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copied!<p>You can't use the 'out' variable (nor any of the other "predeclared" scriptlet variables) inside directives.</p> <p>The JSP page gets translated by your webserver into a Java servlet. Inside tomcats, for instance, everything inside scriptlets (which start "<%"), along with all the static HTML, gets translated into one giant Java method which writes your page, line by line, to a JspWriter instance called "out". This is why you can use the "out" parameter directly in scriptlets. Directives, on the other hand (which start with "<%!") get translated as separate Java methods.</p> <p>As an example, a very simple page (let's call it foo.jsp):</p> <pre><code><html> <head/> <body> <%! String someOutput() { return "Some output"; } %> <% someOutput(); %> </body> </html> </code></pre> <p>would end up looking something like this (with a lot of the detail ignored for clarity):</p> <pre><code>public final class foo_jsp { // This is where the request comes in public void _jspService(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { // JspWriter instance is gotten from a factory // This is why you can use 'out' directly in scriptlets JspWriter out = ...; // Snip out.write("<html>"); out.write("<head/>"); out.write("<body>"); out.write(someOutput()); // i.e. write the results of the method call out.write("</body>"); out.write("</html>"); } // Directive gets translated as separate method - note // there is no 'out' variable declared in scope private String someOutput() { return "Some output"; } } </code></pre>

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