plantuml-server/src/main/java/net/sourceforge/plantuml/servlet/ProxyServlet.java

/* ========================================================================
 * PlantUML : a free UML diagram generator
 * ========================================================================
 *
 * Project Info:  http://plantuml.sourceforge.net
 * 
 * This file is part of PlantUML.
 *
 * PlantUML is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * PlantUML distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 */
package net.sourceforge.plantuml.servlet;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

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

import net.sourceforge.plantuml.FileFormat;
import net.sourceforge.plantuml.FileFormatOption;
import net.sourceforge.plantuml.SourceStringReader;

import java.security.cert.Certificate;

import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLPeerUnverifiedException;

/* 
 * Proxy servlet of the webapp.
 * This servlet retrieves the diagram source of a web resource (web html page)
 * and renders it.
 */
@SuppressWarnings("serial")
public class ProxyServlet extends HttpServlet {

    private String format;

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {

        final String source = request.getParameter("src");
        final String index = request.getParameter("idx");
        final URL srcUrl;
        // Check if the src URL is valid
        try {
            srcUrl = new URL(source);
        } catch (MalformedURLException mue) {
            mue.printStackTrace();
            return;
        } 

        // generate the response
        String diagmarkup = getSource(srcUrl);
        System.out.println("getSource=>" + diagmarkup);
        SourceStringReader reader = new SourceStringReader(diagmarkup);
        int n = index == null ? 0 : Integer.parseInt(index);

        reader.generateImage(response.getOutputStream(), n, new FileFormatOption(getOutputFormat(), false));
    }

    private String getSource(URL url) throws IOException {
        String line;
        BufferedReader rd;
        StringBuilder sb;
        try {
            HttpURLConnection con = getConnection(url);
            rd = new BufferedReader(new InputStreamReader(con.getInputStream()));
            sb = new StringBuilder();

            while ((line = rd.readLine()) != null) {
                sb.append(line + '\n');
            }
            rd.close();
            return sb.toString();
        } catch (IOException e) {
            e.printStackTrace();
        } finally{
            rd = null;
        }
        return "";
    }

    private FileFormat getOutputFormat() {
        if (format == null) {
            return FileFormat.PNG;
        }
        if (format.equals("svg")) {
            return FileFormat.SVG;
        }
        if (format.equals("txt")) {
            return FileFormat.UTXT;
        }
        return FileFormat.PNG;
    }

    private HttpURLConnection getConnection(URL url) throws IOException {
        if (url.getProtocol().startsWith("https")) {
            HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
            con.setRequestMethod("GET");
            con.setReadTimeout(10000); // 10 seconds
            // printHttpsCert(con);
            con.connect();
            return con;
        } else {
            HttpURLConnection con = (HttpURLConnection) url.openConnection();
            con.setRequestMethod("GET");
            con.setReadTimeout(10000); // 10 seconds
            con.connect();
            return con;
        }
    }
    
    /**
     * Debug method used to dump the certificate info 
     * @param con the https connection
     */
    private void printHttpsCert(HttpsURLConnection con) {
        if (con != null) {
            try {
                System.out.println("Response Code : " + con.getResponseCode());
                System.out.println("Cipher Suite : " + con.getCipherSuite());
                System.out.println("\n");

                Certificate[] certs = con.getServerCertificates();
                for (Certificate cert : certs) {
                    System.out.println("Cert Type : " + cert.getType());
                    System.out.println("Cert Hash Code : " + cert.hashCode());
                    System.out.println("Cert Public Key Algorithm : " + cert.getPublicKey().getAlgorithm());
                    System.out.println("Cert Public Key Format : " + cert.getPublicKey().getFormat());
                    System.out.println("\n");
                }

            } catch (SSLPeerUnverifiedException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}