var json_arr = [{"FULL_NAME":"abcsdgdsg","OID":"444"},
{"FULL_NAME":"dedsgg","OID":"3444"},
{"FULL_NAME":"ghi","OID":"3463"},
{"FULL_NAME":"adob","OID":"643634"},
{"FULL_NAME":"dggd","OID":"34634"}];



jQuery( "#client_name" ).autocomplete({
            minLength: 0,
            source: json_arr,
            focus: function( event, ui ) {
                jQuery( "#client_name" ).val( ui.item.FULL_NAME );
                return false;
            },
            select: function( event, ui ) {
                return false;
            }
    })
    .data( "autocomplete" )._renderItem = function( ul, item ) {
            return jQuery( "<li></li>" )
                .data( "item.autocomplete", item )
                .append( "<a>" + item.FULL_NAME +  "</a>" )
                .appendTo( ul );
    };