Eliminating Javac warnings for JSPs in Jasper generated Java source files?

Question

When pre-compiling JSPs with the Jasper compiler (using Tomcat), and then the Java compiler I see javac warnings like this (I have javac's -Xlint flag enabled):

warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.List
_jspx_dependants.add("/some-jsp.jspf");

Now, it's "just a warning," but I like clean builds, so naturally I want to get rid of the warning. Sure, I could turn -Xlint off for JSP compilation, but -Xlint is good stuff, so it stays.

In this example warning, the problem is that generic syntax isn't used. Instead of List<String>, we have only List. I realize that the good folks who write Jasper have to cater to those unfortunate souls who remain locked in a pre-Java5 world. That's fine, but why should I have to suffer these warnings?

Is there some well-known way to eliminate javac warnings caused by the Java source code created by the Jasper JSP compiler? I'm not interested in an IDE-specific solution (though that would be a partial solution for some people who use the particular IDE). I'm looking for a generally applicable solution.

A scan of the Jasper source code didn't reveal any "Java 5+" switches that would cause generic syntax emission. In fact, on the contrary I found this:

apache-tomcat-6.0.18-src/java/org/apache/jasper/compiler/Generator.java:494:            out.printin("_jspx_dependants = new java.util.ArrayList(");

which clearly shows the hardcoded code bereft of any hope for injection of elegant generic syntax.

Answer 1

Disable the warnings you know are there and don't care about with:

-Xlint:-xxx
Disable warning xxx, where xxx is one of the warning names supported for -Xlint:xxx, below.

See here.

Answer 2

I'm using an Ant-based build. My current solution to this problem is to edit the offending Jasper generated Java code in-place with the following Ant filtering code:

<move todir="WEB-INF/src">
    <fileset dir="WEB-INF/src"/>
    <globmapper from="*.java"
                to="*.java.foo"/>
    <filterchain>
        <tokenfilter>
            <replacestring from="private static java.util.List _jspx_dependants;"
                           to="private static java.util.List&lt;String&gt; _jspx_dependants;"/>
            <replacestring from="_jspx_dependants = new java.util.ArrayList"
                           to="_jspx_dependants = new java.util.ArrayList&lt;String&gt;"/>
            <replaceregex pattern="public final class (.*) extends org.apache.jasper.runtime.HttpJspBase"
                          replace="@SuppressWarnings(&quot;serial&quot;)&#xA;public final class \1 extends org.apache.jasper.runtime.HttpJspBase"/>
            <replacestring from="(PageContext)_jspx_page_context"
                           to="_jspx_page_context"/>
        </tokenfilter>
    </filterchain>
</move>
<move todir="WEB-INF/src" overwrite="true">
    <fileset dir="WEB-INF/src"/>
    <globmapper from="*.java.foo" to="*.java"/>
</move>

Please see this question to understand the "double move."