spring oauth2 null pointer on concurrent request - spring-security-oauth2

Question

We have a oAuth server setup using spring oauth2 (version 1.0.4).
On trying to retrieve an access token for the client credentials grant type we get a null pointer error when multiple concurrent requests are made.
Including a snippet of the stack trace:
java.lang.NullPointerException
org.springframework.security.oauth2.provider.token.DefaultAuthenticationKeyGenerator.extractKey(DefaultAuthenticationKeyGenerator.java:43)
org.springframework.security.oauth2.provider.token.JdbcTokenStore.getAccessToken(JdbcTokenStore.java:121)
org.springframework.security.oauth2.provider.token.DefaultTokenServices.createAccessToken(DefaultTokenServices.java:75)
com.marketo.identity.data.impl.IdentityDefaultTokenServices.createAccessToken(IdentityDefaultTokenServices.java:45)
org.springframework.security.oauth2.provider.token.AbstractTokenGranter.getAccessToken(AbstractTokenGranter.java:68)
org.springframework.security.oauth2.provider.token.AbstractTokenGranter.grant(AbstractTokenGranter.java:60)
org.springframework.security.oauth2.provider.client.ClientCredentialsTokenGranter.grant(ClientCredentialsTokenGranter.java:41)
org.springframework.security.oauth2.provider.CompositeTokenGranter.grant(CompositeTokenGranter.java:38)
org.springframework.security.oauth2.provider.endpoint.TokenEndpoint.getAccessToken(TokenEndpoint.java:100)
sun.reflect.GeneratedMethodAccessor167.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:601)
The request is something like this :
http://oauth-server-name/oauth/token?client_id={client_id}&client_secret={client_secret}&grant_type=client_credentials
Again this issue does not occur when a single request is made(or a low number of concurrent requests are made).
Some kind of race condition ?

Answer 1

Here's the example I was looking for (in XML):
<tx:advice id="tokenAdvice">
<tx:attributes>
<tx:method name="*" isolation="REPEATABLE_READ" />
</tx:attributes>
</tx:advice>
<aop:config>
<aop:pointcut id="tokenServicesExecutions" expression="execution(* org.springframework.security.oauth2.provider.token.AuthorizationServerTokenServices.*(..))" />
<aop:advisor advice-ref="tokenAdvice" pointcut-ref="tokenServicesExecutions"/>
</aop:config>