還是轉載一下別人的說法

You have to include/add standard.jar and jstl.jar (or simply addhttp://download.java.net/maven/1/jstl/jars/jstl-1.2.jar - no need to include standard.jar ) to your web-project via:

1. Right mouse click on project name at Project Explorer
2. Build Path + Configure Build Path + Libraries + Add External Jars + Select the downloaded jstl.jar and standard.jar (If you've installed tomcat
    then you will find these .jars at X:\Program Files\Apache Software Foundation\Apache Tomcat 7.0.22\webapps\examples\WEB-INF\lib) folder.

PS: For further information read - http://stackoverflow.com/tags/jstl/info

也就是

1、沒有在WEB-INF目錄下新建tags目錄

2、在確認已經新建了tags目錄的前提下，如果還報錯，就匯入standard.jar和jstl.jar，

maven倉庫連結如下：

standard: http://mvnrepository.com/artifact/taglibs/standard/1.1.2

jstl:    https://mvnrepository.com/artifact/jstl/jstl/1.2

原文：https://blog.csdn.net/yechi9142/article/details/78805202