JNDI Naming - The J2EE 1.4 Tutorial

JNDI Naming

In a distributed application, components need to access other components and resources such as databases. For example, a servlet might invoke remote methods on an enterprise bean that retrieves information from a database. In the J2EE platform, the Java Naming and Directory Interface (JNDI) naming service enables components to locate other components and resources. To locate a JDBC resource, for example, an enterprise bean invokes the JNDI lookup method. The JNDI naming service maintains a set of bindings that relate names to objects. The lookup method passes a JNDI name parameter and returns the related object.

JNDI provides a naming context, which is a a set of name-to-object bindings. All naming operations are relative to a context. A name that is bound within a context is the JNDI name of the object. In Specifying a Resource Reference, for example, the JNDI name for the JDBC resource (or data source) is jdbc/ejbTutorialDB. A Context object provides the methods for binding names to objects, unbinding names from objects, renaming objects, and listing the bindings. JNDI also provides subcontext functionality. Much like a directory in a file system, a subcontext is a context within a context. This hierarchical structure permits better organization of information. For naming services that support subcontexts, the Context class also provides methods for creating and destroying subcontexts.

For detailed information about JNDI, see The JNDI Tutorial:

http://java.sun.com/products/jndi/tutorial 

Table 31-1 describes JNDI subcontexts for connection factories in the Application Server.

Table 31-1 JNDI Subcontexts for Connection Factories 

Resource Manager Type	Connection Factory Type	JNDI Subcontext
JDBC	javax.sql.DataSource	java:comp/env/jdbc
JMS	javax.jms.TopicConnectionFactory javax.jms.QueueConnectionFactory	java:comp/env/jms
JavaMail	javax.mail.Session	java:comp/env/mail
URL	java.net.URL	java:comp/env/url
Connector	javax.resource.cci.ConnectionFactory	java:comp/env/eis
JAXR Resource Adapter	javax.xml.registry.ConnectionFactory	java:comp/env/eis/JAXR

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Note: To avoid collisions with names of other enterprise resources in the JNDI namespace, and to avoid portability problems, all names in a J2EE application should begin with the string java:comp/env.

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