How to use messages included in sensor_msgs with ROSJava?

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I have downloaded the project sensor_msgs from the repository:

roslocate info sensor_msgs
- svn:
        local-name: sensor_msgs
        uri: https://code.ros.org/svn/ros-pkg/stacks/common_msgs/trunk/sensor_msgs

Before downloading this project in my worskspace, when rosmake detect the dependency:

<depend package="sensor_msgs" />

Shell printed the following message:

[rosmake-1] Starting >>> sensor_msgs [ make ]                                   
[rosmake-1] Finished <<< sensor_msgs ROS_NOBUILD in package sensor_msgs

But later, when I download the project, I received the following message when I execute rosmake in my package:

[rosmake-0] Starting >>> sensor_msgs [ make ]                                   
[rosmake-0] Finished <<< sensor_msgs  No Makefile in package sensor_msgs

When I use messages from that package:

            Publisher<org.ros.message.sensor_msgs.JointState> motor =
                node.newPublisher("motor1", "sensor_msgs.JointState");

I receive the following exception when I execute the node:

Jan 8, 2012 10:59:22 PM org.ros.internal.node.RosoutLogger fatal
SEVERE: org.ros.exception.RosRuntimeException: org.ros.exception.RosRuntimeException: java.lang.IllegalArgumentException

But if I use messages from std_msgs, I don't have any problem:

            Publisher<org.ros.message.std_msgs.String> publisher2 =
                node.newPublisher("motor1", "std_msgs/String");

How to use messages from sensor_msgs?

I noticed that the package sensor_msgs doesn't have any makefile to execute rosmake.

Many thanks in advance.