公司网站用Apache+Tomcat集群后，经过观察发现Tomcat之间的Session复制非常的消耗资源。一个Tomcat挂掉后,另外一个要复制很久才能复制完成。导致如果session很多,一个Tomcat挂掉,网站访问变得很慢.

现在改成Cookie来取替Tomcat之间的复制，具体实现方式如下:

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登录时将用户信息存入一份在Session中,然后向用户的本机中插入一条cookie信息。由于去掉了Tomcat之间Session的复制所以需要用到Session业务的时候,在一个Tomcat中有session信息，如果在这个过程中被分配到另外一个Tomcat运行后就会出现找不到Session信息的错误。考虑到这一条我写了一个过滤器来对网站的请求进行过滤，先判断session中有没有值。如果有就过，如果没有就到本地来取一次cookie，如果存在即在当前Tomcat上恢复Session.代码如下

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Cookie工具类

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

/**
 * Cookie 工具类增,删,查
 * 
 * @author ws715
 * 
 */
public class CookieUtil {
	/**
	 * 按名字得到Cookie
	 * 
	 * @param request
	 * @param name
	 * @return
	 */

	private CookieUtil() {
	}

	public static Cookie getCookie(HttpServletRequest request, String name) {
		Cookie cookies[] = request.getCookies();
		if (cookies == null || name == null || name.length() == 0) {
			return null;
		}
		if (cookies != null) {
			for (int i = 0; i < cookies.length; i++) {
				if (name.equals(cookies[i].getName())) {
					return cookies[i];
				}
			}
		}
		return null;
	}

	/**
	 * 将cookie中的数据保存到session中
	 * 
	 * @param request
	 * @param name
	 * @return
	 */
	public static boolean setSessionFormCookie(HttpServletRequest request,
			String name) {

		String target = null;
		Cookie cookies[] = request.getCookies();
		boolean bool = false;
		if (cookies == null || name == null || name.length() == 0) {
			bool = false;
		}

		if (cookies != null) {

			for (int i = 0; i < cookies.length; i++) {

				if (name.equals(cookies[i].getName())) {
					target = cookies[i].getValue();
					break;
				}
			}

		}

		if (target != null && !target.equals("")) {

			HttpSession session = request.getSession();
			session.setAttribute("UserName", target.toString());
			bool = true;
		}
		return bool;
	}

	/**
	 * 删除Cookie
	 * 
	 * @param request
	 * @param response
	 * @param cookie
	 */
	public static void deleteCookie(HttpServletRequest request,
			HttpServletResponse response, Cookie cookie) {
		if (cookie != null) {
			cookie.setPath(getPath(request));
			cookie.setValue("");
			// cookie.setDomain("");
			cookie.setMaxAge(0);
			response.addCookie(cookie);
		}
	}

	/**
	 * 按名字删除
	 * 
	 * @param request
	 * @param response
	 * @param name
	 */
	public static void deleteCookie(HttpServletRequest request,
			HttpServletResponse response, String name) {

		Cookie cookies[] = request.getCookies();
		Cookie myCookie = null;
		boolean bool = false;
		if (cookies == null || name == null || name.length() == 0) {
			throw new NullPointerException(
					"getCookie deleteCookie method name is not null");
		}
		if (cookies != null) {
			for (int i = 0; i < cookies.length; i++) {
				if (name.equals(cookies[i].getName())) {
					myCookie = cookies[i];
					break;
				}
			}

			if (myCookie != null) {
				deleteCookie(request, response, myCookie);
			}
		}
	}

	/**
	 * 保存到Cookie中
	 * 
	 * @param request
	 * @param response
	 * @param name
	 * @param value
	 */
	public static void setCookie(HttpServletRequest request,
			HttpServletResponse response, String name, String value) {
		setCookie(request, response, name, value, 0x278d00);
	}

	/**
	 * 可以设置时间
	 * 
	 * @param request
	 * @param response
	 * @param name
	 * @param value
	 * @param maxAge
	 */
	public static void setCookie(HttpServletRequest request,
			HttpServletResponse response, String name, String value, int maxAge) {
		Cookie cookie = new Cookie(name, value == null ? "" : value);
		cookie.setMaxAge(maxAge);
		// cookie.setDomain(request.getServerName());
		cookie.setPath(getPath(request));
		response.addCookie(cookie);
	}

	private static String getPath(HttpServletRequest request) {
		String path = request.getContextPath();
		return (path == null || path.length() == 0) ? "/" : path;
	}

	/**
	 * 从coo