1-web应用和虚似目录的映射
Web应用开发好后，若想供外界访问，需要把web应用所在目录交给web服务器管理，这个过程称之为虚拟目录的映射。
Tomcat 6帮助文档（文档可以在C:\apache-tomcat-6.0.20\webapps\docs目录下的index.html中找到）中所提到的5种配置方式，这里只说第三种和第五种。
For Tomcat 6, unlike Tomcat 4.x, it is NOT recommended to place <Context> elements directly in the server.xml file. This is because it makes modifing the Context configuration more invasive since the main conf/server.xml file cannot be reloaded without restarting
Tomcat.
Context elements may be explicitly defined:
1.In the $CATALINA_BASE/conf/context.xml file: the Context element information will be loaded by all webapps.
2.In the $CATALINA_BASE/conf/[enginename]/[hostname]/context.xml.default file: the Context element information will be loaded by all webapps of that host.
3.In individual files (with a ".xml" extension) in the $CATALINA_BASE/conf/[enginename]/[hostname]/ directory. The name of the file (less the .xml extension) will be used as the context path. Multi-level context paths may be defined using #, e.g. foo#bar.xml for a context path of /foo/bar. The default web application may be defined by using a file called ROOT.xml.
在C:\apache-tomcat-6.0.20\conf\Catalina\localhost目录下建文档a.xml，内容为：<Context docBase="c:\news" /> 这种方法服务器不需要重启
http://localhost:8080/a/1.html
复制a.xml为b.xml http://localhost:8080/b/1.html
同样方式在这个目录下配置一个ROOT.xml文档，这个缺省的访问路径，配置完后要重启服务器，覆盖原来的缺省目录。
4.Only if a context file does not exist for the application in the $CATALINA_BASE/conf/[enginename]/[hostname]/, in an individual file at /META-INF/context.xml inside the application files. If the web application is packaged as a WAR then /META-INF/context.xml will be copied to $CATALINA_BASE/conf/[enginename]/[hostname]/ and renamed to match the application's context path. Once this file exists, it will not be replaced if a new WAR with a newer /META-INF/context.xml is placed in the host's appBase.
5.Inside a Host element in the main conf/server.xml.
在C:\apache-tomcat-6.0.20\conf目录下的server.xml中配置如下：
<Context path="/itcast" docBase="c:\news"/>
但是这种配置不好，需要重启服务器。
一般在实际开发中使用第三种方式。
2.配置虚拟主机
在C:\apache-tomcat-6.0.20\conf目录下的server.xml中配置如下：
<Host name="www.sina.com" appBase="c:\sina">
<Context path="/mail" docBase="c:\sina\mail"/>
</Host>
可以通过http://www.sina.com/mail/1,html来访问，但是我是在主机的主机上做的，所以这样做是不能访问的，浏览器会去找本地的hosts文件，发现没有这样的映射，然后去找DNS服务器进行域名解析。所以我们可以去hosts文件中进行配置。hosts文件位置：C:\Windows\System32\drivers\etc\hosts
3.配置网站主页
WEB-INF目录下的web.xml中输入如下代码：
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<welcome-file-list>
<welcome-file>1.html</welcome-file> 1.html就是主页，同时要在虚拟主机配置时path设置为缺省值""
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>