Java API bindings

Presentation

The Java bindings are currently a work in progress based mostly on the work of Toth Istvan. The first usable release is 0.2.0, where most of the naming conventions were defined. Futher release will try as much as possible to stay compatible

Getting it

The latest versions of the libvirt Java bindings can be downloaded from:

Hourly development snapshots

Once an hour, an automated snapshot is made from the latest CVS server source tree. These snapshots should be usable, but we make no guarantees about their stability:

CVS repository access

The master source repository uses CVS and anonymous access is provided. Prior to accessing the server is it necessary to authenticate using the password anoncvs. This can be accomplished with the cvs login command: 

  # cvs -d :pserver:anoncvs@libvirt.org:2401/data/cvs login

Once authenticated, a checkout can be obtained using 


  # cvs -d :pserver:anoncvs@libvirt.org:2401/data/cvs co libvirt-java

The libvirt-java build process uses GNU autotools, so after obtaining a checkout it is necessary to generate the configure script and Makefile.in templates using the autogen.sh command. As an example, to do a complete build and install it into your home directory run: 

  ./autogen.sh --prefix=$HOME/usr
  make
  make install

Other build system are not currently available but as usual we take patches (Eclipse/ant/...) would be welcome !

currently libvirt-java requires a version of libvirt >= 0.4.0 to be installed as well as the associated libvirt development files/package. It should compile with any java implementation >= 1.5, the bindings uses the enum construct which appeared only in that version.

Libvirt-java bindings development occurs on the same mailing-list as the normal libvirt work see the associated contact page

GIT repository mirror

The CVS source repository is also mirrored using GIT, and is available for anonymous access via: 

 
  git clone git://git.et.redhat.com/libvirt-java

It can also be browsed at 


  http://git.et.redhat.com/?p=libvirt-java.git;a=summary

Content

The bindings are articulated around a few classes in the org/libvirt namespace, notably the Connect, Domain and Network ones. Functions in the C API taking virConnectPtr, virDomainPtr or virNetworkPtr as their first argument usually become methods for the classes, their name is just stripped from the virConnect or virDomain(Get) prefix and the first letter gets converted to lower case, for example the C functions:

int virConnectNumOfDomains (virConnectPtr conn);

int virDomainSetMaxMemory (virDomainPtr domain, unsigned long memory);

become

virConn::numOfDomains()

virDomain::setMaxMemory(long memory)

There is of course some functions where the mapping is less direct and using extra classes to map complex arguments. The Javadoc is available online or as part of a separate libvirt-java-javadoc package.

So let's look at a simple example inspired from the test.java test found in src in the source tree:

import org.libvirt.*;
public class minitest {
    public static void main(String[] args) {
        Connect conn=null;
        try{
            conn = new Connect("test:///default", true);
        } catch (LibvirtException e){
            System.out.println("exception caught:"+e);
            System.out.println(e.getError());
        }
        try{
            Domain testDomain=conn.domainLookupByName("test");
            System.out.println("Domain:" + testDomain.getName() + " id " +
                               testDomain.getID() + " running " +
                               testDomain.getOSType());
        } catch (LibvirtException e){
            System.out.println("exception caught:"+e);
            System.out.println(e.getError());
        }
    }
}

There is not much to comment about it, it really is a straight mapping from the C API, the only points to notice are: