Tuesday, April 12, 2022

core cannot be resolved

April 12, 2022 jsp, jstl, servlets

Issue

I don't know what I've done incorrectly, but I can't include JSTL. I have jstl-1.2.jar, but unfortunately I get exception:

org.apache.jasper.JasperException: The absolute uri: http://java.sun.com/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application
    at org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:51)
    at org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:409)
    at org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:116)
    at org.apache.jasper.compiler.TagLibraryInfoImpl.generateTLDLocation(TagLibraryInfoImpl.java:315)
    at org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:148)
    at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:429)
    at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:492)
    at org.apache.jasper.compiler.Parser.parseElements(Parser.java:1439)
    at org.apache.jasper.compiler.Parser.parse(Parser.java:137)
    at org.apache.jasper.compiler.ParserController.doParse(ParserController.java:255)
    at org.apache.jasper.compiler.ParserController.parse(ParserController.java:103)
    at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:170)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:332)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:312)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:299)
    at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:586)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
    at java.lang.Thread.run(Thread.java:619)

I have:

pom.xml

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>servlet-api</artifactId>
  <version>2.5</version>
  <scope>provided</scope>
</dependency>
<dependency>
  <groupId>javax.servlet.jsp</groupId>
  <artifactId>jsp-api</artifactId>
  <version>2.1</version>
  <scope>provided</scope>
</dependency>

<dependency>
  <groupId>taglibs</groupId>
  <artifactId>standard</artifactId>
  <version>1.1.2</version>
</dependency>
<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>jstl</artifactId>
  <version>1.2</version>
</dependency>

web.xml

<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_2_5.xsd"
  version="2.5">

index.jsp

<%@ taglib uri="http://java.sun.com/jstl/core" prefix="c" %>
<html> 
<head></head>
<body></body>
</html>

Solution

org.apache.jasper.JasperException: The absolute uri: http://java.sun.com/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application

That URI is for JSTL 1.0, but you're actually using JSTL 1.2 which uses URIs with an additional /jsp path (because JSTL, who invented EL expressions, was since version 1.1 integrated as part of JSP 2.0 (released way back in 2001!) in order to share/reuse the EL logic in plain JSP too).

So, fix the taglib URI accordingly based on JSTL documentation:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

Further you need to make absolutely sure that you do not throw multiple different versioned JSTL JAR files together into the runtime classpath. This is a pretty common mistake among Tomcat users. The problem with Tomcat is that it does not offer JSTL out the box and thus you have to manually install it. This is not necessary in normal Jakarta EE servers. See also What exactly is Java EE?

In your specific case, your pom.xml basically tells you that you have jstl-1.2.jar and standard-1.1.2.jar together. This is wrong. You're basically mixing JSTL 1.2 API+impl from Oracle with JSTL 1.1 impl from Apache. You should stick to only one JSTL implementation and the API version must match the impl version.

Installing JSTL on Tomcat 10+

In case you're already on Tomcat 10 or newer (the first Jakartified version, with jakarta.* package instead of javax.* package), use JSTL 2.0 via this sole dependency:

<dependency>
    <groupId>org.glassfish.web</groupId>
    <artifactId>jakarta.servlet.jsp.jstl</artifactId>
    <version>2.0.0</version>
</dependency>

Non-Maven users can achieve the same by dropping the following two physical files in /WEB-INF/lib folder of the web application project (do absolutely not drop standard*.jar or any loose .tld files in there! remove them if necessary).

jakarta.servlet.jsp.jstl-2.0.0.jar (this is the JSTL 2.0 impl of EE4J)
jakarta.servlet.jsp.jstl-api-2.0.0.jar (this is the JSTL 2.0 API)

Installing JSTL on Tomcat 9-

In case you're not on Tomcat 10 yet, but still on Tomcat 9 or older, use JSTL 1.2 via this sole dependency (this is compatible with Tomcat 9 / 8 / 7 / 6 / 5 but not older):

<dependency>
    <groupId>org.glassfish.web</groupId>
    <artifactId>jakarta.servlet.jsp.jstl</artifactId>
    <version>1.2.6</version>
</dependency>

jakarta.servlet.jsp.jstl-1.2.6.jar (this is the JSTL 1.2 impl of EE4J)
jakarta.servlet.jsp.jstl-api-1.2.7.jar (this is the JSTL 1.2 API)

Installing JSTL on normal JEE server

In case you're actually using a normal Jakarta EE server such as WildFly, Payara, TomEE, GlassFish, WebSphere, OpenLiberty, WebLogic, etc instead of a barebones servletcontainer such as Tomcat, Jetty, Undertow, etc, then you do not need to explicitly install JSTL at all. Normal Jakarta EE servers already provide JSTL out the box. In other words, you don't need to add JSTL to pom.xml nor to drop any JAR/TLD files in webapp. Solely the provided scoped Jakarta EE coordinate is sufficient:

<dependency>
    <groupId>jakarta.platform</groupId>
    <artifactId>jakarta.jakartaee-api</artifactId>
    <version><!-- 9.1.0, 9.0.0, 8.0.0, etc depending on your server --></version>
    <scope>provided</scope>
</dependency>

Make sure web.xml version is right

Further you should also make sure that your web.xml is declared conform at least Servlet 2.4 and thus not as Servlet 2.3 or older. Otherwise EL expressions inside JSTL tags would in turn fail to work. Pick the highest version matching your target container and make sure that you don't have a <!DOCTYPE> anywhere in your web.xml as that would otherwise still trigger Servlet 2.3 modus. Here's a Servlet 5.0 (Tomcat 10) compatible example:

<?xml version="1.0" encoding="UTF-8"?>
<web-app 
    xmlns="https://jakarta.ee/xml/ns/jakartaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
    version="5.0">

    <!-- Config here. -->

</web-app>

And here's a Servlet 4.0 (Tomcat 9) compatible example:

<?xml version="1.0" encoding="UTF-8"?>
<web-app
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
    version="4.0">

    <!-- Config here. -->

</web-app>