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POUse webapp classpath using JavaCompiler in Tomcat within Eclipse with Maven
 

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    <p>I have an existing "Example Webapp" that references "Example Library" using Maven. I'm running Tomcat 7 inside Eclipse 4.3RC3 with the m2e plugin. When I launch Example Webapp on Tomcat inside Eclipse, I have verified that the <code>example-library.jar</code> is probably getting deployed in the Tomcat instance's <code>WEB-INF/lib</code> folder.</p> <p>The Example Webapp has code that compiles certain classes on the fly using <code>JavaCompiler.CompilationTask</code>. These dynamically generated classes reference classes in <code>example-library.jar</code>. Unfortunately the compile task is failing because the referenced classes cannot be found.</p> <p>I understand that I can <a href="https://stackoverflow.com/questions/1563909">set the <code>JavaCompiler</code> classpath</a>, but <code>System.getProperty("java.class.path")</code> only returns me the Tomcat classpath, not the webapp classpath:</p> <pre><code>C:\bin\tomcat\bin\bootstrap.jar;C:\bin\tomcat\bin\tomcat-juli.jar;C:\bin\jdk6\lib\tools.jar </code></pre> <p>Other have <a href="https://stackoverflow.com/questions/4273039">said</a> that I need to get the real path of <code>WEB-INF/lib</code> from the servlet context, but the class generation code doesn't know anything about a servlet context --- it is written to be agnostic of whether it is used on the client or on the server.</p> <p>In <a href="https://stackoverflow.com/questions/274474">another question</a>, one <a href="https://stackoverflow.com/a/665896/421049">answer</a> indicated I could enumerate the classloader URLs, and sure enough this provides me with the jars in <code>WEB-INF/lib</code>, but when I provide this as a <code>-classpath</code> option to <code>compiler.getTask()</code>, the task still fails because it can't find the referenced classes.</p> <p>How can I simply provide the classpath of the currently executing code to the <code>JavaCompiler</code> instance so that it will find the classes from the libraries in <code>WEB-INF/lib</code>? (A <a href="https://stackoverflow.com/questions/16477606">similar question</a> was raised but never answered regarding referencing jars within ear files using <code>JavaCompiler</code>.)</p> <p><em>Example:</em> In an attempt to get things working at any cost, I even tried to hard-code the classpath. For example, I have <code>foobar.lib</code> in my webapp lib directory, so I used the following code, modified from the answers I indicated above:</p> <pre><code>List&lt;String&gt; options = new ArrayList&lt;String&gt;(); options.add("-classpath"); options.add("C:\\work\\.metadata\\.plugins\\org.eclipse.wst.server.core\\tmp0\\wtpwebapps\\FooBar\\WEB-INF\\lib\\foobar.jar"); JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, options, null, compilationUnits); boolean success = task.call(); </code></pre> <p>In the end <code>success</code> is <code>false</code>, and my <code>diaognostics</code> indicates <code>package com.example.foo.bar does not exist...</code>, even though that package is in <code>foobar.jar</code>.</p>
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