jdk/src/share/classes/javax/naming/ldap/package.html

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Provides support for LDAPv3 extended operations and controls.

<p>
This package extends the directory operations of the Java Naming and
Directory Interface<font size=-2><sup>TM</sup></font> (JNDI). &nbsp;
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.

<p>
This package is for applications and service providers that deal with
LDAPv3 extended operations and controls, as defined by
<a href=http://www.ietf.org/rfc/rfc2251.txt>RFC 2251</a>.
The core interface in this package is <tt>LdapContext</tt>, which defines
methods on a context for performing extended operations and handling
controls.

<h4>Extended Operations</h4>
<p>
This package defines the interface <tt>ExtendedRequest</tt>
to represent the argument to an extended operation,
and the interface <tt>ExtendedResponse</tt> 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.
<p>
An application typically does not deal directly with these interfaces.
Instead, it deals with classes that <em>implement</em> 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.
<p>
For example, suppose an LDAP server supports a "get time" extended operation.
It would supply classes such as
<tt>GetTimeRequest</tt> and <tt>GetTimeResponse</tt>,
so that applications can use this feature.
An application would use these classes as follows:
<blockquote><pre>
GetTimeResponse resp =
    (GetTimeResponse) ectx.extendedOperation(new GetTimeRequest());
long time = resp.getTime();
</pre></blockquote>
<p>
The <tt>GetTimeRequest</tt> and <tt>GetTimeResponse</tt> classes might
be defined as follows:
<blockquote><pre>
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;
    }
}
</pre></blockquote>

<h4>Controls</h4>

This package defines the interface <tt>Control</tt> to represent an LDAPv3
control. It can be a control that is sent to an LDAP server
(<em>request control</em>) or a control returned by an LDAP server
(<em>response control</em>).  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.
<p>
An application typically does not deal directly with this interface.
Instead, it deals with classes that <em>implement</em> 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.
<p>
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 <tt>SignedResultsControl</tt>  so that applications
can use this feature.
An application  would use this class as follows:
<blockquote>
<pre>
Control[] reqCtls = new Control[] {new SignedResultsControl(Control.CRITICAL)};
ectx.setRequestControls(reqCtls);
NamingEnumeration enum = ectx.search(...);
</pre>
</blockquote>
The <tt>SignedResultsControl</tt> class might be defined as follows:
<blockquote><pre>
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
    }
    ...
}
</pre></blockquote>
<p>
When a service provider receives response controls, it uses
the <tt>ControlFactory</tt> class to produce specific classes 
that implement the <tt>Control</tt> interface.
<p>
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 <tt>LdapContext</tt> provides a method (<tt>getResponseControls()</tt>)
for getting the response controls sent with an LDAP operation,
while the <tt>HasControls</tt> interface is used to retrieve
response controls associated with enumeration results.
<p>
For example, suppose an LDAP server sends back a "change ID" control in response
to a successful modification. It would supply a class <tt>ChangeIDControl</tt>
so that the application can use this feature.
An application would perform an update, and then try to get the change ID.
<blockquote><pre>
// 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());
        }
    }
}
</pre></blockquote>
The vendor might supply the following <tt>ChangeIDControl</tt> and
<tt>VendorXControlFactory</tt> classes. The <tt>VendorXControlFactory</tt>
will be used by the service provider when the provider receives response
controls from the LDAP server.
<blockquote><pre>
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
    }
}
</pre></blockquote>

<p>

<h2>Package Specification</h2>

The JNDI API Specification and related documents can be found in the
<a href="../../../../technotes/guides/jndi/index.html">JNDI documentation</a>.

@since 1.3

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