Spring Security ログイン失敗時にメールアドレスが残ったままにする

http.formLogin()
	.loginProcessingUrl("/login/auth")
	.loginPage(appConfigLoginUrl)
	.failureHandler(authenticationFailureHandler("/login/index?error", "loginEmail")) // ★ココ！
	.defaultSuccessUrl("/top/index", true)
	.usernameParameter("loginEmail")
	.passwordParameter("loginPassword")
	.and();

	public AuthenticationFailureHandler authenticationFailureHandler(
		String failureUrl, String usernameParameterName) {
		
		UsernameKeepingAuthenticationFailureHandler ukafh = new UsernameKeepingAuthenticationFailureHandler(failureUrl);
		ukafh.setUsernameParameterName(usernameParameterName);
		return ukafh;
	}

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.web.DefaultRedirectStrategy;
import org.springframework.security.web.RedirectStrategy;
import org.springframework.security.web.WebAttributes;
import org.springframework.security.web.authentication.AuthenticationFailureHandler;
import org.springframework.security.web.util.UrlUtils;
import org.springframework.util.Assert;

/**
 * UsernameKeepingAuthenticationFailureHandler
 */
public class UsernameKeepingAuthenticationFailureHandler implements
		AuthenticationFailureHandler {
	protected final Log logger = LogFactory.getLog(getClass());

	private String defaultFailureUrl;
	private String usernameParameterName = "username";
	private boolean forwardToDestination = false;
	private boolean allowSessionCreation = true;
	private RedirectStrategy redirectStrategy = new DefaultRedirectStrategy();

	public UsernameKeepingAuthenticationFailureHandler() {
	}

	public UsernameKeepingAuthenticationFailureHandler(String defaultFailureUrl) {
		setDefaultFailureUrl(defaultFailureUrl);
	}

	/**
	 * Performs the redirect or forward to the {@code defaultFailureUrl} if set, otherwise
	 * returns a 401 error code.
	 * <p>
	 * If redirecting or forwarding, {@code saveException} will be called to cache the
	 * exception for use in the target view.
	 */
	public void onAuthenticationFailure(HttpServletRequest request,
			HttpServletResponse response, AuthenticationException exception)
			throws IOException, ServletException {

		if (defaultFailureUrl == null) {
			logger.debug("No failure URL set, sending 401 Unauthorized error");

			response.sendError(HttpServletResponse.SC_UNAUTHORIZED,
					"Authentication Failed: " + exception.getMessage());
		}
		else {
			saveException(request, exception);	

			if (forwardToDestination) {
				logger.debug("Forwarding to " + defaultFailureUrl);

				request.getRequestDispatcher(defaultFailureUrl)
						.forward(request, response);
			}
			else {
				logger.debug("Redirecting to " + defaultFailureUrl);
				
				request.getSession().setAttribute("loginFailureUsername",
						request.getParameter(this.getUsernameParameterName()));
				
				redirectStrategy.sendRedirect(request, response, defaultFailureUrl);
			}
		}
	}

	/**
	 * Caches the {@code AuthenticationException} for use in view rendering.
	 * <p>
	 * If {@code forwardToDestination} is set to true, request scope will be used,
	 * otherwise it will attempt to store the exception in the session. If there is no
	 * session and {@code allowSessionCreation} is {@code true} a session will be created.
	 * Otherwise the exception will not be stored.
	 */
	protected final void saveException(HttpServletRequest request,
			AuthenticationException exception) {
		if (forwardToDestination) {
			request.setAttribute(WebAttributes.AUTHENTICATION_EXCEPTION, exception);
		}
		else {
			HttpSession session = request.getSession(false);

			if (session != null || allowSessionCreation) {
				request.getSession().setAttribute(WebAttributes.AUTHENTICATION_EXCEPTION,
						exception);
			}
		}
	}

	/**
	 * The URL which will be used as the failure destination.
	 *
	 * @param defaultFailureUrl the failure URL, for example "/loginFailed.jsp".
	 */
	public void setDefaultFailureUrl(String defaultFailureUrl) {
		Assert.isTrue(UrlUtils.isValidRedirectUrl(defaultFailureUrl), "'"
				+ defaultFailureUrl + "' is not a valid redirect URL");
		this.defaultFailureUrl = defaultFailureUrl;
	}

	protected boolean isUseForward() {
		return forwardToDestination;
	}

	/**
	 * If set to <tt>true</tt>, performs a forward to the failure destination URL instead
	 * of a redirect. Defaults to <tt>false</tt>.
	 */
	public void setUseForward(boolean forwardToDestination) {
		this.forwardToDestination = forwardToDestination;
	}

	/**
	 * Allows overriding of the behaviour when redirecting to a target URL.
	 */
	public void setRedirectStrategy(RedirectStrategy redirectStrategy) {
		this.redirectStrategy = redirectStrategy;
	}

	protected RedirectStrategy getRedirectStrategy() {
		return redirectStrategy;
	}

	protected boolean isAllowSessionCreation() {
		return allowSessionCreation;
	}

	public void setAllowSessionCreation(boolean allowSessionCreation) {
		this.allowSessionCreation = allowSessionCreation;
	}

	public String getUsernameParameterName() {
		return usernameParameterName;
	}

	public void setUsernameParameterName(String usernameParameterName) {
		this.usernameParameterName = usernameParameterName;
	}
}