December 2003
Intermediate to advanced
764 pages
24h 58m
English
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Expression Language Syntax Errors
Prior to JSP 2.0, how well EL syntax errors were reported varied between JSTL implementations and web containers, because the EL wasn’t part of the JSP specification. Starting with JSP 2.0, the EL is part of the JSP specification, and all containers are required to analyze the syntax of EL expressions (in attribute values or directly in the template text) during the translation phase and report all syntax errors it finds.
As with the element syntax error messages, the details differ between containers, but let’s look at a few EL syntax error examples in this section so you can see what to expect when you use the EL with Tomcat. Other implementations may do better (or worse), but these examples illustrate what to look for.
Example 9-5 shows a page with a subtle syntax error: the curly braces are missing in the EL expression.
Example 9-5. Missing both curly braces (error5.jsp)
<%@ page contentType="text/html" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>JSP is Easy</title>
</head>
<body bgcolor="white">
<h1>JSP is as easy as ...</h1>
1 + 2 + 3 = <c:out value="$1 + 2 + 3" />
</body>
</html>This is an easy mistake to make, but it’s not
recognized as a syntax error at all. To the container, this means
that the value is a plain-text value, not an expression. When used
with the <c:out> action, it’s easy to figure out what’s wrong because the text value is added to the response as is instead of the being evaluated: ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.