Read/Write Lock Aspect

available within our CVS

Goal

This Aspect is an example of an implementation of the Read/Write Lock pattern. It allows u to define at the method level a read/write lock using either annotation or an XML file The implementation is based on the concurrent package from Doug Lea.

Problem

Let's see a simple example defining the problem to solve. 

public class Account
{
private float balance; 

public Account(float balance) 
{ 
 this.balance=balance; 
} 

public void debit(float amount) 
{ 
// Implementation to debit the account balance 
 ... 
} 

public void credit(float amount) 
{ 
// Implementation to credit the account balance 
... 
} 

public String toString() 
{ 
// Implementation to format the account description 
... 
} 
}

The above class required to support concurrency invocation of the method debit,credit and toString method.

Traditional Implementation.

The traditional solution without AOP would be to implement the same code within the debit and credit account to acquire/release a write lock.A read lock would be required for the toString method.

Solution with Read/Write Lock Aspect

The concurrency code is refactored within the Read/Write Lock Aspect.So the new Aspect can be applied against any method using annotation or an XML file.

Here the new code of the Account class with annotation 

 
public class Account 
{ 
private float balance; 

public Account(float balance) 
this.balance=balance; 
} 

/** 
* @@org.jboss.aop.patterns.readwritelock.writeLockOperation 
*/ 
public void debit(float amount) 
{ 
// Implementation to debit the account balance 
... 
}

/** 
* @@org.jboss.aop.patterns.readwritelock.writeLockOperation 
*/ 
public void credit(float amount) 
{
 // Implementation to credit the account balance 
... 
}

/** 
* @@org.jboss.aop.patterns.readwritelock.readLockOperation 
*/ 
public String toString() 
{
// Implementation to format the account description 
...
}
}

Configuration

The deployment description of the Read/Write Lock Aspect

Author