在多使用者型別下如何對JBOSS的資料庫jaas認證進行配置？

    <application-policy name = "CNInfoStatReport">
       <authentication>
          <login-module code = "org.jboss.security.auth.spi.DatabaseServerLoginModule"
             flag = "required">
             <module-option name = "dsJndiName">java:jdbc/Postgres</module-option>
             <module-option name = "principalsQuery">
              select password from app_user where username=?
              </module-option>
             <module-option name = "rolesQuery">
              select role_name, 'Roles' from user_role where username=?
              </module-option>
            </login-module>
       </authentication>
    </application-policy>
<p class="indent">

<module-option name = "principalsQuery"></module-option>裡怎麼寫？
<p class="indent">