Struts & IBatis

Struts:

What is Struts?

                The core of the Struts framework is a flexible control layer based on standard technologies like Java Servlets, JavaBeans, ResourceBundles, and XML, as well as various Jakarta Commons packages. Struts encourages application architectures based on the Model 2 approach, a variation of the classic Model-View-Controller (MVC) design paradigm.

Struts provides its own Controller component and integrates with other technologies to provide the Model and the View. For the Model, Struts can interact with standard data access technologies, like JDBC and EJB, as well as most any third-party packages, like Hibernate, iBATIS, or Object Relational Bridge. For the View, Struts works well with JavaServer Pages, including JSTL and JSF, as well as Velocity Templates, XSLT, and other presentation systems.

The Struts framework provides the invisible underpinnings every professional web application needs to survive. Struts helps you create an extensible development environment for your application, based on published standards and proven design patterns.

What is Jakarta Struts Framework?

                Jakarta Struts is open source implementation of MVC (Model-View-Controller) pattern for the development of web based applications. Jakarta Struts is robust architecture and can be used for the development of application of any size. Struts framework makes it much easier to design scalable, reliable Web applications with Java.

What is ActionServlet?

                The class org.apache.struts.action.ActionServlet is the called the ActionServlet. In the the Jakarta Struts Framework this class plays the role of controller. All the requests to the server goes through the controller. Controller is responsible for handling all the requests.

How you will make available any Message Resources Definitions file to the Struts Framework Environment?

                T Message Resources Definitions file are simple .properties files and these files contains the messages that can be used in the struts project. Message Resources Definitions files can be added to the struts-config.xml file through tag.

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What is Action Class?

                The Action Class is part of the Model and is a wrapper around the business logic. The purpose of Action Class is to translate the HttpServletRequest to the business logic. To use the Action, we need to Subclass and overwrite the execute() method. In the Action Class all the database/business processing are done. It is advisable to perform all the database related stuffs in the Action Class. The ActionServlet (commad) passes the parameterized class to Action Form using the execute() method. The return type of the execute method is ActionForward which is used by the Struts Framework to forward the request to the file as per the value of the returned ActionForward object.

 What is ActionForm?

                An ActionForm is a JavaBean that extends org.apache.struts.action.ActionForm. ActionForm maintains the session state for web application and the ActionForm object is automatically populated on the server side with data entered from a form on the client side.

What is Struts Validator Framework?

                Struts Framework provides the functionality to validate the form data. It can be use to validate the data on the users browser as well as on the server side. Struts Framework emits the java scripts and it can be used validate the form data on the client browser. Server side validation of form can be accomplished by sub classing your From Bean with DynaValidatorForm class.

The Validator framework was developed by David Winterfeldt as third-party add-on to Struts. Now the Validator framework is a part of Jakarta Commons project and it can be used with or without Struts. The Validator framework comes integrated with the Struts Framework and can be used without doing any extra settings.

Give the Details of XML files used in Validator Framework?

                The Validator Framework uses two XML configuration files validator-rules.xml and validation.xml. The validator-rules.xml defines the standard validation routines, these are reusable and used in validation.xml. to define the form specific validations. The validation.xml defines the validations applied to a form bean.

Struts1 vs Struts 2

Struts1:

Needs ActionForm

No interceptor

Html tags

Needs req and response

Struts2:

Not need form class

Has interceptor

OGNL tags

No need of req and response

Types of Action classes in struts

1.ForwardAction class

2.DispatchAction class

3.IncludeAction class

4.LookUpDispatchAction class

5.MappingDispatchAction class

6.SwitchAction class

7.LocaleDispatchAction class

8.DownloadAction class

IBatis:

What is iBatis ?

A JDBC Framework

Developers write SQL, iBATIS executes it using JDBC.

No more try/catch/finally/try/catch.

An SQL Mapper

Automatically maps object properties to prepared statement parameters.

Automatically maps result sets to objects.

Support for getting rid of N+1 queries.

A Transaction Manager

iBATIS will provide transaction management for database operations if no other transaction manager is available.

iBATIS will use external transaction management (Spring, EJB CMT, etc.) if available.

Great integration with Spring, but can also be used without Spring (the Spring folks were early supporters of iBATIS).

What isn't iBATIS ?

An ORM

Does not generate SQL

Does not have a proprietary query language

Does not know about object identity

Does not transparently persist objects

Does not build an object cache

Essentially, iBatis is a very lightweight persistence solution that gives you most of the semantics of an O/R Mapping toolkit, without all the drama. In other words ,iBATIS strives to ease the development of data-driven applications by abstracting the low-level details involved in database communication (loading a database driver, obtaining and managing connections, managing transaction semantics, etc.), as well as providing higher-level ORM capabilities (automated and configurable mapping of objects to SQL calls, data type conversion management, support for static queries as well as dynamic queries based upon an object's state, mapping of complex joins to complex object graphs, etc.). iBATIS simply maps JavaBeans to SQL statements using a very simple XML descriptor. Simplicity is the key advantage of iBATIS over other frameworks and object relational mapping tools.

Configuring the Environment:

Let see how to configure the iBatis-Spring environment. When working with Spring and iBATIS, you will have a minimum of three XML configuration files, and you will often have even more. It is important that you become familiar with these config files. So how do you make iBATIS available to your application? There are a couple of ways:

Using Spring - iBATIS with a stand-alone application:

You should place the ibatis-2.3.0.677.jar in the application's classpath. At minimum, you must define and place the following three configuration files in the classpath

Spring config - This file defines the database connection parameters, the location of the SQL Map config file, and one or more Spring beans for use within the application. ( applicationContext.xml).

SQL Map config - This file defines any iBATIS-specific configuration settings that you may need and declares the location for any SQL Map files that should be accessible through this config file. (SqlMapConfig.xml)

SQL Map(s) One or more SQL Map files are declared in the SQL Map config and typically mapped to a single business entity within the application ,often represented by a single Java class (domainObject.xml).

Assuming you have no other knowledge of the data and have to use a generic sort method, the best theoretical in-place sort algorithm is O(n*log(n)). The Arrays.sort method should be using one of those, and is your best choice without more info.

If you're willing to use a lot of memory, you can use a non-in place sort such as radix or counting. These can be quicker than n*log(n), some as quick as O(n), but may use O(n) or worse memory. If you have knowledge of the data having special properties (such as it being almost already sorted) an insertion sort or similar algorithms could be quicker than O(n*log(n)) without using memory, but without more info one of those can't be suggested.