I fixed the problem with recompile.
Now i have an ".so" file of my model but when i want to start "wxgazebo bluebotic.world" and have added the line <plugin>/home/mjeanrenaud/Desktop/gazebo-0.7.0 /gazebo-0.7.0/server/models/Bluebotic/Bluebotic.so</plugin>

this error appears:

wxgazebo bluebotic.world
starting server
waiting for server
** Gazebo 0.6.0-rc1 **
* Part of the Player/Stage Project [ http://playerstage.sourceforge.net].
* Copyright 2000-2005 Brian Gerkey, Richard Vaughan, Andrew Howard,
* Nate Koenig and contributors.
* Released under the GNU General Public License.
using display [:0]
rendering: [GLXP pbuffer] direct [yes] RGBA [5 6 5 0] depth [16]
loading /home/mjeanrenaud/Desktop/gazebo-0.7.0/gazebo-0.7.0/server/models/Bluebotic/Bluebotic.so...
error   : plugin init failed [/home/mjeanrenaud/Desktop/gazebo- 0.7.0/gazebo-0.7.0/server/models/Bluebotic/Bluebotic.so: undefined symbol: gazebo_plugin_init]
Initialization failed
server died
stopping server