In this article by, Tejaswini Mandar Jog, author of the book, Learning Spring 5.0, we will cover the following topics:

Introduction to Spring framework

Problems address by Spring in enterprise application development

Spring architecture

What's new in Spring 5.0

Container

Spring the fresh new start after the winter of traditional J2EE, is what Spring framework is in actual. A complete solution to the most of the problems occurred in handling the development of numerous complex modules collaborating with each other in a Java enterprise application. Spring is not a replacement to the traditional Java Development but it is a reliable solution to the companies to withstand in today's competitive and faster growing market without forcing the developers to be tightly coupled on Spring APIs.

Problems addressed by Spring

Java Platform is long term, complex, scalable, aggressive, and rapidly developing platform. The application development takes place on a particular version. The applications need to keep on upgrading to the latest version in order to maintain recent standards and cope up with them. These applications have numerous classes which interact with each other, reuse the APIs to take their fullest advantage so as to make the application is running smoothly. But this leads to some very common problems of as.

Scalability

The growth and development of each of the technologies in market is pretty fast both in hardware as well as software. The application developed, couple of years back may get outdated because of this growth in these areas. The market is so demanding that the developers need to keep on changing the application on frequent basis. That means whatever application we develop today should be capable of handling the upcoming demands and growth without affecting the working application. The scalability of an application is handling or supporting the handling of the increased load of the work to adapt to the growing environment instead of replacing them. The application when supports handling of increased traffic of website due to increase in numbers of users is a very simple example to call the application is scalable. As the code is tightly coupled, making it scalable becomes a problem.

Plumbing code

Let's take an example of configuring the DataSource in the Tomcat environment. Now the developers want to use this configured DataSource in the application. What will we do? Yes, we will do the JNDI lookup to get the DataSource. In order to handle JDBC we will acquire and then release the resources in try catch. The code like try catch as we discuss here, inter computer communication, collections too necessary but are not application specific are the plumbing codes. The plumbing code increases the length of the code and makes debugging complex.

Boilerplate code

How do we get the connection while doing JDBC? We need to register Driver class and invoke the getConnection() method on DriverManager to obtain the connection object. Is there any alternative to these steps? Actually NO! Whenever, wherever we have to do JDBC these same steps have to repeat every time. This kind of repetitive code, block of code which developer write at many places with little or no modification to achieve some task is called as boilerplate code. The boilerplate code makes the Java development unnecessarily lengthier and complex.

Unavoidable non-functional code

Whenever application development happens, the developer concentrate on the business logic, look and feel and persistency to be achieved. But along with these things the developers also give a rigorous thought on how to manage the transactions, how to handle increasing load on site, how to make the application secure and many more. If we give a close look, these things are not core concerns of the application but still these are unavoidable. Such kind of code which is not handling the business logic (functional) requirement but important for maintenance, trouble shooting, managing security of an application is called as non-functional code. In most of the Java application along with core concerns the developers have to write down non-functional code quite frequently. This leads to provide biased concentration on business logic development.

Unit testing of the application

Let's take an example. We want to test a code which is saving the data to the table in database. Here testing the database is not our motive, we just want to be sure whether the code which we have written is working fine or not. Enterprise Java application consists of many classes, which are interdependent. As there is dependency exists in the objects it becomes difficult to carry out the testing.

POJO based development

The class is a very basic structure of application development. If the class is getting extended or implementing an interface of the framework, reusing it becomes difficult as they are tightly coupled with API. The Plain Old Java Object (POJO) is very famous and regularly used terminology in Java application development. Unlike Struts and EJB Spring doesn't force developers to write the code which is importing or extending Spring APIs. The best thing about Spring is that developers can write the code which generally doesn't has any dependencies on framework and for this, POJOs are the favorite choice. POJOs support loosely coupled modules which are reusable and easy to test.

The Spring framework is called to be non-invasive as it doesn't force the developer to use API classes or interfaces and allows to develop loosely coupled application.

Loose coupling through DI

Coupling, is the degree of knowledge in class has about the other. When a class is less dependent on the design of any other class, the class will be called as loosely coupled. Loose coupling can be best achieved by interface programming. In the Spring framework, we can keep the dependencies of the class separated from the code in a separate configuration file. Using interfaces and dependency injection techniques provided by Spring, developers can write loosely coupled code (Don't worry, very soon we will discuss about Dependency Injection and how to achieve it). With the help of loose coupling one can write a code which needs a frequent change, due to the change in the dependency it has. It makes the application more flexible and maintainable.

Declarative programming

In declarative programming, the code states what is it going to perform but not how it will be performed. This is totally opposite of imperative programming where we need to state stepwise what we will execute. The declarative programming can be achieved using XML and annotations. Spring framework keeps all configurations in XML from where it can be used by the framework to maintain the lifecycle of a bean. As the development happened in Spring framework, the 2.0 onward version gave an alternative to XML configuration with a wide range of annotations.

Boilerplate code reduction using aspects and templates

We just have discussed couple of pages back that repetitive code is boilerplate code. The boiler plate code is essential and without which providing transactions, security, logging, and so on, will become difficult. The framework gives solution of writing aspect which will deal with such cross cutting concerns and no need to write them along with business logic code. The use of aspect helps in reduction of boilerplate code but the developers still can achieve the same end effect. One more thing the framework provides, is the templates for different requirements. The JDBCTemplate and HibernateTemplate are couple of more useful concepts given by Spring which does reduction of boilerplate code. But as a matter of fact, you need to wait to understand and discover the actual potential.

Layered architecture

Unlike Struts and Hibernate which provides web persistency solutions respectively, Spring has a wide range of modules for numerous enterprise development problems. This layered architecture helps the developer to choose any one or more of the modules to write solution for his application in a coherent way. E.g. one can choose Web MVC module to handle web request efficiently without even knowing that there are many other modules available in the framework.

Spring architecture

Spring provides more than 20 different modules which can be broadly summaries under 7 main modules which are as follows:

introduction-spring-framework-img-0

Spring modules

What more Spring supports underneath?

The following sections covers the additional features of Spring.

Security module

Now a days the applications alone with basic functionalities also need to provide sound ways to handle security at different levels. Spring5 support declarative security mechanism using Spring AOP.

Batch module

The Java Enterprise Applications needs to perform bulk processing, handling of large amount of data in many business solutions without user interactions. To handle such things in batches is the best solution available. Spring provides integration of batch processing to develop robust application.

Spring integration

In the development of enterprise application, the application may need interaction with them. Spring integration is extension of the core spring framework to provide integration of other enterprise applications with the help of declarative adapters. The messaging is one of such integration which is extensively supported by Spring.

Mobile module

The extensive use of mobiles opens the new doors in development. This module is an extension of Spring MVC which helps in developing mobile web applications known as Spring Android Project. It also provide detection of the type of device which is making the request and accordingly renders the views.

LDAP module

The basic aim of Spring was to simplify the development and to reduce the boilerplate code. The Spring LDAP module supports easy LDAP integration using template based development.

.NEW module

The new module has been introduced to support .NET platform. The modules like ADO.NET, NHibernate, ASP.NET has been in the .NET module includes to simplify the .NET development taking the advantages of features as DI, AOP, loose coupling.

Container – the heart of Spring

POJO development is the backbone of Spring framework. The POJO configured in the and whose object instantiation, object assembly, object management is done by Spring IoC container is called as bean or Spring bean. We use Spring IoC as it on the pattern of Inversion of Control.

Inversion of Control (IoC)

In every Java application, the first important thing which each developer does is, to get an object which he can use in the application. The state of an object can be obtained at runtime or it may be at compile time. But developers creates object where he use boiler plate code at a number of times. When the same developer uses Spring instead of creating object by himself he will be dependent on the framework to obtain object from. The term inversion of control comes as Spring container inverts the responsibility of object creation from developers.

Spring IoC container is just a terminology, the Spring framework provides two containers:

The BeanFactory

The ApplicationContext

Summary

So in this article, we discussed about the general problems faced in Java enterprise application development and how they have been address by Spring framework. We have seen the overall major changes happened in each version of Spring from its first introduction in market.