Java Bean fully encapsulated class in java

Posted by Gyan Guide on May 8th, 2017

Introduction :

A Java Bean is a java class which is fully encapsulated that should follow following things :

- It should have a no-arg constructor.

-It should be Serializable.

-It should provide methods to set and get the values of the properties, known as getter and setter methods.

Java Bean :

Basically, a "Bean":

- is a serializable object (that is, it implements java.io.Serializable and does so correctly), that

- has "properties" whose getters and setters are just methods

- has a public default constructor (so it can be created at will and configured by setting its properties).

Why use Java Bean?

It is a reusable software component. Advanced java training in bangalore A bean encapsulates many objects into one object, so we can access this object from multiple places. And it provides the easy maintenance.

How to access the java bean class?

Methods of java bean class are private .So to access the java bean class, we should use getter and setter methods.

JavaBeans Properties :

A JavaBean property is a named attribute that can be accessed by the user of the object. The attribute can be of any Java data type, including the classes that we define. A JavaBean property may be read, write, read only, or write only.

Accessing JavaBeans Properties :

Along with <jsp:useBean...> action, java /j2ee classes bangalore we can use the <jsp:getProperty/> action to access the get methods and the <jsp:setProperty/> action to access the set methods

JavaBeans API :

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

[1] AppletInitializer : Methods in this interface are used to initialize Beans that are also applets.

[2]BeanInfo : This interface allows the developer to specify information about the events, methods and properties of a Bean.

[3] Customizer : This interface allows the developer to provide a graphical user interface through which a bean may be configured.

[4] DesignMode : Methods in this interface determine if a bean is executing in design mode.

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[5] ExceptionListener : A method in this interface is invoked when an exception has occurred.

[6] PropertyChangeListener : A method in this interface is invoked when a bound property is changed.

[7] PropertyEditor : Objects that implement this interface allow the designer to change and display property values.

[8] VetoableChangeListener : A method in this interface is invoked when a Constrained property is changed.

[9] Visibility : Methods in this interface allow a bean to execute in environments where the GUI is not available.

Advantages of Java Bean :

[1] The properties, events, and methods of a bean that are exposed to another application can be controlled. java course in bangalore

[2] A bean may register to receive events from other objects and can generate events that are sent to those other objects.

[3] Auxiliary software can be provided to help configure a java bean.

[4] The configuration settings of a bean can be saved to persistent storage and restored.

Disadvantages of JavaBean :

A class with a nullary constructor is subject to being instantiated in an invalid state. 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. Best core java training in bangalore The compiler cannot detect such a problem, and even if it is documented, there is no guarantee that the developer will see the documentation.

[1] JavaBeans are inherently mutable and so lack the advantages offered by immutable objects.

[2] 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.

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