How to use MAVSDK-Java

[JoshikaNetha]

Hi,
"I'm new to Mavsdk-Java , and I've successfully used Mavsdk in Python. However, I'm now interested in using it in Java. Could someone kindly assist me in utilizing Mavsdk in Java?

I would like to integrate Mavsdk-Java into my Java web application. Can anyone provide suggestions on how to integrate the necessary dependencies and incorporate Mavsdk-Java within a Java web application.

Thanks in advance.

[JonasVautherin]

Did you check the README and the examples?

[JoshikaNetha]

Yes, I have seen READMe but I tried it , I have downloaded libmavsdk, I'mnot understanding how to run MAVSDK server, So, please help me with this issue.

After some research, I have successfully added the Mavsdk dependencies to my Maven project. I have included all the necessary dependencies, and now I would like to know how to initiate a takeoff from my code
Thanks in advance

[divyanshupundir]

@JoshikaNetha, MAVSDK is divided into two parts, the MAVSDK-Server and the MAVSDK frontend, which in your case is MAVSDK-Java. Now, for your web application, you can download the MAVSDK-Server binary from the MAVSDK-Releases. You'll have to choose one according to the machine on which your web application is running.

Then you can run the MAVSDK-Server like this:

./mavsdk-server-binary udp://:8240 -p 9000

The first argument is the address to which the MAVSDK-Server should listen for MAVLink packets from your drone. There are several interfaces provided by MAVSDK:

• For TCP : tcp://[server_host][:server_port]
• For UDP : udp://[bind_host][:bind_port]
• For Serial : serial:///path/to/serial/dev[:baudrate]

The second argument p is the port to which the server sends the output. The MAVSDK frontends can connect to this port.

In MAVSDK-Java we do it using the io.mavsdk.System class.

System system = new System(address, port)

In the above example, if the MAVSDK-Server is running on the same machine as MAVSDK-Java, the address should be 127.0.0.1, and the port should be 9000.

[JoshikaNetha]

Thanks for response.

As you said I tried to build mavsdk-server from source file and from release, but its showing some error it not building successfully.

From Release , I have downloaded
libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb udp
then I have executed:
sudo dpkg -i libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb
then I have changed permission.

 ./libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb udp://:8240 -p 9000
./libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb: line 1: syntax error near unexpected token `newline'
./libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb: line 1: `!<arch>'

From Source, I have followed steps mentioned in this:

   [https://mavsdk.mavlink.io/main/en/cpp/guide/build_mavsdk_server.html]

After running below command:

cmake -Bbuild/default -DMAVLINK_DIALECT=mydialect -DMAVLINK_HEADERS=../mavlink-headers -H.

Error is:

-- Version: v1.4.0-490-ged7ac077
-- Version major: 1
-- Version minor: 4
-- Version patch: 0
-- Configuring done
-- Generating done
-- Build files have been written to: /home/nsl/MavSDK/Mavsdk server/MAVSDK/build/default/third_party/mavlink
[ 12%] Performing update step for 'mavlink'
[ 25%] Performing configure step for 'mavlink'
-- MAVLink dialect: mydialect
-- MAVLink version: 2.0
-- Configuring done
-- Generating done
-- Build files have been written to: /home/nsl/MavSDK/Mavsdk server/MAVSDK/build/default/third_party/mavlink/mavlink/src/mavlink-build
[ 37%] Performing build step for 'mavlink'
make[5]: *** No rule to make target '/home/nsl/MavSDK/Mavsdk server/MAVSDK/build/default/third_party/mavlink/mavlink/src/mavlink/message_definitions/v1.0/mydialect.xml', needed by 'include/mavlink/mydialect/mavlink.h'.  Stop.
make[4]: *** [CMakeFiles/Makefile2:76: CMakeFiles/generate_c_headers.dir/all] Error 2
make[3]: *** [Makefile:130: all] Error 2
make[2]: *** [CMakeFiles/mavlink.dir/build.make:112: mavlink/src/mavlink-stamp/mavlink-build] Error 2
make[1]: *** [CMakeFiles/Makefile2:76: CMakeFiles/mavlink.dir/all] Error 2
make: *** [Makefile:84: all] Error 2
CMake Error at third_party/cmake/build_target.cmake:51 (message):
  /home/nsl/MavSDK/Mavsdk server/MAVSDK/build/default/third_party/mavlink
  failed to build!
Call Stack (most recent call first):
  third_party/CMakeLists.txt:11 (build_target)


-- Configuring incomplete, errors occurred!
See also "/home/nsl/MavSDK/Mavsdk server/MAVSDK/build/default/CMakeFiles/CMakeOutput.log".
See also "/home/nsl/MavSDK/Mavsdk server/MAVSDK/build/default/CMakeFiles/CMakeError.log".

I have followed Building MAVSDK Library from Source steps also. but not working .

Please help me with this issue.

[divyanshupundir]

@JoshikaNetha No need to build the mavsdk-server. You can simply download the binary from the assets on the release page.

For example, if you have a Windows machine, you can download mavsdk-windows-x64-release.zip

[JoshikaNetha]

I have downloaded mavsdk-binary file as I'm working on ubuntu I have downloaded .deb file, then I have gave execution permission.

./libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb udp://:8240 -p 9000
./libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb: line 1: syntax error near unexpected token `newline'
./libmavsdk-dev_1.4.16_ubuntu20.04_amd64.deb: line 1: `!<arch>'

I'm getting above error.

[divyanshupundir]

Please try mavsdk_server_manylinux2010-x64.

[JoshikaNetha]

Thanks so much It running successfully but, I'm running make px4_sitl gazebo in same system.

In my Java Code I have written as below:

import io.mavsdk.*;
import io.mavsdk.action.Action;
import io.mavsdk.System;
public class MavSDK {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
//		Action action = new Action();
//		action.arm().andThen(action.takeoff()).subscribe();
		System system = new System("127.0.0.1", 9000);
		system.getAction().takeoff();
		
	}

}

I have added all the dependencies in pom.xml as below:

  <dependencies>
  	<dependency>
  		<groupId>io.mavsdk</groupId>
  		<artifactId>mavsdk</artifactId>
  		<version>1.3.1</version>
  	</dependency>
  	<dependency>
  		<groupId>io.reactivex.rxjava2</groupId>
  		<artifactId>rxjava</artifactId>
  		<version>2.2.21</version>
  	</dependency>

  	<dependency>
  		<groupId>io.grpc</groupId>
  		<artifactId>grpc-okhttp</artifactId>
  		<version>1.3.1</version>
  		<scope>runtime</scope>
  	</dependency>
  	<dependency>
  		<groupId>io.grpc</groupId>
  		<artifactId>grpc-stub</artifactId>
  		<version>1.42.1</version>
  		<scope>runtime</scope>
  	</dependency>
  	<dependency>
  		<groupId>org.slf4j</groupId>
  		<artifactId>slf4j-api</artifactId>
  		<version>1.7.35</version>
  		<scope>runtime</scope>
  	</dependency>
  	<dependency>
  		<groupId>io.grpc</groupId>
  		<artifactId>grpc-protobuf-lite</artifactId>
  		<version>1.42.1</version>
  		<scope>runtime</scope>
  	</dependency>
  </dependencies>

Here, I'm running Maven Project as Maven build , I'm getting below error:

[```
[INFO] Scanning for projects...
[INFO]
[INFO] �[1m--------------------------< �[0;36mcom.maven:MavSDK�[0;1m >--------------------------�[m
[INFO] �[1mBuilding MavSDK 0.0.1-SNAPSHOT�[m
[INFO] �[1m--------------------------------[ jar ]---------------------------------�[m
[INFO] �[1m------------------------------------------------------------------------�[m
[INFO] BUILD FAILURE�[m
[INFO] -----------------------------------------------------------------------�[m
[INFO] Total time: 0.306 s
[INFO] Finished at: 2023-06-12T17:10:14+05:30
INFO] �[1m------------------------------------------------------------------------�[m
[ERROR] Unknown lifecycle phase "Run". You must specify a valid lifecycle phase or a goal in the format : or :[:]:. Available lifecycle phases are: validate, initialize, generate-sources, process-sources, generate-resources, process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy, pre-clean, clean, post-clean, pre-site, site, post-site, site-deploy. -> �[1m[Help 1]�[m

[ERROR] To see the full stack trace of the errors, re-run Maven with the �[1m-e�[m switch.
[ERROR] Re-run Maven using the �[1m-X�[m switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] �[1m[Help 1]�[m http://cwiki.apache.org/confluence/display/MAVEN/LifecyclePhaseNotFoundException

[divyanshupundir]

Try running the TakeoffAndLand.java example with the correct address and port.

[divyanshupundir]

Also, you only need to add the mavsdk dependency. No need to add the grpc and rxjava ones.

[JoshikaNetha]

I tried to run TakeOffAndLand.java code I have mentioned

     `System drone = new System("127.0.0.1", 9000); 

`
using below commands:

:~/MavSDK/MAVSDK-Java/examples/java-client/src/main/java/io/mavsdk/example$ javac TakeoffAndLand.java 
TakeoffAndLand.java:3: error: cannot find symbol
import io.mavsdk.System;
                ^
  symbol:   class System
  location: package io.mavsdk
TakeoffAndLand.java:4: error: package io.mavsdk.action does not exist
import io.mavsdk.action.Action;
                       ^
TakeoffAndLand.java:7: error: package org.slf4j does not exist
import org.slf4j.Logger;
                ^
TakeoffAndLand.java:8: error: package org.slf4j does not exist
import org.slf4j.LoggerFactory;
                ^
TakeoffAndLand.java:11: error: cannot find symbol
  private static final Logger logger = LoggerFactory.getLogger(TakeoffAndLand.class);
                       ^
  symbol:   class Logger
  location: class TakeoffAndLand
TakeoffAndLand.java:11: error: cannot find symbol
  private static final Logger logger = LoggerFactory.getLogger(TakeoffAndLand.class);
                                       ^
  symbol:   variable LoggerFactory
  location: class TakeoffAndLand
TakeoffAndLand.java:16: error: constructor System in class System cannot be applied to given types;
    System drone = new System("127.0.0.1", 9000);
                   ^
  required: no arguments
  found:    String,int
  reason: actual and formal argument lists differ in length
TakeoffAndLand.java:19: error: cannot find symbol
    drone.getAction().arm()
         ^
  symbol:   method getAction()
  location: variable drone of type System
TakeoffAndLand.java:22: error: package Action does not exist
                  + ((Action.ActionException) throwable).getCode()))
                            ^
TakeoffAndLand.java:23: error: cannot find symbol
          .andThen(drone.getAction().takeoff()
                        ^
  symbol:   method getAction()
  location: variable drone of type System
TakeoffAndLand.java:26: error: package Action does not exist
                    + ((Action.ActionException) throwable).getCode())))
                              ^
TakeoffAndLand.java:28: error: cannot find symbol
          .andThen(drone.getAction().land()
                        ^
  symbol:   method getAction()
  location: variable drone of type System
TakeoffAndLand.java:31: error: package Action does not exist
                    + ((Action.ActionException) throwable).getCode())))
                              ^
13 errors

[divyanshupundir]

Looks like a build problem. Are you not using a build system like Gradle? For big projects with several dependencies, we should try not to use javac, instead use Gradle or Idea build systems.

If you have IntelliJ installed on your system, you can simply open this project and run the TakeoffAndLand test.

[sannithrao2468]

Hi ,@divyanshupundir .
I have followed all the above steps but i'm stuck at the build step. Here is my error

madhavanenisannith@nhhydl-00271:~/Desktop/Workspace/MAVSDK-Java/examples/java-client$ ./gradlew clean build

Task :compileJava FAILED

FAILURE: Build failed with an exception.

• What went wrong:
  Execution failed for task ':compileJava'.

Could not load class 'com.sun.tools.javac.api.JavacTool

• Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

• Get more help at https://help.gradle.org

BUILD FAILED in 397ms
2 actionable tasks: 2 executed

Previously i got an other error "cannot find tools.jar" , i resolved it , then i got this error. Can you please help?

[divyanshupundir]

This is more of a problem with the project and Java setup than MAVSDK. It looks like Gradle isn't able to find that Java compiler on your machine.

An easy way you can fix it is by opening the project in IntelliJ Idea and it will install all the required dependencies. You can then even run the tests directly from it.

Otherwise, you can follow this StackOverflow answer.