What is java spring

I respect your email privacy. Unsubscribe anytime. I'll send you an update when I publish new guides. I'm MarcoBehler and I share everything I know about making awesome software through my guides , screencasts , talks and courses. Follow me on Twitter to find out what I'm currently working on. What is Spring Framework? An Unorthodox Guide Last updated on August 09, -.

Introduction The complexity of the Spring ecosystem A lot of companies are using Spring, but then you go to spring. The short answer :. What is a dependency? How to instantiate dependencies with new The naive approach would be to simply create a new DataSource through a constructor, every time you need one.

We use our newly created DataSource for the query. This is our newly extracted method, able to create new DataSources. How to 'manage' dependencies in a global Application class To accommodate these issues, you could think about writing a global Application class, that looks something like this:. What is Inversion of Control? The findByX methods will then simply use that DataSource. Dependency Injection Containers Hence, the issue is that you, as a programmer are still actively constructing UserDAOs through their constructor and thus setting the DataSource dependency manually.

The Confident Spring Professional If you want to easily get a deep and practical understanding of the entire Spring Ecosystem or simply refresh your Spring knowledge: I have written a course for you. Interested in trying out the full first module? Learn More. What is an ApplicationContext? ApplicationContext ; import org. AnnotationConfigApplicationContext ; import javax. How to create an ApplicationContext? Bean ; import org. This configuration class is already enough to run your very first Spring application.

Are there alternatives to AnnotationConfigApplicationContext? What does the Bean annotation do? What is a Spring Bean? What are Spring bean scopes? Scope ; import org. What does ComponentScan do? ComponentScan ; import org. We added the ComponentScan annotation. Note, that the UserDAO definition is now missing from the context configuration! DataSource ; import org. Easy, with another marker annotation: Autowired.

Hence, your final code will look like this. Component ; import org. What are Field and Setter Injection? Simply put, Spring does not have to go through a constructor to inject dependencies. Constructor Injection vs. Field Injection There have been a great many debates online, whether constructor injection or field injection is better, with a number of strong voices even claiming that field injection is harmful.

To not add further noise to these arguments, the gist of this article is:. But Spring can cheat and create something else than your UserService class. Why Proxies? Are there alternatives to CGlib proxies? Here are a couple of links if you want to get more information on this topic:.

As always, you need an ApplicationContext to start off. As you can see, it allows you to execute the most common operations on a resource:. Does it exist? What is the filename? Get a reference to the actual File object. Get a direct reference to the raw data InputStream.

Some of them on your classpath, so you have access to some development related passwords. Some could even come in the form of operating system environment variables. The environment on the other hand, lets you, among other things, access properties. In a nutshell, an environment consists of one to many property sources. Let's look at these two words separately. Here the dependency part translates into an association between two classes.

For example, class A is dependent of class B. Now, let's look at the second part, injection. All this means is, class B will get injected into class A by the IoC. Dependency injection can happen in the way of passing parameters to the constructor or by post-construction using setter methods. As Dependency Injection is the heart of Spring Framework, we will explain this concept in a separate chapter with relevant example.

The functions that span multiple points of an application are called cross-cutting concerns and these cross-cutting concerns are conceptually separate from the application's business logic. There are various common good examples of aspects including logging, declarative transactions, security, caching, etc. DI helps you decouple your application objects from each other, while AOP helps you decouple cross-cutting concerns from the objects that they affect.

Spring together with Maven provide a structure that is intuitive to developers. Team work is easy and fast as there is individual elements are kept apart and can be reused. Spring framework is definitely good for web development and to be more specific for restful api services. It is good for the above because of its dependency injection and integration with other modules like spring security , spring aop , mvc framework , microservices.

With in any application, security is most probably a requirement. If you aim to build a product that needs long maintenance, then you will need the utilize the Aop concept. If your application has to much traffic thus increasing the load, you need to use the microservices concept.

Spring is giving all these features in one platform. Support with many modules. Most importantly, spring is open source and an extensible framework,have a hook everywhere to integrate custom code in life cycle. Spring Data is one project which provides integration with your project. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. What exactly is Spring Framework for?

Asked 12 years, 4 months ago. Active 4 months ago. Viewed k times. Improve this question. Maksim Maksim I understand that the question is very broad, but I do think that in this very specific case the question is very important for junion developers who are often spoken about Spring by people who assume it is enough popular that there is no need to even tell what it does.

After all, raise your hand if you never heard about Instagram and what its purpose is Question was asked 10 years ago, and at that time Spring was a bit smaller than now with all its sub projects, such as Spring Boot, Spring Data, Spring Rest, etc. And actually that's why it was closer a year ago, because of the broadness of this question. At the time when I asked this question I just wanted to understand DI and why it is needed.

Add a comment. Active Oldest Votes. Spring Dependency Injection approach What Spring does is to wire the classes up by using an XML file or annotations, this way all the objects are instantiated and initialized by Spring and injected in the right places Servlets, Web Frameworks, Business classes, DAOs, etc, etc, etc Isn't it?

What if you want to use another implementation of your UserLister interface? Just change the XML. What if don't have a UserLister implementation ready? Program a temporal mock implementation of UserLister and ease the development of the view. What if I don't want to use Spring anymore? Just don't use it! Your application isn't coupled to it. Inversion of Control states: "The application controls the framework, not the framework controls the application".

Improve this answer. Whats the difference between having to change a line of code and a line of XML? The effort and maintenance hell is exactly the same, or even worse, since the external xml files arguably adds complexity? Sorry but I just dont get it, I dont see any benefit at all.

Please fill me in if Im missing something. Without dependency injection DI can be used with annotations or with XML you can't properly test, because you can't mock the dependencies. It's a massive overhead to maintain.

Therefor EJB introduced the concept of annotations for injection points. Those are much simpler and a default instance will be injected for unit tests this can be changed once. This worked so well that Spring has now copied this approach. Or, you know, use a factory static method. Change the factory's return type, and now all of the classes that use that return value are changed. Presto Spring is now no longer needed Show 19 more comments. There is lot more to Spring that can be read up in good books like "Pro Spring".

Priyank Priyank Spring contains an MVC framework. So there is no need to write too much code. It hides the basic steps of these technologies. Let's take the example of JdbcTemplate, you don't need to write the code for exception handling, creating connection, creating statement, committing transaction, closing connection etc.

You need to write the code of executing query only. Thus, it save a lot of JDBC code. The Dependency Injection makes easier to test the application. The EJB or Struts application require server to run the application but Spring framework doesn't require server. Spring framework is lightweight because of its POJO implementation. The Spring Framework doesn't force the programmer to inherit any class or implement any interface.

That is why it is said non-invasive. The Dependency Injection feature of Spring Framework and it support to various frameworks makes the easy development of JavaEE application. JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services.

Please mail your requirement at [email protected] Duration: 1 week to 2 week. Spring Tutorial. Spring in Myeclipse Spring in Eclipse.