How to set an intial joint state to a robot arm in gazebo

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Here is an example of how to do it from a launch file:

<node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model"
      args="-urdf -model mbot -param robot_description -x 0.5 -y 0.5 -z 0.01 
      -J left_arm_joint0 0.0
      -J left_arm_joint1 1.18
      -J left_arm_joint2 0.12
      -J left_arm_joint3 0.92
      -J left_arm_joint4 0.24
      -J left_arm_joint5 0.63
      -J left_arm_joint6 0.44" />