h2. Modification

A *Modification* is a class containing an operation applie don one *[DIRAPI:Attribute]* into an *[DIRAPI:Entry]*. This is used by the *[Modify|Message (...)#ModifyRequest]* message.

We can apply more than one *Modification* on an *[DIRAPI:Entry]*.

There are three kind of operation we can do:
* Add : add a new value, or a new attribute if it does not exist already
* Delete : remove a single value, or the attribute if we remove the last value or if the value is null
* Replace : replace the existing values with the newly provided values, or delete the attribute if no values are provided

As usual, we have two kind of *Modification*, schema aware and schema agnostic ones.

h3. Creating a modification
We have two parameters to provide to create a *Modification* :
* an operation (add, delete or replace)
* an *[DIRAPI:Attribute]* instance, containing the values and the attribute type

We can also pass a *[SchemaManager (...)]* instance, if we want the *Modification* to be schema aware.

Changing an operation to make it schema aware is just a matter to call the _apply()_ method.

All the other methods are basic setters and getters.

Let see a simple example :

{code:java}
    @Test
    public void testModification()  throws LdapException
    {
        // Add the test1 and test2 values to the "cn" attribute
        Attribute attribute = new DefaultAttribute( atCn, "test1", "test2" );
        DefaultModification modCn1 = new DefaultModification( ModificationOperation.ADD_ATTRIBUTE, attribute );
        
        // Remove the "test2" value
        attribute = new DefaultAttribute( atCn, "test2" );
        DefaultModification modCn2 = new DefaultModification( ModificationOperation.REMOVE_ATTRIBUTE, attribute );

        // Replace the "cn" values by the test4 "value"
        attribute = new DefaultAttribute( atCn, "test4" );
        DefaultModification modCn3 = new DefaultModification( ModificationOperation.REPLACE_ATTRIBUTE, attribute );
    }
{code}

This code does nothing but creating some modifications. They have to be sent through a *[DIRAPI:Modify]* request to the server to be effective.