What is the difference between Java Beans and EJBs ?

Hi,
Can someone tell me that ? Kind of confused... Thanks !
Philip

Hmm, I'm gonna have a go at this - hopefully someone will build on it with more differences or requirements:
A Java Bean is merely a Java class written to conform to some simply rules for construction and method naming eg:
public class MyBean
private String myField;
public MyBean()
public void setMyField(String myField)
this.myField = myField;
public String getMyField()
return myField;
}Applications can use Java Beans without having to know about the class in advance - a typical situation might be their use in visual GUI editors where the properties of the bean can be exposed and manipulated by the editor through examination of the method names or an accompanying descriptor.
An Enterprise Java Bean doesn't have all that much in common with a Java Bean. An EJB is a small set of classes meeting a single (usually) business requirement written to conform to the EJB specification. This enables them to be used by J2EE Application servers to perform enterprise business functions (data storage, manipulation, business logic etc.). The whole idea is that by writing to the specification the server can automatically provide support for transaction management, concurrent access, scaleability, etc that a mission-critical system might require without the programmer having to understand the workings of the application server.
Essentially an EJB can either
1) maintain the permanent state of a business object (eg, hold the data for a single product in a catalogue)
2) perform a small set of business operations (eg, place an order for a customer)
3) act in response to messages passed around the system (eg, send a mail to the user when the items have been shipped)
I would have a look at the following two pages to get a better overview:
http://java.sun.com/products/javabeans/
http://java.sun.com/products/ejb/
Hope this helps.

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Hi All,
I am new to Java Bean and wonder what is the main difference to use a Bean or an Object in the jsp. I have search on the forum and find some post also asking the question but still answer my doubt. Indeed, what is the real advantage of using bean in jsp.
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I have been searching on this issue on the internet for a long time and most of them just say someting like "persistance of state", "bean follow some conventions of naming", "bean must implement ser" and so on. All of above can be solved by other means, for example, a normal class can also follow the convention. I am really get confused with it, and really want to know what is the main point(s) of using the java bean.
Any help will be highly apprecaited. Thanks!!!
Best Regards,
Alex

Hi All,
I am new to Java Bean and wonder what is the main
difference to use a Bean or an Object in the jsp. The first thing to realize is that JavaBeans are just Plain Old Java Objects (POJOs) that follow a specific set of semantics (get/set methods, etc...). So what is the difference between a Bean and an Object? Nothing.
<jsp:useBean id="cart" scope="session" class="ShoppingCart" />
In the above code, I can also create a object of
ShoppingCart by new operator then get the id at the
following way.
ShoppingCart cart = new ShoppingCart();
out.println(cart.getId());
...Sure you could. And if the Cart was in a package (it has to be) you also need to put an import statement in. Oh, and to make sure the object is accessable in the same scope, you have to put it into the PageContext scope. And to totally equal, you first check to see if that object already exists in scope. So to get the equivalant of this:
<jsp:useBean id="cart" class="my.pack.ShoppingCart"/>Then your scriptlet looks like this:
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<%
ShoppingCart cart = pageContext.getAttribute("cart");
if (cart == null) {
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%>So it is a lot more work.
As in my mind, a normal class can also
have it setter and getter methods for its properties.True ... See below.
But someone may say that, there is a scope="session",
which can be declared in an normal object.As long as the object is serializeable, yes.
It may be
a point but it can be easily solved but putting the
object in session by "session.setAttribute("cart",
cart)".Possible, but if the object isn't serializable it can be unsafe. As the point I mentioned above, the useBean tag allows you to check if the bean exists already, and use that, or make a new one if it does not yet exist in one line. A lot easier than the code you need to use otherwise.
I have been searching on this issue on the internet
for a long time and most of them just say someting
like "persistance of state", "bean follow some
conventions of naming", "bean must implement ser" and
so on. Right, that would go along the lines of the definition of what a JavaBean is.
All of above can be solved by other means, for
example, a normal class can also follow the
convention. And if it does - then it is a JavaBean! A JavaBean is any Object whose class definition would include all of the following:
1) A public, no-argument constructor
2) Implements Serializeable
3) Properties are revealed through public mutator methods (void return type, start with 'set' have a single Object parameter list) and public accessor methods (Object return type, void parameter list, begin with 'get').
4) Contain any necessary event handling methods. Depending on the purpose of the bean, you may include event handlers for when the properties change.
I am really get confused with it, and
really want to know what is the main point(s) of
using the java bean.JavaBeans are normal objects that follow these conventions. Because they do, then you can access them through simplified means. For example, One way of having an object in session that contains data I want to print our might be:
<%@ page import="my.pack.ShoppingCart %>
<%
ShoppingCart cart = session.getAttribute("cart");
if (cart == null) {
    cart = new ShoppingCart();
    session.setAttribute("cart", cart);
%>Then later where I want to print a total:
<% out.print(cart.getTotal() %>Or, if the cart is a JavaBean I could do this:
<jsp:useBean id="cart" class="my.pack.ShoppingCart" scope="session"/>
Then later on:
<jsp:getProperty name="cart" property="total"/>
Or perhaps I want to set some properties on the object that I get off of the URL's parameter group. I could do this:
<%
ShoppingCart cart = session.getAttribute("cart");
if (cart == null) {
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    cart.setZipCode(request.getParameter("zipCode"));
    cart.setRegion(request.getParameter("region"));
    cart.setCountry(request.getParameter("country"));
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}Or you could use:
<jsp:useBean id="cart" class="my.pack.ShoppingCart" scope="session">
<jsp:setProperty name="cart" property="*"/>
</jsp:useBean>The second seems easier to me.
It also allows you to use your objects in more varied cases - for example, JSTL (the standard tag libraries) and EL (expression language) only work with JavaBeans (objects that follow the JavaBeans conventions) because they expect objects to have the no-arg constuctor, and properties accessed/changed via getXXX and setXXX methods.
>
Any help will be highly apprecaited. Thanks!!!
Best Regards,
Alex

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What is the difference between Java Beans and EJBs ?

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