Connectivity > Cross Language Clients > C Integration > Compile ActiveMQ with GCJ
You can use GCJ to build ActiveMQ as a shared library you can reuse from C++.
This document describes how to native compile ActiveMQ for use in a C++ environment. The version of ActiveMQ used is 3.2 in this howto. To compile you'll need GCC 4.0.2, or later, with both Java, and C/C++ support.
If you don't already have GCC 4.0.2 installed you need to download and build it. See GCC manuals for complete instructions on how to build GCC but below is a short descriptions of the steps involved. The GCC build steps assumes that you already have an older GCC compiler installed.
/opt/gccbuild/gcc-4.0.2 /opt/gccbuild/output
cd /opt/gccbuild/output
../gcc-4.0.2/configure --prefix=/opt/gcc402
--enable-shared
--enable-threads=posix
--enable-languages=c,c++,java
make bootstrap make install
activeio-1.1.jar activemq-core-3.2.jar commons-logging-1.0.3.jar concurrent-1.3.4.jar geronimo-spec-j2ee-jacc-1.0-rc4.jar geronimo-spec-j2ee-management-1.0-rc4.jar geronimo-spec-jms-1.1-rc4.jar geronimo-spec-jta-1.0.1B-rc4.jar log4j-1.2.8.jar
Either access the ActiveMQ classes directly from C++ or write a facade object in Java that handles all startup and shutdown logic of ActiveMQ. Save the glue files in the same directory as for the ActiveMQ jars.
An CNI example using a Java object starting the MQ.
#include <gcj/cni.h>
#include <iostream>
#include <java/lang/System.h>
#include <java/lang/Throwable.h>
#include <java/io/PrintStream.h>
#include "MQAdapter.h"
using namespace std;
int main(int argc, char* argv\[\])
{
cout << "Entering main" << endl;
using namespace java::lang;
try
{
// Create and startup Java VM
JvCreateJavaVM(NULL) ;
JvAttachCurrentThread(NULL, NULL) ;
System::out->println(JvNewStringLatin1("Java println")) ;
// Start ActiveMQ
MQAdapter* pAdapter = new MQAdapter() ;
pAdapter->start() ;
// Send a message
pAdapter->send(JvNewStringLatin1("Hello World!")) ;
// Shutdown ActiveMQ
pAdapter->stop() ;
JvDetachCurrentThread() ;
}
catch( Throwable *t )
{
System::err->println(JvNewStringLatin1("Exception")) ;
t->printStackTrace() ;
}
}
import org.activemq.*;
import java.util.Hashtable ;
import javax.jms.*;
import javax.naming.*;
public class MQAdapter
{
private InitialContext jndiContext ;
private QueueConnectionFactory factory ;
private QueueConnection connection ;
private QueueSession session ;
private QueueSender sender ;
private Queue queue ;
public MQAdapter()
{
}
public void start()
{
try
{
Hashtable props = new Hashtable() ;
props.put(Context.INITIAL\_CONTEXT\_FACTORY, "org.activemq.jndi.ActiveMQInitialContextFactory") ;
props.put(Context.PROVIDER_URL, "tcp://localhost:61616") ;
props.put("queue.MyQueue", "example.MyQueue") ;
jndiContext = new InitialContext(props) ;
// Create and configure JMS connection factory
factory = (QueueConnectionFactory)jndiContext.lookup("ConnectionFactory") ;
// Lookup Queue
queue = (Queue)jndiContext.lookup("MyQueue") ;
// Create a JMS connection
connection = (QueueConnection)factory.createQueueConnection() ;
System.out.println("Created connection: " + connection) ;
// Create a JMS session
session = connection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE) ;
System.out.println("Created session: " + session) ;
// Create JMS sender
sender = session.createSender(queue) ;
}
catch( Exception e )
{
e.printStackTrace() ;
try
{
if( connection != null )
connection.close() ;
} catch( JMSException jmse )
{ /* ignore */ }
}
}
public void stop()
{
try
{
if( connection != null )
connection.close() ;
} catch( JMSException e )
{ /* ignore */ }
}
public void send(String msg)
{
TextMessage message ;
try
{
message = session.createTextMessage(msg) ;
sender.send(message) ;
}
catch( JMSException e )
{
e.printStackTrace() ;
}
}
}
The Java code must be BC compiled to be able to dynamically link required classes as needed, see reference for more information on BC compilation. Use the suggested script to compile all ActiveMQ JARs and create a class map database.
Note
Using -Bsymbolic does not seem to work, use -symbolic instead.
compile.sh:
#!/bin/sh
# Create new classmap database
gcj-dbtool -n classmap.db
for JAR_FILE in \`find -iname "*.jar"\`
do
echo "Compiling ${JAR_FILE} to native"
gcj -shared -findirect-dispatch -fjni -fPIC -Wl,-symbolic -o ${JAR\_FILE}.so ${JAR\_FILE}
gcj-dbtool -a classmap.db ${JAR\_FILE} ${JAR\_FILE}.so
done
Run the above script and set environment property GCJ_PROPERTIES.
./compile.sh export GCJ_PROPERTIES="gnu.gcj.precompiled.db.path=/opt/app/classmap.db"
Java compile MQAdapter.java
gcj --classpath=./geronimo-spec-jms-1.1-rc4.jar:./activemq-core-3.2.jar -C MQAdapter.java
Generate CNI header for MQAdapter.class
gcjh MQAdapter
JAR the Java glue code
fastjar cf MQAdapter.jar MQAdapter.class
Native compile the Java JAR into a shared library, add output directory to LD_LIBRARY_PATH.
gcj -shared -findirect-dispatch -fjni -fPIC -Wl,-symbolic -o MQAdapter.so MQAdapter.jar export LD\_LIBRARY\_PATH=$LD\_LIBRARY\_PATH:/opt/app
Compile the C++ code
g++ -c Bootstrap.cpp
Link Bootstrap with the Java code
gcj -o Bootstrap Bootstrap.o -L /opt/app -lgcj -lstdc++ activeio-1.1.jar.so activemq-core-3.2.jar.so
commons-logging-1.0.3.jar.so concurrent-1.3.4.jar.so geronimo-spec-jms-1.1-rc4.jar.so
geronimo-spec-j2ee-management-1.0-rc4.jar.so geronimo-spec-j2ee-jacc-1.0-rc4.jar.so
geronimo-spec-jta-1.0.1B-rc4.jar.so log4j-1.2.8.jar.so MQAdapter.so
Now, if everything went ok you should be able to run the app. with ./Bootstrap.