springMVC 过滤器将二级域名跳转到www域名 无www跳转到www域名过滤器核心代码

	/**
	 * 功能：将http://example.com重定向至http://www.example.com
	 * */
	private static final String DOMAIN = "aaa.com";

	/**
	 * 在DispatcherServlet之前执行
	 * */
	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, 
			Object handler) throws Exception {

		HttpServletRequest httpServletRequest = (HttpServletRequest) request;
		HttpServletResponse httpServletResponse = (HttpServletResponse) response;
		// 获取域名
		String serverName = request.getServerName();
		// 获取请求路径
		String path = httpServletRequest.getRequestURI();
		//queryString 支持多参数 ?a=1&b=2#&c=22## 等
		String queryString = (httpServletRequest.getQueryString() == null ? "" : "?"+httpServletRequest.getQueryString());   // 获取路径中的参数
		int end = serverName.indexOf(DOMAIN);
		if (end!= -1 && end == 0) {  //判断是否是example.com，如果是通过ip地址访问暂时不处理 //end == -1 || end == 0（不是本域名都跳转）
			httpServletResponse.setStatus(301);
			httpServletResponse.setHeader( "Location", "http://www."+DOMAIN+path+queryString);
			httpServletResponse.setHeader( "Connection", "close" );
			return false;
		}


		return true;
	}