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JNC (Java NETCONF Client) is the name of a Java library for communicating with NETCONF agents, and a plugin for pyang ( to generate Java classes from YANG models, to be used by the JNC library.
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Java NETCONF Client.

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JNC (Java NETCONF Client) is the name of both a Java library for NETCONF client code and a Java output format plugin for pyang, an extensible YANG validator and converter in python. You need an installation of pyang to use the JNC plugin. Get it here:

The JNC plugin can be used to generate Java class hierarchies from YANG data models. Together with the JNC library, these generated Java classes may be used as the foundation for a NETCONF client (AKA manager) written in Java. The JNC library is distributed along with the JNC plugin script.

JNC uses Ganymed SSH-2 to communicate with NETCONF servers/agents, you may get it from here: or by using aptitude ( sudo aptitude install libganymed-ssh2-java

This readme proposes two different ways of getting started. If you're running Linux and don't want to use eclipse, feel free to skip the following section.

Get started using eclipse

Make sure you have pyang installed, and that is in the plugins directory of your installation. For instructions on how to use pyang, please see the pyang man page.


Create an eclipse project for JNC: open the "New Java Project" dialog, uncheck the "Use default location" checkbox and choose the jnc folder as the location instead, then Finish.

Now you need to add ganymed ssh2 to the project. Right click on the project folder in the Package Explorer, choose Build Path->Add External Archives and select your ganymed ssh2 Jar file.

If you don't want to run the tests, just delete the test source folder. Otherwise, you need to add JUnit 4 to the build path. This may be done by opening one of the test files, placing the marker on one of the lines which have errors, pressing Ctrl+1, choosing "Fix project setup..." and then OK when eclipse proposes to add the library. You should now be able to run the tests by right clicking on the test source folder and selecting Run As -> JUnit test.

The next step is to generate some Java classes using the JNC pyang plugin and write a client that uses them together with the JNC library. Please see the user manual for instructions on how to do this.

Get started in Linux (without eclipse):

Add the JNC plugin to your existing pyang installation. This may be done in one of the following three ways:

  1. Add to pyang/plugins in your pyang installation,
  2. Add the location of to the $PYANG_PLUGINPATH environment variable, or
  3. Use the --plugindir option of pyang each time you want to use JNC

If more than one of these approaches is used, you will end up with optparse conflicts so please choose one and stick with it. From here on, we will assume that you went for (1), but using (2) or (3) should be anologous.

JNC can be used to generate Java classes from a YANG file of your choice. There are a collection of yang files in the 'examples/yang' directory. To generate classes for a YANG file, open a terminal, change directory to where you want the classes to be generated, launch pyang with the jnc format, specifying the output folder and the yang model file.

For example, to generate the classes for simple.yang to the 'examples' directory with base package gen.simple, type:

 $ pyang -f jnc --jnc-output src/gen/simple yang/simple.yang

There should now be a newly generated 'src' folder in the current directory, containing a directory structure with the generated classes. Note that 'src' is special treated so that it does not become part of the package names of the generated classes.

To get more detailed information on how the generation proceeds the --jnc-debug or --jnc-verbose options can be used. Rerunning JNC silently overwrites any old classes in the output directory.

To actually use the generated classes, you need to compile Java client code using the JNC library. It might be convenient to make a Jar file with the JNC library for this purpose. There are several ways to do this:

  1. Run the ant script located in the jnc directory: ant clean all
  2. Manually: Open a terminal, change directory to jnc, compile the classes with javac -d bin -sourcepath src src/com/tailf/jnc/*.java Now change directory to bin and generate the Jar file with jar cvf ../lib/JNC.jar *
  3. Set up a project in eclipse and export the Jar (see previous section).

If the ant script fails to run, the most probable reason is that ganymed ssh2 is not installed in the expected way. Check that the ganymed.dir variable points to the directory containing your ganymed ssh2 Jar file, and that the classpath in the compile target corresponds to the correct build.

To run the JNC tests, see the previous section or run them with JUnit 4 from commandline if you so prefer. The tests resides in the jnc/test folder.

Please see the user manual for tutorials and further information on how to write a client and how to run it against a server using JNC.

High level description

The different types of generated files are:

Root class -- This class has the name of the prefix of the YANG module, and contains fields with the prefix and namespace as well as methods that enables the JNC library to use the other generated classes when interacting with a NETCONF server.

YangElement -- Each YangElement corresponds to a container or a list in the YANG model. They represent tree nodes of a configuration and provides methods to modify the configuration in accordance with the YANG model that they were generated from. The top-level containers or lists in the YANG model will have their corresponding YangElement classes generated in the output directory together with the root class. Their respective subcontainers and sublists are generated in subpackages with names corresponding to the name of the parent container or list.

YangTypes -- For each derived type in the YANG model, a class is generated to the root of the output directory. The derived type may either extend another derived type class, or the JNC type class corresponding to a built-in YANG type.

Packageinfo -- For each package in the generated Java class hierarchy, a file is generated, which can be useful when generating javadoc for the hierarchy.

Schema file -- If enabled, an XML file containing structured information about the generated Java classes is generated. It contains tagpaths, namespace, primitive-type and other useful meta-information.

The typical use case for these classes is as part of a JAVA network management system (EMS), to enable retrieval and/or storing of configurations on NETCONF agents/servers with specific capabilities.

Release History


Emil starts working at Tail-f and reads up on the NETCONF RFC 6241 and YANG RFC 6020. You should too if you intend to contribute to this project!


JPyang is born as a few lines of python code that integrates with pyang are written.


Empty initial commit of the repository. It will contain the source code for JPyang once it has been decided that it will be open source rather than proprietary to tail-f. The plugin itself is just the single script.


New tests for the INM and ConfM library classes are written.


Work on a new structure for the JPyang code begins, using classes to represent methods and organize functionality.


Unit tests for JPyang functions and class methods are added to pyang.


The ConfM.xs classes are replaced by new internal representations of the YANG built in classes.


The INM and ConfM libraries are merged into the new JNC library, with better support for YANG.


JPyang is now fully object oriented, with method generator classes for all relevant statements. This means that the generated classes should import all JNC, java.util, java.math and generated classes that they use, and no other.


The JPyang project repository is cleaned up, removing all non-comprehensible files and adding a new README and ant build files.


Meeting at Tail-f about the future of the project. The marketing and product management VP seems inclined to release as open source once the most basic functionality has been tested and the documentation is complete.


JPyang is renamed to JNC. So now there is both a JNC library and a JNC pyang plugin.


The GitHub repository is renamed to JNC and its readme is updated.


Support for notifications added, and there is only one thing remaining until it is possible to generate fully compliant junos.yang classes!


JNC is finally made open source! There are some changes remaining before this will be publicly announced however.


Copyright 2012 Tail-f Systems AB

See License File.

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