A bound object can be checked in WebAdmin or the console tool.

This section describes the operation of the JNDI Tree structure.

The JNDI Tree consists of JNSServers and JNSClients. A JNSServer is on the JVM of the MS, and a JNSClient is on the JVM of an MS or a client. As the main element of the JEUS JNDI architecture, the JNS server creates and manages the JNDI Tree. A JNSClient resides below the JNS Server and is managed by the JNSServer.

The following shows the relationship between a JNSServer and JNSClients.

To access the entire JNDI Tree, a JNSClient must send a request to the JNSServer.

A JNSServer is connected to other JNSServers on other MSs to form a cluster. A JNS client interacts with a JNSServer on an MS and handles client access requests. The client does not directly access the JNSServer, but instead binds and looks up objects through a JNSClient.

Each MS is responsible for managing each JNSServer. Each JNSServer starts when JEUS system starts and is connected to JNSServers on other MSs. When each JEUS engine gets an InitialContext object, a JNSClient connects to the JNSServer. When a client looks up a JNDI tree object, the request is sent to the JNSClient and then to the JNSServer on the MS. As a result, the client obtains the requested object.

Each JNSServer of JEUS is connected to other servers and waiting to interact with them. When a new MS joins an existing cluster, its JNSServer sends a notification to other connected JNSServers. Each JNSServer also sends its data to the new JNS server so that the existing bound objects can be looked up on the new JNS server.

Owing to such scalability, a JNS server that is restarted due to an error can continue to operate normally by receiving the JNDI Tree information from the other JNSServers.

Select [Servers] from the left menu of WebAdmin to go to the server list screen.

Select a server from the list to go to the server configuration screen. Select [Naming Server] to go to the JNSServer configuration screen.

The following is the naming server configuration screen.

The configuration of the JNSClient depends on where JNSClient is running.

Set the path for JEUS Client modules, JEUS_CLIENT, in the classpath so that JNDI services can use the classes.

-classpath ${JEUS_CLIENT};

Java clients configure environment properties for the InitialContext before using JEUS JNDI services.

There are two configuration methods.

Using the '-D' option of the JVM is more preferable than creating a hash table.

The following are the properties that must be configured to create the InitialContext of JEUS JNDI.

Objects that are bound to a JNDI Tree can be located by using the lookup() method of the JNDI context. In the following example, 'countermod' is the module name of the object that is going to be looked up, and the 'Count' is the EJB name.

try {
    Context ctx = new InitialContext();
    Count count = (Count)ctx.lookup(“java:global/countermod/Count”);
//    Count count = (Count)ctx.lookup(“java:global/countermod/Count!my.ejb3.tx.Count”);
//    Count count = (Count)ctx.lookup(“Count”);
    // successfully got the object
} catch (NameNotFoundException ex) {
    // no such binding exists
} catch (NamingException e) {
    // an error occurred
}

When there are multiple business interfaces, append '![interface name]' to the name to look up.

Count count = (Count)ctx.lookup(“java:global/countermod/Count!my.ejb3.tx.Count");

When there is an export name, use the export name to look up.

Count count = (Count)ctx.lookup(“Count”);

The following is an example of looking up an EJB 2.x object.

try {
    Context ctx = new InitialContext();
    CountHome countHome = (CountHome)ctx.lookup(“Count”);
    // successfully got the object
} catch (NameNotFoundException ex) {
    // no such binding exists
} catch (NamingException e) {
    // an error occurred
}

In EJB 3.x, a looked-up object can be used immediately as in the following.

count.service();

For EJB 2.x, get the reference of the EJB remote object by using the create() method of the looked-up EJB home object. Execute the create() method to get the home reference of the object and use it to execute a method as in the following.

Count count = countHome.create();
count.service();

When finished with using the context, close the context by executing the close() method as in the following.

try {
    cx.close();
} catch(Exception e) {
    // an error occurred
}

To create a context that is usable in the clustered environment in JEUS, set multiple hosts in the Context.PROVIDER_URL property as in the following.

Hashtable ht = new Hashtable();
ht.put(Context.PROVIDER_URL, "host1:9736,host2:9736");

If the cluster name that is configured in the domain is known, then it can be configured for use as in the following.

Context.PROVIDER_URL에 'jeus://' + <The cluster name> 

However, it is usable only on an MS in the cluster and cannot be used on a standalone client where the cluster information is unknown.

Hashtable ht = new Hashtable();
ht.put(Context.PROVIDER_URL, "jeus://cluster1");

In a context clustered environment, a policy can be configured for selecting an MS to look up.

Jeus.jndi.clusterlink.selection-policy property can be used to configure one of the following three available options.

The following is a configuration example.

Hashtable ht = new Hashtable();
ht.put(Context.PROVIDER_URL, "host1:9736,host2:9736");
ht.put("jeus.jndi.clusterlink.selection-policy", "random");

When an application looks up from a JNDI server on an MS that is not in the cluster, it must create a context by specifying the PROVIDER URL or by using the name that uses the jh (JEUS host) protocol created by JEUS.

The following syntax can be used to look up an object on a remote JEUS JNDI cluster from a clustered environment in JEUS.

jh:<remote JEUS host name>:<remote JEUS base port>/<export name>
("jh" = JEUS host)

The following shows how to implement a lookup. Add the following code to the JNDI context string.

try {
    Context ctx = new InitialContext();
    CountHome countHome = (CountHome)ctx.lookup("jh:dev:9736/Count");
    // successfully got the object
} catch (NameNotFoundException ex) {
    // no such binding exists
} catch (NamingException e) {
    // an error occurred
}