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copied!<blockquote> <p>Is it always used within JSP pages</p> </blockquote> <p>Yes.</p> <blockquote> <p>... and is it used only for getting data from the database.</p> </blockquote> <p>No. In fact, in mast cases it is BAD PRACTICE to access the database from a JSP, using JSTL or using other means (e.g. scriptlets).</p> <blockquote> <p>does it mean like most JSP would have an associated Java file like 1-1 mapped, where the logic to get data using SQL query is written and is given to the JSP page.</p> </blockquote> <p>Sort of. But there is not necessarily a 1 to 1 mapping:</p> <ul> <li>Not all JSPs need to access the database.</li> <li>A Java servlet may use multiple JSPs to render different output pages.</li> <li>Different servlets may share a single JSP; e.g. to render a common error message page.</li> </ul> <blockquote> <p>if yes, what exactly is the role of JSTL code within the JSP.</p> </blockquote> <p>The aim of a JSP is to render output; typically HTML pages, but it could be anything text-based. JSTL is used within JSPs when the the output rendering logic is too complicated or messy to express using JSP EL. </p> <hr> <p><strong>UPDATE</strong></p> <p>The old-fashioned alternative to JSTL and JSP EL is to embed Java code ... i.e. scriptlets ... in the JSPs. For example:</p> <pre><code><c:if test="${a == 'true'}"> hi </c:if> </code></pre> <p>is equivalent to something like this:</p> <pre><code><% if ("true".equals(context.findAttribute("a")) { %> hi <% } %> </code></pre> <blockquote> <p>Also for JSTL use, from what i understand it is used within the JSP for dynamic HTML rendering through if..else statements.</p> </blockquote> <p>You are describing HTML whose structure and content <em>depends</em> request parameters, configuration parameters, data fetched from the database and so in. This is the primary uses of JSTL.</p> <p>However, this is NOT what is normally referred to as "Dynamic HTML". Dynamic HTML is where <em>the browser</em> changes the HTML of the currently displayed page; e.g. when Javascript embedded in the page changes displayed page by modifying the DOM. </p>

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