获取web.xml中参数的几种方法

为了在web容器启动时运行指定的类，我们可以在web.xml中配置一个自定义的servlet，复写init方法即可，如下：web.xml

程序代码

    <servlet>        <servlet-name>tychoLoader</servlet-name>        <servlet-class>org.junesky.tycho.servlet.TychoLoaderServlet</servlet-class>        <load-on-startup>3</load-on-startup></servlet>

TychoLoaderServlet.java

程序代码

public class TychoLoaderServlet extends HttpServlet {    public void init(ServletConfig config) throws ServletException {        //在这里做相应的处理    }    public void destroy() {    }}

在启动时，若要为其配置相应的参数又该如何处理呢？以下介绍几种常用的方法。1、在servlet中获取参数：web.xml

程序代码

    <servlet>        <servlet-name>tychoLoader</servlet-name>        <servlet-class>org.junesky.tycho.servlet.TychoLoaderServlet</servlet-class>        <init-param>            <param-name>filename</param-name>            <param-value>config/constants.properties</param-value>        </init-param>        <load-on-startup>3</load-on-startup></servlet>

TychoLoaderServlet.java

程序代码

public class TychoLoaderServlet extends HttpServlet {    public void init(ServletConfig config) throws ServletException {        super.init(config);        // 利用ServletConfig的getInitParameter来获取参数        String filename = config.getInitParameter("filename");            ……    }    public void destroy() {    }}

2、在jsp中获取参数：web.xml

程序代码

  <context-param>    <param-name>filename</param-name>    <param-value>config/constants.properties</param-value>  </context-param>

jsp

程序代码

String filename = new String(application.getInitParameter("filename"));

3、在struts中获取参数：web.xml

程序代码

    <servlet>        <servlet-name>action</servlet-name>        <servlet-class>org.junesky.tycho.servlet.EncodeActionServlet</servlet-class>        <init-param>            <param-name>config</param-name>            <param-value>/WEB-INF/config/struts-config.xml</param-value>        </init-param>        <init-param>            <param-name>debug</param-name>            <param-value>3</param-value>        </init-param>        <init-param>            <param-name>detail</param-name>            <param-value>3</param-value>        </init-param>        <load-on-startup>2</load-on-startup></servlet>

ContorlSysInfoAction.java

程序代码

public class ContorlSysInfoAction extends TychoAction {    public ActionForward execute(ActionMapping mapping, ActionForm form,            HttpServletRequest request, HttpServletResponse response) {        try {            javax.servlet.ServletConfig config = this.getServlet().getServletConfig();            System.out.println("******" + config.getInitParameter("config"));        } catch (Exception ex) {}        return mapping.findForward("success");    }}

根据使用的框架不同，取得方法都不仅相同。这里仅仅列出几种较常用的方法供大家参考。