Question

在web.xml我有

   <context-param>
      <param-name>email</param-name>
      <param-value>test</param-value>
     </context-param>

在jsp中我有

 <c:out value= "MUST PRINT EMAIL">  
    </c:out> 
    <c:out value= "${applicationScope.email}">  
    </c:out>

但这仅打印MUST PRINT EMAIL。电子邮件＆＃39;测试＆＃39;值不打印。为什么？如何获得上下文参数？

Answer 1

我认为您无法直接执行此操作，您可以通过此代码转储应用程序范围内的所有属性

${pageScope}<br> ${requestScope}<br> ${sessionScope} <br> ${applicationScope}

或更详细

<%
    Enumeration attrNames=request.getServletContext().getAttributeNames();
    while(attrNames.hasMoreElements()){
        String ctxAttribute=(String) attrNames.nextElement();
        out.print("<br> Attribute Name --> "+ctxAttribute+", has value Value --> "+request.getServletContext().getAttribute(ctxAttribute));
    }

out.println("<br><br>");

    attrNames=application.getAttributeNames();
    while(attrNames.hasMoreElements()){
        String ctxAttribute=(String) attrNames.nextElement();
        out.println("<BR> Attribute Name --> "+ctxAttribute+", has value Value --> "+application.getAttribute(ctxAttribute));
    }
%>

如果您希望以这种方式获取此参数，则可以在初始化上下文时将此属性放入应用程序范围：

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class MyContextListener implements ServletContextListener {
    private static final Log logger = LogFactory.getLog(MyContextListener.class);


    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        String email= servletContextEvent.getServletContext().getInitParameter("email");
        logger.info("Use email:" + email);
        servletContextEvent.getServletContext().setAttribute("email", email+"==setbylistener");
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

并且不要忘记在web.xml

中进行配置

  <context-param>
      <param-name>email</param-name>
      <param-value>test123</param-value>
  </context-param>

  <listener>
        <listener-class>MyContextListener</listener-class>
  </listener>

希望这有帮助。

如何使用jstl打印context-param？

1 个答案: