Defining Role Information

Before we can create relation instances, we need a relation type, and before we can define a relation type, we need to represent the information about its roles. This information includes:

• A name string (required)

• The name of the MBean class that fulfills this role (required)

• Read-write permissions (the default is both readable and writeable)

• The multiplicity, expressed as a single range (the default is 1..1)

• A description string (the default is a null string)

The name can be any string that is manipulated by the Java String class. It will be used to retrieve the corresponding MBeans when accessing a relation instance. The multiplicity is limited to the range between the minimum and maximum number of MBeans required for this role to fulfilled. The read-write permissions apply to all of the MBeans in the role, since the value of a role is read or written as a complete list.

The role information is represented by the RoleInfo class. In our example, we define two different roles:

Example 9-2 Instantiating RoleInfo Objects

// Define two roles in an array
// - container: SimpleStandard class/read-write access/multiplicity: 1..1
// - contained: SimpleStandard class/read-write access/multiplicity: 0..n

RoleInfo[] roleInfoArray = new RoleInfo[2];
String role1Name = "container";
roleInfoArray[0] =
    new RoleInfo( role1Name, "SimpleStandard",
                  true, true,
                  1, 1,
                  null);

String role2Name = "contained";
roleInfoArray[1] =
    new RoleInfo( role2Name, "SimpleStandard",
                  true, true,
                  0, -1,
                  null);

We build an array of RoleInfo objects that is intended to define a relation type, so it needs to define a valid set of roles. All role names must be unique within the array, and none of the array's elements may be null. Also, the minimum and maximum cardinalities must define a range of at least one integer.