https://tomcat.apache.org/: Tomcat Servlet Engine Core Classes and Standard implementations 
/*
 * 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.core;

import java.io.IOException;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.servlet.DispatcherType;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.Context;
import org.apache.catalina.Globals;
import org.apache.catalina.Wrapper;
import org.apache.catalina.connector.ClientAbortException;
import org.apache.catalina.connector.Request;
import org.apache.catalina.connector.Response;
import org.apache.catalina.valves.ValveBase;
import org.apache.coyote.ActionCode;
import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
import org.apache.tomcat.util.ExceptionUtils;
import org.apache.tomcat.util.descriptor.web.ErrorPage;
import org.apache.tomcat.util.res.StringManager;


Valve that implements the default basic behavior for the
StandardHost container implementation.


USAGE CONSTRAINT:  This implementation is likely to be useful only
when processing HTTP requests.

Author:Craig R. McClanahan, Remy Maucherat
/**
 * Valve that implements the default basic behavior for the
 * <code>StandardHost</code> container implementation.
 * <p>
 * <b>USAGE CONSTRAINT</b>:  This implementation is likely to be useful only
 * when processing HTTP requests.
 *
 * @author Craig R. McClanahan
 * @author Remy Maucherat
 */
final class StandardHostValve extends ValveBase {

    private static final Log log = LogFactory.getLog(StandardHostValve.class);

    // Saves a call to getClassLoader() on very request. Under high load these
    // calls took just long enough to appear as a hot spot (although a very
    // minor one) in a profiler.
    private static final ClassLoader MY_CLASSLOADER =
            StandardHostValve.class.getClassLoader();

    static final boolean STRICT_SERVLET_COMPLIANCE;

    static final boolean ACCESS_SESSION;

    static {
        STRICT_SERVLET_COMPLIANCE = Globals.STRICT_SERVLET_COMPLIANCE;

        String accessSession = System.getProperty(
                "org.apache.catalina.core.StandardHostValve.ACCESS_SESSION");
        if (accessSession == null) {
            ACCESS_SESSION = STRICT_SERVLET_COMPLIANCE;
        } else {
            ACCESS_SESSION = Boolean.parseBoolean(accessSession);
        }
    }

    //------------------------------------------------------ Constructor
    public StandardHostValve() {
        super(true);
    }


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

    
The string manager for this package.

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


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

    
Select the appropriate child Context to process this request,
based on the specified request URI.  If no matching Context can
be found, return an appropriate HTTP error.

Params:
  • request – Request to be processed
  • response – Response to be produced
Throws:
/**
     * Select the appropriate child Context to process this request,
     * based on the specified request URI.  If no matching Context can
     * be found, return an appropriate HTTP error.
     *
     * @param request Request to be processed
     * @param response Response to be produced
     *
     * @exception IOException if an input/output error occurred
     * @exception ServletException if a servlet error occurred
     */
    @Override
    public final void invoke(Request request, Response response)
        throws IOException, ServletException {

        // Select the Context to be used for this Request
        Context context = request.getContext();
        if (context == null) {
            return;
        }

        if (request.isAsyncSupported()) {
            request.setAsyncSupported(context.getPipeline().isAsyncSupported());
        }

        boolean asyncAtStart = request.isAsync();

        try {
            context.bind(Globals.IS_SECURITY_ENABLED, MY_CLASSLOADER);

            if (!asyncAtStart && !context.fireRequestInitEvent(request.getRequest())) {
                // Don't fire listeners during async processing (the listener
                // fired for the request that called startAsync()).
                // If a request init listener throws an exception, the request
                // is aborted.
                return;
            }

            // Ask this Context to process this request. Requests that are
            // already in error must have been routed here to check for
            // application defined error pages so DO NOT forward them to the the
            // application for processing.
            try {
                if (!response.isErrorReportRequired()) {
                    context.getPipeline().getFirst().invoke(request, response);
                }
            } catch (Throwable t) {
                ExceptionUtils.handleThrowable(t);
                container.getLogger().error("Exception Processing " + request.getRequestURI(), t);
                // If a new error occurred while trying to report a previous
                // error allow the original error to be reported.
                if (!response.isErrorReportRequired()) {
                    request.setAttribute(RequestDispatcher.ERROR_EXCEPTION, t);
                    throwable(request, response, t);
                }
            }

            // Now that the request/response pair is back under container
            // control lift the suspension so that the error handling can
            // complete and/or the container can flush any remaining data
            response.setSuspended(false);

            Throwable t = (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);

            // Protect against NPEs if the context was destroyed during a
            // long running request.
            if (!context.getState().isAvailable()) {
                return;
            }

            // Look for (and render if found) an application level error page
            if (response.isErrorReportRequired()) {
                // If an error has occurred that prevents further I/O, don't waste time
                // producing an error report that will never be read
                AtomicBoolean result = new AtomicBoolean(false);
                response.getCoyoteResponse().action(ActionCode.IS_IO_ALLOWED, result);
                if (result.get()) {
                    if (t != null) {
                        throwable(request, response, t);
                    } else {
                        status(request, response);
                    }
                }
            }

            if (!request.isAsync() && !asyncAtStart) {
                context.fireRequestDestroyEvent(request.getRequest());
            }
        } finally {
            // Access a session (if present) to update last accessed time, based
            // on a strict interpretation of the specification
            if (ACCESS_SESSION) {
                request.getSession(false);
            }

            context.unbind(Globals.IS_SECURITY_ENABLED, MY_CLASSLOADER);
        }
    }


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

    
Handle the HTTP status code (and corresponding message) generated
while processing the specified Request to produce the specified
Response.  Any exceptions that occur during generation of the error
report are logged and swallowed.

Params:
  • request – The request being processed
  • response – The response being generated
/**
     * Handle the HTTP status code (and corresponding message) generated
     * while processing the specified Request to produce the specified
     * Response.  Any exceptions that occur during generation of the error
     * report are logged and swallowed.
     *
     * @param request The request being processed
     * @param response The response being generated
     */
    private void status(Request request, Response response) {

        int statusCode = response.getStatus();

        // Handle a custom error page for this status code
        Context context = request.getContext();
        if (context == null) {
            return;
        }

        /* Only look for error pages when isError() is set.
         * isError() is set when response.sendError() is invoked. This
         * allows custom error pages without relying on default from
         * web.xml.
         */
        if (!response.isError()) {
            return;
        }

        ErrorPage errorPage = context.findErrorPage(statusCode);
        if (errorPage == null) {
            // Look for a default error page
            errorPage = context.findErrorPage(0);
        }
        if (errorPage != null && response.isErrorReportRequired()) {
            response.setAppCommitted(false);
            request.setAttribute(RequestDispatcher.ERROR_STATUS_CODE,
                              Integer.valueOf(statusCode));

            String message = response.getMessage();
            if (message == null) {
                message = "";
            }
            request.setAttribute(RequestDispatcher.ERROR_MESSAGE, message);
            request.setAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR,
                    errorPage.getLocation());
            request.setAttribute(Globals.DISPATCHER_TYPE_ATTR,
                    DispatcherType.ERROR);


            Wrapper wrapper = request.getWrapper();
            if (wrapper != null) {
                request.setAttribute(RequestDispatcher.ERROR_SERVLET_NAME,
                                  wrapper.getName());
            }
            request.setAttribute(RequestDispatcher.ERROR_REQUEST_URI,
                                 request.getRequestURI());
            if (custom(request, response, errorPage)) {
                response.setErrorReported();
                try {
                    response.finishResponse();
                } catch (ClientAbortException e) {
                    // Ignore
                } catch (IOException e) {
                    container.getLogger().warn("Exception Processing " + errorPage, e);
                }
            }
        }
    }


    
Handle the specified Throwable encountered while processing
the specified Request to produce the specified Response.  Any
exceptions that occur during generation of the exception report are
logged and swallowed.

Params:
  • request – The request being processed
  • response – The response being generated
  • throwable – The exception that occurred (which possibly wraps
 a root cause exception
/**
     * Handle the specified Throwable encountered while processing
     * the specified Request to produce the specified Response.  Any
     * exceptions that occur during generation of the exception report are
     * logged and swallowed.
     *
     * @param request The request being processed
     * @param response The response being generated
     * @param throwable The exception that occurred (which possibly wraps
     *  a root cause exception
     */
    protected void throwable(Request request, Response response,
                             Throwable throwable) {
        Context context = request.getContext();
        if (context == null) {
            return;
        }

        Throwable realError = throwable;

        if (realError instanceof ServletException) {
            realError = ((ServletException) realError).getRootCause();
            if (realError == null) {
                realError = throwable;
            }
        }

        // If this is an aborted request from a client just log it and return
        if (realError instanceof ClientAbortException ) {
            if (log.isDebugEnabled()) {
                log.debug
                    (sm.getString("standardHost.clientAbort",
                        realError.getCause().getMessage()));
            }
            return;
        }

        ErrorPage errorPage = context.findErrorPage(throwable);
        if ((errorPage == null) && (realError != throwable)) {
            errorPage = context.findErrorPage(realError);
        }

        if (errorPage != null) {
            if (response.setErrorReported()) {
                response.setAppCommitted(false);
                request.setAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR,
                        errorPage.getLocation());
                request.setAttribute(Globals.DISPATCHER_TYPE_ATTR,
                        DispatcherType.ERROR);
                request.setAttribute(RequestDispatcher.ERROR_STATUS_CODE,
                        Integer.valueOf(HttpServletResponse.SC_INTERNAL_SERVER_ERROR));
                request.setAttribute(RequestDispatcher.ERROR_MESSAGE,
                                  throwable.getMessage());
                request.setAttribute(RequestDispatcher.ERROR_EXCEPTION,
                                  realError);
                Wrapper wrapper = request.getWrapper();
                if (wrapper != null) {
                    request.setAttribute(RequestDispatcher.ERROR_SERVLET_NAME,
                                      wrapper.getName());
                }
                request.setAttribute(RequestDispatcher.ERROR_REQUEST_URI,
                                     request.getRequestURI());
                request.setAttribute(RequestDispatcher.ERROR_EXCEPTION_TYPE,
                                  realError.getClass());
                if (custom(request, response, errorPage)) {
                    try {
                        response.finishResponse();
                    } catch (IOException e) {
                        container.getLogger().warn("Exception Processing " + errorPage, e);
                    }
                }
            }
        } else {
            // A custom error-page has not been defined for the exception
            // that was thrown during request processing. Check if an
            // error-page for error code 500 was specified and if so,
            // send that page back as the response.
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            // The response is an error
            response.setError();

            status(request, response);
        }
    }


    
Handle an HTTP status code or Java exception by forwarding control
to the location included in the specified errorPage object.  It is
assumed that the caller has already recorded any request attributes
that are to be forwarded to this page.  Return true if
we successfully utilized the specified error page location, or
false if the default error report should be rendered.

Params:
  • request – The request being processed
  • response – The response being generated
  • errorPage – The errorPage directive we are obeying
/**
     * Handle an HTTP status code or Java exception by forwarding control
     * to the location included in the specified errorPage object.  It is
     * assumed that the caller has already recorded any request attributes
     * that are to be forwarded to this page.  Return <code>true</code> if
     * we successfully utilized the specified error page location, or
     * <code>false</code> if the default error report should be rendered.
     *
     * @param request The request being processed
     * @param response The response being generated
     * @param errorPage The errorPage directive we are obeying
     */
    private boolean custom(Request request, Response response,
                             ErrorPage errorPage) {

        if (container.getLogger().isDebugEnabled()) {
            container.getLogger().debug("Processing " + errorPage);
        }

        try {
            // Forward control to the specified location
            ServletContext servletContext =
                request.getContext().getServletContext();
            RequestDispatcher rd =
                servletContext.getRequestDispatcher(errorPage.getLocation());

            if (rd == null) {
                container.getLogger().error(
                    sm.getString("standardHostValue.customStatusFailed", errorPage.getLocation()));
                return false;
            }

            if (response.isCommitted()) {
                // Response is committed - including the error page is the
                // best we can do
                rd.include(request.getRequest(), response.getResponse());
            } else {
                // Reset the response (keeping the real error code and message)
                response.resetBuffer(true);
                response.setContentLength(-1);

                rd.forward(request.getRequest(), response.getResponse());

                // If we forward, the response is suspended again
                response.setSuspended(false);
            }

            // Indicate that we have successfully processed this custom page
            return true;

        } catch (Throwable t) {
            ExceptionUtils.handleThrowable(t);
            // Report our failure to process this custom page
            container.getLogger().error("Exception Processing " + errorPage, t);
            return false;
        }
    }
}