On Tue, 28 Jan 2003, Robin Wierenga wrote:
> Date: Tue, 28 Jan 2003 13:09:54 +0100
> From: Robin Wierenga <[EMAIL PROTECTED]>
> Reply-To: Tomcat Users List <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: Tomcat 4.1.18 Anyone know how to define global JNDI resource
>
> Hi !
>
> I want to define some sort of global JNDI resource in my server.xml
> configuration file. I know setting the crossContext="true" will enable
> sharing but has certain security implications which I'm unaware of.
>
Note that "crossContext" is not relevant for sharing JNDI resources.
> A. Is this possible
Yes.
> B. How to do it ?
(1) Define a resource (such as a database connection pool) in the
<GlobalNamingResources> section of server.xml:
<GlobalNamingResources>
...
<Resource name="MyDatabase" auth="Container"
type="javax.sql.DataSource"
description="Shared database connection pool"/>
<ResourceParams name="MyDatabase">
... <parameter> elements to configure your connection pool ...
</ResourceParams>
...
</GlobalNamingResources>
(2) Define a resource link to each shared resource in the <Context>
element for an application:
<Context path="/myapp" ...>
...
<ResourceLink name="jdbc/Customers" global="MyDatabase"/>
...
</Context>
(3) In your web.xml, declare a resource reference:
<resource-ref>
<description>
Symbolic reference to the customer database. Note that the
web application has no idea whether the actual connection pool
is shared or not.
</description>
<res-ref-name>jdbc/Customers</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
(4) In your application, use the connection pool like this:
InitialContext ic = new InitialContext();
Context env = (Context) ic.lookup("java:comp/env");
DataSource ds = (DataSource) env.lookup("jdbc/Customers");
Connection conn = null;
try {
conn = ds.getConnection();
... use the connection for a while ...
} catch (SQLException e) {
... deal with database error ...
} finally {
conn.close(); // Returns connection to the pool
}
You can repeat steps (2)-(4) for as many different apps as you like. As
long as the "global" attribute is the same, the underlying global resource
will be shared.
If you later decided that a particular app needed its own connection pool
(to improve performance or something), all you would need to do is replace
the <ResourceLink> statement for that app with a
<Resource>/<ResourceParams> pair that defined the resource nested inside
the <Context> element. The application cannot tell the difference.
Further info on JNDI resources is available in the Tomcat docs that are
part of a standard installation, or available online:
http://jakarta.apache.org/tomcat/tomcat-4.1-doc/jndi-resources-howto.html
>
> Thanks,
> Robin
>
Craig
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