9.3. The Naming InitialContext Factories

The JBoss JNDI provider currently supports several different InitialContext factory implementations.

9.3.1. The standard naming context factory

The most commonly used factory is the org.jnp.interfaces.NamingContextFactory implementation. Its properties include:
  • java.naming.factory.initial: The name of the environment property for specifying the initial context factory to use. The value of the property should be the fully qualified class name of the factory class that will create an initial context. If it is not specified, a javax.naming.NoInitialContextException will be thrown when an InitialContext object is created.
  • java.naming.provider.url: The name of the environment property for specifying the location of the JBoss JNDI service provider the client will use. The NamingContextFactory class uses this information to know which JBossNS server to connect to. The value of the property should be a URL string. For JBossNS the URL format is jnp://host:port/[jndi_path]. The jnp: portion of the URL is the protocol and refers to the socket/RMI based protocol used by JBoss. The jndi_path portion of the URL is an optional JNDI name relative to the root context, for example, apps or apps/tmp. Everything but the host component is optional. The following examples are equivalent because the default port value is 1099.
    • jnp://www.jboss.org:1099/
    • www.jboss.org:1099
    • www.jboss.org
  • java.naming.factory.url.pkgs: The name of the environment property for specifying the list of package prefixes to use when loading in URL context factories. The value of the property should be a colon-separated list of package prefixes for the class name of the factory class that will create a URL context factory. For the JBoss JNDI provider this must be org.jboss.naming:org.jnp.interfaces. This property is essential for locating the jnp: and java: URL context factories of the JBoss JNDI provider.
  • jnp.socketFactory: The fully qualified class name of the javax.net.SocketFactory implementation to use to create the bootstrap socket. The default value is org.jnp.interfaces.TimedSocketFactory. The TimedSocketFactory is a simple SocketFactory implementation that supports the specification of a connection and read timeout. These two properties are specified by:
  • jnp.timeout: The connection timeout in milliseconds. The default value is 0 which means the connection will block until the VM TCP/IP layer times out.
  • jnp.sotimeout: The connected socket read timeout in milliseconds. The default value is 0 which means reads will block. This is the value passed to the Socket.setSoTimeout on the newly connected socket.
When a client creates an InitialContext with these JBossNS properties available, the org.jnp.interfaces.NamingContextFactory object is used to create the Context instance that will be used in subsequent operations. The NamingContextFactory is the JBossNS implementation of the javax.naming.spi.InitialContextFactory interface. When the NamingContextFactory class is asked to create a Context, it creates an org.jnp.interfaces.NamingContext instance with the InitialContext environment and name of the context in the global JNDI namespace. It is the NamingContext instance that actually performs the task of connecting to the JBossNS server, and implements the Context interface. The Context.PROVIDER_URL information from the environment indicates from which server to obtain a NamingServer RMI reference.
The association of the NamingContext instance to a NamingServer instance is done in a lazy fashion on the first Context operation that is performed. When a Context operation is performed and the NamingContext has no NamingServer associated with it, it looks to see if its environment properties define a Context.PROVIDER_URL. A Context.PROVIDER_URL defines the host and port of the JBossNS server the Context is to use. If there is a provider URL, the NamingContext first checks to see if a Naming instance keyed by the host and port pair has already been created by checking a NamingContext class static map. It simply uses the existing Naming instance if one for the host port pair has already been obtained. If no Naming instance has been created for the given host and port, the NamingContext connects to the host and port using a java.net.Socket, and retrieves a Naming RMI stub from the server by reading a java.rmi.MarshalledObject from the socket and invoking its get method. The newly obtained Naming instance is cached in the NamingContext server map under the host and port pair. If no provider URL was specified in the JNDI environment associated with the context, the NamingContext simply uses the in VM Naming instance set by the Main MBean.
The NamingContext implementation of the Context interface delegates all operations to the Naming instance associated with the NamingContext. The NamingServer class that implements the Naming interface uses a java.util.Hashtable as the Context store. There is one unique NamingServer instance for each distinct JNDI Name for a given JBossNS server. There are zero or more transient NamingContext instances active at any given moment that refers to a NamingServer instance. The purpose of the NamingContext is to act as a Context to the Naming interface adaptor that manages translation of the JNDI names passed to the NamingContext. Because a JNDI name can be relative or a URL, it needs to be converted into an absolute name in the context of the JBossNS server to which it refers. This translation is a key function of the NamingContext.