/*
 * Copyright 2002-2013 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.security.web.authentication.session;

import java.lang.reflect.Method;

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

import org.springframework.util.ReflectionUtils;

/**
 * Uses {@code HttpServletRequest.changeSessionId()} to protect against session fixation
 * attacks. This is the default implementation for Servlet 3.1+.
 *
 * @author Rob Winch
 * @since 3.2
 */
public final class ChangeSessionIdAuthenticationStrategy
		extends AbstractSessionFixationProtectionStrategy {
	private final Method changeSessionIdMethod;

	public ChangeSessionIdAuthenticationStrategy() {
		Method changeSessionIdMethod = ReflectionUtils
				.findMethod(HttpServletRequest.class, "changeSessionId");
		if (changeSessionIdMethod == null) {
			throw new IllegalStateException(
					"HttpServletRequest.changeSessionId is undefined. Are you using a Servlet 3.1+ environment?");
		}
		this.changeSessionIdMethod = changeSessionIdMethod;
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see org.springframework.security.web.authentication.session.
	 * AbstractSessionFixationProtectionStrategy
	 * #applySessionFixation(javax.servlet.http.HttpServletRequest)
	 */
	@Override
	HttpSession applySessionFixation(HttpServletRequest request) {
		ReflectionUtils.invokeMethod(this.changeSessionIdMethod, request);
		return request.getSession();
	}
}
