Using JavaSpaces in Orc#

JavaSpaces is Sun's distributed tuple space service. JavaSpaces is now part of Apache River.

This page supplies a simple example of using JavaSpaces in Orc, based the SDN article Getting Started With JavaSpaces Technology: Beyond Conventional Distributed Programming Paradigms by Q. H. Mamoud.

Installing Apache River#

1. Download the Apache River binary release from URL: http://river.apache.org/downloads.html
2. Expand the downloaded ZIP/GZIP file into a directory, which we will refer to hereinafter as ${RIVER_HOME} .

Installing the example#

1. Download two utility classes from the JavaSpaces article: MessageEntry.java and Lookup.java.
2. Compile them: javac -classpath ${RIVER_HOME}/lib/jini-ext.jar MessageEntry.java Lookup.java
3. Download the Orc program SpaceClient.orc
4. Download a temporary fix needed until Orc issue 84 is fixed: TempHack.java.
5. Compile with: javac -classpath ${RIVER_HOME}/lib/jini-ext.jar TempHack.java

The Orc program#

Contents of SpaceClient.orc:

-- Translation into Orc of SpaceClient.java from
-- Mamoud, Q. H. 2005. Getting Started With JavaSpaces Technology: Beyond
-- Conventional Distributed Programming Paradigms. Sun Developer Network.
-- http://java.sun.com/developer/technicalArticles/tools/JavaSpaces/

import class MessageEntry = "MessageEntry"
import class Lookup = "Lookup"
import class Class = "java.lang.Class"
import class Long = "java.lang.Long"
import class JavaSpace = "net.jini.space.JavaSpace"

MessageEntry() >msg>
msg.content := "Hello there" >>
Println("Searching for a JavaSpace...") >>
Lookup(Class.forName("net.jini.space.JavaSpace")) >finder>
finder.getService() >space>
Println("A JavaSpace has been discovered. ") >>
Println("Writing a message into the space...") >>
space.write(msg, null, 60*60*1000) >>
MessageEntry() >template>
Println("Reading a message from the space...") >>
space.read(template, null, Long.MAX_VALUE?) >result>
Println("The message read is: "+result.content?)

Running Apache River JavaSpaces#

Open three shells and run each of the following, one per shell:

cd ${RIVER_HOME}/examples/hello
./scripts/httpd.sh

cd ${RIVER_HOME}/examples/hello
./scripts/jrmp-reggie.sh

cd ${RIVER_HOME}/examples/hello
java -Djava.security.policy=config/outrigger.policy -jar ../../lib/start.jar config/start-outrigger-group.config

Running the Orc program#

In the directory with the SpaceClient.orc and the compiled MessageEntry and Lookup classfiles, run the Orc example:

java -cp ${ORC_HOME}/orc-2.0.2.jar:${ORC_HOME}/lib/\*:${RIVER_HOME}/lib/jini-ext.jar:${RIVER_HOME}/lib/reggie.jar:${RIVER_HOME}/lib/outrigger.jar:. orc.Main SpaceClient.orc