Where to start with JavaSpaces?

Question

I need to start with JavaSpaces and I found this article. But I found JINI library and downloaded it but couln't find JavaSpaces library. Is it moved to JINI or what?

Answer 1

There are two JavaSpaces implementations of any note: Blitz and GigaSpaces XAP. Blitz is open source; XAP is commercial, but has a community edition that's free for use.

I'm heavily biased towards XAP; I work for them. :) That said, there are a lot of reasons to consider XAP:

Space Aquisition

The mechanism for acquiring a space reference is far easier with GigaSpaces than it is with default JINI:

UrlSpaceConfigurer urlSpaceConfigurer = new UrlSpaceConfigurer("/./space");
IJSpace space = urlSpaceConfigurer.space();
// space is a close JavaSpaces analog, extended because the specification is rather limited

GigaSpace gigaSpace=new GigaSpaceConfigurer(space).gigaSpace();

// gigaSpace has **many** API improvements and is far more flexible.

API Improvements

The default JavaSpace API has no compensation for multiple tuple matches in the space. The more recent (i.e., 8 years old?) does, and Blitz implements it, but it's still not very flexible. Plus, you still get stuck with JINI Entries, which follow something like these rules:

1. Every field must be public. (i.e., "public String foo")
2. Every type must extend Entry.
3. Every field must extend Object. (i.e., Long instead of long, etc.)

XAP allows you to use Entry, but doesn't require it; with XAP, you can use ordinary POJOs. You still want to prefer Object types, because of wildcards (null is the JavaSpaces wildcard) but that's up to you.

XAP also provides a SQL query mechanism, as well as a document-based model (schemaless) for entries, and can also use Spring to manage notifications and remoting.