JavaBeans: Difference between revisions

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{{Short description|Computing technology developer by Sun Microsystems}}

{{Distinguish|Enterprise JavaBeans}}

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{{refimprovemore citations needed|date=June 2016}}

{{manualhow-to|date=October 2012}}

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In computing based on the [[Java (programming language)|Java]] Platform, '''JavaBeans''' is a technology developed by [[Sun Microsystems]] and released in 1996, as part of [[Java Development Kit|JDK]] 1.1.

The 'beans' of JavaBeans are classes that encapsulate one or more [[Object (computer science)|objects]] into a single standardized object (the bean). This standardization allows the beans to be handled in a more generic fashion, allowing easier [[code reuse]] and [[Type introspection|introspection]]. This in turn allows the beans to be treated as [[Component-based software engineering|software components]], and to be manipulated visually by [[Integrated development environment|editors and IDEs]] without needing any initial configuration, or to know any internal implementation details.

As part of the standardization, all beans must be [[Serialization|serializable]], have a [[nullary constructor|zero-argument constructor]], and allow access to properties using [[Mutator method|getter and setter methods]].

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:Persistence is the ability to save the current state of a Bean, including the values of a Bean's properties and instance variables, to nonvolatile storage and to retrieve them at a later time.

;Methods

:A beanBean should use [[Mutator_methodMutator method#Java_exampleJava example|accessor methods]] to [[Encapsulation_Encapsulation (computer_programmingcomputer programming)|encapsulate]] the properties. A beanBean can provide other methods for business logic not related to the access to the properties.

== Advantages ==

* The properties, events, and methods of a bean can be exposed to another application.

* A bean may register to receive events from other objects and can generate events that are sent to those other objects. {{citation needed|date=January 2023}}

* Auxiliary software can be provided to help configure a bean. {{citation needed|date=January 2023}}

*The configuration settings of a bean can be saved to persistent storage and restored. {{citation needed|date=January 2023}}

== Disadvantages ==

* A class with a [[nullary constructor|zero-argument constructor]] is subject to being instantiated in an invalid state.<ref name="Bloch">{{cite book|last1=Bloch|first1=Joshua|authorlink1=Joshua Bloch|title=Effective Java|date=2008|publisher=Addison-Wesley|isbn=978-0-321-35668-0|page=[https://archive.org/details/effectivejava00bloc_0/page/13 13]|edition=Second|url-access=registration|url=https://archive.org/details/effectivejava00bloc_0/page/13}}</ref> If such a class is instantiated manually by a developer (rather than automatically by some kind of framework), the developer might not realize that the class has been improperly instantiated. The compiler cannot detect such a problem, and even if it is documented, there is no guarantee that the developer will see the documentation.

* JavaBeans are inherently mutable and so lack the advantages offered by [[immutable objects]].<ref name="Bloch"/>

* Having to create getters for every property and setters for many, most, or all of them can lead to an immense quantity of [[boilerplate code]]. This can be mitigated using tools like [https://www.baeldung.com/intro-to-project-lombok Lombok].

== JavaBeans API ==

The JavaBeans functionality is provided by a set of classes and interfaces in the <ttcode>java.beans</ttcode> package.

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/**

* Getter for property "deceased"

* Different syntax for a boolean field (is v.s.vs get)

*/

public boolean isDeceased() {

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== See also ==

* [[Software package (disambiguation)|Software packaging]]

==References==

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[[Category:Java platform]]

[[Category:Articles with example Java code]]

[[Category:Architectural pattern (computer science)]]

[[Category:Software design patterns]]