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Provides classes and interfaces for making the server side of your applications
portable across multivendor ORBs.
In Java, Portable Object Adaptor (POA)-based Dynamic Skeleton Interface (DSI)
servants inherit from the standard DynamicImplementation class, which
inherits from the Servant class. The native Servant type is
defined by the PortableServer module for the POA. In Java, the
Servant type is mapped to the Java
org.omg.PortableServer.Servant class.
It serves as the base class for all POA servant
implementations and provides a number of methods that may
be invoked by the application programmer, as well as methods
which are invoked by the POA itself and may be overridden by
the user to control aspects of servant behavior.
Package Specification
For a precise list of supported sections of official OMG specifications with which
the Java[tm] Platform, Standard Edition 6 complies, see Official Specifications for CORBA
support in Java[tm] SE 6.
POA-related Interfaces
The PortableServer module defines the following POA-related interfaces:
- POA
- POAManager
- ServantManager
- ServantActivator
- ServantLocator
- AdapterActivator
- ThreadPolicy
- LifespanPolicy
- IdUniquenessPolicy
- IdAssignmentPolicy
- ImplicitActivationPolicy
- ServantRetentionPolicy
- RequestProcessingPolicy
- Current
In addition, the POA defines the Servant native type.
Operations classes
Each of the interfaces listed above has an associated Operations interface. The Operations interface is generated by the idlj compiler and contains the method signatures for methods defined in its associated interface. The Operations interface can be accessed by both the client and the server, while its associated interface can only be called by the client.
Value Classes
Classes ending in the suffix PolicyValue provide the values used for the create_POA call, which sets the policy for the POA. See the sample code below for a demonstration. PolicyValue files include the following:
IdAssignmentPolicyValue
IdUniquenessPolicyValue
ImplicitActivationPolicyValue
LifespanPolicyValue
RequestProcessingPolicyValue
ServantRetentionPolicyValue
ThreadPolicyValue
Helper Classes
Helper classes, which are generated for all user-defined types in an OMG IDL
interface, supply static methods needed to manipulate those types. There is only one method in a helper class that an application programmer uses: the narrow method. Only Java interfaces mapped from IDL interfaces will have a helper class that includes a narrow method, so in the PortableServer package, only the following classes have a narrow method:
ForwardRequestHelper
ServantActivatorHelper
ServantLocatorHelper
POA Classes
POA classes are used to implement the ServantActivator or ServantLocator.
Exceptions
The ForwardRequest exception indicates to the ORB
that it is responsible for delivering the current request and subsequent ForwardRequest requests to the object denoted in the
forward_reference member of the exception.
Interfaces Implemented by the Application Programmer
Most of what PortableServer does is transparent to the user. The result is that programmers will use only a few of the interfaces mentioned above. The remaining interfaces will be provided by the ORB implementation. The interfaces of interest to application programmers are the following:
AdapterActivator
Adapter activators are associated with POAs. An adapter activator supplies a POA with the ability to create child POAs on demand, as a side-effect of receiving a request that names the child POA (or one of its children), or when find_POA is called with an activate parameter value of TRUE. An application server that creates all its needed POAs at the beginning of execution does not need to use or provide an adapter activator; it is necessary only for the case in which POAs need to be created during request processing.
ServantLocator
When the POA has the NON_RETAIN policy, it uses servant managers that are ServantLocators.
ServantActivator
When the POA has the RETAIN policy, it uses servant managers that are ServantActivators.
Package org.omg.PortableServer.ServantLocatorPackage
This package supplies a CookieHolder class for passing
the Cookie type as an out parameter. The CookieHolder class
follows exactly the same pattern as the other holder classes for basic types.
Related Documentation
For an overview of Java IDL, please see:
Java IDL home page.
Example Code
Example Server Code
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.rmi.PortableRemoteObject ;
import com.sun.corba.se.impl.poa.POAORB;
import org.omg.PortableServer.*;
import java.util.*;
import org.omg.CORBA.*;
import javax.rmi.CORBA.Stub;
import javax.rmi.CORBA.Util;
public class HelloServer {
public HelloServer(String[] args) {
try {
Properties p = System.getProperties();
// p.put("org.omg.CORBA.ORBClass", "com.sun.corba.ee.internal.POA.POAORB");
ORB orb = ORB.init( args, p );
POA rootPOA = (POA)orb.resolve_initial_references("RootPOA");
Policy[] tpolicy = new Policy[3];
tpolicy[0] = rootPOA.create_lifespan_policy(
LifespanPolicyValue.TRANSIENT );
tpolicy[1] = rootPOA.create_request_processing_policy(
RequestProcessingPolicyValue.USE_ACTIVE_OBJECT_MAP_ONLY );
tpolicy[2] = rootPOA.create_servant_retention_policy(
ServantRetentionPolicyValue.RETAIN);
POA tpoa = rootPOA.create_POA("MyTransientPOA", null, tpolicy);
String ObjectId = "MyObjectId";
byte[] oid = ObjectId.getBytes();
org.omg.CORBA.Object obj = tpoa.create_reference_with_id(oid,
new _HelloImpl_Tie()._all_interfaces(tpoa, oid)[0]);
HelloInterface helloRef = (HelloInterface)PortableRemoteObject.narrow(
obj, HelloInterface.class );
Context initialNamingContext = new InitialContext();
initialNamingContext.rebind("HelloService", helloRef);
System.out.println("Hello Server: Ready...");
orb.run();
} catch (Exception e) {
System.out.println("Trouble: " + e);
e.printStackTrace();
}
}
public static void main(String args[]) {
new HelloServer( args );
}
}
@since 1.4
@serial exclude