ListItems中的JSP onclick [英] JSP inside ListItems onclick

问题描述

 < div id =菜单中的
 
 > 
< ul> 
< li class =menuClassonclick =<％session.setAttribute（currentPage，firstPage）;％>>第一页< / a>< / li> 
< li class =menuClassonclick =<％session.setAttribute（currentPage，secondPage）;％>>< a href =/ index.jsp>第二页< / a>< / li> 
< / ul> 
  

然而，这会导致第二页一直显示，即使没有点击。这种方法甚至是合法的，还是有另一种方法来更改会话变量并刷新页面内的页面？ 当解决方案JSP页面被调用，按以下顺序发生：

• 服务器检查是否已经编译了.jsp，以及是否它没有改变，因为它是最后编译。
  
• 服务器通过Jasper编译器运行jsp，它将jsp解释为Java代码，任何不是Java的（CSS，HTML，JavaScript，等等）被放置在一个字符串中。


• Java代码被编译并执行。


• 结果放入响应并发送给用户。
  
  
  

  因此，你的语句： session.setAttribute 在HTML会发送给用户，而且 currentPage 总是设置为 secondPage 。

  
  
  

  ---

  
  
  

  如何验证它？

  
  

  1. 在 div 之前添加下面的行，并查看它打印的内容。

      <％@ taglib prefix =curi =http://java.sun.com/jsp/jstl/core％> 
     < c：out value =$ {sessionScope.currentPage}/> 
       

  
  

  2. 在浏览器中单击右键，查看视图源。在 onclick 属性中没有任何内容，因为 setAttribute 被制作为一个单独的命令并在页面发送给您之前执行。

      < li class =menuClassonclick => 
       

  
  

  
  
  

  ---

  
  
  <您可以尝试按如下所示将它作为查询字符串而不是会话属性传递。

   < a href =/ index.jsp？currentPage = firstPage>第一页< / a> 
  < a href =/ index.jsp？currentPage = secondPage>第二页< / a> 
    

  注意：务必避免使用 Scriplet元素并使用 JSP标准标记库

  
  

  I am trying to set session parameter inside a list items onclick call such as:

  <div id="menu"> 
  <ul>
      <li class="menuClass" onclick="<% session.setAttribute( "currentPage", "firstPage"); %>">First page</a></li>
      <li class="menuClass" onclick="<% session.setAttribute( "currentPage", "secondPage"); %>"><a href="/index.jsp">Second page</a></li>
  </ul>
  

  However this results in secondPage being displayed all the time, even without a click. Is this approach even legitimate or is there another way to change session variable and refresh the page within a list item?

  解决方案

  When a JSP page is called, the following happens, in this order:

  • Server checks to see if the .jsp has already been compiled and whether or not it has changed since it was last compiled.
  • Server runs the jsp through the Jasper compiler, which interprets the jsp into Java code, anything that is not Java (CSS, HTML, JavaScript, etc) is placed in a String.
  • The Java code is compiled and executed.
  • The results are placed in the response and sent to the user.

  So, your statement: session.setAttribute is executed before the the HTML is sent to the user, and does exactly and currentPage is always set to secondPage already.

  ---

  How to verify it?

  1. add below line before div and look what it prints.

     <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
     <c:out value="${sessionScope.currentPage }" />
     

  2. Right click in the browser and look at the view source. There is nothing inside onclick attribute because the setAttribute was made into a separate command and executed before the page was sent to you.

     <li class="menuClass" onclick="">
     

  ---

  You can try as shown below to pass it as query string instead of session attribute.

  <a href="/index.jsp?currentPage=firstPage">First Page</a>
  <a href="/index.jsp?currentPage=secondPage">Second Page</a>
  

  Note: Always try to avoid Scriplet elements and use JSP Standard Tag Library

  这篇关于ListItems中的JSP onclick的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！