Discussion About Dispatcher Servlet in Java?

What is Dispatcher Servlet?

Spring's web MVC framework is, like many other web MVC frameworks, request-driven, designed around a central servlet that dispatches requests to controllers and offers other functionality that facilitates the development of web applications.

Spring's DispatcherServlet however, does more than just that. It is completely integrated with the Spring IoC container and as such allows you to use every other feature that Spring has.

The request processing workflow of the Spring Web MVC DispatcherServlet is illustrated in the following diagram. The pattern-savvy reader will recognize that the DispatcherServlet is an expression of the “Front Controller” design pattern

Front controller is a typical design pattern in the web applications development. In this case, a single servlet receives all requests and transfers them to to all other components of the application. The task of the DispatcherServlet is to send request to the specific Spring MVC controller.

Example:

<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/*</url-pattern>
</servlet-mapping>

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Small Discussion About Spring MVC?

What is Spring MVC?

The Spring Web model-view-controller (MVC) framework is designed around a DispatcherServlet that dispatches requests to handlers, with configurable handler mappings, view resolution, locale and theme resolution as well as support for uploading files.

The default handler is based on the @Controller and @RequestMapping annotations, offering a wide range of flexible handling methods. With the introduction of Spring 3.0, the @Controller mechanism also allows you to create RESTful Web sites and applications, through the @PathVariable annotation and other features.

Spring Web MVC you can use any object as a command or form-backing object; you do not need to implement a framework-specific interface or base class. Spring's data binding is highly flexible: for example, it treats type mismatches as validation errors that can be evaluated by the application, not as system errors.

Thus you need not duplicate your business objects' properties as simple, untyped strings in your form objects simply to handle invalid submissions, or to convert the Strings properly. Instead, it is often preferable to bind directly to your business objects.

Spring's view resolution is extremely flexible. A Controller is typically responsible for preparing a model Map with data and selecting a view name but it can also write directly to the response stream and complete the request. View name resolution is highly configurable through file extension or Accept header content type negotiation, through bean names, a properties file, or even a custom ViewResolver implementation.

The model (the M in MVC) is a Map interface, which allows for the complete abstraction of the view technology. You can integrate directly with template based rendering technologies such as JSP, Velocity and Freemarker, or directly generate XML, JSON, Atom, and many other types of content. The model Map is simply transformed into an appropriate format, such as JSP request attributes, a Velocity template model.

Spring MVC, like many other web frameworks, is designed around the front controller pattern where a central Servlet, the DispatcherServlet, provides a shared algorithm for request processing while actual work is performed by configurable, delegate components. This model is flexible and supports diverse workflows.

The DispatcherServlet, as any Servlet, needs to be declared and mapped according to the Servlet specification using Java configuration or in web.xml. In turn the DispatcherServlet uses Spring configuration to discover the delegate components it needs for request mapping, view resolution, exception handling

Video for Spring MVC

https://www.youtube.com/watch?v=xrExTCcv5Qg

Discussion About Thymeleaf?

What is Thymeleaf ?

Thymeleaf is a modern server-side Java template engine for both web and standalone environments.

Thymeleaf's main goal is to bring elegant natural templates to your development workflow — HTML that can be correctly displayed in browsers and also work as static prototypes, allowing for stronger collaboration in development teams.

With modules for Spring Framework, a host of integrations with your favourite tools, and the ability to plug in your own functionality, Thymeleaf is ideal for modern-day HTML5 JVM web development — although there is much more it can do.

Thymeleaf is Open Source Software originally created by a Spanish Software Engineer called Daniel Fernández and now developed and maintained by a great team of awesome people.

It is neither made nor backed by any software (or any other type of) company, and it is offered to the public totally free of charge, both in binary and in source code forms, under the Apache License 2.0.

Thymeleaf version numbers have three components: x.y.z (like: 2.0.1).

x is the major version number. A change in this number means a rewrite of the core or architecture, or an important amount of changes in the library's APIs which might break backwards compatibility and/or legacy support.
y is the minor version number. A change in this number means a moderate set of changes has been applied, offering new features and improvements without changing APIs significantly and providing deprecation periods for all changed features in order to allow for a period of adaptation to the new interfaces.
z is the build/bugfix version number. A change in this number means the fix of some bugs or the addition of a series of performance or documentation improvements. Bugfix versions should modify no APIs and be therefore drop-in replacements for any previous version within the same major+minor version.

Video for ThemeLeaf

https://www.youtube.com/watch?v=GcqF_Kt1QBQ

Discussion about spring framework?

What is Spring Framework?

The Spring Framework is an open source application framework and inversion of control container for the Java platform. The framework's core features can be used by any Java application, but there are extensions for building web applications on top of the Java EE platform.

Spring enables you to build applications from "plain old Java objects" (POJOs) and to apply enterprise services non-invasively to POJOs. This capability applies to the Java SE programming model and to full and partial Java EE.

The Spring Framework consists of features organized into about 20 modules. These modules are grouped into Core Container, Data Access/Integration, Web, AOP (Aspect Oriented Programming), Instrumentation, and Test

Benefits for Spring Framework

1)Spring enables developers to develop enterprise-class applications using POJOs.

2)Spring is organized in a modular fashion.

3)Spring does not reinvent the wheel instead, it truly makes use of some of the existing technologies like several ORM frameworks, logging frameworks, JEE, Quartz and JDK timers, other view technologies.

4)Testing an application written with Spring is simple because environment-dependent code is moved into this framework.

5)Spring's web framework is a well-designed web MVC framework, which provides a great alternative to web frameworks such as Struts or other over engineered or less popular web frameworks.

6)Spring provides a convenient API to translate technology-specific exceptions (thrown by JDBC, Hibernate, or JDO, for example) into consistent, unchecked exceptions.

Video for Spring Framework

https://www.youtube.com/watch?v=Jjp_EYEn4bc

Discussion About Dispatcher Servlet in Java?

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