$JBOSS_HOME/server/default/lib

$JBOSS_HOME/docs/examples/jca

<datasources>
  <local-tx-datasource>
    <jndi-name>PostgresDS</jndi-name>
    <connection-url>jdbc:postgresql://[servername]:[port]/[database name]</connection-url>
    <driver-class>org.postgresql.Driver</driver-class>
    <user-name>x</user-name>
    <password>y</password>
        <!-- sql to call when connection is created.  Can be anything, select 1 is valid for PostgreSQL
        <new-connection-sql>select 1</new-connection-sql>
        -->

        <!-- sql to call on an existing pooled connection when it is obtained from pool.  Can be anything, select 1 is valid for PostgreSQL
        <check-valid-connection-sql>select 1</check-valid-connection-sql>
        -->

      <!-- corresponding type-mapping in the standardjbosscmp-jdbc.xml (optional) -->
      <metadata>
         <type-mapping>PostgreSQL 7.2</type-mapping>
      </metadata>
  </local-tx-datasource>

</datasources>

Follow the following steps:
taking mysql as database

 1. Add my sql connector jar in main folder.
    eg.(modulessystemlayersbasecommysqlmain).
 2. Add module.xml to this folder consist of following config:

<?xml version="1.0" encoding="UTF-8"?>

  <module xmlns="urn:jboss:module:1.0" name="com.mysql">
     <resources>
        <resource-root path="mysql-connector-java-5.1.17-bin.jar"/>
     </resources>

     <dependencies>
        <module name="javax.api"/>
        <module name="javax.transaction.api"/>
        <module name="javax.servlet.api" optional="true"/>
     </dependencies>
  </module>

 3. Now in stanalone.xml file add mysql driver under drivers tag as following:


    <driver name="mysql" module="com.mysql">
            <driver-class>com.mysql.jdbc.Driver</driver-class>
        </driver>

 4. start the jboss server from command prompt
   In cmd go to location of jboss/bin folder and execute standalone.bat

 5. Now in browser open localhost:8080.
    click on administration console under create a datasource click datasource
    then click on add.
    Add following details:
    Name: MysqlDS5
    JNDI Name : java:/mysql
click next
    under detected driver select mysql.
click next
    Connection url : jdbc:mysql://localhost:3306/sampledb
    UserName:****
    Password:****
click done.
    select the MysqlDS and click on enable.
click on test connection it will successfully connected.