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Tomcat example source code file (InvokerServlet.java)

This example Tomcat source code file (InvokerServlet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Tomcat tags/keywords

context, http, httpservletresponse, invokerhttprequest, io, ioexception, ioexception, request, response, runtimeexception, servlet, servletexception, servletexception, string, string, stringbuffer, unavailableexception, wrapper, wrapper

The Tomcat InvokerServlet.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.apache.catalina.servlets;


import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.UnavailableException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.ContainerServlet;
import org.apache.catalina.Context;
import org.apache.catalina.Globals;
import org.apache.catalina.Wrapper;
import org.apache.catalina.util.StringManager;


/**
 * The default servlet-invoking servlet for most web applications,
 * used to serve requests to servlets that have not been registered
 * in the web application deployment descriptor.
 *
 * @author Craig R. McClanahan
 * @version $Revision: 467222 $ $Date: 2006-10-24 05:17:11 +0200 (mar., 24 oct. 2006) $
 */

public final class InvokerServlet
    extends HttpServlet implements ContainerServlet {


    // ----------------------------------------------------- Instance Variables


    /**
     * The Context container associated with our web application.
     */
    private Context context = null;


    /**
     * The debugging detail level for this servlet.
     */
    private int debug = 0;


    /**
     * The string manager for this package.
     */
    private static StringManager sm =
        StringManager.getManager(Constants.Package);


    /**
     * The Wrapper container associated with this servlet.
     */
    private Wrapper wrapper = null;


    // ----------------------------------------------- ContainerServlet Methods


    /**
     * Return the Wrapper with which we are associated.
     */
    public Wrapper getWrapper() {

        return (this.wrapper);

    }


    /**
     * Set the Wrapper with which we are associated.
     *
     * @param wrapper The new wrapper
     */
    public void setWrapper(Wrapper wrapper) {

        this.wrapper = wrapper;
        if (wrapper == null)
            context = null;
        else
            context = (Context) wrapper.getParent();

    }


    // --------------------------------------------------------- Public Methods


    /**
     * Finalize this servlet.
     */
    public void destroy() {

        ;       // No actions necessary

    }


    /**
     * Process a GET request for the specified resource.
     *
     * @param request The servlet request we are processing
     * @param response The servlet response we are creating
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet-specified error occurs
     */
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException {

        serveRequest(request, response);

    }


    /**
     * Process a HEAD request for the specified resource.
     *
     * @param request The servlet request we are processing
     * @param response The servlet response we are creating
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet-specified error occurs
     */
    public void doHead(HttpServletRequest request,
                       HttpServletResponse response)
        throws IOException, ServletException {

        serveRequest(request, response);

    }


    /**
     * Process a POST request for the specified resource.
     *
     * @param request The servlet request we are processing
     * @param response The servlet response we are creating
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet-specified error occurs
     */
    public void doPost(HttpServletRequest request,
                       HttpServletResponse response)
        throws IOException, ServletException {

        serveRequest(request, response);

    }


    /**
     * Initialize this servlet.
     */
    public void init() throws ServletException {

        // Ensure that our ContainerServlet properties have been set
        if ((wrapper == null) || (context == null))
            throw new UnavailableException
                (sm.getString("invokerServlet.noWrapper"));

        // Set our properties from the initialization parameters
        if (getServletConfig().getInitParameter("debug") != null)
            debug = Integer.parseInt(getServletConfig().getInitParameter("debug"));

        if (debug >= 1)
            log("init: Associated with Context '" + context.getPath() + "'");

    }



    // -------------------------------------------------------- Private Methods


    /**
     * Serve the specified request, creating the corresponding response.
     * After the first time a particular servlet class is requested, it will
     * be served directly (like any registered servlet) because it will have
     * been registered and mapped in our associated Context.
     *
     * @param request The servlet request we are processing
     * @param response The servlet response we are creating
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet-specified error occurs
     */
    public void serveRequest(HttpServletRequest request,
                             HttpServletResponse response)
        throws IOException, ServletException {

        // Disallow calling this servlet via a named dispatcher
        if (request.getAttribute(Globals.NAMED_DISPATCHER_ATTR) != null)
            throw new ServletException
                (sm.getString("invokerServlet.notNamed"));

        // Identify the input parameters and our "included" state
        String inRequestURI = null;
        String inServletPath = null;
        String inPathInfo = null;
        boolean included =
            (request.getAttribute(Globals.INCLUDE_REQUEST_URI_ATTR) != null);

        if (included) {
            inRequestURI =
                (String) request.getAttribute(Globals.INCLUDE_REQUEST_URI_ATTR);
            inServletPath =
                (String) request.getAttribute(Globals.INCLUDE_SERVLET_PATH_ATTR);
            inPathInfo =
                (String) request.getAttribute(Globals.INCLUDE_PATH_INFO_ATTR);
        } else {
            inRequestURI = request.getRequestURI();
            inServletPath = request.getServletPath();
            inPathInfo = request.getPathInfo();
        }
        if (debug >= 1) {
            log("included='" + included + "', requestURI='" +
                inRequestURI + "'");
            log("  servletPath='" + inServletPath + "', pathInfo='" +
                inPathInfo + "'");
        }

        // Make sure a servlet name or class name was specified
        if (inPathInfo == null) {
            if (debug >= 1)
                log("Invalid pathInfo '" + inPathInfo + "'");
            if (included)
                throw new ServletException
                    (sm.getString("invokerServlet.invalidPath", inRequestURI));
            else {
                response.sendError(HttpServletResponse.SC_NOT_FOUND,
                                   inRequestURI);
                return;
            }
        }

        // Identify the outgoing servlet name or class, and outgoing path info
        String pathInfo = inPathInfo;
        String servletClass = pathInfo.substring(1);
        int slash = servletClass.indexOf('/');
        if (slash >= 0) {
            pathInfo = servletClass.substring(slash);
            servletClass = servletClass.substring(0, slash);
        } else {
            pathInfo = "";
        }

        if (servletClass.startsWith("org.apache.catalina")) {
            response.sendError(HttpServletResponse.SC_NOT_FOUND,
                               inRequestURI);
            return;
        }

        if (debug >= 1)
            log("Processing servlet '" + servletClass +
                "' with path info '" + pathInfo + "'");
        String name = "org.apache.catalina.INVOKER." + servletClass;
        String pattern = inServletPath + "/" + servletClass + "/*";
        Wrapper wrapper = null;

        // Synchronize to avoid race conditions when multiple requests
        // try to initialize the same servlet at the same time
        synchronized (this) {

            // Are we referencing an existing servlet class or name?
            wrapper = (Wrapper) context.findChild(servletClass);
            if (wrapper == null)
                wrapper = (Wrapper) context.findChild(name);
            if (wrapper != null) {
                String actualServletClass = wrapper.getServletClass();
                if ((actualServletClass != null)
                    && (actualServletClass.startsWith
                        ("org.apache.catalina"))) {
                    response.sendError(HttpServletResponse.SC_NOT_FOUND,
                                       inRequestURI);
                    return;
                }
                if (debug >= 1)
                    log("Using wrapper for servlet '" +
                        wrapper.getName() + "' with mapping '" +
                        pattern + "'");
                context.addServletMapping(pattern, wrapper.getName());
            }

            // No, create a new wrapper for the specified servlet class
            else {

                if (debug >= 1)
                    log("Creating wrapper for '" + servletClass +
                        "' with mapping '" + pattern + "'");

                try {
                    wrapper = context.createWrapper();
                    wrapper.setName(name);
                    wrapper.setLoadOnStartup(1);
                    wrapper.setServletClass(servletClass);
                    context.addChild(wrapper);
                    context.addServletMapping(pattern, name);
                } catch (Exception e) {
                    log(sm.getString("invokerServlet.cannotCreate",
                                     inRequestURI), e);
                    context.removeServletMapping(pattern);
                    context.removeChild(wrapper);
                    if (included)
                        throw new ServletException
                            (sm.getString("invokerServlet.cannotCreate",
                                          inRequestURI), e);
                    else {
                        response.sendError(HttpServletResponse.SC_NOT_FOUND,
                                           inRequestURI);
                        return;
                    }
                }
            }

        }

        // Create a request wrapper to pass on to the invoked servlet
        InvokerHttpRequest wrequest =
            new InvokerHttpRequest(request);
        wrequest.setRequestURI(inRequestURI);
        StringBuffer sb = new StringBuffer(inServletPath);
        sb.append("/");
        sb.append(servletClass);
        wrequest.setServletPath(sb.toString());
        if ((pathInfo == null) || (pathInfo.length() < 1)) {
            wrequest.setPathInfo(null);
            wrequest.setPathTranslated(null);
        } else {
            wrequest.setPathInfo(pathInfo);
            wrequest.setPathTranslated
                (getServletContext().getRealPath(pathInfo));
        }

        // Allocate a servlet instance to perform this request
        Servlet instance = null;
        try {
            instance = wrapper.allocate();
        } catch (ServletException e) {
            log(sm.getString("invokerServlet.allocate", inRequestURI), e);
            context.removeServletMapping(pattern);
            context.removeChild(wrapper);
            Throwable rootCause = e.getRootCause();
            if (rootCause == null)
                rootCause = e;
            if (rootCause instanceof ClassNotFoundException) {
                response.sendError(HttpServletResponse.SC_NOT_FOUND,
                                   inRequestURI);
                return;
            } else if (rootCause instanceof IOException) {
                throw (IOException) rootCause;
            } else if (rootCause instanceof RuntimeException) {
                throw (RuntimeException) rootCause;
            } else if (rootCause instanceof ServletException) {
                throw (ServletException) rootCause;
            } else {
                throw new ServletException
                    (sm.getString("invokerServlet.allocate", inRequestURI),
                     rootCause);
            }
        }

        // After loading the wrapper, restore some of the fields when including
        if (included) {
            wrequest.setRequestURI(request.getRequestURI());
            wrequest.setPathInfo(request.getPathInfo());
            wrequest.setServletPath(request.getServletPath());
        }

        // Invoke the service() method of the allocated servlet
        try {
            String jspFile = wrapper.getJspFile();
            if (jspFile != null)
                request.setAttribute(Globals.JSP_FILE_ATTR, jspFile);
            else
                request.removeAttribute(Globals.JSP_FILE_ATTR);
            request.setAttribute(Globals.INVOKED_ATTR,
                                 request.getServletPath());
            instance.service(wrequest, response);
        } catch (UnavailableException e) {
            context.removeServletMapping(pattern);
            throw e;
        } finally {
            request.removeAttribute(Globals.INVOKED_ATTR);
            request.removeAttribute(Globals.JSP_FILE_ATTR);
            // Deallocate the allocated servlet instance
            try {
                wrapper.deallocate(instance);
            } catch (ServletException e) {
                log(sm.getString("invokerServlet.deallocate", inRequestURI), e);
                throw e;
            }
        }

    }


}

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