Weblogic Authors: Yeshim Deniz, Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Weblogic

Weblogic: Article

Struts and J2EE

Struts and J2EE

Struts is a framework provided by Apache, designed to handle the presentation layer of your J2EE applications. The J2EE blueprints recommend that you use a Model 2 approach for your presentation layer, and Struts does just that for you. It doesn't try to re-create what is already available, nor is it unnecessarily complex. In fact, it leverages other J2EE technologies you may already know, like servlets, JSP, and JavaBeans, to provide a flexible presentation layer at a minimal cost. Best of all, when you write an application with Struts you'll find that it is easy to maintain and easy to extend because you used a framework rather than just hacking out tons of completely unrelated JSP pages.

The Model 2 pattern, also known as the model, view, controller (MVC) pattern, consists of three components (see Figure 1). The first is a "model," which is an object that represents your data and the state of your application; this object has no need for any logic, it just contains data. The second component is a "view," which is simply a presentation of the data to the user. The view does not change the data directly; it marshals data from the model to the user interface, or it sends user input to the controller. The controller is usually the most complex component of the three. It is responsible for receiving input from the user interface (UI), and for changing the data in the model. Beyond that the controller is where your logic resides, and can control many aspects of an application based on the model data and the user input.

If this paradigm isn't clear to you or seems a bit complex, just read on. In the next few paragraphs you'll see that it's really quite simple. Our example will be a simple form to change a password written with Struts.

Let's start with the model. The Struts component that implements a model is the ActionForm (see Listing 1). It's just a JavaBean with two additional methods. The first is the validate method, which performs simple validation on the data such as the string comparisons, or checking for required values here. The reset method initializes your form.

You may have noticed that over half the code in this simple three-variable form consists of accessors (getter methods) and mutators (setter methods). Struts 1.1 contains features that can help you rid yourself of this redundant code. Instead of extending ActionForm, just extend DynaActionForm. The DynaActionForm contains getters and setters for your data in the form of get(String) and set(String, Object). DynaActionForm also inherits the reset() and validate() methods so you can simply code them normally.

If you want to get rid of your ActionForm class altogether, Struts 1.1 contains a validator plug-in that will allow you to map validation rules to fields via XML configuration files. You can use predefined rules provided by Struts, or even write your own. The validator is actually from the Apache commons project, and was pulled into Struts to satisfy the need for validation without the code. For the sake of brevity I will not go into the details of the validator here. After all, my form is so simple I just want my validation method to verify that the passwords match. Suffice it to say that if you need to perform a validation that is already provided by Apache, it's the way to go.

The second component is the view. You can write this component simply by using JSP, but Struts offers much more for you to use in the view. There are six taglibs provided by Struts: html, logic, bean, nested, template, and tiles. Your bread-and-butter taglibs are html (obviously), bean, and logic (see Listing 2).

Each element of the html library will render html. The errors tag will print out an error to the screen. For example, if your ActionForm fails validation the ActionErrors returned will be printed out here.

The forms "form" tag starts a form and the action attribute matches the action element of an html form, except in this case you want to post to your controller, called an Action. The other html tags here are basic text fields and password fields. When they are rendered the values of their respective ActionForm properties are placed in the fields, and their input will be mapped automatically to your ActionForm properties. Remember that the ChangePasswordActionForm is also a bean so you can use the bean library to access it. If you want to perform some special manipulation of the data, rather than using scriptlets you can use the logic library, which will let you iterate through lists and control blocks with easy-to-read JSP tags. Take note though that your view should contain only presentation logic, nothing more.

There is also another plug-in for the view, called the tiles plug-in. It allows you to create reusable "tiles" and layout "tiles" in JSP. Imagine being able to make a "BorderLayout" tile. Then include your header tile NORTH, and your footer tile SOUTH, by default. Each specific page overrides CENTER. I happen to like this plug-in, but it also requires its own configuration files and a lot more detail. I recommend you look at it, but hold off until your second Struts application.

The third component is the controller. With a Struts application you have two controllers. The "true" controller of the application is the ActionServlet, provided by Struts in the form of a servlet. This servlet is configured with an XML file that tells Struts how to map your action forms to JSP pages to Action classes. That configuration, however, cannot possibly contain all of the possible submissions and appropriate reactions. Since your users are going to input dynamic data, you need to write a class, which extends Action to handle that input. Your action works with the action servlet to control the application.

The action servlet is like an air traffic control center - it controls everything. The action class is like an airplane passing through the control center's air space. The plane has a destination, but it cannot get there without the control center. Conversely, the control center won't have anything to do without a plane to direct. It looks at the plane's destination and based on where it's located (its state), it may send the airplane along or it may tell it to land. Listing 3 is an example action.

The only method you have to write is the execute method (called the "perform" method in Struts 1.0). This method returns an ActionForward, which is also defined in the XML configuration file. The ActionForward tells the action servlet where to direct the application to next. It allows you to redirect the user, based on user input, and it places the destination outside the code, again in the XML configuration file, so we can easily make changes to the application without recompiling anything.

The Action is where your application logic should exist. It is also where Struts meets your EJBs, messaging queues, JDOs, and so on. The trick here is to keep it simple. My changePassword method may contact the local LDAP, a session bean, or an application-specific database. Just put it in another method, or if there is a great deal of business logic being performed here, put it in another business object.

Now that you have your three components, I'll show you how they all fit together. It's all in the Struts configuration file. When you set up the action servlet the typical mapping is to "*.do". The only required parameter is "struts-config". This parameter should name where your XML configuration file is, such as "WEB-INF/struts-config.xml". There are also three other variables I recommend you set initially. Validate=true will turn on validation for your XML configuration file, so you will know if you put something incorrect into it. Debug=true and detail=2 will turn on a good deal of debugging information so you can see what the application is doing. These are good for development, but once your app is ready for production there you will probably want to turn them off (see Listing 4).

The configuration file contains several elements: action mappings, message resources, form beans, forwards, plug-ins, and datasources. This is where you define your forwards and loosely couple all of your components. Don't underestimate the configuration though. The components you have to write are pretty simple, but all it takes is one little typo in your configuration file, to keep it from deploying properly. Rather than editing this file by hand I recommend you use a tool such as the "Struts Console" by James Holmes at www.jamesholmes.com/struts (see Figure 2). It will help get your configuration files together quickly, and make maintenance easier too. It works with both Struts 1.0 and 1.1 dtds, and it will even create tiles and validation and tiles XML files. Most important, it will help you avoid having to waste your valuable time finding a simple mistake in an XML file.

There really isn't much left for you to do. The framework is written for you, and is probably more than flexible enough to suit your needs. All you have to do is write a few lightweight components, set up your configuration file(s), wrap it all up in a war, and deploy it. Stick with the 1.0 features for your first few forms. Once you are comfortable with those you can add in some of the 1.1 features if you desire.

The more you use a framework like this the more you'll appreciate it. Here all of the repetitive parts of your navigation, validation, and display are already written for you. The applications using the framework are easy to maintain and to extend. You can use it to easily lay a Web front end on top of your J2EE infrastructure. You will have to spend a little time up front to learn the framework, but the payoff is worth it. Once you know the framework, you will be able to rapidly create applications that use it, and because of the bump you get in productivity you'll want to use it again.

More Stories By Aristotle Allen

Aristotle Allen is a Senior Development Analyst at PJM Interconnection LLC. Ari has worked in high-tech manufacturing, an ASP and utilities and chooses to specialize in Java, especially J2EE. [email protected] / http://aballen.phathookups.com

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

@ThingsExpo Stories
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
BnkToTheFuture.com is the largest online investment platform for investing in FinTech, Bitcoin and Blockchain companies. We believe the future of finance looks very different from the past and we aim to invest and provide trading opportunities for qualifying investors that want to build a portfolio in the sector in compliance with international financial regulations.
Imagine if you will, a retail floor so densely packed with sensors that they can pick up the movements of insects scurrying across a store aisle. Or a component of a piece of factory equipment so well-instrumented that its digital twin provides resolution down to the micrometer.
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settle...
Product connectivity goes hand and hand these days with increased use of personal data. New IoT devices are becoming more personalized than ever before. In his session at 22nd Cloud Expo | DXWorld Expo, Nicolas Fierro, CEO of MIMIR Blockchain Solutions, will discuss how in order to protect your data and privacy, IoT applications need to embrace Blockchain technology for a new level of product security never before seen - or needed.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, discussed some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he covered some of the best practices for structured team migration an...
No hype cycles or predictions of a gazillion things here. IoT is here. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, an Associate Partner of Analytics, IoT & Cybersecurity at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He also discussed the evaluation of communication standards and IoT messaging protocols, data...
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and B...
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
We are given a desktop platform with Java 8 or Java 9 installed and seek to find a way to deploy high-performance Java applications that use Java 3D and/or Jogl without having to run an installer. We are subject to the constraint that the applications be signed and deployed so that they can be run in a trusted environment (i.e., outside of the sandbox). Further, we seek to do this in a way that does not depend on bundling a JRE with our applications, as this makes downloads and installations rat...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
DX World EXPO, LLC, a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
In this strange new world where more and more power is drawn from business technology, companies are effectively straddling two paths on the road to innovation and transformation into digital enterprises. The first path is the heritage trail – with “legacy” technology forming the background. Here, extant technologies are transformed by core IT teams to provide more API-driven approaches. Legacy systems can restrict companies that are transitioning into digital enterprises. To truly become a lead...
Digital Transformation (DX) is not a "one-size-fits all" strategy. Each organization needs to develop its own unique, long-term DX plan. It must do so by realizing that we now live in a data-driven age, and that technologies such as Cloud Computing, Big Data, the IoT, Cognitive Computing, and Blockchain are only tools. In her general session at 21st Cloud Expo, Rebecca Wanta explained how the strategy must focus on DX and include a commitment from top management to create great IT jobs, monitor ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
The IoT Will Grow: In what might be the most obvious prediction of the decade, the IoT will continue to expand next year, with more and more devices coming online every single day. What isn’t so obvious about this prediction: where that growth will occur. The retail, healthcare, and industrial/supply chain industries will likely see the greatest growth. Forrester Research has predicted the IoT will become “the backbone” of customer value as it continues to grow. It is no surprise that retail is ...