Re: help related to java beans

From:

Lew <lew@nospam.lewscanon.com>

Newsgroups:

comp.lang.java.help

Date:

Thu, 22 Mar 2007 08:33:33 -0400

Message-ID:

<MN2dnZOdG8cD6p_bnZ2dnUVZ_hadnZ2d@comcast.com>

priyanka.nsk@gmail.com wrote:

Hello,
I have been writing a JSP program which uses Java Beans. The
program contains "getProperty" field which is mandatory for accessing
method in java source file.

Can anyone please tell me what "property" field of "getProperty"
method specifies and what value should it contain. Should it contain
anyvalue from Java source file? Like a variable name or a method name?

And similarly what values should be assigned to setProperty method.

get...() and set...() can show or accept any value of the type for the
attribute, as the program needs.

Consider a class:

public class Foo
{
   public int x;
}

Foo has a property 'x' that can hold any int value. You assign to it and
retrieve from it like this:

Foo foo = new Foo();
foo.x = 17;

int y = foo.x;
foo.x = -31;
System.out.println( foo.x );

But x is way too public, and the programmer might want additional checks, like
to ensure that x >= 0. So now we make x private and add methods:

public class Foo
{
   private int x;

   public void setX( int val )\
   {
     if ( x < 0 )
     {
       throw new IllegalArgumentException( "Value must be >= 0" );
     }
     this.x = val;
   }

   public int getX()
   {
     return x;
   }
}

Now you need the methods to set or get any value for x:

Foo foo = new Foo();
foo.setX( 17 );

int y = foo.getX();
foo.setX( -31 );
System.out.println( foo.getX() );

The name of the methods are 'setBlah()' and 'getBlah()' if the property name
is 'blah'. The spelling is the same for the "blah" part, but the first letter
is capitalized in the method (not the variable).

-- Lew