Developing an administrative client program

This topic describes how to develop an administrative client program that utilizes WebSphere Application Server administrative APIs and Java Management Extensions (JMX).

WebSphere Application Server administrative APIs provide control of the operational aspects of your distributed system as well as the ability to update your configuration. This topic also demonstrates examples of MBean operations. For information, view the Administrative API documentation, the JMX API documentation, or the MBean API documentation.

1. Create an AdminClient instance. An administrative client program needs to invoke methods on the AdminService object that is running in the deployment manager or the application server in the base installation. The AdminClient class provides a proxy to the remote AdminService object through one of the supported Java Management Extensions (JMX) connectors. The following example shows how to create an AdminClient instance:

   Properties connectProps = new Properties();
   connectProps.setProperty(
   AdminClient.CONNECTOR_TYPE, AdminClient.CONNECTOR_TYPE_SOAP);
   
   connectProps.setProperty(AdminClient.CONNECTOR_HOST, "localhost");
   connectProps.setProperty(AdminClient.CONNECTOR_PORT, "8879");
   AdminClient adminClient = null;
   try {
          adminClient = AdminClientFactory.createAdminClient(connectProps);
   }
   catch (ConnectorException e)
   {
          System.out.println("Exception creating admin client: " + e);
   }

   1. Set up a Properties object.

      The example sets up a Properties object with the properties that are required to get to your server. In this case, you use the Simple Object Access Protocol (SOAP) connector to reach the server; for the connector type, use the value: AdminClient.CONNECTOR_TYPE_SOAP.

   2. For simplicity, run the client program on the same machine as the server; use localhost for the host name.

      To access a remote host instead of a local host, use a network resolvable name for that host.

   3. Set the port number on which the server SOAP connector is listening.

      In a single server installation, the default port number for the
      application server SOAP connector is 8880. In a Network Deployment installation, the default port number for the deployment manager
      SOAP connector is 8879.

   4. After the connection properties are set, use the AdminClientFactory class and the Properties object to create an AdminClient object that is connected to your chosen server.

      Depending on factors such as your desired protocol and security environment, you might need to set other properties. For more detailed information about the AdminClient interface and additional creation examples, refer to the AdminClient interface in the Java Management Extensions (JMX) API documentation.

2. Find an MBean. When you obtain an AdminClient instance, you can use it to access managed resources in the administration servers and application servers. Each managed resource registers an MBean with the AdminService through which you can access the resource. The MBean is represented by an
   ObjectName instance that identifies the MBean. An ObjectName instance consists of a domain name followed by an unordered set of one or more key properties. The syntax for the domain name follows:

   [domainName]:property=value[,property=value]*
   

   For WebSphere Application Server, the domain name is WebSphere and the key properties defined for administration are as follows:

   type	The type of MBean. For example: Server, TraceService, Java virtual machine (JVM).
   name	The name identifier for the individual instance of the MBean.
   cell	The name of the cell that the MBean is running.
   node	The name of the node that the MBean is running.
   process	The name of the process that the MBean is running.

   Some MBeans in WebSphere Application Server use additional key properties. An MBean without key properties can be registered with the MBean server in a WebSphere Application Server process. However, such an MBean cannot participate in the distributed enhancements that WebSphere Application Server adds, for example, request routing, distributed event notification, and so on. If you know the complete set of key properties for an ObjectName instance, you can use it to find the MBean it identifies. However, finding MBeans without having to know all of their key properties is usually more practical and convenient. Use the wildcard character asterisk (*) for any key properties that you do not need to match. The following table provides some examples of object names with wildcard key properties that match single or multiple MBeans.

   *:type=Server,*	All MBeans of type Server
   *:node=Node1,type=Server,*	All MBeans of type Server on Node1
   *:type=JVM,process=server1,node=Node1,*	The JVM MBean in the server named server1 node Node1
   *:process=server1,*	All MBeans in all servers named server1
   *:process=server1,node=Node1,*	All MBeans in the server named server1 on Node1

   You can locate an MBean by querying for it with object names that match key properties. The following example shows how to find the MBean for the node agent of node, MyNode:

   String nodeName = "MyNode";
   String query = "WebSphere:type=NodeAgent,node=" + nodeName + ",*";
   
   
   ObjectName queryName = new ObjectName(query);
   
   
   ObjectName nodeAgent = null;
   Set s = adminClient.queryNames(queryName, null);
   if (!s.isEmpty())
       nodeAgent = (ObjectName)s.iterator().next();
   else     System.out.println("Node agent MBean was not found");

   1. Build an ObjectName instance with a query string that specifies the key properties of type and node.

      By using a wildcard for the remaining key properties, this pattern matches the object names for all MBeans of the type NodeAgent on the node MyNode. Because only one node agent per node exists, this information is sufficient to identify the MBean that you want.

   2. Give this ObjectName instance to the queryNames method of the AdminClient interface.

      The AdminClient interface performs the remote call to the AdminService interface to obtain the set of MBean object names that match the query. The null second parameter to this method is a query expression (QueryExp) object that you can use as an additional query over the MBeans that match the ObjectName pattern in the first parameter.

   3. Use the set iterator to get the first and, in this case, only element.

      The element is the MBean ObjectName instance of the node agent.

3. Use the MBean. What a particular MBean can do depends on the management interface of that MBean. An MBean can declare:

   • Attributes that you can obtain or set

   • Operations that you can invoke

   • Notifications for which you can register listeners

   For the MBeans provided by WebSphere Application Server, you can find information about the interfaces they support in the MBean API documentation. The following example invokes one of the operations available on the NodeAgent MBean that you located previously. The following example starts the MyServer application server:

   String opName = "launchProcess";
   String signature[] = { "java.lang.String" };
   String params[] = { "MyServer" };
   try {
        adminClient.invoke(nodeAgent, opName, params, signature);
   }
   catch (Exception e)
   {
        System.out.println("Exception invoking launchProcess: " + e);
   }

   The AdminClient.invoke method is a generic means of invoking any operation on any MBean. The parameters are:

   • The object name of the target MBean, nodeAgent

   • The name of the operation, opName

   • An object array that contains the operation parameters, params

   • A string array that contains the operation signature, signature

   The launchProcess operation in the example has a single parameter which is a string that identifies the server to start.

   The invoke method returns an object instance, which the calling code can use to cast to the correct return type for the invoked operation. The launchProcess operation is declared void so that you can ignore the return value in this example.

4. Register for events. In addition to managing resources, the JMX API also supports application monitoring for specific administrative events. Certain events produce notifications, for example, when a server starts. Administrative applications can register as listeners for these notifications. The WebSphere Application Server provides a full implementation of the JMX notification model, and provides additional function so you can receive notifications in a distributed environment. For a complete list of the notifications emitted from WebSphere Application Server MBeans, refer to the com.ibm.websphere.management.NotificationConstants class in the MBean API documentation. The following example shows how an object can register for event notifications that are emitted from an MBean using the ObjectName node agent:

   adminClient.addNotificationListener(nodeAgent, this, null, null);

   In this example, the first parameter is the ObjectName for the node agent MBean. The second parameter identifies the listener object, which must implement the NotificationListener interface. In this case, the calling object is the listener. The third parameter is a filter that you can use to indicate which notifications you want to receive. When you leave this value as null, you receive all notifications from this MBean. The final parameter is a handback object that you can use to set the JMX API to return to you when it emits a notification.

   If your MBean is located on another server in the cell, you can receive its notifications even though your administrative client program might be connected to the deployment manager server. All notifications flow to the upstream server. For example, a notification from an application server first flows to the local node agent and then to the deployment manager.

   Another enhanced feature that Application Server provides is the ability to register as a notification listener of multiple MBeans with one call. This registration is done through the addNotificationListenerExtended method of the AdminClient interface, an extension of the standard JMX addNotificationListener method. This extension method even lets you register for MBeans that are not currently active. This registration is important in situations where you want to monitor events from resources that can be stopped and restarted during the lifetime of your administrative client program.

5. Handle the events. Objects receive JMX event notifications through the handleNotification method, which is defined by the NotificationListener interface and which any event receiver must implement. The following example is an implementation of the handleNotification method that reports the notifications that it receives:

   public void handleNotification(Notification n, Object handback)
   {
        System.out.println("***************************************************");
        System.out.println("* Notification received at " + new Date().toString());
        System.out.println("* type      = " + ntfyObj.getType());
        System.out.println("* message   = " + ntfyObj.getMessage());
        System.out.println("* source    = " + ntfyObj.getSource());
        System.out.println(
        "* seqNum    = " + Long.toString(ntfyObj.getSequenceNumber()));
        System.out.println("* timeStamp = " + new Date(ntfyObj.getTimeStamp()));
        System.out.println("* userData  = " + ntfyObj.getUserData());
        System.out.println("***************************************************");
   }

Related tasks
Creating a custom Java administrative client program using WebSphere Application Server administrative Java APIs
Using application clients