Bean, Serialization Question

Question

Who can give me a good explanation of JavaBean. Or a good URL with examples.
What are the advatages of java beans, how ca I write one.
And what has it to do with Serialization.
Serialization where is it used? Examples.

Answer 1

There's nothing special about a JavaBean. In broad terms a JavaBean is simply a Java class that has been written using a particular style.
The most notable points are:
1) default constructor - ie, a constructor with no arguments
2) property accessors - eg, public String getName(), public void setName(String name), public boolean isEnabled()
The advantage is that you don't need to know about a JavaBean to use it - the methods indicate the various properties available and their data type. So Java can use Reflection to examine the bean and use it appropriately. In other words, you can find out and use the methods an Object has without knowing about its class in advance simply by examining their names.
A good example would be a visual component (like a button). By following the JavaBean conventions you end up with a class that can be distributed to other people and they can just plug it into their applications. Think of how a visual GUI editor gives you a property window for a component - this is simply exposing the information it derives by looking at the bean's method signatures.
There are other things that add extra value to JavaBeans like bean info classes and editor components but that's usually just confusing until you understand beans and their power.
Have a look at http://java.sun.com/products/javabeans (I think)
Serialisation is a somewhat different matter. This basically involves "saving an object". You can get a single instance of a class to be written to (eg) the filesystem and then load it again later. Obviously you can write your own methods for saving an object's state but serialisation is automatic and standard allowing it to be employed by other applications without knowledge of the objects that they're dealing with. Again, as with something like JavaBeans it enables you to represent the state without knowing about how the bean works. For example, a distributed application might serialise an object to transmit it between client and server. Note that serialisation does not require that the class being serialised follows the JavaBeans conventions, though - it's kind of a Java no-brainer if you like.
It would take a long time to explain the full benefits of JavaBeans and serialisation, however.
Hope this helps.