web server - Borland Technical Publications

Implementing an entity bean
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Security Roles: simple definitions of security roles used by the application. Any
security role references you defined for your beans must also be defined here.
Method Permissions: each method of each bean can have certain rules about
their execution. These are set here.
Container-Transactions: this specifies the transaction attributes as per the EJB
2.0 specification for each method participating in a transaction
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Exclude List: methods to be uncalled by anyone
All of these can be accessed through the Deployment Descriptor Editor. You should
refer to the EJB 2.0 specification for DTD information and the proper use of the
descriptor files.
Entity Bean Primary Keys
Each Entity Bean must have a unique primary key that used to identify the bean
instance. The primary key can be represented by a Java class that must be a legal
value type in RMI-IIOP. Therefore, it extends the java.io.Serializable interface. It
must also provide an implementation of the Object.equals(Object other) and
Object.hashCode() methods.
Normally, the primary key fields of entity beans must be set in the ejbCreate() method.
The fields are then used to insert a new record into the database. This can be a difficult
procedure, however, bloating the method, and many databases now have built-in
mechanisms for providing appropriate primary key values. A more elegant means of
generating primary keys is for the user to implement a separate class that generates
primary keys. This class can also implement database-specific programming logic for
generating primary keys.
Generating primary keys from a user class
With enterprise beans, the primary key is represented by a Java class containing the
unique data. This primary key class can be any class as long as that class is a legal
value type in RMI-IIOP, meaning it extends the java.io.Serializable interface. It must
also provide an implementation of the Object.equals(Object other) and
Object.hashCode() methods, two methods which all Java classes inherit by definition.
The primary key class can be specific to an particular entity bean class. That is, each
entity bean can define its own primary key class. Or, multiple entity beans can share
the same primary key class.
The bank application uses two different entity beans to represent savings and checking
accounts. Both types of accounts use the same field to uniquely identify a particular
account record. In this case, they both use the same primary key class, AccountPK, to
represent the unique identifier for either type of account. The following code shows the
definition of the account primary key class:
public class AccountPK implements java.io.Serializable {
public String name;
public AccountPK() {}
public AccountPK(String name) {
this.name = name;
}
}
Chapter 14: Entity Beans and CMP 1.1 in Borland Enterprise Server 113