Provides support for LDAPv3 extended operations and controls.

This package extends the directory operations of the Java Naming and Directory Interface (JNDI). JNDI provides naming and directory functionality to applications written in the Java programming language. It is designed to be independent of any specific naming or directory service implementation. Thus a variety of services--new, emerging, and already deployed ones--can be accessed in a common way.

This package is for applications and service providers that deal with LDAPv3 extended operations and controls, as defined by RFC 2251. The core interface in this package is `LdapContext`, which defines methods on a context for performing extended operations and handling controls.

## Extended Operations

This package defines the interface `ExtendedRequest` to represent the argument to an extended operation, and the interface `ExtendedResponse` to represent the result of the extended operation. An extended response is always paired with an extended request but not necessarily vice versa. That is, you can have an extended request that has no corresponding extended response.

An application typically does not deal directly with these interfaces. Instead, it deals with classes that implement these interfaces. The application gets these classes either as part of a repertoire of extended operations standardized through the IETF, or from directory vendors for vendor-specific extended operations. The request classes should have constructors that accept arguments in a type-safe and user-friendly manner, while the response classes should have access methods for getting the data of the response in a type-safe and user-friendly manner. Internally, the request/response classes deal with encoding and decoding BER values.

For example, suppose an LDAP server supports a "get time" extended operation. It would supply classes such as `GetTimeRequest` and `GetTimeResponse`, so that applications can use this feature. An application would use these classes as follows:

>     GetTimeResponse resp =
>         (GetTimeResponse) ectx.extendedOperation(new GetTimeRequest());
>     long time = resp.getTime();

The `GetTimeRequest` and `GetTimeResponse` classes might be defined as follows:

>     public class GetTimeRequest implements ExtendedRequest {
>         // User-friendly constructor
>         public GetTimeRequest() {
>         };

>         // Methods used by service providers
>         public String getID() {
>             return GETTIME_REQ_OID;
>         }
>         public byte[] getEncodedValue() {
>             return null;  // no value needed for get time request
>         }
>         public ExtendedResponse createExtendedResponse(
>             String id, byte[] berValue, int offset, int length) throws NamingException {
>             return new GetTimeResponse(id, berValue, offset, length);
>         }
>     }
>     public class GetTimeResponse() implements ExtendedResponse {
>         long time;
>         // called by GetTimeRequest.createExtendedResponse()
>         public GetTimeResponse(String id, byte[] berValue, int offset, int length)
>             throws NamingException {
>             // check validity of id
>             long time =  ... // decode berValue to get time
>         }

>         // Type-safe and User-friendly methods
>         public java.util.Date getDate() { return new java.util.Date(time); }
>         public long getTime() { return time; }

>         // Low level methods
>         public byte[] getEncodedValue() {
>             return // berValue saved;
>         }
>         public String getID() {
>             return GETTIME_RESP_OID;
>         }
>     }

## Controls

This package defines the interface `Control` to represent an LDAPv3 control. It can be a control that is sent to an LDAP server (request control) or a control returned by an LDAP server (response control). Unlike extended requests and responses, there is not necessarily any pairing between request controls and response controls. You can send request controls and expect no response controls back, or receive response controls without sending any request controls.

An application typically does not deal directly with this interface. Instead, it deals with classes that implement this interface. The application gets control classes either as part of a repertoire of controls standardized through the IETF, or from directory vendors for vendor-specific controls. The request control classes should have constructors that accept arguments in a type-safe and user-friendly manner, while the response control classes should have access methods for getting the data of the response in a type-safe and user-friendly manner. Internally, the request/response control classes deal with encoding and decoding BER values.

For example, suppose an LDAP server supports a "signed results" request control, which when sent with a request, asks the server to digitally sign the results of an operation. It would supply a class `SignedResultsControl` so that applications can use this feature. An application would use this class as follows:

>     Control[] reqCtls = new Control[] {new SignedResultsControl(Control.CRITICAL)};
>     ectx.setRequestControls(reqCtls);
>     NamingEnumeration enum = ectx.search(...);

The `SignedResultsControl` class might be defined as follows:

>     public class SignedResultsControl implements Control {
>         // User-friendly constructor
>         public SignedResultsControl(boolean criticality) {
>     	// assemble the components of the request control
>         };

>         // Methods used by service providers
>         public String getID() {
>             return // control's object identifier
>         }
>         public byte[] getEncodedValue() {
>             return // ASN.1 BER encoded control value
>         }
>         ...
>     }

When a service provider receives response controls, it uses the `ControlFactory` class to produce specific classes that implement the `Control` interface.

An LDAP server can send back response controls with an LDAP operation and also with enumeration results, such as those returned by a list or search operation. The `LdapContext` provides a method (`getResponseControls()`) for getting the response controls sent with an LDAP operation, while the `HasControls` interface is used to retrieve response controls associated with enumeration results.

For example, suppose an LDAP server sends back a "change ID" control in response to a successful modification. It would supply a class `ChangeIDControl` so that the application can use this feature. An application would perform an update, and then try to get the change ID.

>     // Perform update
>     Context ctx = ectx.createSubsubcontext("cn=newobj");

>     // Get response controls
>     Control[] respCtls = ectx.getResponseControls();
>     if (respCtls != null) {
>         // Find the one we want
>         for (int i = 0; i < respCtls; i++) {
>             if(respCtls[i] instanceof ChangeIDControl) {
>     	    ChangeIDControl cctl = (ChangeIDControl)respCtls[i];
>     	    System.out.println(cctl.getChangeID());
>             }
>         }
>     }

The vendor might supply the following `ChangeIDControl` and `VendorXControlFactory` classes. The `VendorXControlFactory` will be used by the service provider when the provider receives response controls from the LDAP server.

>     public class ChangeIDControl implements Control {
>         long id;

>         // Constructor used by ControlFactory
>         public ChangeIDControl(String OID, byte[] berVal) throws NamingException {
>             // check validity of OID
>             id = // extract change ID from berVal
>         };

>         // Type-safe and User-friendly method
>         public long getChangeID() {
>             return id;
>         }

>         // Low-level methods
>         public String getID() {
>             return CHANGEID_OID;
>         }
>         public byte[] getEncodedValue() {
>             return // original berVal
>         }
>         ...
>     }
>     public class VendorXControlFactory extends ControlFactory {
>         public VendorXControlFactory () {
>         }

>         public Control getControlInstance(Control orig) throws NamingException {
>             if (isOneOfMyControls(orig.getID())) {
>     	    ...

>     	    // determine which of ours it is and call its constructor
>     	    return (new ChangeIDControl(orig.getID(), orig.getEncodedValue()));
>     	}
>             return null;  // not one of ours
>         }
>     }

## Package Specification

The JNDI API Specification and related documents can be found in the {@extLink jndi_overview JNDI documentation}. @since 1.3