web.xml 詳解
web.xml元素介紹
每一個(gè)站的WEB-INF下都有一個(gè)web.xml的設(shè)定文件，它提供了我們站臺(tái)的配置設(shè)定.
web.xml定義：
.站臺(tái)的名稱和說明
.針對(duì)環(huán)境參數(shù)(Context)做初始化工作
.Servlet的名稱和映射
.Session的設(shè)定
.Tag library的對(duì)映
.JSP網(wǎng)頁設(shè)定
.Mime Type處理
.錯(cuò)誤處理
.利用JDNI取得站臺(tái)資源
要了解web.xml的設(shè)定值，必須了解它的schema,從web.xml中知道它的schema是由Sum Microsystems公司定制的，如果你想更為詳細(xì)的了解它，
可以到http://java.sun.com/xml/ns/j2ee/web-mapp_2_4.xsd網(wǎng)頁，那里有更為詳細(xì)的介紹。這里我介紹我們平常見得最都的.
<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
<web-app>
這是一般在寫XML時(shí)所做的聲明,定義了XML的版本，編碼格式,還有重要的指明schema的來源,為http://java.sun.com/xml/ns/j2ee
/web-app_2_4.xsd.
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<description>,<display-name>,<icon>
<description>站臺(tái)描述</discription>
對(duì)站臺(tái)做出描述.
<display-name>站臺(tái)名稱</display-name>
定義站臺(tái)的名稱.
<icon>
icon元素包含small-icon和large-icon兩個(gè)子元素.用來指定web站臺(tái)中小圖標(biāo)和大圖標(biāo)的路徑.
<small-icon>/路徑/smallicon.gif</small-icon>
small-icon元素應(yīng)指向web站臺(tái)中某個(gè)小圖標(biāo)的路徑,大小為16 X 16 pixel,但是圖象文件必須為GIF或JPEG格式,擴(kuò)展名必須為:.gif或
.jpg.
<large-icon>/路徑/largeicon-jpg</large-icon>
large-icon元素應(yīng)指向web站臺(tái)中某個(gè)大圖表路徑,大小為32 X 32 pixel,但是圖象文件必須為GIF或JPEG的格式,擴(kuò)展名必須為; gif
或jpg.
范例:
<display-name>Develop Example</display-name>
<description>JSP 2.0 Tech Book's Examples</description>
<icon>
<small-icon>/images/small.gif</small-icon>
<large-icon>/images/large.gir</large-icon>
</icon>
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<distributable>
<distributable>
distributable 元素為空標(biāo)簽,它的存在與否可以指定站臺(tái)是否可分布式處理.如果web.xml中出現(xiàn)這個(gè)元素,則代表站臺(tái)在開發(fā)時(shí)已經(jīng)
被設(shè)計(jì)為能在多個(gè)JSP Container 之間分散執(zhí)行.
范例:
<distributable/>
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<context-param>
<context-param>
context-param 元素用來設(shè)定web站臺(tái)的環(huán)境參數(shù)(context),它包含兩個(gè)子元素:
param-name和param-value.
<param-name>參數(shù)名稱</param-name>
設(shè)定Context名稱
<param-value>值</param-value>
設(shè)定Context名稱的值
</context-param>
范例:
<context-param>
<param-name>param_name</param-name>
<param-value>param_value</param-value>
</context-param>
此所設(shè)定的參數(shù),在JSP網(wǎng)頁中可以使用下列方法來取得:
${initParam.param_name}
若在Servlet可以使用下列方法來獲得:
String param_name=getServletContext().getInitParamter("param_name");
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<filter>
filter元素用來聲明filter的相關(guān)設(shè)定.filter元素除了下面介紹的的子元素之外,還包括<servlet>介紹過的<icon>,<display-name>
,<description>,<init-param>,其用途一樣.
<filter-name>Filter的名稱</filter-name>
定義Filter的名稱.
<filter-class>Filter的類名稱</filter-class>
定義Filter的類名稱.例如:com.foo.hello
</filter>
范例:
<filter>
<filter-name>setCharacterEncoding</filter-name>
<filter-class>coreservlet.javaworld.CH11.SetCharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>GB2312</param-value>
</init-param>
</filter>
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<filter-mapping>
<filter-mapping>
filter-mapping 元素的兩個(gè)主要子元素filter-name和url-pattern.用來定義Filter所對(duì)應(yīng)的URL.
<filter-name>Filter的名稱</filter-name>
定義Filter的名稱.
<url-pattern>URL</url-pattern>
Filter所對(duì)應(yīng)的RUL.例如:<url-pattern>/Filter/Hello</url-pattern>
<servlet-name>Servlet的名稱<servlet-name>
定義servlet的名稱.
<dispatcher>REQUEST|INCLUDE|FORWARD|ERROR</disaptcher>
設(shè)定Filter對(duì)應(yīng)的請(qǐng)求方式,有RQUEST,INCLUDE,FORWAR,ERROR四種,默認(rèn)為REQUEST.
</filter-mapping>
范例:
<filter-mapping>
<filter-name>GZIPEncoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
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<listener>
<listener>
listener元素用來定義Listener接口,它的主要子元素為<listener-class>
<listen-class>Listener的類名稱</listener-class>
定義Listener的類名稱.例如: com.foo.hello
<listener>
范例:
<listener>
<listener-class>coreservlet.javaworld.CH11.ContenxtListener</listener-class>
</listener>
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<servlet-mapping>
servlet-mapping元素包含兩個(gè)子元素servlet-name和url-pattern.用來定義servlet所對(duì)應(yīng)URL.
<servlet-name>Servlet的名稱</servlet-name>
定義Servlet的名稱.
<url-pattern>Servlet URL</url-pattern>
定義Servlet所對(duì)應(yīng)的RUL.例如:<url-pattern>/Servlet/Hello</url-pattern>
</servlet-mapping>
范例:
<servlet-mapping>
<servlet-name>LoginChecker</servlet-name>
<url-pattern>/LoginChecker</url-pattern>
</servlet-mapping>
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<session-cofing>
<session-config>
session-config包含一個(gè)子元素session-timeout.定義web站臺(tái)中的session參數(shù).
<session-timeout>分鐘</session-timeout>
定義這個(gè)web站臺(tái)所有session的有效期限.單位為分鐘.
</session-config>
范例:
<session-config>
<session-timeout>20</session-timeout>
</session-config>
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<mime-mapping>
<mima-mapping>
mime-mapping包含兩個(gè)子元素extension和mime-type.定義某一個(gè)擴(kuò)展名和某一MIME Type做對(duì)映.
<extension>擴(kuò)展名名稱</extension>
擴(kuò)展名稱
<mime-type>MIME格式</mime-type>
MIME格式.
</mime-mapping>
范例:
<mime-mapping>
<extension>doc</extension>
<mime-type>application/vnd.ms-word</mime-type>
</mime-mapping>
<mime-mapping>
<extension>xls</extension>
<mime-type>application/vnd.ms-excel</mime-type>
</mime-mapping>
<mime-mapping>
<extension>ppt</extesnion>
<mime-type>application/vnd.ms-powerpoint</mime-type>
</mime-mapping>
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<welcome-file-list>
<welcome-file-list>
welcome-file-list包含一個(gè)子元素welcome-file.用來定義首頁列單.
<welcome-file>用來指定首頁文件名稱</welcome-flie>
welcome-file用來指定首頁文件名稱.我們可以用<welcome-file>指定幾個(gè)首頁,而服務(wù)器會(huì)依照設(shè)定的順序來找首頁.
范例:
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
<welcome-file>index.htm</welcome-file>
</welcome-file-list>
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<error-page>
<error-page>
error-page元素包含三個(gè)子元素error-code,exception-type和location.將錯(cuò)誤代碼(Error Code)或異常(Exception)的種類對(duì)應(yīng)
到web站臺(tái)資源路徑.
<error-code>錯(cuò)誤代碼</error-code>
HTTP Error code,例如: 404
<exception-type>Exception</exception-type>
一個(gè)完整名稱的Java異常類型
<location>/路徑</location>
在web站臺(tái)內(nèi)的相關(guān)資源路徑
</error-page>
范例:
<error-page>
<error-code>404</error-code>
<location>/error404.jsp</location>
</error-page>
<error-page>
<exception-type>java.lang.Exception</exception-type>
<location>/except.jsp</location>
</error-page>
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<jsp-config>
<jsp-config>
jsp-config元素主要用來設(shè)定JSP的相關(guān)配置,<jsp:config>包括<taglib>和<jsp-property-group>兩個(gè)子元素.其中<taglib>元素
在JSP 1.2時(shí)就已經(jīng)存在了;而<jsp-property-group>是JSP 2.0新增的元素.
<taglib>
taglib元素包含兩個(gè)子元素taglib-uri和taglib-location.用來設(shè)定JSP網(wǎng)頁用到的Tag Library路徑.
<taglib-uri>URI</taglib-uri>
taglib-uri定義TLD文件的URI,JSP網(wǎng)頁的taglib指令可以經(jīng)由這個(gè)URI存取到TLD文件.
<taglib-location>/WEB-INF/lib/xxx.tld</taglib-laction>
TLD文件對(duì)應(yīng)Web站臺(tái)的存放位置.
</taglib>
<jsp-property-group>
jsp-property-group元素包含8個(gè)元素,分別為:
<description>Description</descrition>
此設(shè)定的說明
<display-name>Name</display-name>
此設(shè)定的名稱
<url-pattern>URL</url-pattern>
設(shè)定值所影響的范圍,如:/CH2 或者/*.jsp
<el-ignored>true|false</el-ignored>
若為true,表示不支持EL語法.
<scripting-invalid>true|false</scripting-invalid>
若為true表示不支持<%scription%>語法.
<page-encoding>encoding</page-encoding>
設(shè)定JSP網(wǎng)頁的編碼
<include-prelude>.jspf</include-prelude>
設(shè)置JSP網(wǎng)頁的抬頭,擴(kuò)展名為.jspf
<include-coda>.jspf</include-coda>
設(shè)置JSP網(wǎng)頁的結(jié)尾,擴(kuò)展名為.jspf
</jsp-property-group>
</jsp-config>
范例:
<jsp-config>
<taglib>
<taglib-uri>Taglib</taglib-uri>
<taglib-location>/WEB-INF/tlds/MyTaglib.tld</taglib-location>
</taglib>
<jsp-property-group>
<description>
Special property group for JSP Configuration JSP example.
</description>
<display-name>JSPConfiguration</display-name>
<uri-pattern>/*</uri-pattern>
<el-ignored>true</el-ignored>
<page-encoding>GB2312</page-encoding>
<scripting-inivalid>true</scripting-inivalid>
............
</jsp-property-group>
</jsp-config>
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<resource-ref>
<resource-ref>
resource-ref元素包括五個(gè)子元素description,res-ref-name,res-type,res-auth,res-sharing-scope.利用JNDI取得站臺(tái)可
利用資源.
<description>說明</description>
資源說明
<rec-ref-name>資源名稱</rec-ref-name>
資源名稱
<res-type>資源種類</res-type>
資源種類
<res-auth>Application|Container</res-auth>
資源由Application或Container來許可
<res-sharing-scope>Shareable|Unshareable</res-sharing-scope>
資源是否可以共享.默認(rèn)值為 Shareable
范例:
<resource-ref>
<description>JNDI JDBC DataSource of JSPBook</description>
<res-ref-name>jdbc/sample_db</res-ref-name>
<res-type>javax.sql.DataSoruce</res-type>
<res-auth>Container</res-auth>
</resource-ref>