javax.naming.AuthenticationException: [LDAP: error code 49 - Invalid Credentials] while authenticating via LDAP in spring security3 - authentication

Question

I am trying to authenticating user via LDAP and authorizing via Database.LDAP directory contains user with corresponding group and I want to fetch this group at the time of successful authentication and fetch ROLE with corresponding group from database after authentication.
My spring security config file is below.
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:security="http://www.springframework.org/schema/security"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/security
http://www.springframework.org/schema/security/spring-security-3.1.xsd">
<bean id="authenticationEntryPoint"
class="org.springframework.security.web.authentication.LoginUrlAuthenticationEntryPoint">
<property name="loginFormUrl" value="/login.htm" />
</bean>
<bean class="org.springframework.security.web.access.expression.DefaultWebSecurityExpressionHandler" />
<security:http security="none" pattern="/login.htm"/>
<security:http security="none" pattern="/js/**"/>
<security:http security="none" pattern="/images/**"/>
<security:http security="none" pattern="/css/**"/>
<security:http security="none" pattern="/ckeditor/**"/>
<security:http security="none" pattern="/dhtmlgrid/**"/>
<security:http security="none" pattern="/xmleditor/**"/>
<security:http auto-config="false" entry-point-ref="authenticationEntryPoint" disable-url-rewriting="true" use-expressions="true">
<security:session-management>
<security:concurrency-control error-if-maximum-exceeded="true" max-sessions="1"/>
</security:session-management>
<security:custom-filter position="FORM_LOGIN_FILTER"
ref="cdlAuthenticationProcessingFilter" />
<security:intercept-url pattern="/displayAdminPage.htm" access="hasRole('admin')" />
<security:intercept-url pattern="/**" access="isFullyAuthenticated()" />
<security:access-denied-handler ref="accessDeniedHandler" />
<security:logout logout-success-url="/login.htm" logout-url="/logout"/>
</security:http>
<security:authentication-manager alias="authenticationManager">
<security:authentication-provider ref="customLdapAuthenticationProvider"/>
<security:authentication-provider user-service-ref="cdlUserDetailService">
</security:authentication-provider>
</security:authentication-manager>
<bean id="customLdapAuthenticationProvider" class="com.qait.cdl.authentication.customfilter.CustomLdapAuthenticationProvider">
<constructor-arg ref="ldapBindAuthenticator"/>
<constructor-arg ref="ldapAuthoritiesPopulator"/>
</bean>
<bean id="ldapBindAuthenticator"
class="org.springframework.security.ldap.authentication.BindAuthenticator">
<constructor-arg ref="ldapContextSource" />
<property name="userDnPatterns"><list><value>uid={0},cn=users</value></list></property>
</bean>
<bean id="ldapAuthoritiesPopulator" class="com.qait.cdl.authentication.customfilter.CdlUserAuthoritiesPopulator">
</bean>
<bean id="ldapContextSource"
class="org.springframework.security.ldap.DefaultSpringSecurityContextSource">
<constructor-arg value="ldap://172.16.1.121:389/dc=nodomain"/>
<property name="userDn" value="cn=users,dc=nodomain"/>
<property name="password" value="ldap_admin"/>
</bean>
<bean id="cdlUserDetailService" class="com.qait.cdl.authentication.service.impl.UserDetailsServiceImpl">
<property name="userDao" ref="userDao"/>
</bean>
<bean id="cdlAuthenticationProcessingFilter"
class="com.qait.cdl.authentication.customfilter.CustomAuthenticationProcessingFilter">
<property name="authenticationManager" ref="authenticationManager" />
<property name="userDao" ref="userDao"/>
</bean>
<bean id="accessDeniedHandler"
class="org.springframework.security.web.access.AccessDeniedHandlerImpl">
<property name="errorPage" value="/WEB-INF/jsp/access-denied/content.jsp"/>
</bean>
</beans>
while debugging whole application I got null value of DirContext in AbstractContextSource that is called by BindAuthenticator.
My LDAP directory structure is below:
dn: uid=user1,cn=users,dc=nodomain
uid: user1
userPassword:user1
I've been struggling with this error from past 2 days.Any help will be appreciated.If you want any extra info, than tell me.May be, my LDAP directory structure is wrong.where I am wrong, I don't know?