每一个站的WEB-INF下都有一个web.xml的设定文件，它提供了我们站台的配置设定.
web.xml定义：
.站台的名称和说明
.针对环境参数(Context)做初始化工作
.Servlet的名称和映射
.Session的设定
.Tag library的对映
.JSP网页设定
.Mime Type处理
.错误处理
.利用JDNI取得站台资源
要了解web.xml的设定值，必须了解它的schema,从web.xml中知道它的schema是由Sum Microsystems公司定制的，如果你想更为详细的了解它，
可以到http://java.sun.com/xml/ns/j2ee/web-mapp_2_4.xsd网页，那里有更为详细的介绍。这里我介绍我们平常见得最多的.
1: <?xml version="1.0" encoding="ISO-8859-1"?>
2:
3: <web-app xmlns="http://java.sun.com/xml/ns/j2ee"
4: xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
5: xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
6: version="2.4">
7: <web-app>
这是一般在写XML时所做的声明,定义了XML的版本，编码格式,还有重要的指明schema的来源,为http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd.
<description>,<display-name>,<icon>
____________________________________________
<description>站台描述</discription>
对站台做出描述.
<display-name>站台名称</display-name>
定义站台的名称.
<icon>
icon元素包含small-icon和large-icon两个子元素.用来指定web站台中小图标和大图标的路径.
<small-icon>/路径/smallicon.gif</small-icon>
small-icon元素应指向web站台中某个小图标的路径,大小为16 X 16 pixel,但是图象文件必须为GIF或JPEG格式,扩展名必须为:.gif或.jpg.
<large-icon>/路径/largeicon-jpg</large-icon>
large-icon元素应指向web站台中某个大图表路径,大小为32 X 32 pixel,但是图象文件必须为GIF或JPEG的格式,扩展名必须为; gif
或jpg.
范例:
1: <display-name>Develop Example</display-name>
2: <description>JSP 2.0 Tech Book's Examples</description>
3: <icon>
4: <small-icon>/images/small.gif</small-icon>
5: <large-icon>/images/large.gir</large-icon>
6: </icon>
7:
8: <distributable>
<distributable>
______________________________________
distributable 元素为空标签,它的存在与否可以指定站台是否可分布式处理.如果web.xml中出现这个元素,则代表站台在开发时已经
被设计为能在多个JSP Container 之间分散执行.
范例:
<context-param>
___________________________________
<context-param>
context-param 元素用来设定web站点的环境参数(context),它包含两个子元素:
param-name和param-value.
<param-name>参数名称</param-name>
设定Context名称
<param-value>值</param-value>
设定Context名称的值
</context-param>
范例:
1: <context-param>
2: <param-name>param_name</param-name>
3: <param-value>param_value</param-value>
4: </context-param>
此所设定的参数,在JSP网页中可以使用下列方法来取得:
1: ${initParam.param_name}
若在Servlet可以使用下列方法来获得:
1: String param_name=getServletContext().getInitParamter("param_name");
又如Spring framework在这里可以设置context参数
1: <!-- spring的配置 -->
2: <context-param>
3: <param-name>contextConfigLocation</param-name>
4: <param-value>classpath:/SpringContext/applicationContext-web.xml
5: </param-value>
6: </context-param>
<filter>
_________________________________
filter元素用来声明filter的相关设定.filter元素除了下面介绍的的子元素之外,还包括<servlet>介绍过的<icon>,<display-name>
,<description>,<init-param>,其用途一样.
<filter-name>Filter的名称</filter-name>
定义Filter的名称.
<filter-class>Filter的类名称</filter-class>
定义Filter的类名称.例如:com.foo.hello
范例:
1: <filter>
2: <filter-name>setCharacterEncoding</filter-name>
3: <filter-class>coreservlet.javaworld.CH11.SetCharacterEncodingFilter</filter-class>
4: <init-param>
5: <param-name>encoding</param-name>
6: <param-value>GB2312</param-value>
7: </init-param>
8: </filter>
9:
10: <filter-mapping>
又如Struts2可以在这里设filter
1: <filter>
2: <filter-name>struts2</filter-name>
3: <filter-class>org.apache.struts2.dispatcher.FilterDispatcher
4: </filter-class>
5: <init-param>
6: <param-name>config</param-name>
7: <param-value>struts-default.xml,struts-plugin.xml,struts/struts.xml</param-value>
8: </init-param>
9: </filter>
10:
11: <filter-mapping>
12: <filter-name>struts2</filter-name>
13: <url-pattern>*.do</url-pattern>
14: </filter-mapping>
<filter-mapping>
______________________________________
filter-mapping 元素的两个主要子元素filter-name和url-pattern.用来定义Filter所对应的URL.
<filter-name>Filter的名称</filter-name>
定义Filter的名称.
<url-pattern>URL</url-pattern>
Filter所对应的RUL.例如:<url-pattern>/Filter/Hello</url-pattern>
<servlet-name>Servlet的名称<servlet-name>
定义servlet的名称.
<dispatcher>REQUEST|INCLUDE|FORWARD|ERROR</disaptcher>
设定Filter对应的请求方式,有RQUEST,INCLUDE,FORWAR,ERROR四种,默认为REQUEST.
</filter-mapping>
范例:
1: <filter-mapping>
2: <filter-name>GZIPEncoding</filter-name>
3: <url-pattern>/*</url-pattern>
4: </filter-mapping>
<servlet>
___________________________________________
<servlet-name>servlet的名称</servlet-name>
<display-name>显示名称</display-name>
<servlet-class>servlet对应的class名</servlet-class>
范例：
1: <servlet>
2: <servlet-name>org.apache.jsp.index_jsp</servlet-name>
3: <servlet-class>org.apache.jsp.index_jsp</servlet-class>
4: </servlet>
<servlet-mapping>
_____________________________________________
servlet-mapping元素包含两个子元素servlet-name和url-pattern.用来定义servlet所对应URL.
<servlet-name>Servlet的名称</servlet-name>
定义Servlet的名称.
<url-pattern>Servlet URL</url-pattern>
定义Servlet所对应的RUL.例如:<url-pattern>/Servlet/Hello</url-pattern>
</servlet-mapping>
范例:
1: <servlet-mapping>
2: <servlet-name>LoginChecker</servlet-name>
3: <url-pattern>/LoginChecker</url-pattern>
4: </servlet-mapping>
<listener>
___________________________________________
<listener>
listener元素用来定义Listener接口,它的主要子元素为<listener-class>
<listen-class>Listener的类名称</listener-class>
定义Listener的类名称.例如: com.foo.hello
<listener>
范例:
1: <listener>
2: <listener-class>coreservlet.javaworld.CH11.ContenxtListener</listener-class>
3: </listener>
又如Spring framework可以在这里设listener
1: <listener>
2: <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
3: </listener>
<session-cofing>
__________________________________
<session-config>
session-config包含一个子元素session-timeout.定义web站台中的session参数.
<session-timeout>分钟</session-timeout>
定义这个web站台所有session的有效期限.单位为分钟.
</session-config>
范例:
1: <session-config>
2: <session-timeout>20</session-timeout>
3: </session-config>
<mime-mapping>
___________________________________________________
<mima-mapping>
mime-mapping包含两个子元素extension和mime-type.定义某一个扩展名和某一MIME Type做对映.
<extension>扩展名名称</extension>
扩展名称
<mime-type>MIME格式</mime-type>
MIME格式.
</mime-mapping>
范例:
1: <mime-mapping>
2: <extension>doc</extension>
3: <mime-type>application/vnd.ms-word</mime-type>
4: </mime-mapping>
5: <mime-mapping>
6: <extension>xls</extension>
7: <mime-type>application/vnd.ms-excel</mime-type>
8: </mime-mapping>
9: <mime-mapping>
10: <extension>ppt</extesnion>
11: <mime-type>application/vnd.ms-powerpoint</mime-type>
12: </mime-mapping>
<welcome-file-list>
_____________________________________________
<welcome-file-list>
welcome-file-list包含一个子元素welcome-file.用来定义首页列单.
<welcome-file>用来指定首页文件名称</welcome-flie>
welcome-file用来指定首页文件名称.我们可以用<welcome-file>指定几个首页,而服务器会依照设定的顺序来找首页.
范例:
1: <welcome-file-list>
2: <welcome-file>index.jsp</welcome-file>
3: <welcome-file>index.htm</welcome-file>
4: </welcome-file-list>
<error-page>
_________________________
<error-page>
error-page元素包含三个子元素error-code,exception-type和location.将错误代码(Error Code)或异常(Exception)的种类对应
到web站台资源路径.
<error-code>错误代码</error-code>
HTTP Error code,例如: 404
<exception-type>Exception</exception-type>
一个完整名称的Java异常类型
<location>/路径</location>
在web站台内的相关资源路径
</error-page>
范例:
1: <error-page>
2: <error-code>404</error-code>
3: <location>/error404.jsp</location>
4: </error-page>
5: <error-page>
6: <exception-type>java.lang.Exception</exception-type>
7: <location>/except.jsp</location>
8: </error-page>
<jsp-config>
_______________________________________________
<jsp-config>
jsp-config元素主要用来设定JSP的相关配置,<jsp:config>包括<taglib>和<jsp-property-group>两个子元素.其中<taglib>元素
在JSP 1.2时就已经存在了;而<jsp-property-group>是JSP 2.0新增的元素.
<taglib>
taglib元素包含两个子元素taglib-uri和taglib-location.用来设定JSP网页用到的Tag Library路径.
<taglib-uri>URI</taglib-uri>
taglib-uri定义TLD文件的URI,JSP网页的taglib指令可以经由这个URI存取到TLD文件.
<taglib-location>/WEB-INF/lib/xxx.tld</taglib-laction>
TLD文件对应Web站台的存放位置.
</taglib>
<jsp-property-group>
jsp-property-group元素包含8个元素,分别为:
<description>Description</descrition>
此设定的说明
<display-name>Name</display-name>
此设定的名称
<url-pattern>URL</url-pattern>
设定值所影响的范围,如:/CH2 或者/*.jsp
<el-ignored>true|false</el-ignored>
若为true,表示不支持EL语法.
<scripting-invalid>true|false</scripting-invalid>
若为true表示不支持<%scription%>语法.
<page-encoding>encoding</page-encoding>
设定JSP网页的编码
<include-prelude>.jspf</include-prelude>
设置JSP网页的抬头,扩展名为.jspf
<include-coda>.jspf</include-coda>
设置JSP网页的结尾,扩展名为.jspf
</jsp-property-group>
</jsp-config>
范例:
1: <jsp-config>
2: <taglib>
3: <taglib-uri>Taglib</taglib-uri>
4: <taglib-location>/WEB-INF/tlds/MyTaglib.tld</taglib-location>
5: </taglib>
6: <jsp-property-group>
7: <description>
8: Special property group for JSP Configuration JSP example.
9: </description>
10: <display-name>JSPConfiguration</display-name>
11: <uri-pattern>/*</uri-pattern>
12: <el-ignored>true</el-ignored>
13: <page-encoding>GB2312</page-encoding>
14: <scripting-inivalid>true</scripting-inivalid>
15: ............
16: </jsp-property-group>
17: </jsp-config>
<resource-ref>
________________________________________________
<resource-ref>
resource-ref元素包括五个子元素description,res-ref-name,res-type,res-auth,res-sharing-scope.利用JNDI取得站点可
利用资源.
<description>说明</description>
资源说明
<rec-ref-name>资源名称</rec-ref-name>
资源名称
<res-type>资源种类</res-type>
资源种类
<res-auth>Application|Container</res-auth>
资源由Application或Container来许可
<res-sharing-scope>Shareable|Unshareable</res-sharing-scope>
资源是否可以共享.默认值为 Shareable
范例:
1: <resource-ref>
2: <description>JNDI JDBC DataSource of JSPBook</description>
3: <res-ref-name>jdbc/sample_db</res-ref-name>
4: <res-type>javax.sql.DataSoruce</res-type>
5: <res-auth>Container</res-auth>
6: </resource-ref>
这些都是些比较常用的,详细可以登录: http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd