OpenID4Java library offers support for OpenID-enabling a consumer site or implementing an OpenID Provider server.
'org.openid4java:openid4java-parent:0.9.6'
<dependency>
<groupId>org.openid4java</groupId>
<artifactId>openid4java-parent</artifactId>
<version>0.9.6</version>
</dependency>
<dependency org="org.openid4java" name="openid4java-parent" rev="0.9.6"/>
"org.openid4java", "openid4java-parent", "0.9.6"