Overview

In ROS, messages which are used to communicate with ROS Services are defined in srv/*.srv files. Each service requires 2 messages: Request, Response (see ROS documentation for defining services in ROS2 or ROS1.

In order to work with ROS Services from jrosservices users need to:

1. Provide a mapping from ROS *.srv file to corresponding jrosservices service definition class. Definition class is described by the ServiceDefinition interface.
2. Define all message classes which are part of service definition class defined above (see jrosclient Defining messages guide).

To simplify this process users are encouraged to use msgmonster application.

Examples

Interacting with ROS add_two_ints service

In this example we are going to send requests to ROS add_two_ints service from Java.

How to create and run add_two_ints service can be found in:

• ROS2 documentation Writing a simple service and client (C++) or Writing a simple service and client (Python).
• ROS1 documentation rospy overview. For C++ the example can be taken from ros_tutorials package.

Creating service definition

ROS add_two_ints service file AddTwoInts.srv looks like this:

int64 a
int64 b
---
int64 sum

We need to map it to the corresponding service definition Java class. Use final results of these definitions for ROS2 or ROS1.

Sending requests

Once we have service definition ready we can use it to send requests to add_two_ints service.

ROS2

Required Java dependencies:

• jros2client - Java client for ROS2
• jros2services - client for ROS2 Services

Code:

var clientFactory = new JRos2ClientFactory();
var serviceClientFactory = new JRos2ServiceClientFactory();
try (var client = clientFactory.createClient();
        var serviceClient = serviceClientFactory
            .createClient(client, new AddTwoIntsServiceDefinition(), "add_two_ints")) {
    var request = new AddTwoIntsRequestMessage(3, 2);
    var response = serviceClient.sendRequestAsync(request).get();
    System.out.println(response);
}

ROS1

Required Java dependencies:

• jros1client - Java client for ROS1
• jros1services - client for ROS1 Services

Code:

var clientFactory = new JRos1ClientFactory();
var serviceClientFactory = new JRos1ServiceClientFactory();
try (var client = clientFactory.createClient();
        var serviceClient = serviceClientFactory
            .createClient(client, new AddTwoIntsServiceDefinition(), "add_two_ints")) {
    var request = new AddTwoIntsRequestMessage(3, 2);
    var response = serviceClient.sendRequestAsync(request).get();
    System.out.println(response);
}