二级域名的java实现

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