150 lines
8.4 KiB
Plaintext
150 lines
8.4 KiB
Plaintext
[[overview]]
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= Spring Framework Overview
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:docinfo1:
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Spring makes it easy to create Java enterprise applications. It provides everything you
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need to embrace the Java language in an enterprise environment, with support for Groovy
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and Kotlin as alternative languages on the JVM, and with the flexibility to create many
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kinds of architectures depending on an application's needs. As of Spring Framework 6.0,
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Spring requires Java 17+.
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Spring supports a wide range of application scenarios. In a large enterprise, applications
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often exist for a long time and have to run on a JDK and application server whose upgrade
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cycle is beyond the developer's control. Others may run as a single jar with the server embedded,
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possibly in a cloud environment. Yet others may be standalone applications (such as batch
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or integration workloads) that do not need a server.
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Spring is open source. It has a large and active community that provides continuous feedback
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based on a diverse range of real-world use cases. This has helped Spring to successfully
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evolve over a very long time.
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[[overview-spring]]
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== What We Mean by "Spring"
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The term "Spring" means different things in different contexts. It can be used to refer to
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the Spring Framework project itself, which is where it all started. Over time, other Spring
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projects have been built on top of the Spring Framework. Most often, when people say
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"Spring", they mean the entire family of projects. This reference documentation focuses on
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the foundation: the Spring Framework itself.
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The Spring Framework is divided into modules. Applications can choose which modules they need.
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At the heart are the modules of the core container, including a configuration model and a
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dependency injection mechanism. Beyond that, the Spring Framework provides foundational
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support for different application architectures, including messaging, transactional data and
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persistence, and web. It also includes the Servlet-based Spring MVC web framework and, in
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parallel, the Spring WebFlux reactive web framework.
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A note about modules: Spring Framework's jars allow for deployment to the module path (Java
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Module System). For use in module-enabled applications, the Spring Framework jars come with
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`Automatic-Module-Name` manifest entries which define stable language-level module names
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(`spring.core`, `spring.context`, etc.) independent from jar artifact names. The jars follow
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the same naming pattern with `-` instead of `.` – for example, `spring-core` and `spring-context`.
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Of course, Spring Framework's jars also work fine on the classpath.
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[[overview-history]]
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== History of Spring and the Spring Framework
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Spring came into being in 2003 as a response to the complexity of the early
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https://en.wikipedia.org/wiki/Java_Platform,_Enterprise_Edition[J2EE] specifications.
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While some consider Java EE and its modern-day successor Jakarta EE to be in
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competition with Spring, they are in fact complementary. The Spring programming
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model does not embrace the Jakarta EE platform specification; rather, it integrates
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with carefully selected individual specifications from the traditional EE umbrella:
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* Servlet API ({JSR}340[JSR 340])
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* WebSocket API ({JSR}356[JSR 356])
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* Concurrency Utilities ({JSR}236[JSR 236])
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* JSON Binding API ({JSR}367[JSR 367])
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* Bean Validation ({JSR}303[JSR 303])
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* JPA ({JSR}338[JSR 338])
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* JMS ({JSR}914[JSR 914])
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* as well as JTA/JCA setups for transaction coordination, if necessary.
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The Spring Framework also supports the Dependency Injection
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({JSR}330[JSR 330]) and Common Annotations
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({JSR}250[JSR 250]) specifications, which application
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developers may choose to use instead of the Spring-specific mechanisms provided
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by the Spring Framework. Originally, those were based on common `javax` packages.
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As of Spring Framework 6.0, Spring has been upgraded to the Jakarta EE 9 level
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(for example, Servlet 5.0+, JPA 3.0+), based on the `jakarta` namespace instead of the
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traditional `javax` packages. With EE 9 as the minimum and EE 10 supported already,
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Spring is prepared to provide out-of-the-box support for the further evolution of
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the Jakarta EE APIs. Spring Framework 6.0 is fully compatible with Tomcat 10.1,
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Jetty 11 as web servers, and also with Hibernate ORM 6.1.
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Over time, the role of Java/Jakarta EE in application development has evolved. In the
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early days of J2EE and Spring, applications were created to be deployed to an application
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server. Today, with the help of Spring Boot, applications are created in a devops- and
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cloud-friendly way, with the Servlet container embedded and trivial to change. As of
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Spring Framework 5, a WebFlux application does not even use the Servlet API directly
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and can run on servers (such as Netty) that are not Servlet containers.
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Spring continues to innovate and to evolve. Beyond the Spring Framework, there are other
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projects, such as Spring Boot, Spring Security, Spring Data, Spring Cloud, Spring Batch,
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among others. It’s important to remember that each project has its own source code repository,
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issue tracker, and release cadence. See {spring-site-projects}[spring.io/projects] for
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the complete list of Spring projects.
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[[overview-philosophy]]
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== Design Philosophy
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When you learn about a framework, it’s important to know not only what it does but what
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principles it follows. Here are the guiding principles of the Spring Framework:
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* Provide choice at every level. Spring lets you defer design decisions as late as possible.
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For example, you can switch persistence providers through configuration without changing
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your code. The same is true for many other infrastructure concerns and integration with
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third-party APIs.
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* Accommodate diverse perspectives. Spring embraces flexibility and is not opinionated
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about how things should be done. It supports a wide range of application needs with
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different perspectives.
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* Maintain strong backward compatibility. Spring’s evolution has been carefully managed
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to force few breaking changes between versions. Spring supports a carefully chosen range
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of JDK versions and third-party libraries to facilitate maintenance of applications and
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libraries that depend on Spring.
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* Care about API design. The Spring team puts a lot of thought and time into making APIs
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that are intuitive and that hold up across many versions and many years.
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* Set high standards for code quality. The Spring Framework puts a strong emphasis on
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meaningful, current, and accurate javadoc. It is one of very few projects that can claim
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clean code structure with no circular dependencies between packages.
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[[overview-feedback]]
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== Feedback and Contributions
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For how-to questions or diagnosing or debugging issues, we suggest using Stack Overflow. Click
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{stackoverflow-spring-tag}+or+spring-mvc+or+spring-aop+or+spring-jdbc+or+spring-r2dbc+or+spring-transactions+or+spring-annotations+or+spring-jms+or+spring-el+or+spring-test+or+spring+or+spring-orm+or+spring-jmx+or+spring-cache+or+spring-webflux+or+spring-rsocket?tab=Newest[here]
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for a list of the suggested tags to use on Stack Overflow. If you're fairly certain that
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there is a problem in the Spring Framework or would like to suggest a feature, please use
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the {spring-framework-issues}[GitHub Issues].
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If you have a solution in mind or a suggested fix, you can submit a pull request on
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{spring-framework-github}[Github]. However, please keep in mind
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that, for all but the most trivial issues, we expect a ticket to be filed in the issue
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tracker, where discussions take place and leave a record for future reference.
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For more details see the guidelines at the {spring-framework-code}/CONTRIBUTING.md[CONTRIBUTING],
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top-level project page.
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[[overview-getting-started]]
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== Getting Started
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If you are just getting started with Spring, you may want to begin using the Spring
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Framework by creating a {spring-site-projects}/spring-boot/[Spring Boot]-based
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application. Spring Boot provides a quick (and opinionated) way to create a
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production-ready Spring-based application. It is based on the Spring Framework, favors
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convention over configuration, and is designed to get you up and running as quickly
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as possible.
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You can use https://start.spring.io/[start.spring.io] to generate a basic project or follow
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one of the {spring-site-guides}["Getting Started" guides], such as
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{spring-site-guides}/gs/rest-service/[Getting Started Building a RESTful Web Service].
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As well as being easier to digest, these guides are very task focused, and most of them
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are based on Spring Boot. They also cover other projects from the Spring portfolio that
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you might want to consider when solving a particular problem.
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