Running JVM COBOL within Apache Tomcat « Back

The existence of Micro Focus JVM COBOL opens up some prospects for deploying COBOL into infrastructure that has previously been tricky to utilise via COBOL. Such a framework is the ubiquitous Apache Tomcat environment for deploying Java servlets and JSPs. Today it is possible to create servlets written using JVM COBOL that can deploy to Tomcat. It is also possible to invoke legacy COBOL applications compiled to JVM COBOL from these servlets to allow them to integrate with JVM web applications.

The JVM COBOL runtime currently accesses native COBOL by default. Specific set up requirements exist before JVM COBOL can be deployed to Tomcat. This document highlights the steps required to deploy JVM COBOL into Tomcat on Windows and Red Hat Enterprise Linux (though the same steps should work for all supported Linux and Unix platforms).

Overview

The normal way of deploying support library jars into a web application is to include the jar files in the WEB-INF/lib directory of the web application in question. This process does not work for the main JVM COBOL runtime. JVM COBOL currently utilises the native COBOL runtime for access to facilities such as file handling (work is in progress to provide a pure JVM solution). Tomcat will launch any jars within the web applications lib directory in a class loader specific to that web application instance. When a native library is loaded in such a class loader it becomes tied to it. Redeploying the application will use a new class loader and thus the application can no longer use the native library.

To make the runtime work with Tomcat you must deploy the jar such that it will load into the system class loader that is the base class loader for the whole system. The document goes into the steps needed to perform such a deployment and the environment configuration needed to ensure the runtime can find the native libraries required.

On Unix there is also a specific issue about the use of cobjrun that requires additional configuration.

Configuring Tomcat 7 for JVM COBOL on Windows

On Windows the process is relatively simple. You need only copy the runtime jars into the Tomcat lib directory and launch Tomcat with the appropriate entries on the PATH variable.

First Time Only

To install Apache Tomcat 7 navigate to http://tomcat.apache.org/download-70.cgi and select the Windows service installer.

Firstly assume we have a Micro Focus COBOL install at %COBDIR% (this is usually at C:\Program Files (x86)\Micro Focus\Visual COBOL 2010 on Windows 7) and an Apache Tomcat install at %CATALINA_HOME% (usually at C:\Program Files (x86)\Apache Software Foundation\Tomcat 7.0). In the %COBDIR%\bin directory the JVM COBOL runtime jars are contained. These are mfcobolrts.jar and mfcobol.jar. Copy these into %CATALINA_HOME%\lib. This will ensure that Tomcat loads the runtime into the system class loader and not into one specific to a particular web app.

To launch Tomcat you’ll need to set the PATH variable correctly. The native runtime and JVM native support libraries need to be on the PATH variable that Tomcat is launched from. For a 32 bit JVM these will be in %COBDIR%\bin. For a 64 bit JVM use %COBDIR%\bin64. You’ll need to stop any tomcat instance currently running and then launch it with the new environment. To do this from the command line run the following commands:
   #set PATH=%PATH%;%COBDIR%\bin;%CATALINA_HOME%\bin
   #tomcat7 //SS//
   #tomcat7

Now navigate to the web page localhost:8080 and you should see your Tomcat landing page. Any web application archive using JVM COBOL classes can now be deployed to this Tomcat instance if it were a normal Java web application.

Configuring Tomcat 7 for JVM COBOL on Red Hat Enterprise Linux

On Linux and Unix platforms the deployment requirements are a little more complex. To deal with signal handling in JVM COBOL programs they must be launched in general with the Micro Focus cobjrun trigger into the JVM runtime. For this reason any Tomcat instance that wishes to use JVM COBOL must be launched using the cobjrun trigger rather than the normal java trigger.

However this isn’t as simple as renaming cobjrun as java and putting it on the path. Tomcat uses JAVA_HOME to find the java trigger and the VM so you need to modify a Java instance specifically for running JVM COBOL on Tomcat.

First Time Only

Create a copy of your Java 6 install and we’ll use this to run Tomcat. Download the Tomcat core zip from http://tomcat.apache.org/download-70.cgi and unpack it.

Assuming your Java copy is at $JAVA_HOME, your Micro Focus COBOL install is at $COBDIR (usually this is /opt/microfocus/VisualCOBOL) and Tomcat is installed to $CATALINA_HOME do the following. Move the java trigger to a back up location:
    #mv $JAVA_HOME/bin/java $JAVA_HOME/bin/javabu

Next link the appropriate cobjrun trigger to replace the java trigger. For a 32 bit JVM this would be cobjrun32, for a 64 bit JVM you want cobjrun64. Assuming 32 bit you do the following:
    #ln -s $COBDIR/bin/cobjrun32 $JAVA_HOME/bin/java

Next you need to copy the impure JVM runtime into Tomcat. This requires that both the JVM runtime jar (mfcobolrts.jar) and JVM native interop jar (mfcobol.jar) are copied into $CATALINA_HOME/lib
    #cp $COBDIR/lib/mfcobolrts.jar $CATALINA_HOME/lib
    #cp $COBDIR/lib/mfcobol.jar $CATALINA_HOME/lib

You may need to set up a user profile for the tomcat manager. To do this edit the file $CATALINA_HOME/conf/tomcat-users.xml and add the following to the tomcat-users node
 <role rolename="manager-gui"/>
 <user username="admin" password="admin" roles="manager-gui"/>

Assuming you’ve created a modified Java and Tomcat install as above do the following to launch it with JVM COBOL support.

Add Java and Tomcat to the path
   #export PATH=$JAVA_HOME/bin:$CATALINA_HOME/bin:$PATH

Setup your COBDIR
   #$COBDIR/bin/cobsetenv $COBDIR

Try to use the java trigger as below
   #java -version

It should put out version information. If instead it puts out the error message ’java: Could not load libjvm.so’ it means that the trigger cannot find the JVM runtime library. This needs to be added to LD_LIBRARY_PATH (LIBPATH on AIX/HP_UX) for the trigger to work. The exact location of libjvm.so varies from JVM to JVM. For the 32bit Oracle 1.6.27 VM on Linux the necessary command is
   #JAVA_LIB=$JAVA_HOME/jre/lib/i386/server
   #export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$JAVA_LIB

To start tomcat run
   #startup.sh

Now navigate to the web page localhost:8080 and you should see your Tomcat landing page. Any web application archive using JVM COBOL classes can now be deployed to this Tomcat instance if it were a normal Java web application.

To stop tomcat run
   #shutdown.sh