# Interface Relation

All Known Subinterfaces:
  `RelationSupportMBean`

All Known Implementing Classes:
  `RelationSupport`

public interface Relation
This interface has to be implemented by any MBean class expected to represent a relation managed using the Relation Service.

Simple relations, i.e. having only roles, no properties or methods, can be created directly by the Relation Service (represented as RelationSupport objects, internally handled by the Relation Service).

If the user wants to represent more complex relations, involving properties and/or methods, he has to provide his own class implementing the Relation interface. This can be achieved either by inheriting from RelationSupport class, or by implementing the interface (fully or delegation to a RelationSupport object member).

Specifying such user relation class is to introduce properties and/or methods. Those have to be exposed for remote management. So this means that any user relation class must be a MBean class.

Since:
  1.5

- ## Method Summary

  Modifier and Type
  Method
  Description
  `RoleResult`
  `getAllRoles()`
  Returns all roles present in the relation.
  `Map<ObjectName, List<String>>`
  `getReferencedMBeans()`
  Retrieves MBeans referenced in the various roles of the relation.
  `String`
  `getRelationId()`
  Returns relation identifier (used to uniquely identify the relation inside the Relation Service).
  `ObjectName`
  `getRelationServiceName()`
  Returns ObjectName of the Relation Service handling the relation.
  `String`
  `getRelationTypeName()`
  Returns name of associated relation type.
  `List<ObjectName>`
  `getRole(String roleName)`
  Retrieves role value for given role name.
  `Integer`
  `getRoleCardinality(String roleName)`
  Returns the number of MBeans currently referenced in the given role.
  `RoleResult`
  `getRoles(String[] roleNameArray)`
  Retrieves values of roles with given names.
  `void`
  `handleMBeanUnregistration(ObjectName objectName, String roleName)`
  Callback used by the Relation Service when a MBean referenced in a role is unregistered.
  `RoleList`
  `retrieveAllRoles()`
  Returns all roles in the relation without checking read mode.
  `void`
  `setRole(Role role)`
  Sets the given role.
  `RoleResult`
  `setRoles(RoleList roleList)`
  Sets the given roles.

- ## Method Details

  - ### getRole

    List<ObjectName> getRole(String roleName) throws IllegalArgumentException, RoleNotFoundException, RelationServiceNotRegisteredException
    Retrieves role value for given role name.

    Checks if the role exists and is readable according to the relation type.

    Parameters:
      `roleName` - name of role
    Returns:
      the ArrayList of ObjectName objects being the role value
    Throws:
      `IllegalArgumentException` - if null role name
      `RoleNotFoundException` - if:

      - there is no role with given name

      - the role is not readable.

      `RelationServiceNotRegisteredException` - if the Relation Service is not registered in the MBean Server
    See Also:
      - `setRole(Role)`

  - ### getRoles

    RoleResult getRoles(String[] roleNameArray) throws IllegalArgumentException, RelationServiceNotRegisteredException
    Retrieves values of roles with given names.

    Checks for each role if it exists and is readable according to the relation type.

    Parameters:
      `roleNameArray` - array of names of roles to be retrieved
    Returns:
      a RoleResult object, including a RoleList (for roles successfully retrieved) and a RoleUnresolvedList (for roles not retrieved).
    Throws:
      `IllegalArgumentException` - if null role name
      `RelationServiceNotRegisteredException` - if the Relation Service is not registered in the MBean Server
    See Also:
      - `setRoles(RoleList)`

  - ### getRoleCardinality

    Integer getRoleCardinality(String roleName) throws IllegalArgumentException, RoleNotFoundException
    Returns the number of MBeans currently referenced in the given role.
    Parameters:
      `roleName` - name of role
    Returns:
      the number of currently referenced MBeans in that role
    Throws:
      `IllegalArgumentException` - if null role name
      `RoleNotFoundException` - if there is no role with given name

  - ### getAllRoles

    RoleResult getAllRoles() throws RelationServiceNotRegisteredException
    Returns all roles present in the relation.
    Returns:
      a RoleResult object, including a RoleList (for roles successfully retrieved) and a RoleUnresolvedList (for roles not readable).
    Throws:
      `RelationServiceNotRegisteredException` - if the Relation Service is not registered in the MBean Server

  - ### retrieveAllRoles

    RoleList retrieveAllRoles()
    Returns all roles in the relation without checking read mode.
    Returns:
      a RoleList.

  - ### setRole

    void setRole(Role role) throws IllegalArgumentException, RoleNotFoundException, RelationTypeNotFoundException, InvalidRoleValueException, RelationServiceNotRegisteredException, RelationNotFoundException
    Sets the given role.

    Will check the role according to its corresponding role definition provided in relation's relation type

    Will send a notification (RelationNotification with type RELATION_BASIC_UPDATE or RELATION_MBEAN_UPDATE, depending if the relation is a MBean or not).

    Parameters:
      `role` - role to be set (name and new value)
    Throws:
      `IllegalArgumentException` - if null role
      `RoleNotFoundException` - if there is no role with the supplied role's name or if the role is not writable (no test on the write access mode performed when initializing the role)
      `InvalidRoleValueException` - if value provided for role is not valid, i.e.:

      - the number of referenced MBeans in given value is less than expected minimum degree

      - the number of referenced MBeans in provided value exceeds expected maximum degree

      - one referenced MBean in the value is not an Object of the MBean class expected for that role

      - a MBean provided for that role does not exist.

      `RelationServiceNotRegisteredException` - if the Relation Service is not registered in the MBean Server
      `RelationTypeNotFoundException` - if the relation type has not been declared in the Relation Service.
      `RelationNotFoundException` - if the relation has not been added in the Relation Service.
    See Also:
      - `getRole(String)`

  - ### setRoles

    RoleResult setRoles(RoleList roleList) throws IllegalArgumentException, RelationServiceNotRegisteredException, RelationTypeNotFoundException, RelationNotFoundException
    Sets the given roles.

    Will check the role according to its corresponding role definition provided in relation's relation type

    Will send one notification (RelationNotification with type RELATION_BASIC_UPDATE or RELATION_MBEAN_UPDATE, depending if the relation is a MBean or not) per updated role.

    Parameters:
      `roleList` - list of roles to be set
    Returns:
      a RoleResult object, including a RoleList (for roles successfully set) and a RoleUnresolvedList (for roles not set).
    Throws:
      `IllegalArgumentException` - if null role list
      `RelationServiceNotRegisteredException` - if the Relation Service is not registered in the MBean Server
      `RelationTypeNotFoundException` - if the relation type has not been declared in the Relation Service.
      `RelationNotFoundException` - if the relation MBean has not been added in the Relation Service.
    See Also:
      - `getRoles(String[])`

  - ### handleMBeanUnregistration

    void handleMBeanUnregistration(ObjectName objectName, String roleName) throws IllegalArgumentException, RoleNotFoundException, InvalidRoleValueException, RelationServiceNotRegisteredException, RelationTypeNotFoundException, RelationNotFoundException
    Callback used by the Relation Service when a MBean referenced in a role is unregistered.

    The Relation Service will call this method to let the relation take action to reflect the impact of such unregistration.

    BEWARE. the user is not expected to call this method.

    Current implementation is to set the role with its current value (list of ObjectNames of referenced MBeans) without the unregistered one.

    Parameters:
      `objectName` - ObjectName of unregistered MBean
      `roleName` - name of role where the MBean is referenced
    Throws:
      `IllegalArgumentException` - if null parameter
      `RoleNotFoundException` - if role does not exist in the relation or is not writable
      `InvalidRoleValueException` - if role value does not conform to the associated role info (this will never happen when called from the Relation Service)
      `RelationServiceNotRegisteredException` - if the Relation Service is not registered in the MBean Server
      `RelationTypeNotFoundException` - if the relation type has not been declared in the Relation Service.
      `RelationNotFoundException` - if this method is called for a relation MBean not added in the Relation Service.

  - ### getReferencedMBeans

    Map<ObjectName, List<String>> getReferencedMBeans()
    Retrieves MBeans referenced in the various roles of the relation.
    Returns:
      a HashMap mapping:

      ObjectName -> ArrayList of String (role names)

  - ### getRelationTypeName

    String getRelationTypeName()
    Returns name of associated relation type.
    Returns:
      the name of the relation type.

  - ### getRelationServiceName

    ObjectName getRelationServiceName()
    Returns ObjectName of the Relation Service handling the relation.
    Returns:
      the ObjectName of the Relation Service.

  - ### getRelationId

    String getRelationId()
    Returns relation identifier (used to uniquely identify the relation inside the Relation Service).
    Returns:
      the relation id.