# Class RelationSupport

java.lang.Object
javax.management.relation.RelationSupport

All Implemented Interfaces:
  `MBeanRegistration, Relation, RelationSupportMBean`

public class RelationSupport extends Object implements RelationSupportMBean, MBeanRegistration
A RelationSupport object is used internally by the Relation Service to represent simple relations (only roles, no properties or methods), with an unlimited number of roles, of any relation type. As internal representation, it is not exposed to the user.

RelationSupport class conforms to the design patterns of standard MBean. So the user can decide to instantiate a RelationSupport object himself as a MBean (as it follows the MBean design patterns), to register it in the MBean Server, and then to add it in the Relation Service.

The user can also, when creating his own MBean relation class, have it extending RelationSupport, to retrieve the implementations of required interfaces (see below).

It is also possible to have in a user relation MBean class a member being a RelationSupport object, and to implement the required interfaces by delegating all to this member.

RelationSupport implements the Relation interface (to be handled by the Relation Service).

It implements also the MBeanRegistration interface to be able to retrieve the MBean Server where it is registered (if registered as a MBean) to access to its Relation Service.

Since:
  1.5

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `RelationSupport(String relationId, ObjectName relationServiceName, String relationTypeName, RoleList list)`
  Creates a `RelationSupport` object.
  `RelationSupport(String relationId, ObjectName relationServiceName, MBeanServer relationServiceMBeanServer, String relationTypeName, RoleList list)`
  Creates a `RelationSupport` object.

- ## 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.
  `Boolean`
  `isInRelationService()`
  Returns an internal flag specifying if the object is still handled by the Relation Service.
  `void`
  `postDeregister()`
  Allows the MBean to perform any operations needed after having been unregistered in the MBean server.
  `void`
  `postRegister(Boolean registrationDone)`
  Allows the MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.
  `void`
  `preDeregister()`
  Allows the MBean to perform any operations it needs before being unregistered by the MBean server.
  `ObjectName`
  `preRegister(MBeanServer server, ObjectName name)`
  Allows the MBean to perform any operations it needs before being registered in the MBean Server.
  `RoleList`
  `retrieveAllRoles()`
  Returns all roles in the relation without checking read mode.
  `void`
  `setRelationServiceManagementFlag(Boolean flag)`
  Specifies whether this relation is handled by the Relation Service.
  `void`
  `setRole(Role role)`
  Sets the given role.
  `RoleResult`
  `setRoles(RoleList list)`
  Sets the given roles.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### RelationSupport

    public RelationSupport(String relationId, ObjectName relationServiceName, String relationTypeName, RoleList list) throws InvalidRoleValueException, IllegalArgumentException
    Creates a `RelationSupport` object.

    This constructor has to be used when the RelationSupport object will be registered as a MBean by the user, or when creating a user relation MBean whose class extends RelationSupport.

    Nothing is done at the Relation Service level, i.e. the `RelationSupport` object is not added to the `RelationService` and no checks are performed to see if the provided values are correct. The object is always created, EXCEPT if:

    - any of the required parameters is `null`.

    - the same name is used for two roles.

    To be handled as a relation, the `RelationSupport` object has to be added to the Relation Service using the Relation Service method addRelation().

    Parameters:
      `relationId` - relation identifier, to identify the relation in the Relation Service.

      Expected to be unique in the given Relation Service.

      `relationServiceName` - ObjectName of the Relation Service where the relation will be registered.

      This parameter is required as it is the Relation Service that is aware of the definition of the relation type of the given relation, so that will be able to check update operations (set).

      `relationTypeName` - Name of relation type.

      Expected to have been created in the given Relation Service.

      `list` - list of roles (Role objects) to initialize the relation. Can be `null`.

      Expected to conform to relation info in associated relation type.

    Throws:
      `InvalidRoleValueException` - if the same name is used for two roles.
      `IllegalArgumentException` - if any of the required parameters (relation id, relation service ObjectName, or relation type name) is `null`.

  - ### RelationSupport

    public RelationSupport(String relationId, ObjectName relationServiceName, MBeanServer relationServiceMBeanServer, String relationTypeName, RoleList list) throws InvalidRoleValueException, IllegalArgumentException
    Creates a `RelationSupport` object.

    This constructor has to be used when the user relation MBean implements the interfaces expected to be supported by a relation by delegating to a RelationSupport object.

    This object needs to know the Relation Service expected to handle the relation. So it has to know the MBean Server where the Relation Service is registered.

    According to a limitation, a relation MBean must be registered in the same MBean Server as the Relation Service expected to handle it. So the user relation MBean has to be created and registered, and then the wrapped RelationSupport object can be created within the identified MBean Server.

    Nothing is done at the Relation Service level, i.e. the `RelationSupport` object is not added to the `RelationService` and no checks are performed to see if the provided values are correct. The object is always created, EXCEPT if:

    - any of the required parameters is `null`.

    - the same name is used for two roles.

    To be handled as a relation, the `RelationSupport` object has to be added to the Relation Service using the Relation Service method addRelation().

    Parameters:
      `relationId` - relation identifier, to identify the relation in the Relation Service.

      Expected to be unique in the given Relation Service.

      `relationServiceName` - ObjectName of the Relation Service where the relation will be registered.

      This parameter is required as it is the Relation Service that is aware of the definition of the relation type of the given relation, so that will be able to check update operations (set).

      `relationServiceMBeanServer` - MBean Server where the wrapping MBean is or will be registered.

      Expected to be the MBean Server where the Relation Service is or will be registered.

      `relationTypeName` - Name of relation type.

      Expected to have been created in the given Relation Service.

      `list` - list of roles (Role objects) to initialize the relation. Can be `null`.

      Expected to conform to relation info in associated relation type.

    Throws:
      `InvalidRoleValueException` - if the same name is used for two roles.
      `IllegalArgumentException` - if any of the required parameters (relation id, relation service ObjectName, relation service MBeanServer, or relation type name) is `null`.

- ## Method Details

  - ### getRole

    public 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.

    Specified by:
      `getRole` in interface `Relation`
    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

    public 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.

    Specified by:
      `getRoles` in interface `Relation`
    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)`

  - ### getAllRoles

    public RoleResult getAllRoles() throws RelationServiceNotRegisteredException
    Returns all roles present in the relation.
    Specified by:
      `getAllRoles` in interface `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

    public RoleList retrieveAllRoles()
    Returns all roles in the relation without checking read mode.
    Specified by:
      `retrieveAllRoles` in interface `Relation`
    Returns:
      a RoleList

  - ### getRoleCardinality

    public Integer getRoleCardinality(String roleName) throws IllegalArgumentException, RoleNotFoundException
    Returns the number of MBeans currently referenced in the given role.
    Specified by:
      `getRoleCardinality` in interface `Relation`
    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

  - ### setRole

    public 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).

    Specified by:
      `setRole` in interface `Relation`
    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

    public RoleResult setRoles(RoleList list) 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.

    Specified by:
      `setRoles` in interface `Relation`
    Parameters:
      `list` - 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

    public 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.

    Specified by:
      `handleMBeanUnregistration` in interface `Relation`
    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

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

      ObjectName -> ArrayList of String (role names)

  - ### getRelationTypeName

    public String getRelationTypeName()
    Returns name of associated relation type.
    Specified by:
      `getRelationTypeName` in interface `Relation`
    Returns:
      the name of the relation type.

  - ### getRelationServiceName

    public ObjectName getRelationServiceName()
    Returns ObjectName of the Relation Service handling the relation.
    Specified by:
      `getRelationServiceName` in interface `Relation`
    Returns:
      the ObjectName of the Relation Service.

  - ### getRelationId

    public String getRelationId()
    Returns relation identifier (used to uniquely identify the relation inside the Relation Service).
    Specified by:
      `getRelationId` in interface `Relation`
    Returns:
      the relation id.

  - ### preRegister

    public ObjectName preRegister(MBeanServer server, ObjectName name) throws Exception
    Description copied from interface: `MBeanRegistration`
    Allows the MBean to perform any operations it needs before being registered in the MBean Server. If the name of the MBean is not specified, the MBean can provide a name for its registration. If any exception is raised, the MBean will not be registered in the MBean Server.
    Specified by:
      `preRegister` in interface `MBeanRegistration`
    Parameters:
      `server` - The MBean Server in which the MBean will be registered.
      `name` - The object name of the MBean. This name is null if the name parameter to one of the `createMBean` or `registerMBean` methods in the `MBeanServer` interface is null. In that case, this method must return a non-null ObjectName for the new MBean.
    Returns:
      The name under which the MBean is to be registered. This value must not be null. If the `name` parameter is not null, it will usually but not necessarily be the returned value.
    Throws:
      `Exception` - This exception will be caught by the MBean Server and re-thrown as an `MBeanRegistrationException`.

  - ### postRegister

    public void postRegister(Boolean registrationDone)
    Description copied from interface: `MBeanRegistration`
    Allows the MBean to perform any operations needed after having been registered in the MBean server or after the registration has failed.

    If the implementation of this method throws a `RuntimeException` or an `Error`, the MBean Server will rethrow those inside a `RuntimeMBeanException` or `RuntimeErrorException`, respectively. However, throwing an exception in `postRegister` will not change the state of the MBean: if the MBean was already registered (`registrationDone` is `true`), the MBean will remain registered.

    This might be confusing for the code calling `createMBean()` or `registerMBean()`, as such code might assume that MBean registration has failed when such an exception is raised. Therefore it is recommended that implementations of `postRegister` do not throw Runtime Exceptions or Errors if it can be avoided.

    Specified by:
      `postRegister` in interface `MBeanRegistration`
    Parameters:
      `registrationDone` - Indicates whether or not the MBean has been successfully registered in the MBean server. The value false means that the registration phase has failed.

  - ### preDeregister

    public void preDeregister() throws Exception
    Description copied from interface: `MBeanRegistration`
    Allows the MBean to perform any operations it needs before being unregistered by the MBean server.
    Specified by:
      `preDeregister` in interface `MBeanRegistration`
    Throws:
      `Exception` - This exception will be caught by the MBean server and re-thrown as an `MBeanRegistrationException`.

  - ### postDeregister

    public void postDeregister()
    Description copied from interface: `MBeanRegistration`
    Allows the MBean to perform any operations needed after having been unregistered in the MBean server.

    If the implementation of this method throws a `RuntimeException` or an `Error`, the MBean Server will rethrow those inside a `RuntimeMBeanException` or `RuntimeErrorException`, respectively. However, throwing an exception in `postDeregister` will not change the state of the MBean: the MBean was already successfully deregistered and will remain so.

    This might be confusing for the code calling `unregisterMBean()`, as it might assume that MBean deregistration has failed. Therefore it is recommended that implementations of `postDeregister` do not throw Runtime Exceptions or Errors if it can be avoided.

    Specified by:
      `postDeregister` in interface `MBeanRegistration`

  - ### isInRelationService

    public Boolean isInRelationService()
    Returns an internal flag specifying if the object is still handled by the Relation Service.
    Specified by:
      `isInRelationService` in interface `RelationSupportMBean`
    Returns:
      a Boolean equal to `Boolean.TRUE` if the object is still handled by the Relation Service and `Boolean.FALSE` otherwise.

  - ### setRelationServiceManagementFlag

    public void setRelationServiceManagementFlag(Boolean flag) throws IllegalArgumentException
    Description copied from interface: `RelationSupportMBean`

    Specifies whether this relation is handled by the Relation Service.

    BEWARE, this method has to be exposed as the Relation Service will access the relation through its management interface. It is RECOMMENDED NOT to use this method. Using it does not affect the registration of the relation object in the Relation Service, but will provide wrong information about it!

    Specified by:
      `setRelationServiceManagementFlag` in interface `RelationSupportMBean`
    Parameters:
      `flag` - whether the relation is handled by the Relation Service.
    Throws:
      `IllegalArgumentException` - if null parameter