Index: core/src/main/java/org/quickfixj/jmx/JmxExporter.java
===================================================================
--- core/src/main/java/org/quickfixj/jmx/JmxExporter.java	(revision 899)
+++ core/src/main/java/org/quickfixj/jmx/JmxExporter.java	(working copy)
@@ -17,30 +17,73 @@
 
 package org.quickfixj.jmx;
 
+import javax.management.InstanceAlreadyExistsException;
+import javax.management.InstanceNotFoundException;
 import javax.management.JMException;
 import javax.management.MBeanServer;
 import javax.management.MBeanServerFactory;
+import javax.management.ObjectName;
 
 import org.quickfixj.jmx.mbean.connector.ConnectorJmxExporter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import quickfix.Connector;
 import quickfix.mina.SessionConnector;
 
 public class JmxExporter {
 
+    /**
+     * Constant indicating that registration should fail when
+     * attempting to register an MBean under a name that already exists.
+     * <p>This is the default registration behaviour.
+     */
+    public static final int REGISTRATION_FAIL_ON_EXISTING = 0;
+    /**
+     * Constant indicating that registration should ignore the affected MBean
+     * when attempting to register an MBean under a name that already exists.
+     */
+    public static final int REGISTRATION_IGNORE_EXISTING = 1;
+    /**
+     * Constant indicating that registration should replace the affected MBean
+     * when attempting to register an MBean under a name that already exists.
+     */
+    public static final int REGISTRATION_REPLACE_EXISTING = 2;
+
+    private int registrationBehaviour;
+
+    private final Logger log = LoggerFactory.getLogger(getClass());
+
     private final MBeanServer mbeanServer;
 
     private ConnectorJmxExporter connectorExporter = new ConnectorJmxExporter();
     
-    public JmxExporter(MBeanServer mbeanServer) {
+    public JmxExporter(MBeanServer mbeanServer, int registrationBehaviour) {
         this.mbeanServer = mbeanServer;
+        this.registrationBehaviour = registrationBehaviour;
     }
 
+    public JmxExporter(MBeanServer mbeanServer) {
+        this(mbeanServer, REGISTRATION_FAIL_ON_EXISTING);
+    }
+
     public JmxExporter() throws JMException {
-        this.mbeanServer = createMBeanServer();
+        this(createMBeanServer());
     }
 
-    private MBeanServer createMBeanServer() throws JMException {
+    /**
+     * Specify  what action should be taken when attempting to register an MBean
+     * under an {@link javax.management.ObjectName} that already exists.
+     * <p>Default is REGISTRATION_FAIL_ON_EXISTING.
+     * @see #REGISTRATION_FAIL_ON_EXISTING
+     * @see #REGISTRATION_IGNORE_EXISTING
+     * @see #REGISTRATION_REPLACE_EXISTING
+     */
+    public void setRegistrationBehavior(int registrationBehaviour) {
+        this.registrationBehaviour = registrationBehaviour;
+    }
+
+    private static MBeanServer createMBeanServer() throws JMException {
         try {
             Class<?> factoryClass = Class.forName("java.lang.management.ManagementFactory");
             try {
@@ -63,4 +106,42 @@
     public MBeanServer getMBeanServer() {
         return mbeanServer;
     }
+
+    /**
+     * Actually register the MBean with the server. The behaviour when encountering
+     * an existing MBean can be configured using the registrationBehaviour constructor or {@link #setRegistrationBehavior(int)}.
+     * This design (and also code) was unashamedly cribbed from Spring's 
+     * <a href="http://static.springframework.org/spring/docs/2.0.x/api/org/springframework/jmx/support/MBeanRegistrationSupport.html">MBeanRegistrationSupport</a> 
+     * class. Thanks Spring team!
+     * @see #REGISTRATION_FAIL_ON_EXISTING
+     * @see #REGISTRATION_IGNORE_EXISTING
+     * @see #REGISTRATION_REPLACE_EXISTING
+     * @param mbean
+     * @param objectName
+     * @throws JMException
+     */
+    public void registerMBean(Object mbean, ObjectName objectName) throws JMException {
+        try {
+            mbeanServer.registerMBean(mbean, objectName);
+        } catch (InstanceAlreadyExistsException ex) {
+            if (this.registrationBehaviour == REGISTRATION_IGNORE_EXISTING) {
+                if (log.isDebugEnabled()) {
+                    log.debug("Ignoring existing MBean at [" + objectName + "]");
+                }
+            } else if (this.registrationBehaviour == REGISTRATION_REPLACE_EXISTING) {
+                try {
+                    if (log.isDebugEnabled()) {
+                        log.debug("Replacing existing MBean at [" + objectName + "]");
+                    }
+                    mbeanServer.unregisterMBean(objectName);
+                    mbeanServer.registerMBean(mbean, objectName);
+                } catch (InstanceNotFoundException ex2) {
+                    log.error("Unable to replace existing MBean at [" + objectName + "]", ex2);
+                    throw ex;
+                }
+            } else {
+                throw ex;
+            }
+        }
+    }
 }
Index: core/src/main/java/org/quickfixj/jmx/mbean/connector/ConnectorJmxExporter.java
===================================================================
--- core/src/main/java/org/quickfixj/jmx/mbean/connector/ConnectorJmxExporter.java	(revision 899)
+++ core/src/main/java/org/quickfixj/jmx/mbean/connector/ConnectorJmxExporter.java	(working copy)
@@ -20,11 +20,11 @@
 import java.util.ArrayList;
 import java.util.concurrent.atomic.AtomicInteger;
 
-import javax.management.MBeanServer;
 import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 
 import org.quickfixj.QFJException;
+import org.quickfixj.jmx.JmxExporter;
 import org.quickfixj.jmx.mbean.ObjectNameFactory;
 import org.quickfixj.jmx.mbean.session.SessionJmxExporter;
 import org.slf4j.Logger;
@@ -42,11 +42,11 @@
     private final SessionJmxExporter sessionExporter = new SessionJmxExporter();
     private final static AtomicInteger connectorIdCounter = new AtomicInteger();
     
-    public void export(MBeanServer mbeanServer, SessionConnector connector) {
-        export(mbeanServer, connector, Integer.toString(connectorIdCounter.incrementAndGet()));
+    public void export(JmxExporter jmxExporter, SessionConnector connector) {
+        export(jmxExporter, connector, Integer.toString(connectorIdCounter.incrementAndGet()));
     }
     
-    public void export(MBeanServer mbeanServer, SessionConnector connector, String connectorId) {
+    public void export(JmxExporter jmxExporter, SessionConnector connector, String connectorId) {
         try {
             ConnectorAdmin connectorAdmin;
             if (connector instanceof AbstractSocketAcceptor) {
@@ -59,11 +59,11 @@
 
             ObjectName connectorName = getConnectorName(connector, connectorId);
             
-            mbeanServer.registerMBean(connectorAdmin, connectorName);
+            jmxExporter.registerMBean(connectorAdmin, connectorName);
             ArrayList<SessionID> sessionIDs = connector.getSessions();
             for (int i = 0; i < sessionIDs.size(); i++) {
                 SessionID sessionID = (SessionID) sessionIDs.get(i);
-                sessionExporter.export(mbeanServer, Session.lookupSession(sessionID),
+                sessionExporter.export(jmxExporter, Session.lookupSession(sessionID),
                         connectorName, connector.getSettings());
             }
         } catch (Exception e) {
Index: core/src/main/java/org/quickfixj/jmx/mbean/session/SessionJmxExporter.java
===================================================================
--- core/src/main/java/org/quickfixj/jmx/mbean/session/SessionJmxExporter.java	(revision 899)
+++ core/src/main/java/org/quickfixj/jmx/mbean/session/SessionJmxExporter.java	(working copy)
@@ -7,10 +7,10 @@
 import java.util.TreeMap;
 
 import javax.management.JMException;
-import javax.management.MBeanServer;
 import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 
+import org.quickfixj.jmx.JmxExporter;
 import org.quickfixj.jmx.mbean.ObjectNameFactory;
 
 import quickfix.ConfigError;
@@ -21,17 +21,17 @@
 public class SessionJmxExporter {
     private Map<SessionID, ObjectName> sessionObjectNames = new HashMap<SessionID, ObjectName>();
 
-    public void export(MBeanServer mbeanServer, Session session, ObjectName connectorName,
+    public void export(JmxExporter jmxExporter, Session session, ObjectName connectorName,
             SessionSettings settings) throws JMException, ConfigError {
         ObjectName sessionName = createSessionName(session.getSessionID());
         sessionObjectNames.put(session.getSessionID(), sessionName);
         SessionAdmin sessionAdmin = new SessionAdmin(session, connectorName);
         session.addStateListener(sessionAdmin);
-        mbeanServer.registerMBean(sessionAdmin, sessionName);
+        jmxExporter.registerMBean(sessionAdmin, sessionName);
         ObjectNameFactory settingsNameFactory = new ObjectNameFactory();
         settingsNameFactory.addProperty("type", "Settings");
         addSessionIdProperties(session.getSessionID(), settingsNameFactory);
-        mbeanServer.registerMBean(new SessionSettingsAdmin(session.getSessionID(), settings),
+        jmxExporter.registerMBean(new SessionSettingsAdmin(session.getSessionID(), settings),
                 settingsNameFactory.createName());
     }