Equality test for entity bean

[Stephen Selvaraj]

Hi All,
I jus took a mock test,
A client can determine whether two entity beans are same by comparing their primary key using equals method (true/false)
I responded true, but the correct ans was false.

any comments..
- Stephen

[Sirajudeen Mohamed]

hi,
It is true in case of isIdentical(EJBObject o)

Thanks
Siraj

[sawan parihar]

A client can determine whether two entity beans are same by comparing their primary key using equals method (true/false)

This is true. If the PKs are equal then the two entity beans are same.

[Praveen Kumar Mathaley]

a primary key can be simple string, which may be same for two different beans, but it doesn't mean that the two entity beans are same,
it's just an possibility...

[sawan parihar]

a primary key can be simple string, which may be same for two different beans, but it doesn't mean that the two entity beans are same,
it's just an possibility...

If the Pk is same then that means the beans are same. Think about it , you have a database table and two records can't have the same primary key becuase pk is ment to be unique. That means if PK is same then the entity objects are same.

[Praveen Kumar Mathaley]

dear parihar,
what i meant was two different beans ( i.e two different tables ) can have same primary key.. hope this clears the issue...

[Mikalai Zaikin]

Howdy !

The primary key class can be specific to a 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.

If two entity objects with the SAME home interface have the SAME primary key, they are considered IDENTICAL entity objects. If they have a different primary key, they are considered different entity objects.

There are 2 ways of comparing Entity Beans:

1. Using isIdentical(EJBObject obj) method of javax.ejb.EJBObject interface on bean's REMOTE interface, or isIdentical(EJBLocalObject obj) method of javax.ejb.EJBLocalObject interface on bean's LOCAL
interface.

Item item1 = ...;
Item item2 = ...;
if (item1.isIdentical(item2)) {
// item1 and item2 refer to the same entity object
}

2. Comparing primary keys of two entity object references (ONLY FROM THE SAME HOME INTERFACE !) :

ItemHome itemHome = ...; // get home interface
Item item1 = itemHome.findByName(...);
Item item2 = itemHome.findByCountry(...);
if (item1.getPrimaryKey().equals(item2.getPrimaryKey())) {
// item1 and item2 refer to the same entity object
}

More details here :
http://java.boot.by/bcd-guide/ch08s02.html

regards,
MZ

[Thomas Vezhambacheril]

Dear Stephan,

You can conclude the answer is true only if

A client can determine whether two entity beans are same by comparing their primary key using equals method if the entity beans are from same Home

Am I correct ?

means if they includeed the clause "and the entity beans are from same Home " the answer was true.

Best Regards
Thomas