Looking for logging into the Java Portal User site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Java Portal User site. After that you can login as usual with your login credentials.
https://archive.sap.com/thread/3335546
https://community.liferay.com/forums/-/message_boards/message/91247360
https://github.com/gatein/gatein-portal/blob/master/component/web/security/src/main/java/org/exoplatform/web/login/LoginServlet.java
https://github.com/liferay/com-liferay-portal-security-sso/blob/master/portal-security-sso-cas/src/main/java/com/liferay/portal/security/sso/cas/internal/auto/login/CASAutoLogin.java
https://github.com/liferay/liferay-faces-portal/blob/master/demo/jsf-login-portlet/src/main/java/com/liferay/faces/demos/bean/LoginBackingBean.java
https://www.fasihi.net/portal/streamer?fid=228493
https://auth0.com/docs/quickstart/webapp/java/01-login
https://www.ibm.com/support/knowledgecenter/en/SSYJ99_8.5.0/admin-system/adauthflt.html
https://www.jahia.com/
https://www.programcreek.com/java-api-examples/?api=com.liferay.portal.model.User
https://www.youtube.com/watch?v=uOeTa7qQ8PA
https://stormpath.com/blog/java-webapp-instant-user-management
https://stackoverflow.com/questions/16627910/how-to-code-a-very-simple-login-system-with-java