setting ros parameters via launch files

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I need to set controller joint names as rosparameters which has values as list type. From terminal, I can set that parameter value as below

rosparam set controller_joint_names "[joint_1,joint_2]"

However, I want that parameter value to be set from the launch file. For that, I have used the following command in the launch file.

<param name=controller_joint_names value="[joint_1,joint_2]" />

Using the above command in roslaunch file throws the error saying rosparameter value is not list type. Any help in resolving the error will be appreciated.