You can follow these step

1) In your file standalone.xml  after </extensions>

    you have to add

    <vault>

        <vault-option name="KEYSTORE_URL" value="/home/mino/jboss-eap7/vault.keystore"/>

        <vault-option name="KEYSTORE_PASSWORD" value="MASK-1l/Uou6siko"/>

        <vault-option name="KEYSTORE_ALIAS" value="vault"/>

        <vault-option name="SALT" value="12345678"/>

        <vault-option name="ITERATION_COUNT" value="44"/>

        <vault-option name="ENC_FILE_DIR" value="/home/mino/jboss7/"/>

    </vault>

2) In datasources tag

    you have add

  <datasource jta="true" jndi-name="java:/mydb" pool-name="my_pool" enabled="true" use-java-context="true" use-ccm="true">

                    <connection-url>jdbc:mysql://localhost:3306/mydb</connection-url>

                    <driver>mysql</driver>

                    <security>

                        <user-name>root</user-name>

                        <password>${VAULT::password::password::ODRkMGMwYjMtMjVmYy00YmUyLTk0MjQtNTk0MTdmZDA4ZDY5TElORV9CUkVBS3ZhdWx0}</password>

                    </security>

                    <validation>

                        <check-valid-connection-sql>select 1</check-valid-connection-sql>

                        <exception-sorter class-name="org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter"/>

                    </validation>

                    <statement>

                        <prepared-statement-cache-size>100</prepared-statement-cache-size>

                        <share-prepared-statements>true</share-prepared-statements>

                    </statement>

   </datasource>

If you don't know VAULT follow these step:

1) YOU RUN vault.sh

root@mino-giralatina:/home/mino/jboss7maven/jboss/bin# ./vault.sh

=========================================================================

  JBoss Vault

  JBOSS_HOME: /home/mino/jboss7maven/jboss-eap-6.0

  JAVA: java

  VAULT Classpath: /home/mino/jboss7maven/jboss/modules/org/picketbox/main/*:/home/mino/jboss7maven/jboss/modules/org/jboss/logging/main/*:/home/mino/jboss7maven/jboss/modules/org/jboss/common-core/main/*:/home/mino/jboss7maven/jboss/modules/org/jboss/as/security/main/*

=========================================================================

**********************************

****  JBoss Vault ********

**********************************

Please enter a Digit::   0: Start Interactive Session  1: Remove Interactive Session  2: Exit

// YOU HAVE DIGIT 0

0

Starting an interactive session

//in this path will be saved the encrypted files

Enter directory to store encrypted files (end with either / or \ based on Unix or Windows:/home/enac/jdk1.6.0_14/bin/asdoc7/

//you must have the keystore file

Enter Keystore URL:/home/enac/jdk1.6.0_14/bin/vault.keystore

Enter Keystore password:

Enter Keystore password again:

Values match

Enter 8 character salt:12345678

Enter iteration count as a number (Eg: 44):44

//Save these notes you will need to use tags in vault, See above

Please make note of the following:

********************************************

Masked Password:MASK-1l/Uou6siko

salt:12345678

Iteration Count:44

********************************************

Enter Keystore Alias:vault

8-ott-2012 15.41.10 org.jboss.security.vault.SecurityVaultFactory get

INFO: Getting Security Vault with implementation of org.picketbox.plugins.vault.PicketBoxSecurityVault

Obtained Vault

Initializing Vault

8-ott-2012 15.41.11 org.picketbox.plugins.vault.PicketBoxSecurityVault init

INFO: Default Security Vault Implementation Initialized and Ready

Vault is initialized and ready for use

Handshake with Vault complete

Please enter a Digit::   0: Store a password  1: Check whether password exists  2: Exit

0

Task:  Store a password

//the encrypt attribute (in this case password)

Please enter attribute value:

Please enter attribute value again:

Values match

Enter Vault Block:password

Enter Attribute Name:password

Attribute Value for (password, password) saved

Please make note of the following:

********************************************

Vault Block:password

Attribute Name:password

Shared Key:NWUyNTNhZjMtMzgxOS00YjkwLTk1YmEtMzI1NjE2OTlmODViTElORV9CUkVBS3ZhdWx0

Configuration should be done as follows:

// Now, you can copy this string forn encrypt password database

VAULT::password::password::NWUyNTNhZjMtMzgxOS00YjkwLTk1YmEtMzI1NjE2OTlmODViTElORV9CUkVBS3ZhdWx0

ain't that simple

Utils link for generate keystore file.

You have to follow alone first spep

https://community.jboss.org/wiki/CREATEKEYSTORECONNECTORHTTPS