jsp request.getParameter

Question

编辑，仍然这是不准确的工作，但我需要设置一个网站的每个页面的page_type。该page_type需要通过一些java进行检查，并基于page_type编写代码。问题是，if else语句没有正确执行。没有发生任何事情，因为参数似乎没有被放置。设置page_type的主页：

<div id="DYK_area">
 <jsp:include page="/imgs/random_dyk.jsp" flush="true">
 <jsp:param name="Page_type" value="prenatalOverviewArea"></jsp:param>
 </jsp:include>
</div>

检查代码的位置

<% String pageType = request.getParameter("page_type")==null?"": request.getParameter("page_type"); 
String image_name="";   
    if(pageType.equals("prenatalOverviewArea")){
        int random = (int )(Math.random() * 10 + 1);
        image_name= "/images/did_you_know/dyk_p_" + random + ".png";
    }
    else if(pageType.equals("prenatalNorm")){
        int random = (int )(Math.random() * 25 + 1);
        image_name= "/images/did_you_know/dyk_p_" + random + ".png";
    }
    else if(pageType.equals("overviewArea")){
        int random = (int )(Math.random() * 20 + 1);
        image_name= "/images/did_you_know/dyk_" + random + ".png";
    }
    else if(pageType.equals("overviewNorm")){
        int random = (int )(Math.random() * 45 + 1);
        image_name= "/images/did_you_know/dyk_" + random + ".png";
    }

if(!image_name.equals("")){
%>

<img id="dyk_random" src="<%=image_name%>"/>

<%}%>

Answer 1

您使用type变量从请求参数中获取值，但在if条件下您使用的是Page_type

像这样的包含了

<div id="DYK_area">
   <jsp:include page="/imgs/random_dyk.jsp" flush="true">
     <jsp:param name="Page_type" value="prenatalOverviewArea" />
   </jsp:include>
</div> 

包含的JSP上的

<%
    System.out.println("Page type is : "+request.getParameter("Page_type"));
    String Page_type = request.getParameter("Page_type");
    if(Page_type.equalsIgnoreCase("prenatalOverviewArea")){
        int random = (int )(Math.random() * 10 + 1);
        image_name= "/images/did_you_know/dyk_" + random + ".png";
    }

    else if(Page_type.equalsIgnoreCase("prenatalNorm")){
        int random = (int )(Math.random() * 25 + 1);
        image_name= "/images/did_you_know/dyk_p_" + random + ".png";
    }
%><img id="dyk_random" src="<%=image_name%>"/>

Answer 2

我不确定/imgs/random_dyk.jsp中的代码是否正确。您可以使用变量Page_type，尽管它并不存在。

您应该在前面的request.getParameter("Page_type");行中初始化它，如下所示：

<%! String xxx = request.getParameter("Page_type"); %>

然后，

<% if(xxx.equals("prenatalOverviewArea")){
...

Answer 3

这就是有效的方法，无论如何，谢谢你们，至少你们让我更接近了！

<div id="DYK_area">
 <jsp:include page="/imgs/random_dyk.jsp" flush="true">
 <jsp:param name="page_type" value="prenatalOverviewArea"></jsp:param>
 </jsp:include>
</div>

<%@ page contentType="text/html; charset=UTF-8" language="java"  errorPage="" %>

<% String pageType = request.getParameter("page_type")==null?"": request.getParameter("page_type"); 
String image_name="";   
    if(pageType.equals("prenatalOverviewArea")){
        int random = (int )(Math.random() * 10 + 1);
        image_name= "/images/did_you_know/dyk_p_" + random + ".png";
    }
    else if(pageType.equals("prenatalNorm")){
        int random = (int )(Math.random() * 25 + 1);
        image_name= "/images/did_you_know/dyk_p_" + random + ".png";
    }
    else if(pageType.equals("overviewArea")){
        int random = (int )(Math.random() * 20 + 1);
        image_name= "/images/did_you_know/dyk_" + random + ".png";
    }
    else if(pageType.equals("overviewNorm")){
        int random = (int )(Math.random() * 45 + 1);
        image_name= "/images/did_you_know/dyk_" + random + ".png";
    }

if(!image_name.equals("")){
%>

<img id="dyk_random" src="<%=image_name%>"/>

<%}%>