Getting started with spring
The Spring Framework is an open source application framework and inversion of control container for the Java platform.
Setup (XML Configuration)
Steps to create Hello Spring:
- Investigate Spring Boot to see if that would better suit your needs.
- Have a project set up with the correct dependencies. It is recommended that you are using Maven or Gradle.
- create a POJO class, e.g.
- create a XML file where you can define your class and variables. e.g
- create your main class e.g.
- Include spring-beans (and its transitive dependencies!) as a dependency.
Showcasing Core Spring Features by example
This is a self-contained running example including/showcasing: minimum dependencies needed, Java Configuration, Bean declaration by annotation and Java Configuration, Dependency Injection by Constructor and by Property, and Pre/Post hooks.
These dependencies are needed in the classpath:
Starting from the end, this is our Main class that serves as a placeholder for the
main() method which initialises the Application Context by pointing to the Configuration class and loads all the various beans needed to showcase particular functionality.
Application Configuration file
The configuration class is annotated by
@Configuration and is used as a parameter in the initialised Application Context. The
@ComponentScan annotation at the class level of the configuration class points to a package to be scanned for Beans and dependencies registered using annotations. Finally the
@Bean annotation serves as a bean definition in the configuration class.
Bean Declaration by Annotation
@Component annotation serves to demarcate the POJO as a Spring bean available for registration during component scanning.
Bean Declaration by Application Configuration
Notice that we don't need to annotate or otherwise mark our POJO since the bean declaration/definition is happening in the Application Configuration class file.
Notice that the
@Autowired annotation is set at the constructor level. Also notice that unless explicitely defined by name the default autowiring is happening based on the type of the bean (in this instance
Notice that the
@Autowired annotation demarcates the setter method whose name follows the JavaBeans standard.
PostConstruct / PreDestroy hooks
We can intercept initialisation and destruction of a Bean by the
What is Spring Framework, why should we go for it ?
Spring is a framework, which provides bunch of classes, by using this we don't need to write boiler plate logic in our code, so Spring provides an abstract layer on J2ee.
For Example in Simple JDBC Application programmer is responsible for
- Loading the driver class
- Creating the connection
- Creating statement object
- Handling the exceptions
- Creating query
- Executing query
- Closing the connection
Which is treated as boilerplate code as every programmer write the same code. So for simplicity the framework takes care of boilerplate logic and the programmer has to write only business logic. So by using Spring framework we can develop projects rapidly with minimum lines of code, without any bug, the development cost and time also reduced.
So Why to choose Spring as struts is there
Strut is a framework which provide solution to web aspects only and struts is invasive in nature. Spring has many features over struts so we have to choose Spring.
- Spring is Noninvasive in nature: That means you don't need to extend any classes or implement any interfaces to your class.
- Spring is versatile: That means it can integrated with any existing technology in your project.
- Spring provides end to end project development: That means we can develop all the modules like business layer, persistence layer.
- Spring is light weight: That means if you want to work on particular module then , you don't need to learn complete spring, only learn that particular module(eg. Spring Jdbc, Spring DAO)
- Spring supports dependency injection.
- Spring supports multiple project development eg: Core java Application, Web Application, Distributed Application, Enterprise Application.
- Spring supports Aspect oriented Programming for cross cutting concerns.
So finally we can say Spring is an alternative to Struts. But Spring is not a replacement of J2EE API, As Spring supplied classes internally uses J2EE API classes. Spring is a vast framework so it has divided into several modules. No module is dependent to another except Spring Core. Some Important modules are
- Spring Core
- Spring JDBC
- Spring AOP
- Spring Transaction
- Spring ORM
- Spring MVC