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What is the differences between bean and ejb ?



A Java Bean is defined as an instance of a class that contains private attributes (data), and getter & setter methods. If you have:
private String myString; in your class, you should have the methods public String getMyString (); and public void setMyString (String settingString); defined in your code. Although, I have found that it is not absolutely nessary to have everything defined; just don't be surprised if something breaks!


An EJB (Enterprise Java Bean) is much more complex They only reside in application servers that handle EJBs (Tomcat doesn't hold EJBs). There are 3 types of EJBs:
1) Session Usually contain some business logic.
2) Entity Usually interface with a data store (such as a database).
3) Message-Driven Receives messages from JMS




An Entity Bean is written for a particular table. What it means, if there is more than one object of this particular bean in the EJB container?
Entity Bean class represents a table and every Entity bean instance (object) represents a row in this table. Hence if there is more than more object of this particular bean in the EJB container you will have that many no. of rows in the table.
There is one Entity Bean object for each row in the database that you have accessed. This is one reason why many people don't like Entity Beans.
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