如何让EL关系运算符在Tomcat 8 / JSTL 1.2上运行[重复]

时间：2021-06-03 22:33:26

This question already has an answer here:

这个问题在这里已有答案:

I'm having a strange behavior since our upgrade from Tomcat 6 to Tomcat 8.0.32.

自从我们从Tomcat 6升级到Tomcat 8.0.32以来,我有一种奇怪的行为。

Relational operators (<, >, <=, >=) are not working with variables defined with c:set

关系运算符(<,>,<=,> =)不适用于使用c:set定义的变量

public class ServiceConstants {
  public static final Integer MY_CONST = 15;
}

Below is my code (updated):

以下是我的代码(更新):

<%@ page isELIgnored="false"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:set var="a" value="<%=ServiceConstants.MY_CONST%>"/>
<c:set var="b" value="${127}" />
<html>
<body>
<br/>a: ${a}
<br/>b: ${b}
<br/>Using variables {b > a}: ${b > a}
<br/>Using variables {b gt a}: ${b gt a}
<br/>Hardcoded values {127 > 15}: ${127 > 15}
</body>
</html>

And below is what is rendered

以下是渲染的内容

a: 15 
b: 127 
Using variables {b > a}: false 
Using variables {b gt a}: false 
Hardcoded values {127 > 15}: true

When comparing a and b set by c:set it is returning the wrong answer.

当比较由c:set设置的a和b时,它返回错误的答案。

Below is my web.xml file

下面是我的web.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                  http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
  version="3.0" metadata-complete="true">

  <absolute-ordering />

  <distributable/>

  <display-name>App name</display-name>

  <jsp-config>
    <taglib>
      <taglib-uri>http://xyzo.org/app</taglib-uri>
      <taglib-location>/WEB-INF/tld/app.tld</taglib-location>
    </taglib>
  </jsp-config>
</web-app>

I tried several solutions posted, changing to Tomcat 8.0.37 (latest), change my web.xml file header and such.

我尝试了几个解决方案,更改为Tomcat 8.0.37(最新),更改我的web.xml文件头等。

Any help is much appreciated.

任何帮助深表感谢。

EDIT BELOW:

I've found out that the numbers are being interpreted as strings by EL. If I force cohersion it works but seems cumbersome.

我发现这些数字被EL解释为字符串。如果我强迫凝聚它有效,但似乎很麻烦。

<%@ page isELIgnored="false"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:set var="a" value="<%=ServiceConstants.MY_CONST%>"/>
<c:set var="b" value="${127}" />
<html>
<body>
<br/>a: ${a}
<br/>b: ${b}
<br/>Using variables {b > a}: ${b > a}
<br/>Using variables {b gt a}: ${b gt a}
<br/>Hardcoded values {127 > 15}: ${127 > 15}
<br/>...
<br/>Forcing cohersion
<br/>Using variables {b > (0 + a)}: ${b > (0 + a)}
</body>
</html>

It results:

a: 15 
b: 127 
Using variables {b > a}: false 
Using variables {b gt a}: false 
Hardcoded values {127 > 15}: true 
...
Forcing cohersion 
Using variables {b > (0 + a)}: true

Any tips on how to make EL to do the 'right thing' still would be appreciated.

任何有关如何让EL做“正确的事情”的提示仍然会受到赞赏。

1 个解决方案

#1

1  

If you use expressions when setting the variables it's less cumbersome:

如果在设置变量时使用表达式,则不那么麻烦:

<c:set var="a" value="${15}"/>
<c:set var="b" value="${127}" />

#1

1  

If you use expressions when setting the variables it's less cumbersome:

如果在设置变量时使用表达式,则不那么麻烦:

<c:set var="a" value="${15}"/>
<c:set var="b" value="${127}" />
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