1.What is JNDI

JNDI is Java Naming and Directory Interface. When developer needs to operate the DB in application, he/she doesn’t need to write DB url, user name, password etc in code with the help of JNDI. All developer needs to do is use name to map to DB.

2.How to do

2.1.Code

Context ctx = null; Connection con = null; try { ctx = new InitialContext(); DataSource ds = (DataSource) ctx.lookup("java:/comp/env/jdbc/testJNDI"); con = ds.getConnection();

For connecting to DB, name “java:/comp/env/jdbc” is fixed, data source name is developer/deployer defined, e.g. testJNDI in this example.

Table 13-1  Standard JNDI Subcontexts for Connection Factories

Resource Manager	Connection Factory Type	JNDI Subcontext
JDBC™	javax.sql.DataSource	java:comp/env/jdbc
Transaction Service	javax.transaction.UserTransaction	java:comp/UserTransaction
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

2.2.Configuration

The configuration can be placed in 3 places :

2.2.1.application META-INF/context.xml

<?xml version='1.0' encoding='utf-8'?> <Context> <Resource name="jdbc/testJNDI" auth="Container" type="javax.sql.DataSource" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/test" username="root" maxActive="10" maxIdle="3" minIdle="1" maxWait="100" /> </Context>

The resource name is part of java:/comp/env/jdbc/testJNDI which described in 2.1.

2.2.2.server(e.g. Tomcat) conf/context.xml

The configuration is the same as 2.2.1.

2.2.3.server(Tomcat) conf/server.xml and context.xml

In this case, context.xml looks like :

<ResourceLink name="jdbc/testJNDI" global="jdbc/MyDB" auth="Container" type="javax.sql.DataSource"/>

and server.xml is :

<Resource name="jdbc/MyDB" global="jdbc/MyDB" auth="Container" type="javax.sql.DataSource" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/test" username="root" maxActive="10" maxIdle="3" minIdle="1" maxWait="100" />

Note that the global value of context.xml is the value of resource name of server.xml.