelixis Media Ltd | Terms of Use | Privacy Policy
All trademarks and registered trademarks appearing on Examples Java Code Geeks are the property of their respective owners.
Java is a trademark or registered trademark of Oracle Corporation in the United States and other countries.
Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation.
Do you want to know how to develop your skillset and become a ...
Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you two of our best selling eBooks for FREE!

Get ready to Rock!
You can download the complementary eBooks using the links below:
Close