NullPointerException occurs in running a tutorial code building a simple LwM2M Client

[JeonghyunJoo]

Question

I am new to this leshan LwM2M library so please understand me even if my question is a stupid one.

I tried to strictly follow the instructions given by https://github.com/eclipse-leshan/leshan/wiki/Getting-Started-:-Client but I failed to run the tutorial code.

I added specified maven dependencies with 2.0.0-m14 for the leshan library version under the tag in my pom.xml.

I put the example code in my main function, resulting in the following code:

package com.jjh.maven.leshan_client_example;

import org.eclipse.leshan.client.LeshanClient;
import org.eclipse.leshan.client.LeshanClientBuilder;
import org.eclipse.leshan.client.endpoint.LwM2mClientEndpointsProvider;

public class App 
{
    public static void main( String[] args )
    {
    	String endpoint = "..." ; // choose an endpoint name
    	LeshanClientBuilder builder = new LeshanClientBuilder(endpoint);
    	LeshanClient client = builder.build();
    	client.start();
    }
}

It successfully compiled but gave me a NullPointerException with endpointsProvider. The full error message looks like this:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "org.eclipse.leshan.client.endpoint.LwM2mClientEndpointsProvider.init(org.eclipse.leshan.client.resource.LwM2mObjectTree, org.eclipse.leshan.client.request.DownlinkRequestReceiver, org.eclipse.leshan.client.endpoint.ClientEndpointToolbox)" because "endpointsProvider" is null
	at org.eclipse.leshan.client.LeshanClient.<init>(LeshanClient.java:123)
	at org.eclipse.leshan.client.LeshanClientBuilder.createLeshanClient(LeshanClientBuilder.java:364)
	at org.eclipse.leshan.client.LeshanClientBuilder.build(LeshanClientBuilder.java:328)
	at com.jjh.maven.leshan_client_example.App.main(App.java:13)

In my understanding it seems that I need to call builder.setEndpointsProviders explicitly as builder.endpointsProvider is never initialized with the example code.

Is the tutorial code incomplete? or did I miss something?
If the example code is incomplete, can I ask where I can find a working and concise tutorial code for building a simple client (expecting much simpler code than LeshanClientDemo.java)

Thanks in advance.

[sbernard31]

Is the tutorial code incomplete? or did I miss something?

Not really the turorial says : "To develop your client you need to use the leshan-client-cf module. To know the last 1.x version."

👆 it is about Leshan version 1.x

For now there is no tutorial for version 2.x. 😞

So

• either you can live with LWM2M v1.0.x and you can use Leshan v1.x and use the tutorial as it.
• or if you need LWM2M v1.1.x, you need to go with the in-developement version of Leshan v2.x. and there is no tutorial for now, but you could look at leshan-client-demo as example to fix the tutorial OR look at Add Transport Layer abstraction at Client side. #1323 (for client API).

To learn more about new endpoint provider API (client, server, bootstrap server) : #1025 (comment)

[JeonghyunJoo]

Thanks @sbernard31

You are right! I could make it run by modifying the Leshan version from 2.0.0-m14 to 1.5.0