利用泛解析和Filter实现动态二级域名

itEye等网站有个很不错的机制，就是每个用户都有一个永久的二级域名 正好所在的项目也想实现这样的功能，研究了一下，发现用过滤器实现最简单，

http://7784.namezhou.com 实际打开的是 http://www.namezhou.com/7784

步骤如下:

1.去DNS供应商开启泛解析，就是加一条cname记录*.namezhou.com 指向www.namezhou.com

2.编写一个Filter，当检测到是二级域名xxx.namezhou.com时，把地址跳转成http://www.namezhou.com/xxx

代码如下:

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 泛域名解析过滤器
 * @author namezhou
 * @since Dec 26, 2015
 */
public class DomainFilter implements Filter{
	private String mainDomain;//主域名裸域地址
	private String expectDomain;//排除域名，分号隔开
	public String getMainDomain() {
		return mainDomain;
	}
	public void setMainDomain(String mainDomain) {
		this.mainDomain = mainDomain;
	}
	public String getExpectDomain() {
		return expectDomain;
	}
	public void setExpectDomain(String expectDomain) {
		this.expectDomain = expectDomain;
	}
	@Override
	public void destroy() {
		
	}
	@Override
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		String url = ((HttpServletRequest)request).getRequestURI();
		String host = request.getServerName();
		boolean redirect = false;
		if(host.equals(mainDomain)){
			//访问的裸域
			chain.doFilter(request, response);
		}else if(expectDomain!=null&&expectDomain.trim().length()>0){
			String[] arr = expectDomain.split(";");
			if(arr!=null&&arr.length>0){
				for (int i = 0; i < arr.length; i++) {
					if(host.equals(arr[i]+"."+mainDomain)){
						//排除的域，直接显示
						redirect = true;
						chain.doFilter(request, response);
					}
				}
			}
		}
		if(!redirect){
			//检查是不是有
			String id = host.replace("."+mainDomain, "");
			((HttpServletResponse)response).sendRedirect("http://www.namezhou.com/"+id);
		}
	}
	@Override
	public void init(FilterConfig arg0) throws ServletException {
		expectDomain = arg0.getInitParameter("expectDomain");
		mainDomain = arg0.getInitParameter("mainDomain");
	}
}

 3.配置该Filter

<!-- 泛域名解析过滤器 start -->
	<filter>
		<filter-name>domainFilter</filter-name>
		<filter-class>com.namezhou.common.filter.DomainFilter</filter-class>
		<init-param>
			<param-name>mainDomain</param-name>
			<param-value>namezhou.com</param-value>
		</init-param>
		<init-param>
			<param-name>expectDomain</param-name>
			<param-value>www;dev</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>domainFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
	<!-- 泛域名解析过滤器 end -->

博客里面还有另外一种基于Apache rewrite模块的实现方法，与那种方法比较起来，过滤器实现方式

优点：简单，逻辑清晰，实现方便，

缺点：访问地址会变，当然也可以弄一个空iframe页面，去嵌入需要显示的页面，但略显山寨