web.xml

作者: xzz4632 | 来源:发表于2019-07-06 08:23 被阅读0次

1. <web-app>

web-app元素是web应用程序部署描述符的根元素。这个元素的子元素可以是任意顺序的。

2. <display-name>

定义web应用的名称

3. <distributable>

告诉servlet/JSP容器，Web容器中部署的应用程序适合在分布式环境下运行。

4. <context-param>

上下文初始化参数.含有一对参数名和参数值，用作应用的Servlet上下文初始化参数，参数名在整个Web应用中必须是惟一的，在web应用的整个生命周期中上下文初始化参数都存在，任意的Servlet和jsp都可以随时随地访问它。

子元素:

<param-name> : 参数名
<param-value>: 参数值
<description>: 参数说明

spring配置文件
配置Spring，必须需要<listener>，而<context-param>可有可无，如果在web.xml中不写<context-param>配置信息，默认的路径是/WEB-INF/applicationontext.xml，在WEB-INF目录下创建的xml文件的名称必须是applicationContext.xml。如果是要自定义文件名可以在web.xml里加入contextConfigLocation这个context参数; 在<param-value>
</param-value>里指定相应的xml文件名，如果有多个xml文件，可以写在一起并以“,”号分隔:

<context-param>  
    <param-name>contextConfigLocation</param-name>  
    <param-value>/WEB-INF/spring-configuration/*.xml</param-value>  
</context-param>  
<listener>  
     <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  
</listener>

在不同环境下如何获取

在JSP网页中可以使用下列方法来取得：

${initParam.param_name}

在Servlet可以使用下列方法来获得：

String param_name=request.getServletContext().getInitParamter("param_name");

Servlet的ServletConfig对象拥有该Servlet的ServletContext的一个引用，所以可这样取得上下文初始化参数, getServletConfig().getServletContext().getInitParameter(), 也可以在Servlet中直接调用getServletContext().getInitParameter()，两者是等价的。

5. <session-config>

设置容器的session参数.

子元素

<session-timeout>
定义session会话的超时时间, 设置为0或负数则表示永不超时, 单位为分钟.
<cookie-config>
定义session跟踪的cookie配置.
子元素:
- <comment> :说明
- <http-only> : 会话跟踪cookie是否将标记为HttpOnly
- <max-age>: 会话跟踪cookie的生存期(以秒为单位)
- <domain>
- <name>: 会话跟踪cookie的名称。缺省值是JSESSIONID
- <path>cookie的路径
- <secure> 会话跟踪cookie是否将被标记为安全的
<tracking-mode>
定义了session会话的跟踪模式. 有三个选项: COOKIE, URL, SSL

6. <listener>

为web应用程序定义监听器，用来监听各种事件，比如：application和session事件，所有的监听器按照相同的方式定义，功能取决去它们各自实现的接口，常用的Web事件接口有如下几个：

ServletContextListener:
监听Web应用的启动和关闭.
ServletContextAttributeListener:
用于监听ServletContext范围（application）内属性的改变.
ServletRequestListener:
监听用户的请求
ServletRequestAttributeListener:
监听ServletRequest范围（request）内属性的改变；
HttpSessionListener:
监听用户session的开始和结束；
HttpSessionAttributeListener:
监听HttpSession范围（session）内属性的改变。

配置
配置Listener只要向Web应用注册Listener实现类即可，无序配置参数之类的东西，因为Listener获取的是Web应用ServletContext（application）的配置参数。为Web应用配置Listener的两种方式：

使用@WebListener修饰Listener实现类即可。
在web.xml文档中使用<listener>进行配置。

子元素

<listener-class> : Listener的实现类(全限定类名).

7. <filter>

过滤器, 其功能是对用户请求request进行预处理，对Response进行后处理.使用Filter的完整流程是：Filter对用户请求进行预处理，接着将请求HttpServletRequest交给Servlet进行处理并生成响应，最后Filter再对服务器响应HttpServletResponse进行后处理。Filter与Servlet具有完全相同的生命周期，且Filter也可以通过<init-param>来配置初始化参数，获取Filter的初始化参数则使用FilterConfig的getInitParameter()。

配置
Filter必须实现javax.servlet.Filter接口.在该接口中定义了三个方法：

void init(FilterConfig config):
用于完成Filter的初始化。FilteConfig用于访问Filter的配置信息。
void destroy()：
用于Filter销毁前，完成某些资源的回收。
void doFilter(ServletRequest request, ServletResponse response, FilterChain chain):
过滤功能的核心方法，对每个请求及响应增加额外的处理。它们的分界线为是否调用了chain.doFilter(request，response)，执行该方法之前，即对用户请求request进行预处理，执行该方法之后，即对服务器响应response进行后处理。

子元素

<filter-name>
定义过滤器的名称，该名称在整个程序中都必须唯一。
<filter-class>
指定过滤器类的完全限定的名称
<init-param>
为Filter配置参数，与<context-param>具有相同的元素描述符<param-name>和<param-value>

<filter-mapping>
指定Filter所拦截的URL。必须与其对应的<filter>具有相同的<filter-name>.

常用过滤器

字符集过滤器:
org.springframework.web.filter.CharacterEncodingFilter.

8. <servlet>

Servlet是个特殊的java类，继承于javax.servlet.http.HttpServlet.

子元素

<servlet-name>:
定义servlet的名称，该名称在整个应用中必须是惟一的。
<servlet-class>:
指定servlet的完全限定的名称。
<jsp-file>
指定应用中JSP文件的完整路径。这个完整路径必须由/开始。
<load-on-startup>
内容可以为空，或者是一个整数。这个值表示由Web容器载入内存的顺序。如果有两个Servlet元素都含有<load-on-startup>子元素，则<load-on-startup>子元素值较小的Servlet将先被加载。如果是正整数或0, 表示启动容器时，初始化Servlet。如果值是负整数，或者元素不存在，容器可以在它选择的任何时候加载servlet。
<init-param> 初始化参数
<multipart-config> 文件上传参数
- <file-size-threshold>
  将上传文件写入磁盘的大小阈值
- <location>
  文件存储路径
- <max-file-size>
  上传文件的最大大小限制
- <max-request-size>
  请求的multipart/form-data最大大小

<servlet-mapping>
含有<servlet-name>和<url-pattern>, 指定servlet所处理的请求路径.

9. <welcome-file-list>

包含一个子元素<welcome-file>，<welcome-file>用来指定首页文件名称。可以包含一个或多个<welcome-file>子元素。如果在第一个<welcome-file>元素中没有找到指定的文件，Web容器就会尝试显示第二个，以此类推。

9. <env-entry>

定义JNDI环境变量
子元素

<env-entry-name> 变量名
<env-entry-value> 变量值
<env-entry-type> 变量类型

附: web.xml示例

<?xml version="1.0" encoding="UTF-8"?> 
<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 http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" 
    version="2.4"> 

    <!-- ========================================================== --> 
    <!-- General --> 
    <!-- ========================================================== --> 

    <!-- 定义应用名称 --> 
    <display-name>Example App</display-name> 
    <description>一个示例应用程序，适用于处理Tomcat的一些特性</description> 

    <!-- 是否支持分布式 --> 
    <distributable /> 

    <!-- session超时时间 --> 
    <session-config> 
        <session-timeout>120</session-timeout> 
    </session-config> 


    <!-- ========================================================== --> 
    <!-- 自定义标签库 --> 
    <!-- ========================================================== --> 

    <!-- 自JSP 2.0以来不再需要Taglib声明，请参见从web.xml中删除Taglib --> 
    <!-- 注意，每个web.xml只能有一个<jsp-config>元素 --> 

    <!-- ========================================================== --> 
    <!-- JSP 配置 --> 
    <!-- ========================================================== --> 

    <jsp-config> 
        <jsp-property-group> 
            <url-pattern>*.jsp</url-pattern> 
            <include-prelude>/WEB-INF/jspf/prelude1.jspf</include-prelude> 
            <include-coda>/WEB-INF/jspf/coda1.jspf</include-coda> 
        </jsp-property-group> 
    </jsp-config> 


    <!-- ========================================================== --> 
    <!-- Context 参数 --> 
    <!-- ========================================================== --> 

    <context-param> 
        <description>Enable debugging for the application</description> 
        <param-name>debug</param-name> 
        <param-value>true</param-value> 
    </context-param> 
    <context-param> 
        <description>The email address of the administrator, used to send error reports.</description> 
        <param-name>webmaster</param-name> 
        <param-value>address@somedomain.com</param-value> 
    </context-param> 


    <!-- ========================================================== --> 
    <!-- JNDI 环境变量 --> 
    <!-- ========================================================== --> 

    <env-entry> 
        <env-entry-name>webmasterName</env-entry-name> 
        <env-entry-value>Ms. W. Master</env-entry-value> 
        <env-entry-type>java.lang.String</env-entry-type> 
    </env-entry> 
    <env-entry> 
        <env-entry-name>cms/defaultUserSettings/recordsPerPage</env-entry-name> 
        <env-entry-value>30</env-entry-value> 
        <env-entry-type>java.lang.Integer</env-entry-type> 
    </env-entry> 
    <env-entry> 
        <env-entry-name>cms/enableXMLExport</env-entry-name> 
        <env-entry-value>false</env-entry-value> 
        <env-entry-type>java.lang.Boolean</env-entry-type> 
    </env-entry> 
    <env-entry> 
        <env-entry-name>cms/enableEmailNotifications</env-entry-name> 
        <env-entry-value>true</env-entry-value> 
        <env-entry-type>java.lang.Boolean</env-entry-type> 
    </env-entry> 


    <!-- ========================================================== --> 
    <!-- Servlets --> 
    <!-- ========================================================== --> 

    <!-- 简单 Servlet, provide a name, class, description and map to URL /servlet/SimpleServlet --> 
    <servlet> 
        <servlet-name>Simple</servlet-name> 
        <servlet-class>SimpleServlet</servlet-class> 
        <description>This is a simple Hello World servlet</description> 
    </servlet> 
    <servlet-mapping> 
        <servlet-name>Simple</servlet-name> 
        <url-pattern>/servlet/SimpleServlet</url-pattern> 
    </servlet-mapping> 

    <!-- CMS Servlet, responds to *.cms URL's --> 
    <servlet> 
        <!-- Identification --> 
        <servlet-name>cms</servlet-name> 
        <servlet-class>com.metawerx.servlets.ContentManagementSystem</servlet-class> 
        <description>This servlet handles requests for the CMS (it is a controller in an MVC architecture)</description> 

        <!-- This servlet has two parameters --> 
        <init-param> 
            <param-name>debug</param-name> 
            <param-value>true</param-value> 
        </init-param> 
        <init-param> 
            <param-name>detail</param-name> 
            <param-value>2</param-value> 
        </init-param> 

        <!-- 容器启动时加载servlet (调用这个servlet的init()) --> 
        <load-on-startup>5</load-on-startup> 
        <!-- <run-at>0:00, 6:00, 12:00, 18:00</run-at> 这个标签仅在使用Resin服务器时有效 --> 
    </servlet> 

    <!-- 映射一些url到cms Servlet (demonstrates *.extension mapping) -->
    <servlet-mapping> 
        <!-- cms servlet将会处理任何以.cms结尾的url --> 
        <servlet-name>cms</servlet-name> 
        <url-pattern>*.cms</url-pattern> 
    </servlet-mapping> 

    <!-- Rewriter Servlet, responds to /content/* and /admin/RewriterStatistics URL's --> 
    <!-- Define a servlet to respond to /content/* URL's --> 
    <servlet> 
        <servlet-name>rewriter</servlet-name> 
        <servlet-class>com.metawerx.servlets.URLRewriter</servlet-class> 
    </servlet> 

    <!-- Map some URL's to the rewriter servlet (demonstrates /path/* and specific URL mapping) --> 
    <servlet-mapping> 
        <!-- For any URL starting with /content/, the rewriter servlet will be called --> 
        <servlet-name>rewriter</servlet-name> 
        <url-pattern>/content/*</url-pattern> 
    </servlet-mapping> 
    <servlet-mapping> 
        <!-- The rewriter servlet can also be called directly as /admin/RewriterStatistics, to return stats --> 
        <servlet-name>rewriter</servlet-name> 
        <url-pattern>/admin/RewriterStatistics</url-pattern> 
    </servlet-mapping> 

    <!-- PathJSP Servlet, maps /shop/item/* URL's to a JSP file --> 
    <!-- Define a JSP file to respond to /shop/item/* URL's --> 
    <servlet> 
        <servlet-name>pathjsp</servlet-name> 
        <jsp-file>pathfinder.jsp</jsp-file> 
    </servlet> 

    <!-- Map some URL's to the pathjsp servlet (demonstrates /long/path/* URL mapping) --> 
    <servlet-mapping> 
        <!-- For any URL starting with /shop/item/, the pathjsp servlet will be called --> 
        <servlet-name>pathjsp</servlet-name> 
        <url-pattern>/shop/item/*</url-pattern> 
    </servlet-mapping> 


    <!-- ========================================================== --> 
    <!-- 过滤器 --> 
    <!-- ========================================================== --> 

    <!-- Example filter to set character encoding on each request (from Tomcat servlets-examples context) --> 
    <filter> 
        <filter-name>Set Character Encoding</filter-name> 
        <filter-class>filters.SetCharacterEncodingFilter</filter-class> 
        <init-param> 
            <param-name>encoding</param-name> 
            <param-value>EUC_JP</param-value> 
        </init-param> 
    </filter> 
    <filter-mapping> 
        <filter-name>Set Character Encoding</filter-name> 
        <url-pattern>/*</url-pattern> 
    </filter-mapping> 

    <!-- Example filter to dump the HTTP request at the top of each page (from Tomcat servlets-examples context) --> 
    <filter> 
        <filter-name>Request Dumper Filter</filter-name> 
        <filter-class>filters.RequestDumperFilter</filter-class> 
    </filter> 
    <filter-mapping> 
        <filter-name>Request Dumper Filter</filter-name> 
        <url-pattern>/*</url-pattern> 
    </filter-mapping> 


    <!-- ========================================================== --> 
    <!-- 监听器 --> 
    <!-- ========================================================== --> 

    <!-- Define example application events listeners --> 
    <listener> 
        <listener-class>com.metawerx.listener.ContextListener</listener-class> 
    </listener> 
    <listener> 
        <listener-class>com.metawerx.listener.SessionListener</listener-class> 
    </listener> 


    <!-- ========================================================== --> 
    <!-- Security --> 
    <!-- ========================================================== --> 

    <!-- 定义角色 --> 
    <security-role> 
        <role-name>admin</role-name> 
    </security-role> 
    <security-role> 
        <role-name>cms_editors</role-name> 
    </security-role> 
     
    <!-- Define a constraint to restrict access to /private/* --> 
    <security-constraint> 

        <display-name>Security constraint for the /private folder</display-name> 

        <web-resource-collection> 
                 
            <web-resource-name>Protected Area</web-resource-name> 
            <url-pattern>/private/*</url-pattern> 
             
            <!-- If you list http methods, only those methods are protected. --> 
            <!-- Leave this commented out to protect all access --> 
            <!-- 
            <http-method>DELETE</http-method> 
            <http-method>GET</http-method> 
            <http-method>POST</http-method> 
            <http-method>PUT</http-method> 
            --> 

        </web-resource-collection> 

        <auth-constraint> 
            <!-- Only only administrator and CMS editors to access this area --> 
            <role-name>admin</role-name> 
            <role-name>cms_editors</role-name> 
        </auth-constraint> 

    </security-constraint> 

    <!-- FORM based authentication --> 
    <!-- Leave this commented out, we will use BASIC (HTTP) authentication instead --> 
    <!-- 
    <login-config> 
        <auth-method>FORM</auth-method> 
        <form-login-config> 
            <form-login-page>/login.jsp</form-login-page> 
            <form-error-page>/error.jsp</form-error-page> 
        </form-login-config> 
    </login-config> 
    --> 
    <!-- This application uses BASIC authentication --> 
    <login-config> 
        <auth-method>BASIC</auth-method> 
        <realm-name>Editor Login</realm-name> 
    </login-config> 

    <!-- Define a constraint to force SSL on all pages in the application --> 
    <security-constraint> 

        <web-resource-collection> 
            <web-resource-name>Entire Application</web-resource-name> 
            <url-pattern>/*</url-pattern> 
        </web-resource-collection> 

        <user-data-constraint> 
            <transport-guarantee>CONFIDENTIAL</transport-guarantee> 
        </user-data-constraint> 

    </security-constraint> 


    <!-- ========================================================== --> 
    <!-- 错误页面 --> 
    <!-- ========================================================== --> 

    <!-- Define an error handler for 404 pages --> 
    <error-page> 
        <error-code>404</error-code> 
        <location>/error404.jsp</location> 
    </error-page> 

    <!-- Define an error handler for java.lang.Throwable --> 
    <error-page> 
        <exception-type>java.lang.Throwable</exception-type> 
        <location>/errorThrowable.jsp</location> 
    </error-page> 


    <!-- ========================================================== --> 
    <!-- Extra MIME types --> 
    <!-- ========================================================== --> 

    <!-- Set XML mime-mapping so spreadsheets open properly instead of being sent as an octet/stream --> 
    <mime-mapping> 
        <extension>xls</extension> 
        <mime-type>application/vnd.ms-excel</mime-type> 
    </mime-mapping> 


    <!-- ========================================================== --> 
    <!-- Locale --> 
    <!-- ========================================================== --> 

    <!-- Set Locale Encoding --> 
    <locale-encoding-mapping-list> 
        <locale-encoding-mapping> 
            <locale>ja</locale> 
            <encoding>Shift_JIS</encoding> 
        </locale-encoding-mapping> 
    </locale-encoding-mapping-list> 


    <!-- ========================================================== --> 
    <!-- Welcome Files --> 
    <!-- ========================================================== --> 

    <!-- Define, in order of preference, which file to show when no filename is defined in the path --> 
    <!-- eg: when user goes to http://yoursite.com/ or http://yoursite.com/somefolder --> 
    <!-- Defaults are provided in the server-wide web.xml file, such as index.jsp, index.htm --> 
    <!-- Note: using this tag overrides the defaults, so don't forget to add them here --> 
    <welcome-file-list> 
        <!-- Use index.swf if present, or splash.jsp, otherwise just look for the normal defaults --> 
        <welcome-file>index.swf</welcome-file> 
        <welcome-file>splash.jsp</welcome-file> 
        <welcome-file>index.html</welcome-file> 
        <welcome-file>index.htm</welcome-file> 
        <welcome-file>index.jsp</welcome-file> 
    </welcome-file-list> 

</web-app>

web.xml

1. <web-app>

2. <display-name>

3. <distributable>

4. <context-param>

5. <session-config>

6. <listener>

7. <filter>

8. <servlet>

9. <welcome-file-list>

9. <env-entry>

附: web.xml示例

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