Using the Java Naming and Directory Interface

16 Using the Java Naming and Directory Interface

A naming service maintains a set of bindings, which relate names to objects. The Java EE naming service is based on the Java Naming and Directory Interface (JNDI) API. The JNDI API allows application components and clients to look up distributed resources, services, and EJB components. For general information about the JNDI API, see http://www.oracle.com/technetwork/java/jndi/index.html. You can also see the JNDI tutorial at http://docs.oracle.com/javase/jndi/tutorial/.

The following topics are addressed here:

Accessing the Naming Context
Configuring Resources
Using a Custom jndi.properties File
Mapping References

Note	The Web Profile of the GlassFish Server supports the EJB 3.1 Lite specification, which allows enterprise beans within web applications, among other features. The full GlassFish Server supports the entire EJB 3.1 specification. For details, see JSR 318 (`http://jcp.org/en/jsr/detail?id=318`).

Accessing the Naming Context

The Oracle GlassFish Server provides a naming environment, or context, which is compliant with standard Java EE requirements. A Context object provides the methods for binding names to objects, unbinding names from objects, renaming objects, and listing the bindings. The InitialContext is the handle to the Java EE naming service that application components and clients use for lookups.

The JNDI API 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.

The following topics are addressed here:

Portable Global JNDI Names
GlassFish Server V2 Vendor-Specific Global JNDI Names
Disabling GlassFish Server V2 JNDI Names
Accessing EJB Components Using the CosNaming Naming Context
Accessing EJB Components in a Remote GlassFish Server
Naming Environment for Lifecycle Modules

Note	Each resource within a server instance must have a unique name. However, two resources in different server instances or different domains can have the same name.

Portable Global JNDI Names

If an EJB component is a kind of session bean and it is deployed to any implementation supporting the EJB 3.1specification (for example, GlassFish Server 5.0), it automatically has one or more portable JNDI names defined based on the syntax in the specification. Note that this is true of existing EJB 3.0 and 2.x applications that are deployed to an implementation supporting EJB 3.1. No code changes are required to the bean class itself in order to have the portable global JNDI name automatically assigned when deployed to an EJB 3.1 container.

For more information, see the Java EE 8 Platform Specification, section EE.5.2.2, "Application Component Environment Namespaces" (http://jcp.org/en/jsr/detail?id=366), and the EJB 3.1 Specification, section 4.4, "Global JNDI Access" (http://jcp.org/en/jsr/detail?id=318).

If the disable-nonportable-jndi-names property is set to false (the default), a GlassFish Server V2-specific JNDI name is assigned in addition to a portable global JNDI name. For more information, see GlassFish Server V2 Vendor-Specific Global JNDI Names and Disabling GlassFish Server V2 JNDI Names.

GlassFish Server V2 Vendor-Specific Global JNDI Names

GlassFish Server v2 vendor-specific global JNDI names are assigned according to the following precedence rules:

A global JNDI name assigned in the glassfish-ejb-jar.xml, glassfish-web.xml, or glassfish-application-client.xml deployment descriptor file has the highest precedence. See Mapping References.
A global JNDI name assigned in a mapped-name element in the ejb-jar.xml, web.xml, or application-client.xml deployment descriptor file has the second highest precedence. The following elements have mapped-name subelements: resource-ref, resource-env-ref, ejb-ref, message-destination, message-destination-ref, session, message-driven, and entity.
A global JNDI name assigned in a mappedName attribute of an annotation has the third highest precedence. The following annotations have mappedName attributes: @javax.annotation.Resource, @javax.ejb.EJB, @javax.ejb.Stateless, @javax.ejb.Singleton, @javax.ejb.Stateful, and @javax.ejb.MessageDriven.
In most cases, a default global JNDI name is assigned (and recorded in the server log) if no name is assigned in deployment descriptors or annotations.
- For a session or entity bean, a GlassFish Server V2-specific JNDI name is assigned as follows:
  - For an EJB 2.x dependency or a session or entity bean with a remote interface, the default is the fully qualified name of the home interface.
  - For an EJB 3.0 dependency or a session bean with a remote interface, the default is the fully qualified name of the remote business interface.
  - If both EJB 2.x and EJB 3.0 remote interfaces are specified, or if more than one 3.0 remote interface is specified, there is no GlassFish Server V2-specific default. For an entity bean, a global JNDI name must be assigned.
- For all other component dependencies that must be mapped to global JNDI names, the default is the name of the dependency relative to java:comp/env. For example, in the @Resource(name="jdbc/Foo") DataSource ds; annotation, the global JNDI name is jdbc/Foo.

Disabling GlassFish Server V2 JNDI Names

The EJB 3.1 specification supported by GlassFish Server 5.0 defines portable EJB JNDI names for session beans. Because of this, there is less need to continue to use older vendor-specific JNDI names.

By default, GlassFish Server V2-specific JNDI names are applied automatically by GlassFish Server 5.0 for backward compatibility. However, this can lead to some ease-of-use issues. For example, deploying two different applications containing a remote EJB component that exposes the same remote interface causes a conflict between the default JNDI names.

The default handling of V2-specific JNDI names in GlassFish Server 5.0 can be managed by using the asadmin command:

asadmin> set server.ejb-container.property.disable-nonportable-jndi-names="true"

The disable-nonportable-jndi-names property is a boolean flag that can take the following values:

false: Enables the automatic use of GlassFish Server V2-specific JNDI names in addition to portable global JNDI names. This is the default setting.
true: Disables the automatic use of V2-specific JNDI names. In all cases, only portable global JNDI names are used.

Note that this setting applies to all session beans deployed to the server.

Accessing EJB Components Using the `CosNaming` Naming Context

The preferred way of accessing the naming service, even in code that runs outside of a Java EE container, is to use the no-argument InitialContext constructor. However, if EJB client code explicitly instantiates an InitialContext that points to the CosNaming naming service, it is necessary to set the java.naming.factory.initial property to com.sun.jndi.cosnaming.CNCtxFactory in the client JVM software when accessing EJB components. You can set this property using the asadmin create-jvm-options command, as follows:

asadmin> create-jvm-options -Djava.naming.factory.initial=com.sun.jndi.cosnaming.CNCtxFactory

For details about asadmin create-jvm-options, see the GlassFish Server Open Source Edition Reference Manual.

Or you can set this property in the code, as follows:

Properties properties = null;
      try {
            properties = new Properties();
            properties.put("java.naming.factory.initial",
                  "com.sun.jndi.cosnaming.CNCtxFactory");
            ...
          }
      ...

The java.naming.factory.initial property applies to only one instance. The property is not cluster-aware.

Accessing EJB Components in a Remote GlassFish Server

The recommended approach for looking up an EJB component in a remote GlassFish Server from a client that is a servlet or EJB component is to use the Interoperable Naming Service syntax. Host and port information is prepended to any global JNDI names and is automatically resolved during the lookup. The syntax for an interoperable global name is as follows:

corbaname:iiop:host:port#a/b/name

This makes the programming model for accessing EJB components in another GlassFish Server exactly the same as accessing them in the same server. The deployer can change the way the EJB components are physically distributed without having to change the code.

For Java EE components, the code still performs a java:comp/env lookup on an EJB reference. The only difference is that the deployer maps the ejb-ref element to an interoperable name in a GlassFish Server deployment descriptor file instead of to a simple global JNDI name.

For example, suppose a servlet looks up an EJB reference using java:comp/env/ejb/Foo, and the target EJB component has a global JNDI name of a/b/Foo.

The ejb-ref element in glassfish-web.xml looks like this:

<ejb-ref>
   <ejb-ref-name>ejb/Foo</ejb-ref-name>
   <jndi-name>corbaname:iiop:host:port#a/b/Foo</jndi-name>
</ejb-ref>

The code looks like this:

Context ic = new InitialContext();
Object o = ic.lookup("java:comp/env/ejb/Foo");

For a client that doesn’t run within a Java EE container, the code just uses the interoperable global name instead of the simple global JNDI name. For example:

Context ic = new InitialContext();
Object o = ic.lookup("corbaname:iiop:host:port#a/b/Foo");

Objects stored in the interoperable naming context and component-specific (java:comp/env) naming contexts are transient. On each server startup or application reloading, all relevant objects are re-bound to the namespace.

Naming Environment for Lifecycle Modules

Lifecycle listener modules provide a means of running short or long duration tasks based on Java technology within the GlassFish Server environment, such as instantiation of singletons or RMI servers. These modules are automatically initiated at server startup and are notified at various phases of the server life cycle. For details about lifecycle modules, see Developing Lifecycle Listeners.

The configured properties for a lifecycle module are passed as properties during server initialization (the INIT_EVENT). The initial JNDI naming context is not available until server initialization is complete. A lifecycle module can get the InitialContext for lookups using the method LifecycleEventContext.getInitialContext() during, and only during, the STARTUP_EVENT, READY_EVENT, or SHUTDOWN_EVENT server life cycle events.

Configuring Resources

The GlassFish Server exposes special resources in the naming environment.

External JNDI Resources
Custom Resources
Built-in Factories for Custom Resources
Using Application-Scoped Resources

External JNDI Resources

An external JNDI resource defines custom JNDI contexts and implements the javax.naming.spi.InitialContextFactory interface. There is no specific JNDI parent context for external JNDI resources, except for the standard java:comp/env/.

Create an external JNDI resource in one of these ways:

To create an external JNDI resource using the Administration Console, open the Resources component, open the JNDI component, and select External Resources. For details, click the Help button in the Administration Console.
To create an external JNDI resource, use the asadmin create-jndi-resource command. For details, see the GlassFish Server Open Source Edition Reference Manual.

Custom Resources

A custom resource specifies a custom server-wide resource object factory that implements the javax.naming.spi.ObjectFactory interface. There is no specific JNDI parent context for external JNDI resources, except for the standard java:comp/env/.

Create a custom resource in one of these ways:

To create a custom resource using the Administration Console, open the Resources component, open the JNDI component, and select Custom Resources. For details, click the Help button in the Administration Console.
To create a custom resource, use the asadmin create-custom-resource command. For details, see the GlassFish Server Open Source Edition Reference Manual.

Built-in Factories for Custom Resources

The GlassFish Server provides built-in factories for the following types of custom resources:

JavaBeanFactory
PropertiesFactory
PrimitivesAndStringFactory
URLFactory

Template glassfish-resources.xml files for these built-in factories and a README file are available at as-install`/lib/install/templates/resources/custom/. For more information about the `glassfish-resources.xml file, see the GlassFish Server Open Source Edition Application Deployment Guide.

JavaBeanFactory

To create a custom resource that provides instances of a JavaBean class, follow these steps:

Set the custom resource’s factory class to org.glassfish.resources.custom.factory.JavaBeanFactory.
Create a property in the custom resource for each setter method in the JavaBean class.
For example, if the JavaBean class has a method named setAccount, specify a property named account and give it a value.
Make sure the JavaBean class is accessible to the GlassFish Server.
For example, you can place the JavaBean class in the as-install`/lib` directory.

PropertiesFactory

To create a custom resource that provides properties to applications, set the custom resource’s factory class to org.glassfish.resources.custom.factory.PropertiesFactory, then specify one or both of the following:

Create a property in the custom resource named org.glassfish.resources.custom.factory.PropertiesFactory.fileName and specify as its value the path to a properties file or an XML file.
The path can be absolute or relative to as-install. The file must be accessible to the GlassFish Server.
If an XML file is specified, it must match the document type definition (DTD) specified in the API definition of java.util.Properties (http://docs.oracle.com/javase/8/docs/api/java/util/Properties.html).
Create the desired properties directly as properties of the custom resource.
If both the fileName property and other properties are specified, the resulting property set is the union. If the same property is defined in the file and directly in the custom resource, the value of the latter takes precedence.

PrimitivesAndStringFactory

To create a custom resource that provides Java primitives to applications, follow these steps:

Set the custom resource’s factory class to org.glassfish.resources.custom.factory.PrimitivesAndStringFactory.
Set the custom resource’s resource type to one of the following or its fully qualified wrapper class name equivalent:
- int
- long
- double
- float
- char
- short
- byte
- boolean
- String
Create a property in the custom resource named value and give it the value needed by the application.
For example, If the application requires a double of value 22.1, create a property with the name value and the value 22.1.

URLFactory

To create a custom resource that provides URL instances to applications, follow these steps:

Set the custom resource’s factory class to org.glassfish.resources.custom.factory.URLObjectFactory.
Choose which of the following constructors to use:
- URL(protocol, host, port, file)
- URL(protocol, host, file)
- URL(spec)
Define properties according to the chosen constructor.
For example, for the first constructor, define properties named protocol, host, port, and file. Example values might be http, localhost, 8085, and index.html, respectively.
For the third constructor, define a property named spec and assign it the value of the entire URL.

Using Application-Scoped Resources

You can define an application-scoped JNDI or other resource for an enterprise application, web module, EJB module, connector module, or application client module by supplying a glassfish-resources.xml deployment descriptor file. For details, see "Application-Scoped Resources" in GlassFish Server Open Source Edition Application Deployment Guide.

Using a Custom `jndi.properties` File

To use a custom jndi.properties file, JAR it and place it in the domain-dir`/lib` directory. This adds the custom jndi.properties file to the Common class loader. For more information about class loading, see Class Loaders.

For each property found in more than one jndi.properties file, the Java EE naming service either uses the first value found or concatenates all of the values, whichever makes sense.

Mapping References

The following XML elements in the GlassFish Server deployment descriptors map resource references in application client, EJB, and web application components to JNDI names configured in GlassFish Server:

resource-env-ref - Maps the @Resource or @Resources annotation (or the resource-env-ref element in the corresponding Java EE XML file) to the absolute JNDI name configured in GlassFish Server.
resource-ref - Maps the @Resource or @Resources annotation (or the resource-ref element in the corresponding Java EE XML file) to the absolute JNDI name configured in GlassFish Server.
ejb-ref - Maps the @EJB annotation (or the ejb-ref element in the corresponding Java EE XML file) to the absolute JNDI name configured in GlassFish Server.
JNDI names for EJB components must be unique. For example, appending the application name and the module name to the EJB name is one way to guarantee unique names. In this case, mycompany.pkging.pkgingEJB.MyEJB would be the JNDI name for an EJB in the module pkgingEJB.jar, which is packaged in the pkging.ear application.

These elements are part of the glassfish-web.xml, glassfish-application-client.xml, glassfish-ejb-jar.xml, and glassfish-application.xml deployment descriptor files. For more information about how these elements behave in each of the deployment descriptor files, see "Elements of the GlassFish Server Deployment Descriptors" in GlassFish Server Open Source Edition Application Deployment Guide.

The rest of this section uses an example of a JDBC resource lookup to describe how to reference resource factories. The same principle is applicable to all resources (such as JMS destinations, JavaMail sessions, and so on).

The @Resource annotation in the application code looks like this:

@Resource(name="jdbc/helloDbDs") javax.sql.DataSource ds;

This references a resource with the JNDI name of java:jdbc/helloDbDs. If this is the JNDI name of the JDBC resource configured in the GlassFish Server, the annotation alone is enough to reference the resource.

However, you can use a GlassFish Server specific deployment descriptor to override the annotation. For example, the resource-ref element in the glassfish-web.xml file maps the res-ref-name (the name specified in the annotation) to the JNDI name of another JDBC resource configured in GlassFish Server.

<resource-ref>
   <res-ref-name>jdbc/helloDbDs</res-ref-name>
   <jndi-name>jdbc/helloDbDataSource</jndi-name>
</resource-ref>