What are beans in Java and Spring?
In 1996, Sun Microsystems introduced its JavaBeans application programming interface for writing a Java component. Continuing with its coffee analogy, Sun called that component a bean. It also developed the Java programming language and platform. The company was acquired by Oracle in 2010, but its technology pioneered the standard for reusable Java components.
In object-oriented programming and distributed object technology, a component is a reusable program building block that can be combined with other components in the same or other computers in a distributed network to form an application. Examples of components include the following:
- A single button in a graphical user interface (GUI) that triggers an action once pressed.
- A calculator that uses logic gates to perform operations, such as calculating interest.
- A database manager interface that enables applications to interact with the database.
Components can be deployed on different servers in a network and communicate with each other for needed services. A component runs within a context called a container. Examples of containers include website pages, web browsers and word processors.
What are JavaBeans and what are they used for?
JavaBeans are reusable software components that follow a set of conventions that make them easy to manage, configure and embed in an application. JavaBeans are part of a serializable Java class with a no-argument constructor whose properties can be accessed using getter and setter methods.
Typically, JavaBeans are used for the following:
- Encapsulating data.
- Representing data models with fields and accessor or getter methods.
- As application components, passing between servlets to encapsulate data and results.
- Within frameworks like Spring Framework, employing dependency injection and configuration techniques.
What are the advantages and disadvantages of JavaBeans?
JavaBeans offer the following benefits:
- Reusability. They are modular, making code cleaner and easier to maintain.
- Compatibility. They are friendly to visual development tools, such as Eclipse and NetBeans, speeding up GUI development.
- Encapsulation. JavaBeans are ideal for bundling data and behavior together using private fields and public getter and setter methods, making them useful in object-oriented design.
- Serialization. They can be easily persisted in distributed applications.
JavaBeans also have the following disadvantages:
- Not immutable. They can be problematic in multithreaded environments because they are not immutable; their properties can be changed after object creation.
- Weak as business logic containers. They are designed to hold data, not to implement complex behaviors.
- Leaner, cleaner alternatives. JavaBeans have been around for decades, and their verbose syntax makes them cumbersome compared to Kotlin data classes.
What are Spring beans and what are they used for?
A Spring bean is an object managed within a Spring Framework Inversion of Control (IoC) container. In essence, Spring beans are Java classes configured to be automatically detected and injected whenever they are needed.
They might be needed for tasks such as dependency injection, component management, application configuration and service-layer abstraction.
They can be declared using annotation, Extensible Markup Language (XML) configuration or Java-based configuration.
What are the advantages and disadvantages of Spring beans?
Spring beans offer the following benefits:
- Centralized configuration. With IoC container management, object creation and wiring are centralized.
- Reusability. Because of their modularity, Spring beans are easily reused across different parts of a project.
- Loose coupling. Dependency injection enables Spring bean classes to rely on interfaces, rather than discrete implementations.
But Spring beans also have the following disadvantages:
- High overhead. There is often considerable runtime overhead when Spring beans are deployed in an application.
- Complex configuration. In large-scale applications, many Spring beans can create complicated configurations due to excessive, hard-to-trace dependencies.
- Tough learning curve. Spring beans are complex, making it difficult for beginners to learn.
JavaBeans vs. Spring beans
How do JavaBeans compare to Spring beans?
- JavaBeans are primarily used for data encapsulation and transfer, while Spring beans are general application components.
- JavaBeans are framework-independent; Spring beans are part of Spring Framework.
- JavaBeans are manually configured; Spring beans use XML configuration, annotation or Java-based configuration.
- JavaBeans have manual lifecycle management; Spring beans are managed by Spring Framework.
- JavaBeans do not have annotation support, while Spring beans have annotation-based configuration.
Examine this tutorial to learn how to create a functioning Hello World application using Spring.
