omg/CORBA/ORB.java

/* ORB.java --
   Copyright (C) 2005, 2006 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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exception statement from your version. */


package org.omg.CORBA;

import gnu.CORBA.OrbFocused;
import gnu.CORBA.ObjectCreator;
import gnu.CORBA.OrbRestricted;
import gnu.CORBA.typecodes.FixedTypeCode;
import gnu.CORBA.typecodes.GeneralTypeCode;
import gnu.CORBA.typecodes.RecordTypeCode;
import gnu.CORBA.typecodes.RecursiveTypeCode;

import org.omg.CORBA.ORBPackage.InconsistentTypeCode;
import org.omg.PortableInterceptor.ObjectReferenceTemplate;

import java.applet.Applet;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

import java.util.Properties;

/**
 * A central class in CORBA implementation, responsible for sending and handling
 * remote invocations. ORB also works as a factory for creating instances of
 * certain CORBA classes.
 *
 * Despite the core library contains the fully working CORBA implementation, it
 * also provides a simple way to plug-in the alternative CORBA support. This is
 * done by replacing the ORB. The alternative ORB can be specified via
 * properties, passed to ORB.Init(...).
 *
 * When creating an ORB instance, the class name is searched in the following
 * locations:
 * <p>
 * 1. Applet parameter or application string array, if any.<br>
 * 2. The properties parameter, if any.<br>
 * 3. The System properties.<br>
 * 4. The orb.properties file located in the user.home directory (if any).<br>
 * 5. The orb.properties file located in the java.home/lib directory (if any).
 * </p>
 *
 * The supported properties are: <table border="1">
 * <tr>
 * <td> org.omg.CORBA.ORBClass</td>
 * <td>The class, implementing the functional ORB, returned by
 * {@link #init(Applet, Properties)} or {@link #init(String[], Properties)}
 * </td>
 * </tr>
 * <tr>
 * <td>org.omg.CORBA.ORBSingletonClass</td>
 * <td>The class, implementing the restricted ORB, returned by {@link #init()}.
 * </td>
 * </tr>
 * <tr>
 * <td>org.omg.CORBA.ORBInitRef</td>
 * <td>Specifies the initial reference, accessible by name with the method
 * {@link #resolve_initial_references(String)}.</td>
 * </tr>
 * <tr>
 * <td>org.omg.CORBA.ORBid</td>
 * <td>Specifies the name (ORB Id) of this ORB. The ORB Id is later accessible
 * by {@link ObjectReferenceTemplate#orb_id}. The default value includes the
 * hashcode of the ORB instance that is normally different for each ORB.
 * </td>
 * </tr>
 * <tr>
 * <td>org.omg.CORBA.ServerId</td>
 * <td>Specifies the name (Server Id) of this server. This property assigns
 * value to the <i>static</i> field, ensuring that all ORB's on the same jre
 * have the same Server Id. It is normally set as the system property. The
 * server Id is later accessible as {@link ObjectReferenceTemplate#server_id}.
 * </td>
 * </tr>
 * <tr>
 * <td>gnu.CORBA.ListenerPort</td>
 * <td>Specifies that this ORB should serve all its objects on a single port
 * (for example, "1234") or on a specified port range (for example,
 * "1100-1108"). The property is used when working with firewals and serves as a
 * replacement for the proprietary properties like com.ibm.CORBA.ListenerPort
 * or com.sun.CORBA.POA.ORBPersistentServerPort. The specified port or range
 * should not overlap with the values, specified for other ORB's.
 * </td>
 * </tr>
 * <tr>
 * <td>gnu.Corba.SocketFactory</td>
 * <td>Sets the user-defined server and client socket factory for the ORB being
 * currently instantiated. Serves as a replacement of the proprietary
 * property com.sun.CORBA.connection.ORBSocketFactoryClass. To have multiple
 * types of sockets, instantiate several ORB's with this property each time
 * set to the different value.
 * The factory must implement gnu.CORBA.interfaces.SocketFactory.
 * </td>
 * </tr>
 * </table>
 * <p>The command line accepts the same properties as a keys. When
 * specifying in the command line, the prefix org.omg.CORBA can be omitted, for
 * instance<code> -ORBInitRef NameService=IOR:aabbccdd....</code>
 * </p>
 *
 * @author Audrius Meskauskas (AudriusA@Bioinformatics.org)
 */
public abstract class ORB
{
  /**
  * By default, {@link #init(String[], Properties)} and
  * {@link #init(Applet, Properties)} return
  * the built-in fully functional ORB is returned. If the
  * <code>props</code> contains the property org.omg.CORBA.ORBClass,
  * the value of this property is used as a class name to instantiate
  * a user-defined ORB.
  */
  private static final String FUNCTIONAL_ORB = "org.omg.CORBA.ORBClass";

  /**
   * The name of the restricted ORB property.
   */
  private static final String RESTRICTED_ORB =
    "org.omg.CORBA.ORBSingletonClass";

  private static final String LISTENER_PORT =
    OrbFocused.LISTENER_PORT;

  /**
   * The class, implementing the default fully functional ORB.
   */
  private static final String DEFAULT_FUNCTIONAL_ORB =
    gnu.CORBA.Poa.ORB_1_4.class.getName();

  private static final String DEFAULT_FOCUSED_ORB =
    gnu.CORBA.OrbFocused.class.getName();

  // There is no need for name of the default restricted ORB as it is
  // singleton and it is more effectively referred directly.

  /**
   * Connect the given CORBA object to this ORB. After the object is
   * connected, it starts receiving remote invocations via this ORB.
   *
   * The OMG group recommends to use Portable Object Adapter (POA) instead
   * of calling this method.
   *
   * This method is implemented in the derived Gnu Classpah classes,
   * returned by ORB.init(..). In this abstract class, the implementation
   * just throws {@link NO_IMPLEMENT}.
   *
   * @param object the org.omg.CORBA.Object to connect.
   */
  public void connect(org.omg.CORBA.Object object)
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * Disconnect the given CORBA object from this ORB. The object will be
   * no longer receiving the remote invocations. In response to the
   * remote invocation on this object, the ORB will send the
   * exception {@link OBJECT_NOT_EXIST}. The object, however, is not
   * destroyed and can receive the local invocations.
   *
   * This method is implemented in the derived Gnu Classpah classes,
   * returned by ORB.init(..). In this abstract class, the implementation
   * just throws {@link NO_IMPLEMENT}.
   *
   * @param object the object to disconnect.
   */
  public void disconnect(org.omg.CORBA.Object object)
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * Create a typecode, representing a tree-like structure.
   * This structure contains a member that is a sequence of the same type,
   * as the structure itself. You can imagine as if the folder definition
   * contains a variable-length array of the enclosed (nested) folder
   * definitions. In this way, it is possible to have a tree like
   * structure that can be transferred via CORBA CDR stream.
   *
   * @deprecated It is easier and clearler to use a combination of
   * create_recursive_tc and create_sequence_tc instead.
   *
   * @param bound the maximal expected number of the nested components
   * on each node; 0 if not limited.
   *
   * @param offset the position of the field in the returned structure
   * that contains the sequence of the structures of the same field.
   * The members before this field are intialised using parameterless
   * StructMember constructor.
   *
   * @return a typecode, defining a stucture, where a member at the
   * <code>offset</code> position defines an array of the identical
   * structures.
   *
   * @see #create_recursive_tc(String)
   * @see #create_sequence_tc(int, TypeCode)
   */
  public abstract TypeCode create_recursive_sequence_tc(int bound, int offset);

  /**
   * Create alias typecode for the given typecode.
   */
  public abstract TypeCode create_alias_tc(String id, String name,
                                           TypeCode typecode
                                          );

  /**
   * Create an instance of the CORBA {@link Any} with the type, intialised
   * to {@link TCKind#tk_null}
   */
  public abstract Any create_any();

  /**
   * Create a typecode, defining an array of the given elements.
   *
   * @param length the size of array
   * @param element_type the array component type.
   *
   * @return the corresponding typecode.
   */
  public abstract TypeCode create_array_tc(int length, TypeCode element_type);

  /**
   * Creates an empty CORBA <code>ContextList</code>.
   *
   * @return the newly created context list.
   */
  public abstract ContextList create_context_list();

  /**
   * The support for {@link DynAny} and derived interfaces
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynAny create_basic_dyn_any(org.omg.CORBA.TypeCode t)
                              throws InconsistentTypeCode
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * The support for {@link DynAny} and derived interfaces
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynAny create_dyn_any(org.omg.CORBA.Any a)
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * The support for {@link DynArray}
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynArray create_dyn_array(org.omg.CORBA.TypeCode t)
                            throws InconsistentTypeCode
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * The support for {@link DynEnum}
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynEnum create_dyn_enum(org.omg.CORBA.TypeCode t)
                          throws InconsistentTypeCode
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * The support for {@link DynSequence}
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynSequence create_dyn_sequence(org.omg.CORBA.TypeCode t)
                                  throws InconsistentTypeCode
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * The support for {@link DynStruct} and derived interfaces
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynStruct create_dyn_struct(org.omg.CORBA.TypeCode t)
                              throws InconsistentTypeCode
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * The support for {@link DynUnion} and derived interfaces
   * has never been implemented in Sun's java releases,
   * at least till v1.4 inclusive.
   *
   * Since v1.4 this stil missing implementation was replaced
   * by the new DynamicAny package.
   *
   * @deprecated Use {@link org.omg.DynamicAny.DynAnyFactory}
   *
   * @throws NO_IMPLEMENT, always.
   */
  public DynUnion create_dyn_union(org.omg.CORBA.TypeCode t)
                            throws InconsistentTypeCode
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * Create a typecode, defining the given enumeration.
   *
   * @param id the id.
   * @param name the name.
   * @param members the memebers
   * @return the created enumeration.
   */
  public abstract TypeCode create_enum_tc(String id, String name,
                                          String[] members
                                         );

  /**
   * Create an environment (container for exceptions).
   *
   * @return the created container.
   */
  public abstract Environment create_environment();

  /**
   * Creates an empty exception list.
   *
   * @return the newly created list.
   */
  public abstract ExceptionList create_exception_list();

  /**
   * Create the exception typecode.
   *
   * @param id the id of exception.
   * @param name the name of exception.
   * @param members the members of exception.
   */
  public abstract TypeCode create_exception_tc(String id, String name,
                                               StructMember[] members
                                              );

  /**
   * Creates a TypeCode object for CORBA <code>fixed</code> that is
   * mapped to java {@link java.math.BigDecimal}.
   *
   * @param digits the number of digits in that <code>fixed</code>.
   * @param scale the number of digits after the decimal point.
   *
   * @return the corresponding TypeCode.
   */
  public TypeCode create_fixed_tc(short digits, short scale)
  {
    FixedTypeCode r = new FixedTypeCode();
    r.setDigits(digits);
    r.setScale(scale);
    return r;
  }

  /**
   * Creates a typecode, representing the IDL interface.
   *
   * @param id the interface repository id.
   * @param name the interface name.
   *
   * @return the created typecode.
   */
  public abstract TypeCode create_interface_tc(String id, String name);

  /**
   * Create an instance of a new {@link NVList}.
   *
   * @param count the initial size of the list. If more elements are added,
   * the list automatically expands.
   *
   * @return the created list.
   */
  public abstract NVList create_list(int count);

  /**
   * Create a new named value.
   *
   * @param name the name of the named value
   * @param any the content of the named value.
   * @param flags the flags of the named value
   *
   * @return the named value.
   */
  public abstract NamedValue create_named_value(String name, Any any, int flags);

  /**
   * Send multiple prepared requests one way, do not caring about the answer.
   * The messages, containing requests, will be marked, indicating that
   * the sender is not expecting to get a reply.
   *
   * @param requests the prepared array of requests.
   *
   * @see Request#send_oneway()
   */
  public abstract void send_multiple_requests_oneway(Request[] requests);

  /**
   * Send multiple prepared requests expecting to get a reply. All requests
   * are send in parallel, each in its own separate thread. When the
   * reply arrives, it is stored in the agreed fields of the corresponing
   * request data structure. If this method is called repeatedly,
   * the new requests are added to the set of the currently sent requests,
   * but the old set is not discarded.
   *
   * @param requests the prepared array of requests.
   *
   * @see #poll_next_response()
   * @see #get_next_response()
   * @see Request#send_deferred()
   */
  public abstract void send_multiple_requests_deferred(Request[] requests);

  /**
   * Find if any of the requests that have been previously sent with
   * {@link #send_multiple_requests_deferred}, have a response yet.
   *
   * @return true if there is at least one response to the previously
   * sent request, false otherwise.
   */
  public abstract boolean poll_next_response();

  /**
   * Get the next instance with a response being received. If all currently
   * sent responses not yet processed, this method pauses till at least one of
   * them is complete. If there are no requests currently sent, the method
   * pauses till some request is submitted and the response is received.
   * This strategy is identical to the one accepted by Suns 1.4 ORB
   * implementation.
   *
   * @return the previously sent request that now contains the received
   * response.
   *
   * @throws WrongTransaction If the method was called from the transaction
   * scope different than the one, used to send the request. The exception
   * can be raised only if the request is implicitly associated with some
   * particular transaction.
   */
  public abstract Request get_next_response()
                                     throws WrongTransaction;

  /**
   * Create a new CDR output stream, where the parameter values can be written
   * during the method invocation.
   *
   * @return a stream to write values into.
   */
  public abstract org.omg.CORBA.portable.OutputStream create_output_stream();

  /**
   * This should create the list, initialised with the argument descriptions
   * for the given operation definition (CORBA <code>OperationDef</code>).
   * The information should be obtained from the interface repository.
   * However this method is oficially documented as not implemented at least
   * till v1.4 inclusive.
   *
   * @param operation_definition the operation definition, must be
   * CORBA <code>OperationDef</code>.
   *
   * @return never
   *
   * @throws NO_IMPLEMENT, always.
   */
  public NVList create_operation_list(Object operation_definition)
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * <p>Creates the new policy of the specified type, having the given value.
   * This method looks for the policy factory that was previously registered
   * during ORB initialization by
   * {@link org.omg.PortableInterceptor#ORBInitialiser}.
   *
   * If the suitable factory is found, this factory creates the requested policy,
   * otherwise the PolicyError is thrown.
   * </p><p>
   * The POA policies should be created by POA, not by this method.
   * </p>
   * @param type the policy type.
   * @param value the policy value, wrapped into Any.
   *
   * @throws PolicyError if the ORB fails to instantiate the policy object.
   *
   * @throws NO_IMPLEMENT always (in this class). Overridden in derived classes
   * returned by ORB.init(..).
   *
   * @see org.omg.PortableInterceptor.ORBInitInfoOperations#register_policy_factory
   * @see org.omg.PortableInterceptor.PolicyFactoryOperations
   */
  public Policy create_policy(int type, Any value)
                       throws PolicyError
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * Create typecode, defining the sequence of the elements, having
   * the given type.
   *
   * @param bound the maximal length of the sequence, 0 if not restricted.
   *
   * @param element_type the sequence element type.
   *
   * @return the typecode.
   */
  public abstract TypeCode create_sequence_tc(int bound, TypeCode element_type);

  /**
   * Create a TypeCode, representing the CORBA <code>string</code>.
   *
   * @param bound the maximal length of the string, 0 is unlimited.
   *
   * @return the corresponding string typecode.
   */
  public abstract TypeCode create_string_tc(int bound);

  /**
   * Create the typecode, defining the given IDL structure.
   *
   * The TypeCode object is initialized with the given id, name, and members.
   * @param id the Id of this type.
   * @param name the name of this type.
   * @param members the member list.
   *
   * @return the typecode.
   */
  public abstract TypeCode create_struct_tc(String id, String name,
                                            StructMember[] members
                                           );

  /**
   * Create the typecode, defining the given IDL union.
   *
   * The TypeCode object is initialized with the given id, name, discriminator
   * and members.
   *
   * @param id the Id of this type.
   * @param name the name of this type.
   * @param discriminator the union discriminator.
   * @param members the member list.
   *
   * @return the typecode.
   */
  public abstract TypeCode create_union_tc(String id, String name,
                                           TypeCode discriminator,
                                           UnionMember[] members
                                          );

  /**
   * Create a TypeCode, representing the CORBA <code>wstring</code>.
   *
   * @param bound the maximal length of the string, 0 is unlimited.
   *
   * @return the corresponding string typecode.
   */
  public abstract TypeCode create_wstring_tc(int bound);

  /**
   * Create a typecode for an abstract interface. The abstract interface
   * can be either CORBA object or CORBA value type.
   *
   * @param id the id of the abstract interface.
   * @param name the name of the abstract interface.
   *
   * @return the created typecode.
   */
  public TypeCode create_abstract_interface_tc(String id, String name)
  {
    GeneralTypeCode t = new GeneralTypeCode(TCKind.tk_abstract_interface);
    t.setName(name);
    t.setId(id);
    return t;
  }

  /**
   * Create a typecode for a native interface.
   *
   * @param id the id of the native interface.
   * @param name the name of the native interface.
   *
   * @return the created typecode.
   */
  public TypeCode create_native_tc(String id, String name)
  {
    GeneralTypeCode t = new GeneralTypeCode(TCKind.tk_native);
    t.setName(name);
    t.setId(id);
    return t;
  }


  /**
   * Create a typecode which serves as a placeholder for typcode, containing
   * recursion.
   *
   * @param id the id of the recursive typecode, for that this typecode
   * serves as a placeholder.
   */
  public TypeCode create_recursive_tc(String id)
  {
    return new RecursiveTypeCode(id);
  }

  /**
   * Create value box typecode.
   */
  public TypeCode create_value_box_tc(String id, String name,
                                      TypeCode boxed_type
                                     )
  {
    GeneralTypeCode t = new GeneralTypeCode(TCKind.tk_value_box);
    t.setName(name);
    t.setId(id);
    t.setContentType(boxed_type);
    return t;
  }

  /**
   * Create IDL value type code.
   */
  public TypeCode create_value_tc(String id, String name, short type_modifier,
                                  TypeCode concrete_base, ValueMember[] members
                                 )
  {
    RecordTypeCode r = new RecordTypeCode(TCKind.tk_value);
    r.setId(id);
    r.setName(name);
    r.setTypeModifier(type_modifier);
    r.setConcreteBase_type(concrete_base);

    for (int i = 0; i < members.length; i++)
      {
        r.add(members [ i ]);
      }

    return r;
  }

  /**
   * This should return the information, related to the current thread.
   * The information is needed, for instance, to get the current object
   * from the code that serves several objects in parallel threads.
   * The {@link Current} is very general interface, with no fields and
   * operations defined. This method is not implemented in Suns
   * releases at least till v1.5 inclusive. To obtain the
   * {@link org.omg.PortableServer.Current}, use
   * {@link #resolve_initial_references}, passing "POACurrent".
   *
   * @deprecated since 1.2, use {@link #resolve_initial_references}.
   *
   * @return never
   *
   * @throws NO_IMPLEMENT always.
   */
  public Current get_current()
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * This should return the information about the CORBA facilities and
   * services, available from this ORB. However this method is oficially
   * documented as not implemented at least till v1.5 inclusive.
   *
   * @param service_type a type of the service being requested. The OMG
   * specification currently defines only one value, 1, for security
   * related services.
   *
   * @param service_info a holder, where the returned information should
   * be stored.
   *
   * @return should return true if the service information is available
   * from the ORB, but this method never returns.
   *
   * @throws NO_IMPLEMENT always.
   */
  public boolean get_service_information(short service_type,
                                         ServiceInformationHolder service_info
                                        )
  {
    throw new NO_IMPLEMENT();
  }

  /**
   * Get the default context of this ORB. This is an initial root of all
   * contexts.
   *
   * The default method returns a new context with the empty name and
   * no parent context.
   *
   * @return the default context of this ORB.
   *
   * @throws NO_IMPLEMENT for the Singleton ORB, returned by
   * the parameterless {@link #init()}.
   */
  public abstract Context get_default_context();

  /**
   * Return thg typecode, representing the given primitive object type.
   *
   * @param tcKind the kind of the primitive typecode.
   *
   * @return the typecode of the primitve typecode.
   */
  public abstract TypeCode get_primitive_tc(TCKind tcKind);

  /**
   * Returns so-called Singleton ORB, a highly restricted version
   * that cannot communicate over network. This ORB is provided
   * for the potentially malicious applets with heavy security restrictions.
   *
   * The returned Singleton ORB can only create typecodes,
   * {@link Any}, {@link ContextList}, {@link NVList} and
   * {@link org.omg.CORBA.portable.OutputStream} that writes to an
   * internal buffer.
   *
   * All other methods throw the {@link NO_IMPLEMENT} exception, additionally
   * printing the error message about the potential attempt to violate
   * the security rules.
   *
   * The implementing ORB class, used in this method, is found as described
   * in the header.
   *
   * @return the working derivative of ORB, implementing the methods
   * of this abstract class.
   */
  public static ORB init()
  {
    String orb_cn = getCumulatedProperty(null, RESTRICTED_ORB);
    if (orb_cn == null)
      return OrbRestricted.Singleton;
    else
      return createORB(null, orb_cn);
  }

  /**
   * Creates the working instance of ORB for an applet.
   *
   * By default the built-in fully functional ORB is returned. The ORB class
   * is found as described in the header of this class.
   *
   * @param applet the applet. The property org.omg.CORBA.ORBClass,
   * if present, defines the used ORB implementation class. If this
   * property is not present, the ORB class is found as described in the
   * class header.
   *
   * @param props the properties, may be <code>null</code>.
   *
   * @return a newly created functional derivative of this abstract class.
   */
  public static ORB init(Applet applet, Properties props)
  {
    String ocn = applet.getParameter(FUNCTIONAL_ORB);
    String lp = applet.getParameter(LISTENER_PORT);

    if (ocn==null && lp!=null)
      ocn = DEFAULT_FOCUSED_ORB;

    ORB orb = createORB(props, ocn);
    orb.set_parameters(applet, props);

    return orb;
  }

  /**
   * Creates the working instance of ORB for a standalone application.
   *
   * By default the built-in fully functional ORB is returned. The ORB class is
   * found as described in the header of this class.
   *
   * @param args the parameters, passed to the applications
   * <code>main(String[] args)</code> method, may be <code>null</code>. The
   * parameter -org.omg.CORBA.ORBClass <class name> if present, defines the used
   * ORB implementation class. If this property is not present, the ORB class is
   * found as described in the class header.
   *
   * @param props application specific properties, may be <code>null</code>.
   *
   * @return a newly created functional derivative of this abstract class.
   */
  public static ORB init(String[] args, Properties props)
  {
    String ocn = null;
    String lp = null;

    String orbKey = "-" + FUNCTIONAL_ORB;
    String lpKey = "-" + LISTENER_PORT;

    if (args != null)
      if (args.length >= 2)
        {
          for (int i = 0; i < args.length - 1; i++)
            {
              if (args[i].equals(orbKey))
                ocn = args[i + 1];
              if (args[i].equals(lpKey))
                lp = args[i + 1];
            }
        }

    if (lp != null && ocn == null)
      ocn = DEFAULT_FOCUSED_ORB;

    ORB orb = createORB(props, ocn);

    orb.set_parameters(args, props);
    return orb;
  }

  /**
   * List the initially available CORBA objects (services).
   *
   * @return a list of services.
   *
   * @see #resolve_initial_references(String)
   */
  public abstract String[] list_initial_services();

  /**
   * Find and return the easily accessible CORBA object, addressed
   * by name.  The returned object is typically casted to the more
   * specific reference using the <code>narrow(Object)</code> method
   * of its helper. The method resolves the following string values,
   * returning the working objects:
   * <table border="1"><tr><th>String</th><th>Object class</th>
   * <th>Object use</th></tr>
   *
   * <tr><td>NameService</td><td>{@link org.omg.CosNaming.NamingContextExt}</td>
   * <td>Finds (usually remote) object by its name.</td></tr>
   *
   * <tr><td>RootPOA</td><td>{@link org.omg.PortableServer.POA}</td>
   * <td>Holds the POA tree for this ORB, where since 1.4 all servants
   * should be connected.</td></tr>
   *
   * <tr><td>RootPOAManager</td><td>{@link org.omg.PortableServer.POAManager}
   * </td><td>Regulates (suspends/resumes) the root POA
   * activity</td></tr>
   *
   * <tr><td>POACurrent</td><td>{@link org.omg.PortableServer.Current}
   * </td><td>Informs the current thread about the Id and POA of the
   * object being currently served (the methods of
   * <code>Current</code> return different values for
   * different threads).
   * </td></tr>
   *
   * <tr><td>CodecFactory</td><td>{@link org.omg.IOP.Codec}</td>
   * <td>Encodes/decodes IDL data types into/from byte arrays.</td>
   * </tr>
   *
   * <tr><td>DynAnyFactory</td><td>{@link org.omg.DynamicAny.DynAnyFactory}</td>
   * <td>Creates DynAny's.</td>
   * </tr>
   *
   * <tr><td>PICurrent</td><td>{@link org.omg.PortableInterceptor.Current}</td>
   * <td>Contains multiple slots where an interceptor can rememeber the
   * request - specific values between subsequent
   * calls of the interceptor methods.</td>
   * </tr>
   *
   * </table>
   *
   * @param name the object name.
   * @return the object
   * @throws org.omg.CORBA.ORBPackage.InvalidName if the given name
   * is not associated with the known object.
   */
  public abstract Object resolve_initial_references(String name)
    throws org.omg.CORBA.ORBPackage.InvalidName;

  /**
   * Get the IOR reference string for the given object.
   * IOR can be compared with the Internet address for a web page,
   * it provides means to locate the CORBA service on the web.
   * IOR contains the host address, port number, the object identifier
   * (key) inside the server, the communication protocol version,
   * supported charsets and so on.
   *
   * @param forObject the CORBA object
   * @return the object IOR representation.
   * @see #string_to_object(String)
   */
  public abstract String object_to_string(Object forObject);

  /**
   * This should perform the implementation dependent unit of work in the
   * main thread.
   *
   * This method is part of the support for the distribute use of the
   * single execution thread.
   *
   * Same as in Suns releases at least till 1.4 inclusive,
   * the distribute use of the single thread is not implemented.
   * Use multiple threads, provided by jre.
   *
   * The method returns without action.
   */
  public void perform_work()
  {
  }

  /**
  * Checks if the ORB needs the main thread to perform some work.
  * The method should return true if the ORB needs the main thread,
  * and false if it does not.
  *
  * This method is part of the support for the distribute use of the
  * single execution thread.
  *
  * Same as in Suns releases at least till 1.4 inclusive,
  * the distributed use of the single thread is not implemented.
  * Use multiple threads, provided by jre.
  *
  * @return false, always.
  */
  public boolean work_pending()
  {
    return false;
  }

  /**
   * <p>Find and return the CORBA object, addressed by the given
   * string representation. The object can be (an usually is)
   * located on a remote computer, possibly running a different
   * (not necessary java) CORBA implementation. The returned
   * object is typically casted to the more specific reference
   * using the <code>narrow(Object)</code> method of its helper.
   * </p><p>
   * This function supports the following input formats:<br>
   * 1. IOR reference (<b>ior:</b>nnnnn ..), usually computer generated.<br>
   * 2. <b>corbaloc:</b>[<b>iiop</b>][version.subversion<b>@</b>]<b>:</b>host[<b>:</b>port]<b>/</b><i>key</i>
   * defines similar information as IOR reference, but is more human readable.
   * This type of reference may also contain multiple addresses (see
   * OMG documentation for complete format).<br>
   * 3. <b>corbaloc:rir:/</b><i>name</i> defines internal reference on this
   * ORB that is resolved using {@link #resolve_initial_references}, passing
   * the given <i>name</i> as parameter.<br>
   * 4. <b>corbaname:rir:#</b><i>name</i> states that the given <i>name</i>
   * must be resolved using the naming service, default for this ORB.<br>
   * 5. <b>corbaname:</b>[<b>iiop</b>][version.subversion<b>@</b>]<b>:</b>host[<b>:</b>port]<b>#</b><i>name</i>
   * states that the <i>name</i> must be resolved using the naming service
   * that runs on the given host at the given port. The ORB expects to find
   * there the {@link org.omg.CosNaming.NamingContext} under the key
   * "NameService.<br>
   * 7. file://[file name] Read the object definition string from the
   * file system<br>
   * 8. http://[url] Read the object definition string from the provided
   * url.<br>
   * 9. ftp://[url] Read the object definition string from the provided
   * url.<br>
   *
   * <p>The default port is always 2809. The default iiop version is 1.0
   * that now may not always be supported, so we would recommend to specify
   * the version explicitly.</p>
   * <p>
   * The examples of the corbaloc and corbaname addresses:<br>
   * corbaname:rir:#xobj - ask local naming service for "xobj".<br>
   * corbaname:rir:/NameService#xobj - same (long form).<br>
   * corbaname:iiop:1.2@localhost:900#xobj - same, assuming that the naming
   * service runs at port 900 on the local host and supports iiop 1.2.<br>
   * corbaname:iiop:localhost#xobj - same, assuming that the naming
   * service runs at port 2809 on the local host and supports iiop 1.0.<br>
   * corbaloc::gnu.xxx.yy/Prod/TradingService - the object exists on the
   * host gnu.xxx.yy, port 2809 having the key "Prod/TradingService". Its ORB
   * supports iiop 1.0.<br>
   * corbaloc::gnu.xxx.yy/Prod/TradingService:801 - the object exists on the
   * host gnu.xxx.yy, port 801 having the key "Prod/TradingService". Its ORB
   * supports iiop 1.0 (iiop keyword ommitted).<br>
   * corbaloc:iiop:1.1@gnu.xxx.yy/Prod/TradingService - the object exists on the
   * host gnu.xxx.yy, port 801 having the key "Prod/TradingService". Its ORB
   * supports iiop 1.1.<br>
   * corbaloc:rir:/NameService - the default naming service.
   *
   * @param IOR the object IOR representation string.
   *
   * @return the found CORBA object.
   *
   * @throws BAD_PARAM if the string being parsed is invalid.
   * @throws DATA_CONVERSION if the string being parsed contains unsupported
   * prefix or protocol.
   *
   * @see #object_to_string(org.omg.CORBA.Object)
   */
  public abstract Object string_to_object(String IOR);

  /**
   * Start listening on the input socket. This method
   * blocks the current thread until {@link #shutdown(boolean)}
   * is called and shutdown process is completed.
   */
  public void run()
  {
  }

  /**
   * Shutdown the ORB server.
   *
   * @param wait_for_completion if true, the current thread is
   * suspended untile the shutdown process is complete.
   */
  public void shutdown(boolean wait_for_completion)
  {
  }

  /**
   * Destroy this server, releasing the occupied resources.
   * The default method returns without action.
   */
  public void destroy()
  {
  }

  /**
   * Set the ORB parameters. This method is normally called from
   * {@link #init(String[], Properties)}.
   *
   * @param para the parameters, that were passed as the parameters
   * to the  <code>main(String[] args)</code> method of the current standalone
   * application.
   *
   * @param props application specific properties that were passed
   * as a second parameter in {@link #init(String[], Properties)}).
   * Can be <code>null</code>.
   */
  protected abstract void set_parameters(String[] para, Properties props);

  /**
   * Set the ORB parameters. This method is normally called from
   * {@link #init(Applet, Properties)}.
   *
   * @param app the current applet.
   *
   * @param props application specific properties, passed as the second
   * parameter in {@link #init(Applet, Properties)}.
   * Can be <code>null</code>.
   */
  protected abstract void set_parameters(Applet app, Properties props);

  /**
   * Get the property with the given name, searching in the standard
   * places for the ORB properties.
   */
  private static String getCumulatedProperty(Properties props, String property)
  {
    String orb_cn = null;

    if (props != null)
      orb_cn = props.getProperty(property, null);

    if (orb_cn == null)
      orb_cn = System.getProperty(property, null);

    if (orb_cn == null)
      orb_cn = checkFile(property, "user.home", null);

    if (orb_cn == null)
      orb_cn = checkFile(property, "java.home", "lib");

    return orb_cn;
  }

  /**
   * Check if the property is defined in the existsting file orb.properties.
   *
   * @param property the property
   * @param dir the system property, defining the folder where the
   * file could be expected.
   * @param subdir subfolder where to look for the file.
   *
   * @return the property value, null if not found or file does not exist.
   */
  private static String checkFile(String property, String dir, String subdir)
  {
    try
      {
        File f = new File(dir);
        if (!f.exists())
          return null;

        if (subdir != null)
          f = new File(f, subdir);

        f = new File(f, "orb.properties");

        if (!f.exists())
          return null;

        Properties p = new Properties();
        p.load(new BufferedInputStream(new FileInputStream(f)));

        return p.getProperty(property, null);
      }
    catch (IOException ex)
      {
        return null;
      }
  }

  /**
   * Create ORB when its name is possibly known.
   *
   * @param props properties, possibly containing the ORB name.
   * @param orbClassName the direct ORB class name, overriding other possible
   * locations, or null if not specified.
   */
  private static ORB createORB(Properties props, String orbClassName)
  {
    ORB orb = null;

    if (orbClassName == null)
      {
        orbClassName = getCumulatedProperty(props, FUNCTIONAL_ORB);

        if (orbClassName == null)
          {
            String lp = getCumulatedProperty(props, LISTENER_PORT);
            if (lp != null)
              orbClassName = DEFAULT_FOCUSED_ORB;
            else
              orbClassName = DEFAULT_FUNCTIONAL_ORB;
          }
      }

    try
      {
        orb = (ORB) ObjectCreator.forName(orbClassName).newInstance();
      }
    catch (ClassNotFoundException ex)
      {
        noORB(orbClassName, ex);
      }
    catch (IllegalAccessException ex)
      {
        noORB(orbClassName, ex);
      }
    catch (InstantiationException ex)
      {
        noORB(orbClassName, ex);
      }

    return orb;
  }

  /**
   * Throw the runtime exception.
   *
   * @param orb_c the ORB class name.
   * @param why the explaining chained exception.
   */
  private static void noORB(String orb_c, Throwable why)
  {
    throw new RuntimeException("The ORB " + orb_c + " cannot be instantiated.",
                               why
                              );
  }
}