WebLogic RMI provides a rich descriptor framework to associate various security, transactions, clustering, and timeout attributes to a remote class and its methods. These attributes can be specified as annotations in plain java implementation classes with non-remote interfaces when the remote object implementation is bound to a WebLogic JNDI tree. See weblogic.rmi.annotation in Java API Reference for Oracle WebLogic Server.
This chapter includes the following sections:
WebLogic RMI provides annotation support that can be embedded inside a remote java object and simplifies development by allowing you to avoid running weblogic.rmic tool on the compiled class.
To make a plain java object remotely accessible, do the following:
Example 4-1 Example RMI Annotation
package myrmi.example;
import java.rmi.RemoteException;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import weblogic.rmi.annotation.Rmi;
import weblogic.rmi.annotation.RmiMethod;
@Rmi(remoteInterfaces={MyRemoteInterface.class})
public class RmiMethodAnnotations implements MyRemoteInterface{
public RmiMethodAnnotations() {
}
public int getIndex() throws RemoteException {
return 0;
}
@RmiMethod(asynchronousResult=true)
public Future<String> ejbAsynchronousSayHello(String name) {
return new FutureTask(new MyRunnable(), new Object());
}
class MyRunnable implements Runnable {
public void run() {
}
}
}
Example 4-2 Example RMI without Annotations
package myrmi.example;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.util.concurrent.Future;
public interface MyRemoteInterface extends Remote {
int getIndex() throws RemoteException;
public Future<String> ejbAsynchronousSayHello(String name);
public String sayBye();
}
This allows the WebLogic RMI layer to treat the RmiMethodAnnotations object as remote object when it is bound to the WLS JNDI tree.
Example 4-2 provides an example of code that implements the same methods without using annotations.
The following sections describe the annotation in more detail.
Provides class-level annotation support for remote objects that specify the remote implementation class.
The following table summarizes the attributes.
Table 4-1 Attributes of the Rmi Annotation
| Name | Description | Data Type | Default Value |
|---|---|---|---|
|
|
The |
|
"" |
|
|
Indicates if the remote object is clusterable. |
|
|
|
|
Default RMI Method annotation. Can be over-ridden with a method annotation. |
|
|
|
|
Load Algorithm for clustered remote object. Legal Values are:
Default is |
|
|
|
|
Enables sticky load balancing. The server chosen for servicing the first request is used for all subsequent requests. Only used for a clusterable remote object. |
|
|
|
|
A comma-separated list of Interface class names to be treated as remote interface |
|
"" |
The following sections describe the annotation in more detail.
Provides method-level annotation support for remote objects that specify the remote implementation class.
The following table summarizes the attributes.
Table 4-2 Attributes of the RmiMethod Annotation
| Name | Description | Data Type | Default Value |
|---|---|---|---|
|
|
If |
|
|
|
|
Specifies the Work Manager used to schedule remote object requests. |
|
"" |
|
|
Specifies an Idempotent method. |
|
|
|
|
Specifies a one-way call. |
|
|
|
|
Specifies a timeout for a remote call. |
|
0 |
|
|
Specifies a transactional method. If not, suspend a transaction before making the RMI call and resume the transaction after the call completes. |
|
|
The following sections provide information on WebLogic RMI annotation exception handling:
Client receive all the errors and runtime exceptions encountered during remote method invocation.
Remote exceptions are handled as follows:
Checked exceptions are thrown directly to a client.
Unchecked exceptions are wrapped in a RuntimeException and then thrown to the client.
Generated EJB 3.0 objects annotate the remoteExceptionWrapper to be EJBException for all EJB methods. Clients then receive all remote exceptions wrapped in EJBException.
You can specify the remoteExceptionWrapper annotation for an entire implementation class or for a particular method which wraps all remote exceptions in the specified runtime exception before throwing it back to the client. If the remoteExceptionWrapper annotation is not specified then the remote exceptions are wrapped as shown in Table 4-3.
Table 4-3 Exception Wrapping in WebLogic Clients
| Client | Exception Wrapping |
|---|---|
|
WL Full Client |
|
|
WL Thin T3 Client |
|
|
WLS-IIOP ClientFoot 3 |
or
|
|
Thin Client |
or
|
|
Java SE Client |
or
|
Footnote 1
weblogic.rmi.extensions.RemoteRuntimeException is a sub-class of RuntimeException
Footnote 2
weblogic.rmi.extensions.RemoteRuntimeException is a sub-class of RuntimeException
Footnote 3
The existing T3 protocol layer doesn't always wraps the RemoteException as java.rmi.ServerException but the IIOP protocol always does it on the Server.
Clustered stubs automatically handle the failover of a remote call to another node in the cluster based on the type of exception received. Wrapping remote exceptions, such as RuntimeException, in the stub does not change the failover behavior for a remote object.
Passing a callback object with an annotated remote object requires the callback remote object to extend java.rmi.Remote interface.
Note:
Some client types can not support callback objects because they do not have access to WebLogic classes. For example, the Java SE client.