Cajo project
The Cajo Project is a framework that enables multiple Java applications that are spread across multiple machines to work together as one transparently and dynamically. This framework is useful for both open/free and proprietary applications that need distributed computing capabilities. It is capable of being used on almost any Java-equipped platform (JRE/JME 1.2 or higher) (mobile phones, mainframes, servers, embedded devices etc.) It is a “drop-in” framework, because it does not impose any structural requirements or source code changes and is 100% pure Java with no XML code. It also is not dependent on any other frameworks and can work behind NAT, firewalls, even HTTP proxies.
History[edit]
The Cajo Project has been issued by the IANA port number 1198 and UDP Multicast address 224.0.23.162.
License[edit]
The source code is free under the LGPL, and the documentation is free under the GFDL.
Usage[edit]
Overview[edit]
Using the Cajo Project, ordinary unmodified Java objects, can be remote using a single line of code:[1]
- Itemserver.bind(someObject, "someName")
These can then be used by remote machines either statically, or dynamically.
Static remote object usage[edit]
Static remote object usage is typically performed when there are one or more interfaces to the object, defining how the client may use it, known at Compile time. For example:
- public interface SomeInterface { ... // method signatures}
The remote object implements this interface, and possibly others, then remotes the object as shown previously.
Static remote object usage is provided through a TransparentItemProxy.[2] The user of a remote object can create a reference to this object, which actually implements the shared interface, as follows:
- SomeInterface si = (SomeInterface)TransparentItemProxy.getItem("//someHost:1198/someName", new Class[...] {SomeInterface.class} )
A remote machine may now invoke methods on the remote object, with the exact Java syntax and semantics, as if it were local.
Dynamic remote object usage[edit]
Dynamic remote object usage is typically performed when the interface to an object will be determined at runtime. This is often the case when using Cajo remote objects in a scripting.[3] A machine dynamically uses a remote object reference as follows:
- // obtain reference
Object object = Remote.getItem("//someHost:1198/someName");
- // typically obtained at runtime
String someMethod = "someMethod";
- // also obtained at runtime
Object someArgs = new Object[...] { someArgs, ... };
- Object result = Remote.invoke(object, someMethod, someArgs);
This snippet invokes a method on a remote object, providing the arguments, (if any) and returning the result. (if any)
The cajo framework can allow a machine to remote its object reference using UDP with IP multicast.[4] This technique lets machines interested to use remote references, simply listen for the announcements. This provides a One-to-many linkage mechanism, where the users of the remote object do not need to know the TCP/IP address of the host machine.
Remote graphical user interfaces[edit]
The Cajo Project is also used to remote graphical user interfaces.[5] This allows an application to run its view on separate machines from its model, and even its controller objects.
See also[edit]
References[edit]
- ^ "Adding cajo to existing applications". Cajo project. 2007-08-04. Archived from the original on 2006-09-25. Retrieved 2008-01-19.
- ^ "Using remote objects as if they were local". Cajo project. 2007-08-04. Archived from the original on 2007-12-23. Retrieved 2008-01-19.
- ^ "Why script cajo?". Cajo project. 2007-08-04. Archived from the original on 2008-01-03. Retrieved 2008-01-19.
- ^ "Using cajo Multicasting". Cajo project. 2007-08-04. Archived from the original on 2007-12-23. Retrieved 2008-01-19.
- ^ "Using the cajo proxy mechanism". Cajo project. 2007-08-04. Archived from the original on 2007-12-23. Retrieved 2008-01-19.
External links[edit]
- https://web.archive.org/web/20060925101254/https://cajo.dev.java.net/ The cajo project page
- http://java.net/projects/cajo[permanent dead link] The cajo SDK project page
- Official IANA port number Announcement [permanent dead link]
- IANA Multicast Address Announcement [permanent dead link]
- Internet Multicast Addresses