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/*
 * 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.ssi;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.Locale;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet to process SSI requests within a webpage. Mapped to a path from within web.xml.
 *
 * @author Bip Thelin
 * @author Amy Roh
 * @author Dan Sandberg
 * @author David Becker
 */
public class SSIServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /** Debug level for this servlet. */
    protected int debug = 0;
    /** Should the output be buffered. */
    protected boolean buffered = false;
    /** Expiration time in seconds for the doc. */
    protected Long expires = null;
    /** virtual path can be webapp-relative */
    protected boolean isVirtualWebappRelative = false;
    /** Input encoding. If not specified, uses platform default */
    protected String inputEncoding = null;
    /** Output encoding. If not specified, uses platform default */
    protected String outputEncoding = "UTF-8";
    /** Allow exec (normally blocked for security) */
    protected boolean allowExec = false;


    // ----------------- Public methods.

    @Override
    public void init() throws ServletException {

        if (getServletConfig().getInitParameter("debug") != null) {
            debug = Integer.parseInt(getServletConfig().getInitParameter("debug"));
        }

        isVirtualWebappRelative = Boolean.parseBoolean(getServletConfig().getInitParameter("isVirtualWebappRelative"));

        if (getServletConfig().getInitParameter("expires") != null) {
            expires = Long.valueOf(getServletConfig().getInitParameter("expires"));
        }

        buffered = Boolean.parseBoolean(getServletConfig().getInitParameter("buffered"));

        inputEncoding = getServletConfig().getInitParameter("inputEncoding");

        if (getServletConfig().getInitParameter("outputEncoding") != null) {
            outputEncoding = getServletConfig().getInitParameter("outputEncoding");
        }

        allowExec = Boolean.parseBoolean(getServletConfig().getInitParameter("allowExec"));

        if (debug > 0) {
            log("SSIServlet.init() SSI invoker started with 'debug'=" + debug);
        }

    }


    /**
     * Process and forward the GET request to our requestHandler().
     *
     * @param req a value of type 'HttpServletRequest'
     * @param res a value of type 'HttpServletResponse'
     *
     * @exception IOException      if an error occurs
     * @exception ServletException if an error occurs
     */
    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException {
        if (debug > 0) {
            log("SSIServlet.doGet()");
        }
        requestHandler(req, res);
    }


    /**
     * Process and forward the POST request to our requestHandler().
     *
     * @param req a value of type 'HttpServletRequest'
     * @param res a value of type 'HttpServletResponse'
     *
     * @exception IOException      if an error occurs
     * @exception ServletException if an error occurs
     */
    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException {
        if (debug > 0) {
            log("SSIServlet.doPost()");
        }
        requestHandler(req, res);
    }


    /**
     * Process our request and locate right SSI command.
     *
     * @param req a value of type 'HttpServletRequest'
     * @param res a value of type 'HttpServletResponse'
     *
     * @throws IOException an IO error occurred
     */
    protected void requestHandler(HttpServletRequest req, HttpServletResponse res) throws IOException {
        ServletContext servletContext = getServletContext();
        String path = SSIServletRequestUtil.getRelativePath(req);
        if (debug > 0) {
            log("SSIServlet.requestHandler()\n" + "Serving " + (buffered ? "buffered " : "unbuffered ") + "resource '" +
                    path + "'");
        }
        // Exclude any resource in the /WEB-INF and /META-INF subdirectories
        // (the "toUpperCase()" avoids problems on Windows systems)
        if (path == null || path.toUpperCase(Locale.ENGLISH).startsWith("/WEB-INF") ||
                path.toUpperCase(Locale.ENGLISH).startsWith("/META-INF")) {
            res.sendError(HttpServletResponse.SC_NOT_FOUND);
            return;
        }
        URL resource = servletContext.getResource(path);
        if (resource == null) {
            res.sendError(HttpServletResponse.SC_NOT_FOUND);
            return;
        }
        String resourceMimeType = servletContext.getMimeType(path);
        if (resourceMimeType == null) {
            resourceMimeType = "text/html";
        }
        res.setContentType(resourceMimeType + ";charset=" + outputEncoding);
        if (expires != null) {
            res.setDateHeader("Expires", (new java.util.Date()).getTime() + expires.longValue() * 1000);
        }
        processSSI(req, res, resource);
    }


    protected void processSSI(HttpServletRequest req, HttpServletResponse res, URL resource) throws IOException {
        SSIExternalResolver ssiExternalResolver = new SSIServletExternalResolver(getServletContext(), req, res,
                isVirtualWebappRelative, debug, inputEncoding);
        SSIProcessor ssiProcessor = new SSIProcessor(ssiExternalResolver, debug, allowExec);
        PrintWriter printWriter = null;
        StringWriter stringWriter = null;
        if (buffered) {
            stringWriter = new StringWriter();
            printWriter = new PrintWriter(stringWriter);
        } else {
            printWriter = res.getWriter();
        }

        URLConnection resourceInfo = resource.openConnection();
        InputStream resourceInputStream = resourceInfo.getInputStream();
        String encoding = resourceInfo.getContentEncoding();
        if (encoding == null) {
            encoding = inputEncoding;
        }
        InputStreamReader isr;
        if (encoding == null) {
            isr = new InputStreamReader(resourceInputStream);
        } else {
            isr = new InputStreamReader(resourceInputStream, encoding);
        }

        try (BufferedReader bufferedReader = new BufferedReader(isr)) {
            long lastModified = ssiProcessor.process(bufferedReader, resourceInfo.getLastModified(), printWriter);
            if (lastModified > 0) {
                res.setDateHeader("last-modified", lastModified);
            }
            if (buffered) {
                printWriter.flush();
                @SuppressWarnings("null")
                String text = stringWriter.toString();
                res.getWriter().write(text);
            }
        }
    }
}