Struts, Hibernate and Spring_ a Guide to Creating a Dynamic Web Application

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Struts, Hibernate and Spring: A guide to creating a dynamic web application

By: Christopher Moeller

Abstract: A tutorial which uses the Struts, Hibernate and Spring frameworks to create a complete website registration page.

Note: This tutorial does not necessarily require the use of an IDE, but explanations (in green) will be provided that assumethe use of the JBuilder IDE (version 2006 or prior). This document assumes basic knowledge of Java and web applications.

I. Creating a project

Using JBuilder, complete the following steps to setup a project in the IDE:

1. Create a new project in JBuilder with a unique name. (e.g. StrtusTutorial.jpx).2. Set the server for the project in the 'Project Properties' to Tomcat 5.5.3. Create a new web module with a unique name (e.g. StrutsTutorial) -- by default, this will determine

the name of the WAR file that will be eventually created. Then, choose 'Servlet 2.4' and 'JSP 2.0'standards (Step 2 of 3). Next, make sure to check 'Struts 1.2' and 'Validation' (Step 3 of 3). Finally,click finish.

Now, let's take stock of our project. You should have a directory under your project with a name that matches your web modulename. In that directory you will have only a WEB-INF folder. Within that folder you will have several (xml and tdl) files, like so:

<Web Module>

WEB-INF

strtus-config.xml

validation.xml

validation-rules.xml

web.xml

struts-bean.tld

struts-html.tld

struts-logic.tld

struts-nested.tld

struts-tiles.tld

The .tld files are located within the struts JAR files. JBuilder automatically copies them to your web module's WEB-INF folder after youselected the Struts framework during the web module wizard. If you are not using JBuilder or an IDE, you will need to downloadStruts 1.2, and then open the struts.jar using WinZip (or other unarchiving tool), find the.tld files (usually under Struts.jar/META-INF/tlds), and extract them to your <web module>/WEB-INF folder.

The xml files are provided below:

struts-config.xml:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD StrutsConfiguration 1.2//EN" "http://struts.apache.org/dtds/struts-config_1_2.dtd">

<struts-config><message-resources parameter="ApplicationResources" /><plug-in className="org.apache.struts.validator.ValidatorPlugIn"><set-property property="pathnames" value="/WEB-INF/validator-rules.xml,/WEB-INF/validation.xml" /></plug-in></struts-config>

Note: The struts-config.xml file is the configuration file that defines the flow in Struts webapplications. This configuration file defines data sources (parameters needed to use JDBC objects),form beans (mappings/definitions for beans that hold information that has been submitted by theuser from a web form), forwards (mappings that provide an easy way to send the user to aspecified page depending on business logic) and actions (mapping to an object that handlesbusiness logic).

validation.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE form-validation PUBLIC "-//Apache Software Foundation//DTD CommonsValidator Rules Configuration 1.1.3//EN""http://jakarta.apache.org/commons/dtds/validator_1_1_3.dtd">

<form-validation />

Note: The validator.xml defines specific validations which apply to form beans.

validation-rules.xml

<!DOCTYPE form-validation PUBLIC"-//Apache Software Foundation//DTD Commons Validator Rules Configuration1.1.3//EN"

I. Creating a project

II. Creating anApplicationResource.propertiesfile.

III. Implementing a registrationpage.

IV. Setting up the database andcreating the a table for registeredusers.

V. Creating the user class

VI. Configuring Hibernate

VII. Adding Struts, Hibernate andSpring libraries

VIII. Configuring Spring

IX. Validation

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# Struts Validator Error Messageserrors.required={0} is required.errors.minlength={0} can not be less than {1} characters.errors.maxlength={0} can not be greater than {1} characters.errors.invalid={0} is invalid.

errors.byte={0} must be a byte.errors.short={0} must be a short.errors.integer={0} must be an integer.errors.long={0} must be a long.errors.float={0} must be a float.errors.double={0} must be a double.

errors.date={0} is not a date.errors.range={0} is not in the range {1} through {2}.errors.creditcard={0} is an invalid credit card number.errors.email={0} is an invalid e-mail address.

Note: Starting in Struts 1.2.0 the default javascript definitions havebeen consolidated to commons-validator. The default can be overriddenby supplying a <javascript> element with a CDATA section, just asin struts 1.1.

-->

<form-validation>

<global>

<validator name="required"classname="org.apache.struts.validator.FieldChecks"method="validateRequired"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"msg="errors.required"/>

<validator name="requiredif"classname="org.apache.struts.validator.FieldChecks"method="validateRequiredIf"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,org.apache.commons.validator.Validator,javax.servlet.http.HttpServletRequest"msg="errors.required"/>

<validator name="validwhen"msg="errors.required"classname="org.apache.struts.validator.validwhen.ValidWhen"method="validateValidWhen"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,org.apache.commons.validator.Validator,javax.servlet.http.HttpServletRequest"/>

<validator name="minlength"classname="org.apache.struts.validator.FieldChecks"method="validateMinLength"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.minlength"jsFunction="org.apache.commons.validator.javascript.validateMinLength"/>

<validator name="maxlength"classname="org.apache.struts.validator.FieldChecks"method="validateMaxLength"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.maxlength"jsFunction="org.apache.commons.validator.javascript.validateMaxLength"/>

<validator name="mask"classname="org.apache.struts.validator.FieldChecks"method="validateMask"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.invalid"/>

<validator name="byte"classname="org.apache.struts.validator.FieldChecks"method="validateByte"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.byte"jsFunctionName="ByteValidations"/>



jsFunctionName="IntegerValidations"/>

<validator name="long"classname="org.apache.struts.validator.FieldChecks"method="validateLong"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.long"/>

<validator name="float"classname="org.apache.struts.validator.FieldChecks"method="validateFloat"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.float"jsFunctionName="FloatValidations"/>

<validator name="double"classname="org.apache.struts.validator.FieldChecks"method="validateDouble"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.double"/>

<validator name="date"classname="org.apache.struts.validator.FieldChecks"method="validateDate"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.date"jsFunctionName="DateValidations"/>

<validator name="intRange"classname="org.apache.struts.validator.FieldChecks"method="validateIntRange"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends="integer"msg="errors.range"/>

<validator name="floatRange"classname="org.apache.struts.validator.FieldChecks"method="validateFloatRange"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends="float"msg="errors.range"/>

<validator name="creditCard"classname="org.apache.struts.validator.FieldChecks"method="validateCreditCard"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.creditcard"/>

<validator name="email"classname="org.apache.struts.validator.FieldChecks"method="validateEmail"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.email"/>

<validator name="url"classname="org.apache.struts.validator.FieldChecks"method="validateUrl"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"depends=""msg="errors.url"/>

<hibernate-configuration><session-factory><property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property><property name="hibernate.connection.url">jdbc:mysql://localhost/tutorial</property><property name="hibernate.connection.username">root</property><property name="hibernate.connection.password"></property><property name="hibernate.connection.pool_size">10</property><property name="show_sql">true</property><property name="dialect">org.hibernate.dialect.MySQLDialect</property><property name="hibernate.hbm2ddl.auto">update</property><propertyname="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</property><property name="hibernate.cache.use_query_cache">true</property><property name="hibernate.jdbc.batch_size">20</property><property name="hibernate.cglib.use_reflection_optimizer">true</property><mapping resource="user.hbm.xml"/></session-factory></hibernate-configuration>

You may wonder, how does our hibernate.cfg.xml get read in by our application? The answer is through implementation of ahibernate plug-in class. A default class can be used, but it is often useful to have access to a custom implementation.We shall use thefollowing simple implementation:

HibernatePlugin.java:

package com.codesoup.archangel.hibernate;

import java.net.URL;import javax.servlet.ServletException;

import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.apache.struts.action.ActionServlet;import org.apache.struts.action.PlugIn;import org.apache.struts.config.ModuleConfig;import org.hibernate.cfg.*;import org.hibernate.*;

public class HibernatePlugin implements PlugIn{private Configuration config;private SessionFactory factory;private String path = "/hibernate.cfg.xml";private static Class hpclass = HibernatePlugin.class;public static final String KEY_NAME = hpclass.getName();private static Log log = LogFactory.getLog(hpclass);

public void setPath(String path) { this.path = path; }

public void init(ActionServlet servlet, ModuleConfig modConfig) throws ServletException{try{URL url = HibernatePlugin.class.getResource(path);config = new Configuration().configure(url);factory = config.buildSessionFactory();servlet.getServletContext().setAttribute(KEY_NAME, factory);}catch (MappingException e){log.error("Mapping errors:", e);String[] messages = e.getMessages();for (int i = 0; i < messages.length; i++)log.error(messages[i], e);throw new ServletException();}catch (HibernateException e){log.error("Hibernate errors:", e);String[] errors = e.getMessages();for (int i = 0; i < errors.length; i++)log.error(errors[i], e);

throw new ServletException();}}



</form-bean></form-beans><action-mappings><action input="/register1.jsp" name="registerActionForm" path="/registerAction" scope="session"type="com.tutorial.struts.action.RegisterAction" validate="yes"><forward name="register" path="/register1.jsp" /><forward name="login" path="/login.jsp" /></action></action-mappings><message-resources parameter="ApplicationResources" /><plug-in className="org.apache.struts.validator.ValidatorPlugIn"><set-property property="pathnames" value="/WEB-INF/validator-rules.xml,/WEB-INF/validation.xml" /></plug-in><plug-in className="com.tutorial.hibernate.HibernatePlugin"><set-property property="path" value="/hibernate.cfg.xml" /></plug-in></struts-config>

Now, let us create the file which Hibernate uses to map the properties in the user class to the corresponding columns in thedatabase. This file will also be placed in the root of the source folder.

user.hbm.xml:

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.tutorial.beans.User" table="users"><id name="id" type="long" column="id" ><generator class="increment"/></id><property name="email"><column name="email"/></property><property name="password"><column name="password"/></property></class></hibernate-mapping>

In order to make the xml files [or other file types] appear in JBuilder (within the Project Pane), open Project Properties |Build | Resource | scroll down and select 'xml' | and select the 'Copy' radio button | OK. Double-clicking on the file in theProject Pane will open it in the Editor.

VII. Adding Struts, Hibernate and Spring librariesFor development purposes, it is a good idea to add all required libraries and their dependancies to the classpath, even if they arecurrently not explicitly needed by your application. Look in the extracted download directory for each of the third-party frameworksand add references to all of the necessary JARs. How will you know exactly what to add? Well, the first rule is more is better thanless. Take Hibernate for example, there should be a hibernate3.jar sitting in the main Hibernate folder, so make sure to grab that.Then you will need all of the libraries that hibernate3.jar depends on. Luckly they provide all of those in the .../hibernate/lib folder, sograb all of those files as well.

At this point, it would be a good idea to take a moment to compile and perform a test run of the application. If all of the pieces are inplace, and all of the required libraries are available, the project should work without throwing any exceptions.

Later we will work on adding custom code to our RegisterAction class to make it use the values submitted by the client using the webform to perform custom validation, and then if all goes well, post the new registeree through a database transaction using Spring.

Troubleshooting:Issue:

You receive the following message either during compilation, or later when Tomcat is starting up:

log4j:WARN No appenders could be found for logger (org.apache.commons.digester.Digester.sax).

Solution:

There are at least two ways:

a. If you want to modify Tomcat in general to resolve this issue (this will affect all webapps running inTomcat):

The solution is the following:

Place both log4j.jar and the Jakarta commons-logging.jar here:

$TOMCAT_HOME/common/lib directory.

Next, create your log4j properties file here:

$TOMCAT_HOME/common/classes/log4j.properties

b. If you want to resolve this issue only for your particular application (e.g. if you are using Tomcat insideJBuilder):

The solution is the following:

Make sure that a version of log4j.jar and the Jakarta commons-logging.jar are onyour classpath:

Next, place a log4j properties file in the root of your source tree.

Here is a sample log4j.properties file, which you can use right away. Note that the log4j.rootLogger is set todebug. This will help you troubleshoot subtle problems immediately, though you may wich to change thisvalue to info, once your application is working and stable.

### standard log4j.properties file to control logging output ###

### direct log messages to stdout ###log4j.appender.stdout=org.apache.log4j.ConsoleAppenderlog4j.appender.stdout.Target=System.outlog4j.appender.stdout.layout=org.apache.log4j.PatternLayoutlog4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p%c{1}:%L - %m%n



#log4j.logger.org.hibernate.cache=info

### log transaction activity#log4j.logger.org.hibernate.transaction=debug

### log JDBC resource acquisition#log4j.logger.org.hibernate.jdbc=debug

### enable the following line if you want to track down connection ###### leakages when using DriverManagerConnectionProvider ####log4j.logger.org.hibernate.connection.DriverManagerConnectionProvider=trace

Issue:

If you run your application in JBuilder and receive the following log message [Note:you must enable logging to see this message -- see above]:

07:53:32,637 ERROR HibernatePlugin:36 - Mapping errors:org.hibernate.MappingException: Could not read mappings from resource:user.hbm.xml

Solution:

After compiling your project, look in your module directory for your User class (e.g..../<StrutsTutorial>/<WEB-INF>/classes/com/tutorial/beans/User.class). If youdon't see it, then in JBuilder right-click on your web module | Properties | Content |and uncheck 'Only include module specific Java classes'. Then just recompile yourproject and retest.

VIII. Configuring SpringThe first thing you will need to create is an xml file that will provide a definition to allow Spring to create a User bean for us. These xml file allow usto define a simple and consistent way of creating a namespace of JavaBeans objects which will be managed by a Spring BeanFactory. This ishandy because then it is quite easy to save our new user into the database (i.e. no SQL needed).

So, create the following file in the root of your source tree:

user.xml:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd"><beans><bean id="user" class="com.tutorial.beans.User"></bean></beans>

Now let's take a look at an updated version of our RegisterAction.java class, which is provided in its entirty below:

RegisterAction.java:

package com.tutorial.struts.action;

import javax.servlet.http.*;import org.apache.commons.logging.*;import org.apache.commons.validator.*;import org.apache.struts.*;import org.apache.struts.action.*;import org.apache.struts.validator.*;import org.hibernate.*;import org.hibernate.criterion.*;import org.springframework.beans.factory.*;import org.springframework.beans.factory.xml.*;import org.springframework.core.io.*;import com.tutorial.beans.*;import com.tutorial.hibernate.*;

public class RegisterAction extends Action{

private static Class thisClass = RegisterAction.class;private static Log log = LogFactory.getLog(thisClass);

/*Method checks to see if password and verify password match, if not return false*/private boolean isValidPassword(HttpServletRequest request, String password, Stringverify_password){

boolean valid = false;if (password.matches(verify_password)) { valid = true; }return valid;

}

/*Method checks database for email and returns false if it already exists*/private boolean isUniqueEmail(Session session, HttpServletRequest request, String email){

boolean result = true; // assume that it isCriteria criteria = session.createCriteria(User.class);criteria.add(Expression.eq("email", email));criteria.setMaxResults(1);User duplicate = (User)criteria.uniqueResult();if (duplicate != null){

if (duplicate.getEmail().matches(email)){

result = false; // set to false when we find the same emailin the database

}



}

/*** Save the specified error messages keys into the appropriate request* attribute for use by the <html:errors> tag, if any messages* are required. Otherwise, ensure that the request attribute is not* created.** @param request The servlet request we are processing* @param errors Error messages object*/protected void saveErrors(HttpServletRequest request, ActionMessages errors){

// Remove any error messages attribute if none are requiredif ((errors == null) || errors.isEmpty()){

request.removeAttribute(Globals.ERROR_KEY);return;

}// Save the error messages we needrequest.setAttribute(Globals.ERROR_KEY, errors);

}

public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequestrequest, HttpServletResponse response){

String forward = "register";SessionFactory sessionFactory = (SessionFactory)servlet.getServletContext().getAttribute(HibernatePlugin.KEY_NAME);Session session = sessionFactory.openSession();DynaValidatorActionForm dform = (DynaValidatorActionForm) form;ActionMessages errors = dform.validate(mapping, request);if (errors.isEmpty()){

try{

if (!isValidPassword(request, (String)dform.get("password"), (String)dform.get("verify_password"))){

errors.add(Globals.ERROR_KEY, newActionMessage("errors.passwords.different"));

}else if (!isUniqueEmail(session, request, (String)dform.get("email"))){

errors.add(Globals.ERROR_KEY, newActionMessage("errors.email.found"));

}else{

registerUser(session, request, dform);forward = "success";

}

}catch (Exception e) { e.printStackTrace(); }finally{

session.flush();session.close();

}

}saveErrors(request, errors);return mapping.findForward(forward);

}

}

Let's look at a few methods in this class:

RegisterAction.execute(...):

This method first creates a Hibernate session using the plug-in class we provided. The sessionobject is what we will use to create custom queries against the database. Next, we create aDynaValidatorActionForm class and cast the ActionForm object that is passed into this methodinto it. Then we use the DynaValidatorActionForm to create an instance of our ActionMessagesclass, which we use to keep track of any validation errors. We check to see if there are anyerrors already existing and if so, we forward the user back to the register page to resolvethose problems. If there are no errors, then we need to perform two other customervalidations before we register this new user by adding them to the database. The first thing weneed to check is if the 'password' field matches the 'validate_password' field, we do this withisValidPassword(...). If it not valid, we add an error message 'errors.passwords.different' thatrefers back to the ApplicationResources.properties. So if the password was valid, we thencheck to make sure that the submitted email is unique (i.e. there should never be two userswith the same e-mail) by calling isUniqueEmail(...). If it is not a unique e-mail, then we add an



Now, at this point, you should be able to run the application, open the register.jsp in a browser, add and e-mail address, password, (matching)verify password and click 'submit' to add the row to the users table in the database. If you have a way to view the database data directly, youshould see a new row with your submitted information.

In JBuilder, you can open the Database Pilot to view the row you added (Tools | Database Pilot | expand'mysql://localhost/tutorial' | expand 'Tables' | expand 'users' | and click on the 'Data' tab.

IX. ValidationI promised earlier to return to the subject of validation, so here we go. Nearly all of the elements are in place to start implementing validation, wejust need to provide a more detailed validation.xml. Lets look at an updated version:

validation.xml:

<?xml version="1.0" encoding="ISO-8859-1" ?><!DOCTYPE form-validation PUBLIC"-//Apache Software Foundation//DTD Commons Validator Rules Configuration 1.0//EN""http://jakarta.apache.org/commons/dtds/validator_1_0.dtd"><form-validation><formset><form name="/registerAction"><fieldproperty="email"depends="required,email"><arg0 key="label.email"/></field><fieldproperty="password"depends="required,minlength,maxlength"><arg0 key="label.password"/><arg1name="minlength"key="${var:minlength}"resource="false"/><var><var-name>minlength</var-name><var-value>8</var-value></var><arg2name="maxlength"key="${var:maxlength}"resource="false"/><var><var-name>maxlength</var-name><var-value>36</var-value></var></field><fieldproperty="verify_password"depends="required,minlength,maxlength"><arg0 key="label.verify_password"/><arg1name="minlength"key="${var:minlength}"resource="false"/><var><var-name>minlength</var-name><var-value>8</var-value></var><arg2name="maxlength"key="${var:maxlength}"resource="false"/><var><var-name>maxlength</var-name><var-value>36</var-value></var></field></form></formset></form-validation>

Let's look at this file in more detail:

<form-validation><formset>

<form name="/registerAction">

...

</form>

</formset></form-validation>

The above form tag (in bold) indicates which JSP form is being validated. You can add more form tags underthe formset tag as you create new actions.

<fieldproperty="email"depends="required,email"><arg0 key="label.email"/></field>

The above field tag is used to describe how the e-mail field should be validated. The depends attribute listswhich particular rules found in the validator-rules.xml should be enforced for this field. In this case, we seethat required and email rules are used. Let take a moment and examine the relevant part of the associatedvalidator-rules.xml:

<validator name="required"classname="org.apache.struts.validator.FieldChecks"method="validateRequired"methodParams="java.lang.Object,org.apache.commons.validator.ValidatorAction,org.apache.commons.validator.Field,org.apache.struts.action.ActionMessages,javax.servlet.http.HttpServletRequest"msg="errors.required"/>



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<arg2name="maxlength"key="${var:maxlength}"resource="false"/><var><var-name>maxlength</var-name><var-value>36</var-value></var></field>

I did not mention the arg0 attribute in the last discussion of email, so lets talk about it now. Thearg0 attribute replaces the {0} found in the ApplicationResources.properties file under the textvalues for errors.required, errors.minlength, and errors.maxlength with the text value underlabel.password. That sounds more complicated that it really is. Really we just want to find a wayto be able to resource all our strings (including validation error messages) back to theApplicationResources.properties file (or a region specific one). When you see an arg1, or arg2attribute, then these would replace a {1} or {2} respectively, and so on.

Remember how we used the following in our register.jsp as a quick and dirty way to display validation errors?

<html:errors/>

Well, now we have a chance to improve on it. Replace the above with what is shown below:

<%-- Improved error display --%><logic:messagesPresent><ul class="error"><html:messages id="error"><li style="color: red;"><bean:write name="error"/></li></html:messages></ul></logic:messagesPresent>

You may be asking, why take something that was simple and do the same thing in a more complicated way? Well, the above will allow us morecontrol over the display of the errors (e.g. carriage returns and color).

Now when you run this application, you should get errors displayed in red when you submit the form without having the fields correct filled out.

Now that validation has been introduced, this tutorial should provide enough information to get you started working with Struts, Spring andHibernate. This concludes this tutorial.

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Struts, Hibernate and Spring_ a Guide to Creating a Dynamic Web Application