There is a term for it, because the standard allows libraries to programmatically do things with class instances you define in a predefined way. For example, if a library wants to stream any object you pass into it, it knows it can because your object is serializable assuming the library requires your objects be proper JavaBeans. As for Serializable : That is nothing but a "marker interface" an interface that doesn't declare any functions that tells Java that the implementing class consents to and implies that it is capable of "serialization" -- a process that converts an instance into a stream of bytes.
Those bytes can be stored in files, sent over a network connection, etc. Of course, in order to do that, the class has to abide by certain limitations. Chief among them is that all instance fields must be either primitive types int, bool, etc. This of course means that transient fields will not survive the trip over a stream. A class that has transient fields should be prepared to reinitialize them if necessary. A class that can not abide by those limitations should not implement Serializable and, IIRC, the Java compiler won't even let it do so.
JavaBeans are Java classes which adhere to an extremely simple coding convention. All you have to do is to. The JavaBean class must implement either Serializable or Externalizable. As for the Serialization, see the documentation.
Fields should be private for prevent outer classes to easily modify those fields. Java Beans are used throughout Java EE as a universal contract for runtime discovery and access. In object serialization an object can be represented as a sequence of bytes that includes the object's data as well as information about the object's type and the types of data stored in the object.
After a serialized object has been written into a file, it can be read from the file and deserialized that is, the type information and bytes that represent the object and its data can be used to recreate the object in memory.
You will find serialization useful when deploying your project across multiple servers since beans will be persisted and transferred across them. JavaBeans is a standard, and its basic syntax requirements have been clearly explained by the other answers. However, IMO, it is more than a simple syntax standard. The real meaning or intended usage of JavaBeans is, together with various tool supports around the standard, to facilitate code reuse and component-based software engineering, i.
Unfortunately this technology is way under-estimated and under-utilized by the industry, which can be told from the answers in this thread. If you read Oracle's tutorial on JavaBeans , you can get a better understanding in that. Many other answers actually have the what but not so much why of them. They were invented early on in Java as part of building GUIs.
They followed patterns that were easy for tools to pull apart letting them create a properties panel so you could edit the attributes of the Bean. In general, the Bean properties represented a control on the screen Think x,y,width,height,text,.. Over time these became useful for lots of tools that used the same type of access For example, Hibernate to persist data structures to the database. Now most systems don't require beans, they can take any plain old Java object with annotated properties to tell them how to manipulate them.
Now I see beans as annotated property balls--they are really only useful for the annotations they carry. Beans themselves are not a healthy pattern. They destroy encapsulation by their nature since they expose all their properties to external manipulation and as they are used there is a tendency by no means a requirement to create code to manipulate the bean externally instead of creating code inside the bean violates "don't ask an object for its values, ask an object to do something for you".
Using annotated POJOs with minimal getters and no setters is much more OO restoring encapsulation and with the possibility of immutability. By the way, as all this stuff was happening someone extended the concept to something called Enterprise Java Beans. These are The class must have a public default constructor with no arguments.
This allows easy instantiation within editing and activation frameworks. The class properties must be accessible using get, set, is can be used for boolean properties instead of get , and other methods so-called accessor methods and mutator methods according to a standard naming convention.
This allows easy automated inspection and updating of bean state within frameworks, many of which include custom editors for various types of properties. Setters can have one or more than one argument. The class should be serializable. This allows applications and frameworks to reliably save, store, and restore the bean's state in a manner independent of the VM and of the platform.
For more information follow this link. Regarding the second part of your question, serialization is a persistence mechanism used to store objects as a sequence of signed bytes. Put less formally, it stores the state of an object so you can retrieve it later, by deserialization. It is a reusable software component. It can encapsulate many objects into one object so that same object can be accessed from multiples places and is a step towards easy maintenance of code.
They are serializable, have a zero-argument constructor, and allow access to properties using getter and setter methods. The name "Bean" was given to encompass this standard, which aims to create reusable software components for Java. According to Wikipedia. The objects that form the backbone of your application and that are managed by the Spring IoC container are called beans. A bean is an object that is instantiated, assembled, and otherwise managed by a Spring IoC container. Otherwise, a bean is simply one of many objects in your application.
According to Spring IoC. A bean is a Java class with method names that follow the JavaBean guidelines also called design patterns for properties , methods , and events. Thus, any public method of the bean class that is not part of a property definition is a bean method. Minimally, a Java class, even with either a property as the sole member of course, accompanying public getter and setter required , a public method as the sole member or just one public event listener registration method is a Java bean.
Furthermore, the property can either be read-only property has a getter method but no setter or write-only property has a setter method only. The Java bean needs to be a public class to be visible to any beanbox tool or container. The container must be able to instantiate it; thus, it should have a public constructor too. If you could provide a file with extension.
Otherwise, the bean would need a public zero-args constructor, either explicit or default. If no class implementing the interface BeanInfo or extending a BeanInfo implementation , SimpleBeanInfo class, is available, the introspection involves using reflection implicit introspection to study the methods supported by a target bean and then apply simple design patterns the guidelines to deduce from those methods what properties, events, and public methods are supported.
A bean needs to be instantiated anyway even if no implicit introspection is carried on it. Thus, the requirement of a public zero-args constructor. You don't need a special tool and you don't have to implement any interfaces. Writing beans is simply a matter of following certain coding conventions.
All you have to do is make your class look like a bean — tools that use beans will be able to recognize and use your bean. These descriptions illustrate further the underlying ideas as explained above. Say, a bean constructor has some parameters. Suppose some are simple types. The container might not know what values to assign to them; even if it does, the resulting instance might not be reusable. It may make sense only if the user can configure specify values by say annotations or xml configuration files as in Spring beans.
And suppose some parameters are class or interface types. Again, the container might not know what values to assign to it. It may make sense only if the user can configure specify specific objects by say annotations or xml configuration files.
Techopedia Terms. Connect with us. Sign up. Term of the Day. Best of Techopedia weekly. News and Special Offers occasional. Techopedia Explains JavaBeans. What Does JavaBeans Mean? Techopedia Explains JavaBeans Reusability is the main concern behind the component model. It is easy to use serialized objects from handwritten Java code as well, so we can freely mix serialized beans with plain-old bean classes and other Java code. The bean examples we mentioned have ranged from simple buttons to spreadsheets.
At what level are beans intended to be used? The JavaBeans architecture is supposed to scale well from small to large; simple beans can be used to build larger beans. A small bean may consist of a single class; a large bean may have many.
Beans can also work together through their container to provide services to other beans. Simple beans are little more than ordinary Java objects. In fact, any Java class that has a default empty constructor could be considered a bean. These two criteria ensure that we can create an instance of the bean dynamically and that we can later save the bean as part of a group or composition of beans.
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