Java EE container authentication on Jboss using Spring Security - spring

Question

I'm trying to implement client authentication on Jboss EAP 6.2 with Spring Security in order to protect my REST api (with no login page), but I've stucked.
Trying to send authentication request with ajax:
$.ajax({
type : "POST",
url : '/client-web/j_security_check',
data : {
j_username : user,
j_password : pass
}
}).done(function(data) {
$('div#result').append($('div').text('Login ' + user + ' OK'));
}).fail(function(data) {
console.log(data)
$('div#result').append($('div').text('Login ' + user + ' FAIL'));
});
I received '404 Not Found' as response. I've also tried to access j_spring_security_check but result was the same.
Sending request to one of my /rest/ methods always returned '403 Forbidden', even if I sent username and password fields in ajax request or provided "Authorization" : "Basic *XXXX*" header.
So now I cannot realize what should I do to authenticate my user against my application and how to check the authentication on subsequent requests.
I'm new to Spring Security and security at all as well as Java EE technologies and a spent two whole days trying make it work but with no luck. So that's why I'm here asking you guys for help. I would appreciate any useful advice or the link to appropriate resources.
Here are the contents of my configuration files which I messed with:
root-context.xml:
<http entry-point-ref="preAuthEntryPoint"
authentication-manager-ref="authenticationManager" auto-config="false"
realm="ApplicationRealm">
<intercept-url pattern="/rest/**" access="ROLE_CUSTOMER" />
<!-- <form-login /> -->
<http-basic />
<logout />
<jee mappable-roles="customer" />
</http>
<beans:bean name="preAuthEntryPoint" class="org.springframework.security.web.authentication.Http403ForbiddenEntryPoint">
</beans:bean>
<authentication-manager alias="authenticationManager"
id="authenticationManager">
<sec:authentication-provider
ref="org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationProvider" />
</authentication-manager>
<beans:bean
class="org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationProvider"
id="org.springframework.security.web.authentication.preauth.PreAuthenticatedAuthenticationProvider">
<beans:property name="preAuthenticatedUserDetailsService">
<beans:bean
class="org.springframework.security.web.authentication.preauth.PreAuthenticatedGrantedAuthoritiesUserDetailsService">
</beans:bean>
</beans:property>
</beans:bean>
web.xml:
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/root-context.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<servlet>
<servlet-name>clientServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/clientServlet/servlet-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>clientServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>/resources/home.html</welcome-file>
</welcome-file-list>
<filter>
<filter-name>springSecurityFilterChain</filter-name>
<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
<filter-name>springSecurityFilterChain</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<security-constraint>
<web-resource-collection>
<web-resource-name>All Content</web-resource-name>
<url-pattern>/rest/*</url-pattern>
</web-resource-collection>
<auth-constraint>
<role-name>ROLE_CUSTOMER</role-name>
</auth-constraint>
</security-constraint>
<security-role>
<role-name>ROLE_CUSTOMER</role-name>
</security-role>
jboss-web.xml has only one node: <security-domain>mySecurity</security-domain>
And in the jboss standalone.xml config file there is a <security-domain>:
<security-domain name="mySecurity" cache-type="default">
<authentication>
<login-module code="org.jboss.security.auth.spi.DatabaseServerLoginModule" flag="required">
<module-option name="dsJndiName" value="java:jboss/datasources/myDs"/>
<module-option name="principalsQuery" value="select u.password from users u where u.username=?"/>
<module-option name="rolesQuery" value="select r.name as rolename, 'Roles' as rolegroup from users u inner join users_roles ur on (ur.users_id = u.id) inner join roles r on (ur.roles_id = r.id) where u.username=?"/>
</login-module>
</authentication>
</security-domain>