Package net.jini.discovery

Class ConstrainableLookupLocator

java.lang.Object
net.jini.core.discovery.LookupLocator
net.jini.discovery.ConstrainableLookupLocator
All Implemented Interfaces:
Serializable, RemoteMethodControl
public final class ConstrainableLookupLocator extends LookupLocator implements RemoteMethodControl
LookupLocator subclass which supports constraint operations through the RemoteMethodControl interface. The constraints of a ConstrainableLookupLocator instance control how it performs unicast discovery, and apply only to its getRegistrar() and getRegistrar(int) methods. The constraints may also be used by other utilities, such as LookupLocatorDiscovery, to determine how unicast discovery should be performed on behalf of a given ConstrainableLookupLocator instance. Untrusted ConstrainableLookupLocator instances can be verified using the ConstrainableLookupLocatorTrustVerifier trust verifier.
Since:
2.0 This class supports use of the following constraint types to control unicast discovery behavior:
  • DiscoveryProtocolVersion: this constraint can be used to control which version of the unicast discovery protocol is used.
  • UnicastSocketTimeout: this constraint can be used to control the read timeout set on sockets over which unicast discovery is performed.
  • ConnectionRelativeTime: this constraint can be used to control the relative connection timeout set on sockets over which unicast discovery is performed.
  • ConnectionAbsoluteTime: this constraint can be used to control the absolute connection timeout set on sockets over which unicast discovery is performed.

In addition, the MulticastMaxPacketSize and MulticastTimeToLive constraint types are trivially supported, but do not have any effect on unicast discovery operations. Constraints other than those mentioned above are passed on to the underlying implementations of versions 1 and 2 of the discovery protocols.

An example of using constraints with ConstrainableLookupLocator is: 

 new ConstrainableLookupLocator("target_host", 4162, new BasicMethodConstraints(
     new InvocationConstraints(
         DiscoveryProtocolVersion.TWO, new UnicastSocketTimeout(120000))));
The resulting ConstrainableLookupLocator instance would (when used) perform unicast discovery to the host target_host on port 4162 using discovery protocol version 2, with a socket read timeout of 120000 milliseconds unless one was explicitly specified using the getRegistrar(int) method.
Author:
Sun Microsystems, Inc.
See Also:

  • Constructor Details

    • ConstrainableLookupLocator

      public ConstrainableLookupLocator(String url, MethodConstraints constraints) throws MalformedURLException
      Constructs a new ConstrainableLookupLocator instance which can be used to perform unicast discovery to the host and port named by the given URL with the provided constraints applied. This constructor invokes its superclass LookupLocator(String) constructor. Any exceptions thrown by the superclass constructor are rethrown.

      The url must be a valid URL of scheme "jini" as described in LookupLocator(String). A null constraints value is interpreted as mapping both getRegistrar methods to empty constraints.

      Parameters:
      url - the URL to use
      constraints - the constraints to apply to unicast discovery, or null
      Throws:
      MalformedURLException - if url cannot be parsed
      NullPointerException - if url is null

    • ConstrainableLookupLocator

      public ConstrainableLookupLocator(String host, int port, MethodConstraints constraints)
      Constructs a new ConstrainableLookupLocator instance which can be used to perform unicast discovery to the given host and port with the provided constraints applied. This constructor invokes its superclass LookupLocator(String, int) constructor. Any exceptions thrown by the superclass constructor are rethrown.

      A null constraints value is interpreted as mapping both getRegistrar methods to empty constraints. The host and port must satisfy the requirements of the LookupLocator(String, int) constructor.

      Parameters:
      host - the name of the host to contact
      port - the number of the port to connect to
      constraints - the constraints to apply to unicast discovery, or null
      Throws:
      NullPointerException - if host is null
      IllegalArgumentException - if the port and host do not meet the requirements of LookupLocator(String, int).

  • Method Details

    • getRegistrar

      public ServiceRegistrar getRegistrar() throws IOException, ClassNotFoundException
      Performs unicast discovery as specified by LookupLocator.getRegistrar() with the following differences.
      • It applies the supplied constraints (if any) for this method.
      • It does not invoke the getRegistrar(int) method.
      • If no timeout constraints are specified, this method assumes a default timeout of 60 seconds. A non default timeout can only be specified through the supplied constraints, the net.jini.discovery.timeout system property is ignored.
      ConstrainableLookupLocator implements this method to use the values of the host and port field in determining the host and port to connect to.
      Overrides:
      getRegistrar in class LookupLocator
      Returns:
      the ServiceRegistrar for the lookup service denoted by this LookupLocator object
      Throws:
      UnsupportedConstraintException - if the discovery-related constraints contain conflicts, or otherwise cannot be processed
      IOException - an error occurred during discovery
      ClassNotFoundException - if a class required to unmarshal the ServiceRegistrar proxy cannot be found

    • getRegistrar

      public ServiceRegistrar getRegistrar(int timeout) throws IOException, ClassNotFoundException
      Performs unicast discovery as specified by LookupLocator.getRegistrar(int), additionally applying the supplied discovery constraints. The timeout is considered a requirement with respect to other constraints specified for this instance.
      Overrides:
      getRegistrar in class LookupLocator
      Parameters:
      timeout - the maximum time to wait for a response, in milliseconds. A value of 0 specifies an infinite timeout.
      Returns:
      the ServiceRegistrar for the lookup service denoted by this LookupLocator object
      Throws:
      UnsupportedConstraintException - if the discovery-related constraints contain conflicts, or otherwise cannot be processed
      IOException - an error occurred during discovery
      ClassNotFoundException - if a class required to unmarshal the ServiceRegistrar proxy cannot be found

    • toString

      public String toString()
      Returns a string representation of this object.
      Overrides:
      toString in class LookupLocator
      Returns:
      the string representation

    • setConstraints

      public RemoteMethodControl setConstraints(MethodConstraints constraints)
      Description copied from interface: RemoteMethodControl
      Returns a new copy of this proxy with the client constraints set to the specified constraints. These constraints completely replace (in the copy) any client constraints previously placed on this proxy; calling the getConstraints method of the copy returns the identical constraints instance. The original proxy is not modified. A null value is interpreted as mapping all methods to empty constraints (one that has no requirements and no preferences). For any given remote call, the specific client requirements and preferences to be satisfied are given by the return value of invoking the getConstraints method of the specified MethodConstraints instance with a Method object representing the remote method.

      Client constraints placed on a proxy are included in the serialized state of the proxy. This allows third-party services to be transparent to the client's needs. For example, if remote object s1 obtains a proxy for remote object s2, and passes that proxy to remote object s3, expecting s3 to invoke a remote method on s2, then s1 can control that call by placing its constraints directly on the proxy before passing it to s3. If s3 does not wish to be transparent in this way, then it should explicitly replace the client constraints on received proxies with whatever constraints are appropriate to implement its own policy.

      Specified by:
      setConstraints in interface RemoteMethodControl
      Parameters:
      constraints - client constraints, or null
      Returns:
      a new copy of this proxy with the client constraints set to the specified constraints
      See Also:

    • getConstraints

      public MethodConstraints getConstraints()
      Description copied from interface: RemoteMethodControl
      Returns the client constraints placed on this proxy. The return value can be null, which is interpreted as mapping all methods to empty constraints (one that has no requirements and no preferences).
      Specified by:
      getConstraints in interface RemoteMethodControl
      Returns:
      the client constraints, or null
      See Also: