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I have one database JNDI connection pooling setup context.xml JNDI resources and web.xml env-ref and initial context. It is working good. But I need to build two more database for my application.

So do I have to configure two more JNDI resources and env-ref and initial context separately? Or same env-ref for three databases?

What is the efficient way to build connection pooling for more than one database? Please advise.

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You are pretty much right about having to configure JNDI resources separately. The only thing that in web.xml there is NO <env-ref> element, but <resource-env-ref> and <resource-ref> elements.

In order to use more databases, you have to make the following additional configurations for each resource:

  1. add a new <Resource> in context.xml file
  2. add a new <resource-ref> or <resource-env-ref> in web.xml file

NOTE:
If you use @Resource annotation, the new resource no longer needs to be defined in the deployment descriptor (web.xml). This annotation is equivalent to declaring a resource-ref, message-destination-ref or env-ref, or resource-env-ref element in the deployment descriptor.

And accordingly you have to separately lookup each DataSource from the InitialContext (you can look up the required DataSource once and then just use the same instance).

Example

The below is an example of configuring two MySQL databases from one of my projects. One database is configured utilizing The Tomcat JDBC Connection Pool, another without connection pooling (you can do it however you like/need).

context.xml (located in /META-INF directory):

<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <!-- Configuration for primary DB -->
    <Resource   name="jdbc/TestShopDB"
                type="javax.sql.DataSource"
                auth="Container"
                factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
                driverClassName="com.mysql.jdbc.Driver"
                url="jdbc:mysql://localhost:3306/test_shop"
                username="root"
                password="mysql"
                maxActive="100"
                minIdle="10"
                initialSize="10"
                validatonQuery="SELECT 1"
                validationInterval="30000"
                removeAbandoned="true"
                removeAbandonedTimeout="60"
                abandonWhenPercentageFull="50"
                closeMethod="close"/>

    <!-- Configuration for administration DB -->            
    <Resource   name="jdbc/TestShopAdminDB"
                type="javax.sql.DataSource"
                auth="Container"
                driverClassName="com.mysql.jdbc.Driver"
                url="jdbc:mysql://localhost:3306/test_shop_admin"
                username="root"
                password="mysql"/>      
</Context>


web.xml (located in /WEB-INF directory; unrelated parts are omitted for the sake of brevity):

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://java.sun.com/xml/ns/javaee"
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                            http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
        version="3.0">

    ...

    <!-- Configuration for primary DB -->
    <resource-ref>
        <res-ref-name>jdbc/TestShopDB</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>

    <!-- Configuration for administration DB -->
    <resource-ref>
        <res-ref-name>jdbc/TestShopAdminDB</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>

    ...

</web-app>

Additional reading

于 2013-11-22T00:21:44.473 回答