Development Overview

When writing an m-bean, you must:

• Create an m-let text file.

  The information on each m-bean is specified in a single instance of a tag, called the MLET tag. When an m-let text file is loaded, an instance of each m-bean specified in the file is created. For example, the m-let text file for the QDatabaseAccounting m-bean is contained in the file QDatabaseAccounting.html and looks like this:

  <MLET
  								CODE=com.sun.ba.beans.QDatabaseAccounting
  								ARCHIVE="qdatabaseaccounting.jar, dbaccess.jar
  >
  <PARAM NAME=jdbcDriverName		VALUE=com.sun.jdbc.SimpleText.SimpleTextDriver>
  <PARAM NAME=jdbcURLName			VALUE=jdbc:SimpleText:/var/opt/SUNWconn/ba>
  </MLET>

  The attributes used in this example are:

  CODE

  The full Java class name of the m-bean

  ARCHIVE

  The files containing m-beans and other resources used by the QDataBaseAccounting m-bean. In this case the file qdatabaseaccounting.jar contains the required classes and dbaccess.jar contains the database driver.

  PARAM

  A list of the parameters required by the QDataBaseAccounting m-bean. These will be passed as a modification list to the initCmf() method.

• Implement the initCmf() method. The prototype of the initCmf() method must look like this:

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  public void initCmf(Framework cmf, ObjectName name, boolean db, 
  ModificationList list)
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  The ModificationList parameter is required in order to contain the list of parameters defined in the MLET tag.

  You can also provide the bean and class names of the m-bean(s) to initialize:

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  ObjectName statsName = new ObjectName(cmf.getDomain(), beanName);
                  stats = (className) cmf.retrieveObject(statsName);
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  The initCmf() method in the QDatabaseAccounting.java file looks like this:

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  public void initCmf(Framework cmf, ObjectName name, boolean db, 
  ModificationList list)
     throws InstanceNotFoundException, InstanceAlreadyExistException, 
     ServiceNotFoundException
     {
        this.cmf = cmf;
  
        if (name == null) {
           name = new ObjectName(cmf.getDomain(), getClass().getName());
        }
        if (db) {
           cmf.addDBObject(this, name);
        } else {
           cmf.addObject(this, name);
        }
        this.name = name;
  
        ObjectName statsName = new ObjectName(cmf.getDomain(), statsMOName);
        stats = (QStatsInterface) cmf.retrieveObject(statsName);
  
        String jdbcDriverName = null;
  
        Enumeration enum = list.elements();
        while (enum.hasMoreElements()) {
           Modification modif = (Modification) enum.nextElement();
           String property = modif.getProperty();
           String value = (String) modif.getValue();
           if (property.equalsIgnoreCase("jdbcDriverName")) {
              jdbcDriverName = value;
           } else if (property.equalsIgnoreCase("jdbcUrlName")) {
              jdbcUrlName = value;
           } else if (property.equalsIgnoreCase("jdbcUserName")) {
              jdbcUserName = value;
           } else if (property.equalsIgnoreCase("jdbcPassword")) {
              jdbcPassword = value;
           } else if (property.equalsIgnoreCase("jdbcTableName")) {
              jdbcTableName = value;
           }
        }
  
        try {
           Class.forName(jdbcDriverName);
        } catch (ClassNotFoundException e) {
           throw new 
           ServiceNotFoundException("cannot load JDBC driver " + jdbcDriverName);
        }
  
   }
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• Make sure that the m-bean declaration implements the ActivatableIf interface:

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  public class QDatabaseAccounting implements QConstants, QFlowAccountingListene
  r, ActivatableIf
  {
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  This makes the performStart() and performStop() methods available.

• Implement the performStart() method. In the case of the QDatabaseAccounting m-bean the performStart() method calls a method to start an event listener for flow accounting:

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  public void performStart()
     {
        if (!isActive()) {
           try {
              jdbcConnection = DriverManager.getConnection(jdbcUrlName, jdbcUserName, 
              jdbcPassword);
              flowTable = new QFlowTable(jdbcConnection, jdbcTableName);
  
              stats.addQFlowAccountingListener(this);
                 } catch (SQLException e) {
                    e.printStackTrace();
                 }
        }
     }
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• Implement the performStop() method. For the QDatabaseAccounting m-bean, the performStop() method looks like this:

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  public void performStop()
     {
        if (isActive()) {
           stats.removeQFlowAccountingListener(this);
  
           try {
              jdbcConnection.commit();
              jdbcConnection.close();
              jdbcConnection = null;
              flowTable = null;
           } catch (SQLException e) {
              e.printStackTrace();
           }
        }
     }
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• Implement the isActive() method:

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  public boolean isActive()
  {
  
     return (jdbcConnection != null && flowTable != null);
  }
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