Compile ActiveMQ Classic with GCJ

Connectivity > Cross Language Clients > C Integration > Compile ActiveMQ Classic with GCJ

You can use GCJ to build ActiveMQ Classic as a shared library you can reuse from C++.

Native compile ActiveMQ Classic HOWTO

Abstract

This document describes how to native compile ActiveMQ Classic for use in a C++ environment. The version of ActiveMQ Classic 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.

Tools Setup

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.

• Unpack GCC into an arbitrary directory, for example /opt/gccbuild, and then create a separate output directory. Your directory structure should look similar to this;

  /opt/gccbuild/gcc-4.0.2
  /opt/gccbuild/output
  

• Go to the output directory and run configure.

  cd /opt/gccbuild/output
  ../gcc-4.0.2/configure --prefix=/opt/gcc402
   --enable-shared
   --enable-threads=posix
   --enable-languages=c,c++,java
  

• Run make.

  make bootstrap
  make install
  

• Download ActiveMQ Classic and copy the JARs to a new empty directory /opt/app, including

  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
  

Write the Glue Code

Either access the ActiveMQ Classic classes directly from C++ or write a facade object in Java that handles all startup and shutdown logic of ActiveMQ Classic. Save the glue files in the same directory as for the ActiveMQ Classic jars.

An CNI example using a Java object starting the MQ.

Bootstrap.cpp

#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 Classic
 MQAdapter* pAdapter = new MQAdapter() ;
 pAdapter->start() ;
 // Send a message
 pAdapter->send(JvNewStringLatin1("Hello World!")) ;
 // Shutdown ActiveMQ Classic
 pAdapter->stop() ;
 
 JvDetachCurrentThread() ;
 }
 catch( Throwable *t )
 {
 System::err->println(JvNewStringLatin1("Exception")) ;
 t->printStackTrace() ;
 }
}

MQAdapter.java

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() ;
 }
 }
}

Compile the Java and C++ Code

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 Classic 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.

References

How to BC compile with GCJ

The state of Java on Linux