JNDI - Java Naming and Directory Interface
JNDI enables a Java program or JSP page to reference resources specified in or outside the application.
JNDI names are specified as a URI. They point to anything from simple strings to complex data structures such as a JDBC data source.
For example, here is a JSP <sql:query> tag that uses JNDI to access a data source. The data source object has a JNDI address of java:comp/env/jdbc/mydatabase. In JSP, this can be refered to simply as jdbc/mydatabase.
<sql:query var="result" dataSource="jdbc/mydatabase">
SELECT product_id, name, price FROM products
</sql:query>
The following example references the same information using Java, which uses the full JNDI URI.
DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/mydatabase");
For both of the examples given above, the actual JDBC data source information is defined in META-INF/context.xml as a JNDI Resource.
JNDI Resources can be defined in:
- server.xml in the <Context> tag
- context.xml in the <Context> tag, as Resources (prefered)
- web.xml as environment variables using the <env-entry> tag, although this is only useful for simple values
An example context.xml is displayed below, containing a single JNDI Resource, of the type javax.sql.DataSource.
<?xml version="1.0" encoding="UTF-8"?>
<Context>
<Resource name="jdbc/mydatabase"
auth="Container"
type="javax.sql.DataSource"
username="YOUR_USERNAME"
password="YOUR_PASSWORD"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://mysql.metawerx.net:3306/YOUR_DATABASE_NAME?autoReconnect=true"
validationQuery="select 1"
maxActive="10"
maxIdle="4"/>
</Context>
