最近在做一个自建网站平台(
http://www.yowob.com )，其他涉及到为用户提供一个二级域名功能，实现方法如下：
(1)首先要在域名服务商端做一个泛域名解析. 我用的是godaddy.com,就新建一个A记录(host=*,point to指向我的服务器的ip),这样所有二级域名都会转到我的服务器来了
(2)接着在web.xml配一个自已写的域名过滤器,
<filter>
<filter-name>URLFilter</filter-name>
<filter-class>com.yowob.commons.URLFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>URLFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
过滤器的代码如下。这里先将二级域名和全球域名和用户ID的映射,保存在一个数据表里, 然后访问进来时对地址做一个判断, 再取出对应的用户ID. 再转一下就行了. 我的静态文件都在static目录，所以还加了一个static的判断。
比如:
http://time.you.com/board/21 用time对应用户ID为6,则访问效果有
http://www.you.com/6/board/21相同, 不过地址栏还是显示
http://time.you.com/board/21。
再比如：htttp://www.userdomain.com/board/21，这个是用户ID为6的全球域名，访问效果也和上面一样。
package com.yowob.commons;
import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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 org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.math.NumberUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import com.yowob.Constants;
import com.yowob.dao.SiteDAO;
import com.yowob.dto.SiteDTO;
public class URLFilter implements Filter {
private static final Log log = LogFactory.getLog(URLFilter.class);
private static final String DOMAIN_END = "." + Constants.DOMAIN; //.you.com
private static final Map<String, Long> NAME_MAP = new HashMap<String, Long>();
private static final Map<String, Long> DOMAIN_MAP = new HashMap<String, Long>();
@Override
public void init(FilterConfig filterConfig) throws ServletException {
log.info("------------------------------init");
SiteDAO siteDAO = new SiteDAO();
List<SiteDTO> list = siteDAO.getAll();
for (SiteDTO siteDTO : list) {
String name = siteDTO.getName();
if (StringUtils.isNotEmpty(name)) {
NAME_MAP.put(name, siteDTO.getId());
}
String domain = siteDTO.getDomain();
if (StringUtils.isNotEmpty(domain)) {
DOMAIN_MAP.put(domain, siteDTO.getId());
}
}
}
public static void updateName(String oldValue, String newValue, Long siteId) {
if (StringUtils.equals(oldValue, newValue)) {
return;
}
if (StringUtils.isNotEmpty(oldValue)) {
NAME_MAP.remove(oldValue);
}
if (StringUtils.isNotEmpty(newValue)) {
NAME_MAP.put(newValue, siteId);
}
}
public static void updateDomain(String oldValue, String newValue, Long siteId) {
if (StringUtils.equals(oldValue, newValue)) {
return;
}
if (StringUtils.isNotEmpty(oldValue)) {
DOMAIN_MAP.remove(oldValue);
}
if (StringUtils.isNotEmpty(newValue)) {
DOMAIN_MAP.put(newValue, siteId);
}
}
@Override
public void destroy() {
log.info("------------------------------destroy");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) servletRequest;
String requestURI = request.getRequestURI();
String serverName = request.getServerName().toLowerCase();
String realURI = getRealRequestURI(serverName, requestURI);
request.getRequestDispatcher(realURI).forward(request, response);
}
private String getRealRequestURI(String serverName, String requestURI) {
if (Constants.WWW_DOMAIN.equals(serverName) || requestURI.startsWith("/static/") || Constants.DOMAIN.equals(serverName)) {
return requestURI;
}
if (serverName.endsWith(DOMAIN_END)) {
String secondDomain = serverName.substring(0, serverName.indexOf("."));
//网站id
if (NumberUtils.isNumber(secondDomain))
return getURI(secondDomain, requestURI);
//网站英文名
Long siteId = NAME_MAP.get(secondDomain);
if (siteId == null) {
//保留的二级域名
if (Constants.isPrivateSecondDomain(secondDomain)) {
return requestURI;
}
return "/message?msg=不存在二级域名" + secondDomain;
// throw new RuntimeException("do not exist second domain: " + secondDomain);
}
return getURI(siteId + "", requestURI);
}
//域名
Long siteId = DOMAIN_MAP.get(serverName);
if (siteId == null) {
return requestURI;
} else {
return getURI(siteId + "", requestURI);
}
}
private static String getURI(String siteId, String requestURI) {
if (requestURI.equals("/")) {
return "/" + siteId;
} else {
return "/" + siteId + requestURI;
}
}
}
其他一些小技巧：
（１）为了便于本机测试，可以修改windows 的hosts文件。我的如下：
127.0.0.1 localhost
127.0.0.1 you.com
127.0.0.1 www.you.com
127.0.0.1 time1.you.com
127.0.0.1 time2.you.com
127.0.0.1 6.you.com
127.0.0.1 www.bobo.com
（２）web页的各种地址则要注意相对路径的问题。主要考虑
首先设置<base href="http://www.yowob.com/" />，或<base href="http://www.yowob.com/6/" />其中地址最后要加一个/
然后页面中其他地址前面不加/，就是相对地址（以地址栏为基础）。加上/，则是绝对地址。