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From: "Peter Yared" <peter.yared@heliopolis.Eng.Sun.COM>
To: <tomcat-dev@jakarta.apache.org>
Subject: Using Tomcat/Jasper as a code generator/template language
Date: Wed, 27 Sep 2000 15:27:38 -0700
Message-ID: <NEBBKJNFHKCCNDJDDOBFEEFBCAAA.peter.yared@heliopolis.eng.sun.com>
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Hi everyone,

Enclosed is a file that enables people to use Tomcat/Jasper as a code
generator.  What is nice is that it invokes Tomcat/Jasper directly, so it
doesn't use Apache, ports, etc., and therefore can very easily be integrated
into an application.

It also lets you pass session variables that can then be used by the JSP
page to help generate code.  Following is an example of how to use the
JspTemplateCompiler.  The source file is enclosed.  Enjoy!

Peter Yared
SunLabs
SunMicrosystems, Inc.
peter.yared(remove me)eng.sun.com


You can make a template like the following JSP:

<%@ page %>
<jsp:useBean id="packageName" scope="session" class="java.lang.String" />
<jsp:useBean id="className" scope="session" class="java.lang.String" />
<jsp:useBean id="myString" scope="session" class="java.lang.String" />

<% if (packageName != null && packageName.length() > 0) { %>
package <%= packageName %>;
<% } %>

public class <%= className %> {

    public <%= className %>() {
    }

    public int returnCustomNumber() {
        return <%= 3+3 %>;
    }

    public String returnSessionString() {
        return "<%= myString %>";
    }
}

Which is then used to generate a .java file:

import java.io.IOException;
import java.util.Hashtable;
import javax.servlet.ServletException;
import org.apache.jasper.JspTemplateCompiler;

public class ServletTest {

    public ServletTest() {
        try {
            Hashtable properties = new Hashtable();
            properties.put("myString", "Yo");
            org.apache.jasper.JspTemplateCompiler.debug = true;

org.apache.jasper.JspTemplateCompiler.processTemplate("D:\\jsps\\My.jsp",
"D:\\jsps\\MyClass.java", null, "MyClass", properties, null, null, true);
        }
        catch (IOException e) {
            e.printStackTrace();
        }
        catch (ServletException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        ServletTest servletTest = new ServletTest();
    }
}

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/*
 *
 * =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
 *=20
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights=20
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.=20
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement: =20
 *       "This product includes software developed by the=20
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software =
itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products =
derived
 *    from this software without prior written permission. For written=20
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */=20

package org.apache.jasper;

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;

import sun.tools.javac.*;

import org.apache.jasper.*;
import org.apache.tomcat.core.*;
import org.apache.tomcat.loader.*;
import org.apache.tomcat.session.*;
import org.apache.jasper.runtime.*;

/**
 * The JspTemplateCompiler compiles JSP pages that render Java code.  =
This is a useful way of
 * creating Java code templates to dynamically generate Java code.  =
JspTemplateCompiler uses
 * the sun.tools.javac compiler, which is available in many Java =
Development Kit implementations.
 *
 * @author Peter Yared, SunLabs, peter.yared@eng.sun.com
 */
public class JspTemplateCompiler {

    /**
     * Debug flag that prints JSP result to System.out.
     */
    public static boolean debug =3D false;
   =20
    /**
     * Generates a Java file from a JSP template and compiles it.
     *
     * @param templatePath Path to .jsp to use to generate file
     * @param targetPath File path to place the generated file
     * @param targetPackage Package name to use in the JSP template =
(passed as session parameter packageName)
     * @param targetClassName Class name to use in the JSP template =
(passed as session parameter className)
     * @param properties Hashtable of session properties to be made =
available to the jsp template
     * @param classPath Classpath to use when compiling files
     * @param compile Flag to specify if result of servlet should be =
compiled with javac
     * @returns boolean Successful t/f
     */
    public static boolean processTemplate(String templatePath, String =
targetPath, String targetPackage, String targetClassName, Hashtable =
properties, String servletClassPath, String templateClassPath, boolean =
compile) throws IOException, ServletException {
       =20
        // Get the path, file name, and servlet name from templatePath =
variable
        int fileNameIndex =3D =
templatePath.lastIndexOf(File.separatorChar);
        String path =3D null;
        String fileName =3D null;
        if (fileNameIndex =3D=3D -1) {
            fileName =3D templatePath;
        }
        else {
            fileName =3D templatePath.substring(fileNameIndex + 1);
            path =3D templatePath.substring(0, fileNameIndex + 1);
        }
        String servletName =3D fileName.substring(0, fileName.length() - =
4); // Remove ".jsp" from end
       =20
        // Convert the JSP to a Servlet
        String[] jspcArgs =3D new String[5];
        jspcArgs[0] =3D "-uriroot";
        jspcArgs[1] =3D path;
        jspcArgs[2] =3D "-d";
        jspcArgs[3] =3D path;
        jspcArgs[4] =3D fileName;
        JspC.main(jspcArgs);
       =20
        // Compile the Servlet - need to do it ourselves since tomcat =
does it for you on a HTTP request
        if (!compile(servletClassPath, path + File.separatorChar + =
servletName + ".java"))
            return false;
       =20
        // Pass the target path to the session so it can be used
        if (properties =3D=3D null) {
            properties =3D new Hashtable();
        }
        if (targetPackage !=3D null) {
            properties.put("packageName", targetPackage);
        }
        properties.put("className", targetClassName);
       =20
        // Write the result of the servlet to disk
        File file =3D new File(targetPath);
        file.delete(); // Delete it if it already exists
        FileWriter fw =3D new FileWriter(file);
        String jspResult =3D runServlet(path, servletName, =
properties).toString();
        if (debug) {
            System.out.println(jspResult);
        }
        fw.write(jspResult);
        fw.close();
       =20
        // Compile the output of the servlet
        if (compile) {
            return compile(templateClassPath, targetPath);
        }
        return true;
    }
=20
    /**
     * Compiles a file using the sun.tools.javac compiler.
     *
     * @param classPath The classpath to use when compiling, can be null
     * @param file to compile
     * @returns boolean Successful t/f
     */=20
    protected static boolean compile(String classPath, String file) {
        String[] args =3D new String[(classPath =3D=3D null) ? 1 : 3];
        args[0] =3D file;
        if (classPath !=3D null) {
            args[1] =3D "-classpath";
            args[2] =3D classPath;
        }
        Main compiler =3D new Main(System.out, "JSP Template Compiler");
        return compiler.compile(args);
    }
=20
    /**
     * Runs a servlet and returns its result as a StringBuffer
     *
     * @param docBase The location of the servlet
     * @param servletName The name of the servlet to run
     * @param properties Hashtable of session properties to be made =
available to the jsp template
     * @param returns StringBuffer with result of the servlet
     */
    public static StringBuffer runServlet(String docBase, String =
servletName, Hashtable properties) throws IOException, =
javax.servlet.ServletException {
        org.apache.tomcat.core.ServletWrapper servletWrapper =3D new =
org.apache.tomcat.core.ServletWrapper();
           =20
        org.apache.tomcat.core.Context cntx =3D new =
org.apache.tomcat.core.Context();
       =20
        org.apache.tomcat.core.ContextManager cm =3D new =
org.apache.tomcat.core.ContextManager();
        cntx.setContextManager(cm);
           =20
        org.apache.tomcat.core.ServletLoader sloader =3D new =
org.apache.tomcat.loader.ServletClassLoaderImpl();
        sloader.addRepository(new File(docBase));
        cntx.setServletLoader(sloader);
           =20
        org.apache.tomcat.core.SessionManager sm =3D new =
org.apache.tomcat.session.StandardSessionManager();
        cntx.setSessionManager(sm);
           =20
        servletWrapper.setContext(cntx);
        servletWrapper.setServletName(servletName);
        servletWrapper.setServletClass(servletName);
        javax.servlet.Servlet servlet =3D servletWrapper.getServlet();
           =20
        javax.servlet.jsp.JspFactory myFactory =3D new =
org.apache.jasper.runtime.JspFactoryImpl();
        JspFactory.setDefaultFactory(myFactory);

        org.apache.tomcat.core.RequestImpl request =3D new =
RequestImpl();
        org.apache.tomcat.core.ResponseImpl response =3D new =
ResponseImpl();           =20
        request.setContextManager(cm);
        request.setContext(cntx);
       =20
        response.setRequest(request);
        request.setResponse(response);
 =20
        HttpSession session =3D request.getFacade().getSession(true);
        if (properties !=3D null) {
            Enumeration e =3D properties.keys();
            while (e.hasMoreElements()) {
                String key =3D (String) e.nextElement();
                session.setAttribute(key, properties.get(key));
            }
        }

        servlet.service(request.getFacade(), response.getFacade());
        response.finish();
           =20
        return ((ResponseImpl) response).getBody();
    }
}
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