Java Annotations

Question

What is the purpose of annotations in Java? I have this fuzzy idea of them as somewhere in between a comment and actual code. Do they affect the program at run time?

Answer 1

Annotations when it comes to EJB is known as choosing Implicit middle-ware approach over an explicit middle-ware approach , when you use annotation you're customizing what you exactly need from the API for example you need to call transaction method for a bank transfer : without using annotation : the code will be

transfer(Account account1, Account account2, long amount)    
{
   // 1: Call middleware API to perform a security check
   // 2: Call middleware API to start a transaction
   // 3: Call middleware API to load rows from the database
   // 4: Subtract the balance from one account, add to the other
   // 5: Call middleware API to store rows in the database
   // 6: Call middleware API to end the transaction
}

while using Annotation your code contains no cumbersome API calls to use the middle- ware services. The code is clean and focused on business logic

transfer(Account account1, Account account2, long amount) 
{
   // 1: Subtract the balance from one account, add to the other
}