Using JNDI binding for dynamic values from the server configuration files

You can bind a reference for dynamic values into the default Java™ Naming and Directory Interface (JNDI) namespace from the server configuration files by using the jndiReferenceEntry element in Liberty.

About this task

The default JNDI namespace is available in Liberty to provide bindings to miscellaneous objects that are required by applications. Based on the features that are enabled in your server, you can bind a predetermined set of objects to the default JNDI namespace. Additionally, you can bind a reference to an object factory, which dynamically determines the value that it returns. You can also use this object factory to return custom object types to an application.

For more information about the JNDI naming, see Naming.

1. Add the jndi-1.0 Liberty feature to the server.xml file.

   <featureManager>
      <feature>jndi-1.0</feature>
   </featureManager>

2. Create an ObjectFactory class that returns a programmatically defined value.

   import javax.naming.spi.ObjectFactory;
   
   public class MyObjectFactory implements ObjectFactory {
     @Override
     public Object getObjectInstance(Object o, Name n, Context c, Hashtable<?, ?> envmt) throws Exception { 
       Properties p = new Properties();
       p.put("abc", 123);
       return p; 
     }
   }    

3. Include the ObjectFactory in a library element in the server.xml file:

   <library id="objectFactoryLib"> 
      <fileset dir="${server.config.dir}/lib" includes="factory.jar"/>   
   </library>

4. Declare the factory in a jndiObjectFactory element in the server.xml file and reference the previously declared library.

   <jndiObjectFactory id="objectFactory" libraryRef="objectFactoryLib"                      
            className="com.ibm.example.factory.MyObjectFactory"/>

   You can also declare the type of object that the factory returns. The type is returned by the javax.naming.Context.list() method.

   <jndiObjectFactory id="objectFactory" libraryRef="objectFactoryLib"                      
            className="com.ibm.example.factory.MyObjectFactory"                      
            objectClassName="java.util.Properties"/>

5. Declare the entry in a jndiReferenceEntry element in the server.xml file and reference the previously declared factory.

   <jndiReferenceEntry id="refEntry" jndiName="ref/entry" factoryRef="objectFactory"/>

6. To declare more properties for the jndiReferenceEntry element in the server.xml file:

   <jndiReferenceEntry id="refEntry" jndiName="ref/entry" factoryRef="objectFactory"> 
      <properties abc="123"/>   
   </jndiReferenceEntry>

   These additional properties are represented as javax.naming.StringRefAddr on the javax.naming.Reference that is passed to the factory:

   import javax.naming.spi.ObjectFactory; 
   
   public class MyObjectFactory implements ObjectFactory { 
     @Override 
     public Object getObjectInstance(Object o, Name n, Context c, Hashtable<?, ?> envmt) throws Exception {
       Properties p = new Properties();           
       Reference ref = (Reference) o;
       RefAddr refAddr = ref.get("abc"); 
       p.put("abc", refAddr == null ? 123 : refAddr.getContent()); 
       return p; 
     }   
   }

7. You can inject the resulting object to an application by using a resource environment reference:

   @Resource(name="ref/entry")
   private Properties properties;