In the previous section, we looked at each of the relation service classes that are necessary to create internal and external relations. In this section, we will look at source code examples for creating internal relations, as these are the easiest type to create. All of the source code examples in this section are taken from the relation package of the sample application that we have used throughout this book.

Before we can create a relation, we have to create the MBean server and an instance of the relation service MBean, and then register the relation service MBean with the MBean server:

try {
  MBeanServer server = MBeanServerFactory.createMBeanServer(  );
  boolean purgeImmediate = true;
  RelationService rs = new RelationService(purgeImmediate);
  ObjectName rsObjName = new ObjectName("AgentServices:name=Relation");
  server.registerMBean(rs, rsObjName);
  // . . .
} catch (Exception e) {
  // . . .
}

Next, we describe the roles in the relation using one or more RoleInfo objects:

try {
  // . . .
  server.registerMBean(rs, rsObjName);
  RoleInfo[] roleInfo = new RoleInfo[2];
  roleInfo[0] = new RoleInfo(
    "Consumer",                 // role name
    "sample.standard.Consumer", // class name
    true,                       // role can be read
    true,                       // role can be modified
    1,                          // must be at least one
    2,                          // no more than two
    "Consumer Role Information" // description
  );
  roleInfo[1] = new RoleInfo(
    "Supplier",                 // role name
    "sample.standard.Supplier", // class name
    true,                       // role can be read
    true,                       // role can be modified
    1,                          // must be at least one
    1,                          // no more than one
    "Supplier Role Information" // description
  );
} catch (Exception e) {
  // . . .
}

In this case, the relation consists of two roles, Consumer and Supplier, performed by two MBean classes, also called Consumer and Supplier (in the sample application, we reuse the MBean classes from the standard package). There must be at least one and no more than two Consumer MBeans in the relation. Only one Supplier MBean is allowed in the relation. Once the roles have been described using RoleInfo objects, we are ready to describe the relationship between these two roles by creating an internal relation type:

try {
  // . . .
  roleInfo[1] = new RoleInfo(
    "Supplier",                 // role name
    "sample.standard.Supplier", // class name
    true,                       // role can be read
    true,                       // role can be modified
    1,                          // must be at least one
    1,                          // no more than one
    "Supplier Role Information" // description
  );
  rs.createRelationType(
    "ConsumerSupplierRelationType_Internal",
    roleInfo
  );
  // . . .
} catch (Exception e) {
  // . . .
}

Once the relation type has been created, we instantiate the role by creating a Role object for each group of MBeans to participate in the relation:

try {
  // . . .
  rs.createRelationType(
    "ConsumerSupplierRelationType_Internal",
    roleInfo
  );
  // Create and register a Consumer MBean
  ObjectName consumerObjName = createWorker("Consumer", 100);
  ArrayList consumerList = new ArrayList(  );
  consumerList.add(consumerObjName);
  Role consumerRole = new Role("Consumer", consumerList);
  // Create and register a Supplier MBean
  ObjectName supplierObjName = createWorker("Supplier", 100);
  ArrayList supplierList = new ArrayList(  );
  supplierList.add(supplierObjName);
  Role supplierRole = new Role("Supplier", supplierList);
              RoleList roles = new RoleList(  );
              roles.add(consumerRole);
              roles.add(supplierRole);
  // . . .
} catch (Exception e) {
  // . . .
}

In this example, we use the createWorker( ) method to create and register with the MBean server an instance of each worker type. Once the Role objects are created, we create a RoleList object to contain the Role objects. The final step is to use the relation service to create an internal relation:

try {
  // . . .
  RoleList roles = new RoleList(  );
  roles.add(consumerRole);
  roles.add(supplierRole);
  rs.createRelation(
                "ConsumerSupplierRelation_Internal",
                "ConsumerSupplierRelationType_Internal",
                roles
              );
} catch (Exception e) {
  // . . .
}

Example 11-1 shows a complete source listing of how to create the internal Consumer/Supplier relation we’ve been examining.

try {
  MBeanServer server = MBeanServerFactory.createMBeanServer(  );
  boolean purgeImmediate = true;
  RelationService rs = new RelationService(purgeImmediate);
  ObjectName rsObjName = new ObjectName("AgentServices:name=Relation");
  server.registerMBean(rs, rsObjName);
  RoleInfo[] roleInfo = new RoleInfo[2];
  roleInfo[0] = new RoleInfo(
    "Consumer",                 // role name
    "sample.standard.Consumer", // class name
    true,                       // role can be read
    true,                       // role can be modified
    1,                          // must be at least one
    2,                          // no more than two
    "Consumer Role Information" // description
  );
  roleInfo[1] = new RoleInfo(
    "Supplier",                 // role name
    "sample.standard.Supplier", // class name
    true,                       // role can be read
    true,                       // role can be modified
    1,                          // must be at least one
    1,                          // no more than one
    "Supplier Role Information" // description
  );
  rs.createRelationType(
    "ConsumerSupplierRelationType_Internal",
    roleInfo
  );
  // Create and register a Consumer MBean
  ObjectName consumerObjName = createWorker("Consumer", 100);
  ArrayList consumerList = new ArrayList(  );
  consumerList.add(consumerObjName);
  Role consumerRole = new Role("Consumer", consumerList);
  // Create and register a Supplier MBean
  ObjectName supplierObjName = createWorker("Supplier", 100);
  ArrayList supplierList = new ArrayList(  );
  supplierList.add(supplierObjName);
  Role supplierRole = new Role("Supplier", supplierList);
  RoleList roles = new RoleList(  );
  roles.add(consumerRole);
  roles.add(supplierRole);
  rs.createRelation(
    "ConsumerSupplierRelation_Internal",
    "ConsumerSupplierRelationType_Internal",
    roles
  );
} catch (Exception e) {
  // . . .
}