Added PreLoginFilter for destroying current session before login

package it.inaf.ia2.vospace.ui;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpSession;

/**

 * Destroys the current session before a new login.

 */

public class PreLoginFilter implements Filter {

    @Override

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain fc) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) req;

        HttpSession session = request.getSession();

        if (session != null && request.getParameter("code") == null) {

            session.invalidate();

        }

        fc.doFilter(req, res);

    }

}

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.boot.web.servlet.FilterRegistrationBean;

import org.springframework.context.annotation.Bean;

import org.springframework.core.Ordered;

@SpringBootApplication

public class VOSpaceUiApplication {

        SpringApplication.run(VOSpaceUiApplication.class, args);

    }

    @Bean

    public FilterRegistrationBean preLoginFilterRegistration() {

        FilterRegistrationBean bean = new FilterRegistrationBean();

        bean.setFilter(new PreLoginFilter());

        bean.addUrlPatterns("/login");

        bean.setOrder(Ordered.HIGHEST_PRECEDENCE);

        return bean;

    }

    @Bean

    public FilterRegistrationBean loginFilterRegistration() {

        FilterRegistrationBean registration = new FilterRegistrationBean();