●プログラム・リスト●

※LoginCheckFilter.javaのソースコード

package jp.tuyano;

import java.io.IOException;
import java.security.Principal;

import javax.servlet.*;
import javax.servlet.http.*;

import com.google.appengine.api.users.*;

public class LoginCheckFilter implements Filter {
	
	@Override
	public void init(FilterConfig conf) throws ServletException {}

	@Override
	public void doFilter(ServletRequest req,
			ServletResponse resp, FilterChain chain)
			throws IOException, ServletException {
		UserService service = UserServiceFactory.getUserService();
		HttpServletRequest request = (HttpServletRequest)req;
		HttpServletResponse response = (HttpServletResponse)resp;
		HttpSession session = request.getSession();
		if (service.isUserLoggedIn()){
			session.setAttribute("user", service.getCurrentUser());
		} else {
			session.removeAttribute("user");
			String url = request.getRequestURI();
			String loginurl = service.createLoginURL(url);
			response.sendRedirect(loginurl);
		}
        chain.doFilter(request, response);
	}
	
	@Override
	public void destroy() {}

}


※appengine-web.xmlへの追記
<sessions-enabled>true</sessions-enabled>