Java Naming and Directory Interface (JNDI)

Using JNDI, applications running in distributed environment, helps to look up services independently.

How JNDI is useful?

1.  During deployment sequence, the same JNDI name can be used in different servers.
2.  It helps to provide security of credential leakage to the user groups like developer, testers, stagers etc, because the credentials are configured in the server not in the application.
3.  Connection Pooling can be achieved

How to use JNDI?
In order to use, JNDI classes and service providers should be there
The service provider may be :

1. Lightweight Directory Access Protocol (LDAP)
2. Common Object Request Broker Architecture (CORBA)
3. Common Object Services (COS) name service
4. Java Remote Method Invocation (RMI) RegistryThe objects needs to be created and registered so that , they can be further used for lookup.

How to configure JNDI in tomcat?
In tomcat environment we can configure JNDI in 3 different places
1. Inside the application using context.xml in META-INF directory.
2. Inside the tomcat server context.xml : Inside the apache-tomcat/conf directory we can configure. This can be helpful when multiple application needs the same database.
3. Both in server.xml and context.xml

NB: The database driver jar should be present in the tomcat lib directory

<Resource name="jdbc/lookupName" 
global="jdbc/lookupName" 
auth="Container" 
type="javax.sql.DataSource" 
driverClassName="com.mysql.jdbc.Driver" 
url="jdbc:mysql://localhost:3306/hdi" 
username="hiuser" 
password="hiuser" 

maxActive="100" 
maxIdle="20" 
minIdle="5" 
maxWait="10000"/>

In order to use it in java program we have to use the followng
DataSource ds = (DataSource) ctx.lookup(“java:/comp/env/jdbc/lookupName”);

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