It is helpful to understand how the JSP compiler transforms the page into a Java servlet. For example, consider the following input JSP and its resulting generated Java Servlet.
Input JSP
Code:
<%@ page errorPage="myerror.jsp" %>
<%@ page import="com.foo.bar" %>
<html>
<head>
<%! int serverInstanceVariable = 1;%>
<% int localStackBasedVariable = 1; %>
<table>
<tr><td><%= toStringOrBlank( "expanded inline data " + 1 ) %></td></tr>
Resulting servlet
Code:
package jsp_servlet;
import java.util.*;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import javax.servlet.jsp.tagext.*;
import com.foo.bar; // Imported as a result of <%@ page import="com.foo.bar" %>
import …
class _myservlet implements javax.servlet.Servlet, javax.servlet.jsp.HttpJspPage {
// Inserted as a
// result of <%! int serverInstanceVariable = 1;%>
int serverInstanceVariable = 1;
…
public void _jspService( javax.servlet.http.HttpServletRequest request,
javax.servlet.http.HttpServletResponse response )
throws javax.servlet.ServletException,
java.io.IOException
{
javax.servlet.ServletConfig config = …; // Get the servlet config
Object page = this;
PageContext pageContext = …; // Get the page context for this request
javax.servlet.jsp.JspWriter out = pageContext.getOut();
HttpSession session = request.getSession( true );
try {
out.print( "<html>\r\n" );
out.print( "<head>\r\n" );
…
// From <% int localStackBasedVariable = 1; %>
int localStackBasedVariable = 1;
…
out.print( "<table>\r\n" );
out.print( " <tr><td>" );
// From <%= toStringOrBlank( "expanded inline data " + 1 ) %>
out.print( toStringOrBlank( "expanded inline data " + 1 ) );
out.print( " </td></tr>\r\n" );
…
} catch ( Exception _exception ) {
// Clean up and redirect to error page in <%@ page errorPage="myerror.jsp" %>
}
}
}
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