javax.naming.ldap

## Class ControlFactory

- java.lang.Object
- - javax.naming.ldap.ControlFactory

-     public abstract class ControlFactory
      extends Object

  This abstract class represents a factory for creating LDAPv3 controls. LDAPv3 controls are defined in RFC 2251.

  When a service provider receives a response control, it uses control factories to return the specific/appropriate control class implementation.

  Since:
    1.3
  See Also:
    `Control`

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `ControlFactory()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract Control` | `getControlInstance(Control ctl)` Creates a control using this control factory.
    `static Control` | `getControlInstance(Control ctl, Context ctx, Hashtable<?,?> env)` Creates a control using known control factories.

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### ControlFactory

          protected ControlFactory()

  - ### Method Detail

    - #### getControlInstance

          public abstract Control getControlInstance(Control ctl)
                                              throws NamingException

      Creates a control using this control factory.

      The factory is used by the service provider to return controls that it reads from the LDAP protocol as specialized control classes. Without this mechanism, the provider would be returning controls that only contained data in BER encoded format.

      Typically, `ctl` is a "basic" control containing BER encoded data. The factory is used to create a specialized control implementation, usually by decoding the BER encoded data, that provides methods to access that data in a type-safe and friendly manner.

      For example, a factory might use the BER encoded data in basic control and return an instance of a VirtualListReplyControl.

      If this factory cannot create a control using the argument supplied, it should return null. A factory should only throw an exception if it is sure that it is the only intended factory and that no other control factories should be tried. This might happen, for example, if the BER data in the control does not match what is expected of a control with the given OID. Since this method throws `NamingException`, any other internally generated exception that should be propagated must be wrapped inside a `NamingException`.

      Parameters:
        `ctl` - A non-null control.
      Returns:
        A possibly null Control.
      Throws:
        `NamingException` - If `ctl` contains invalid data that prevents it from being used to create a control. A factory should only throw an exception if it knows how to produce the control (identified by the OID) but is unable to because of, for example invalid BER data.

    - #### getControlInstance

          public static Control getControlInstance(Control ctl,
                                   Context ctx,
                                   Hashtable<?,?> env)
                                            throws NamingException

      Creates a control using known control factories.

      The following rule is used to create the control:

      - Use the control factories specified in the `LdapContext.CONTROL_FACTORIES` property of the environment, and of the provider resource file associated with `ctx`, in that order. The value of this property is a colon-separated list of factory class names that are tried in order, and the first one that succeeds in creating the control is the one used. If none of the factories can be loaded, return `ctl`. If an exception is encountered while creating the control, the exception is passed up to the caller.

      Note that a control factory must be public and must have a public constructor that accepts no arguments.

      Parameters:
        `ctl` - The non-null control object containing the OID and BER data.
        `ctx` - The possibly null context in which the control is being created. If null, no such information is available.
        `env` - The possibly null environment of the context. This is used to find the value of the `LdapContext.CONTROL_FACTORIES` property.
      Returns:
        A control object created using `ctl`; or `ctl` if a control object cannot be created using the algorithm described above.
      Throws:
        `NamingException` - if a naming exception was encountered while attempting to create the control object. If one of the factories accessed throws an exception, it is propagated up to the caller. If an error was encountered while loading and instantiating the factory and object classes, the exception is wrapped inside a `NamingException` and then rethrown.

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