Question about using EL expression ieelignoed in JSP

When using the El expression in JSP, You need to identify iselignored = "false". Otherwise, the El expression is compiled as a normal string and the correct value is not displayed on the page.

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isELIgnored="false"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><c:out value="${param.para1}" default="hello world">

You can see this in the apache-tomcat-6.0.35-src:

protected String[] generateJava() throws Exception {        String[] smapStr = null;        long t1, t2, t3, t4;        t1 = t2 = t3 = t4 = 0;        if (log.isDebugEnabled()) {            t1 = System.currentTimeMillis();        }        // Setup page info area        pageInfo = new PageInfo(new BeanRepository(ctxt.getClassLoader(),                errDispatcher), ctxt.getJspFile());        JspConfig jspConfig = options.getJspConfig();        JspConfig.JspProperty jspProperty = jspConfig.findJspProperty(ctxt                .getJspFile());        /*         * If the current uri is matched by a pattern specified in a         * jsp-property-group in web.xml, initialize pageInfo with those         * properties.         */        if (jspProperty.isELIgnored() != null) {            pageInfo.setELIgnored(JspUtil.booleanValue(jspProperty                    .isELIgnored()));        }