web.xml配置文件元素详解

约定不等于承诺〃 2021-09-14 23:24 495阅读 0赞

### web.xml配置文件常用元素及其意义预览 ###

<web-app>
    
          
          <display-name></display-name>
    
          
          <description></description>
    
          
          <context-param></context-param>
    
          
          <filter></filter>
    
          
          <filter-mapping></filter-mapping>
    
          
          <listener></listener>
    
          
          <servlet></servlet>
    
          
          <servlet-mapping></servlet-mapping>
    
          
          <session-config></session-config>
    
          
          <mime-mapping></mime-mapping>
    
          
          <welcome-file-list></welcome-file-list>
    
          
          <error-page></error-page>
    
          
          <taglib></taglib>
    
          
          <resource-env-ref></resource-env-ref>
    
          
          <resource-ref></resource-ref>
    
          
          <security-constraint></security-constraint>
    
          
          <login-config></login-config>
    
          
          <security-role></security-role>
    
          
          <env-entry></env-entry>
    
          
          <ejb-ref></ejb-ref>
    
          
          <ejb-local-ref></ejb-local-ref>
    
      </web-app>

### 各个配置元素详解 ###

**1.Web应用图标：指出IDE和GUI工具用来表示Web应用的大图标和小图标**

<icon>  
          <small-icon>/images/app_small.gif</small-icon>  
          <large-icon>/images/app_large.gif</large-icon>  
     </icon>

**2.Web 应用名称：提供GUI工具可能会用来标记这个特定的Web应用的一个名称**

<display-name>Tomcat Example</display-name>

**3.Web 应用描述：给出于此相关的说明性文本**

<desciption>Tomcat Example servlets and JSP pages.</desciption>

**4.上下文参数：声明应用范围内的初始化参数**

<context-param> <param-name>参数名</para-name> <param-value>参数值</param-value> <description>参数描述</description </context-param>

在servlet里面可以通过 getServletContext().getInitParameter(“context/param”)得到

**5.过滤器配置：将一个名字与一个实现javaxs.servlet.Filter接口的类相关联**

<filter>
        <filter-name>setCharacterEncoding</filter-name>
        <filter-class>com.myTest.setCharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>GB2312</param-value>
        </init-param>
    </filter>
    <filter-mapping>
       <filter-name>setCharacterEncoding</filter-name>
       <url-pattern>/*</url-pattern>
    </filter-mapping>

**注意：**  
• 过滤器位于客户端和web应用程序之间，用于检查和修改两者之间流过的请求和响应。  
• 在请求到达Servlet/JSP之前，过滤器截获请求。  
• 在响应送给客户端之前，过滤器截获响应。  
• 多个过滤器形成一个过滤器链，过滤器链中不同过滤器的先后顺序由部署文件web.xml中过滤器映射<filter-mapping>的顺序决定。  
• 最先截获客户端请求的过滤器将最后截获Servlet/JSP的响应信息。

**6.监听器配置**

<listener>
          <listerner-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener>

**7.Servlet配置**

<servlet>
         <servlet-name>servlet名称</servlet-name>
         <servlet-class>servlet类全路径</servlet-class>
         <init-param>
             <param-name>参数名</param-name>
             <param-value>参数值</param-value>
         </init-param>
         <run-as>
             <description>Security role for anonymous access</description>
            <role-name>tomcat</role-name>
        </run-as>
     　 <load-on-startup>指定当Web应用启动时，装载Servlet的次序</load-on-startup>
     </servlet>
     <servlet-mapping>
       <servlet-name>servlet名称</servlet-name>
       <url-pattern>映射路径</url-pattern>
     </servlet-mapping>

**8.会话超时配置（单位为分钟）**

<session-config>
          <session-timeout>120</session-timeout>
      </session-config>

**9.MIME类型配置**

<mime-mapping>
          <extension>htm</extension>
          <mime-type>text/html</mime-type>
      </mime-mapping>

**10.指定欢迎文件页配置**

<welcome-file-list>
          <welcome-file>index.jsp</welcome-file>
          <welcome-file>index.html</welcome-file>
          <welcome-file>index.htm</welcome-file>
      </welcome-file-list>

**11.配置错误页面**

*  通过错误码来配置error-page

<error-page>
           <error-code>404</error-code>
           <location>/NotFound.jsp</location>
     </error-page>

**- 通过异常的类型配置error-page**

<error-page>
           <exception-type>java.lang.NullException</exception-type>
           <location>/error.jsp</location>
     </error-page>

**12.TLD配置**

<taglib>
          <taglib-uri>http://jakarta.apache.org/tomcat/debug-taglib</taglib-uri>
          <taglib-location>/WEB-INF/jsp/debug-taglib.tld</taglib-location>
     </taglib>

**如果开发工具一直在报错,应该把<taglib> 放到 <jsp-config>中**

<jsp-config>
          <taglib>
              <taglib-uri>http://jakarta.apache.org/tomcat/debug-taglib</taglib-uri>
              <taglib-location>/WEB-INF/pager-taglib.tld</taglib-location>
          </taglib>
      </jsp-config>

**13.资源管理对象配置**

<resource-env-ref>
          <resource-env-ref-name>jms/StockQueue</resource-env-ref-name>
     </resource-env-ref>

**14.资源工厂配置**

<resource-ref>
          <res-ref-name>mail/Session</res-ref-name>
          <res-type>javax.mail.Session</res-type>
          <res-auth>Container</res-auth>
     </resource-ref>

**配置数据库连接池就可在此配置**

<resource-ref>
          <description>JNDI JDBC DataSource of shop</description>
          <res-ref-name>jdbc/sample_db</res-ref-name>
          <res-type>javax.sql.DataSource</res-type>
          <res-auth>Container</res-auth>
      </resource-ref>

**15.安全限制配置**

<security-constraint>
           <display-name>Example Security Constraint</display-name>
           <web-resource-collection>
               <web-resource-name>Protected Area</web-resource-name>
               <url-pattern>/jsp/security/protected/*</url-pattern>
               <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>
              <role-name>tomcat</role-name>
              <role-name>role1</role-name>
          </auth-constraint>
    </security-constraint>

**16.登陆验证配置**

<login-config>
          <auth-method>FORM</auth-method>
          <realm-name>Example-Based Authentiation Area</realm-name>
          <form-login-config>
              <form-login-page>/jsp/security/protected/login.jsp</form-login-page>
              <form-error-page>/jsp/security/protected/error.jsp</form-error-page>
          </form-login-config>
      </login-config>

**17.安全角色：security-role元素给出安全角色的一个列表，这些角色将出现在servlet元素内的security-role-ref元素的role-name子元素中。**  
分别地声明角色可使高级IDE处理安全信息更为容易。

<security-role>
          <role-name>tomcat</role-name>
     </security-role>

**18.Web环境参数：env-entry元素声明Web应用的环境项**

<env-entry>
          <env-entry-name>minExemptions</env-entry-name>
          <env-entry-value>1</env-entry-value>
          <env-entry-type>java.lang.Integer</env-entry-type>
     </env-entry>

**19.EJB 声明**

<ejb-ref>
          <description>Example EJB reference</decription>
          <ejb-ref-name>ejb/Account</ejb-ref-name>
          <ejb-ref-type>Entity</ejb-ref-type>
          <home>com.mycompany.mypackage.AccountHome</home>
          <remote>com.mycompany.mypackage.Account</remote>
     </ejb-ref>

**20.本地EJB声明**

<ejb-local-ref>
          <description>Example Loacal EJB reference</decription>
          <ejb-ref-name>ejb/ProcessOrder</ejb-ref-name>
          <ejb-ref-type>Session</ejb-ref-type>
          <local-home>com.mycompany.mypackage.ProcessOrderHome</local-home>
          <local>com.mycompany.mypackage.ProcessOrder</local>
     </ejb-local-ref>