Logging using the Eclipse Logging Framework

if you are using eclipse in your day to day work and you want to log activities using the in built eclipse logging frame work .

Here is a small example to do the same ,

if u have a plugin class then say MyPlugin that extends AbstrarctUIPlugin then u can a have method in that class that does the logging for you .

public static void log(String message , int status ){
getDefault().getLog().log(new Status(status, getPluginID( ), message,null) );
}

the values , status can take are like :

• IStatus.ERROR
• IStatus.WARNING

Immutable Objects In Java

What is an Immutable Object ?

An immutable object is an object that does not change its state once its created .Java has a number of inbuilt classes that provide that functionality e.g String , Integer etc..

So how do you create an immutable object :

• Remove or make setters less accessible.
  
• Preveting methods from getting overriden.
• Make all fields final.
• Make defensive copies of mutable objects.
• Do not provide a clone method
• Do not provide a copy constructor
• return a fuctional object

Returning a functional object means applyting a function on the parameters of a method and returning the function rather than calculating the function and returning the value . e.g

public class Complex {
public Complex(int real, int imaginery){
this.real = real;
this.imaginery = imaginery;
}

public Complex add(Complex left , Complex right) {

// fuctional return
return new Complex(left.real + right.real , left.imaginery + right.imaginery);
}
}

The advantage of having an immutable class is that its thread safe.
The disadvantage being creating many new objects for different operations can lead to memory bloat

Little Sugar ( Mixins in Java)

Mixin ?? what is a mixin ...

Thats what i wondered when i cam accross the phrase . A Mixin is a way of adding features to the core functionlaity of a class . It is different from extending the class , cause it generally pertains to adding features not related to the core or default behaviour of a class .

A little example will make things clear . Say you have a small class Person that represents a person wholly . Not if you want to compare 2 instances of Person , you could implement the Comparable interface . By implementing the Comparable interface you add a functionlity that is not directly related to a Person object but is a help ful feature .

So a simple way to implement a Mixin is to implement an interface .. so much for buzz words...

Little Sugar (Security Manager , Java)

Today i ll gloss over a few small things worth remembering about security
in java . So lets get started :

In Java , we hava a Java API . The java API provides us with a lot methods to accomplish different type of tasks . Now if for some reason we want to enforce security on these tasks so that only selected operation can be performed and that to by selected users . In that case we need to create a security policy file.

In the security policy file , we specifiy how permissions are applied to different code sources . We specify differnt permissions in terms of Permission objects that are applied to CodeSource objects .

At runtime a policy object is created corresponding to the policy file .

For the policies to take effect a SecurityManager needs to be installed . Once the security manager is installed it uses the AccessController ,which inturn checks the different permissions based on different permission objects .

When the class loader loads a type in the JVM . It places the type in a protection domain , which encapsulates the permissions . At runtime , when methods on the type instance are invoked the security manger is checked to see if the method can be invoked .